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Time
Time
Ausarbeitung zum Englisch Spezialgebiet by
Marcus Meisel, 8C
Betreuerin: Mag.
Rauchenwald
B)
CONTENTS
A) Title Page page 1
B) Contents page 2
C) Introduction page 4
1) Time is an Arrow page
5
Seeing Things Different
- The Last Century page 5
- The Beginning of Time page 5
- Sensing Time page 5
- The Arrows of Time page 5
- Which Direction? page 6
- Intelligent Life page 6
- A fourth Arrow? page
7
Summary page 7
2) Relativity of Time
page 8
The Beginning page 8
- Einstein`s Start page 8
- The Twin Paradoxon page
8
It`s all Relative page 9
- Einstein page 9
- Day-to-Day Experiences page 10
- A Clue page 10
- The Solution page 11
- Light page
11
Einstein`s Dreams page 11
- Plot page 11
- Results page
12
New Findings page 12
- Consequences page 12
- Faster than Light page
12
General Relativity page 13
- A Solution page 13
- The Trojan Horse page 13
- Questions page
13
3) Space and
Time page 14
A Brief History of Time page 14
Sinking into Space-Time page 14
- Einstein page 14
- The Universe as a Sheet page 15
- Einstein as Idol page 15
- Dynamic Space and Time page 15
- Gravitational Effects page 16
- Solutions? page 16
- A Unifying Theory page 16
- Dreams page 17
- The Physics of Star Trek page
17
4) To Build a Time
Machine page 19
The First Thoughts
- Change Time page 19
- The Time Machine page 19
- Time Travel page 20
- Introducing a New Theory page
21
Problem: Time Travel page 21
- Logical Paradoxon page 21
- The Risks of Time Travel page 21
- Time Paradoxes page 22
- My Favourite page
23
Creating the Impossible? page 23
- Theoretical Basis page 23
- Multiply Connected Universes page
24
- Time Travel and Baby Universes page
24
- Evading the Light Barrier page
25
- Inside Out page
25
I) Conclusion page 27
II) Glossary page 28
III) Bibliography page 29
IV) Cover sheet page 30
V) Bookreports page 31
i) Einstein`s Dreams page 32
ii) The Time Machine page 39
iii) A Brief History of Time page 45
iiii) The Physics of Star Trek page 61
VI) Cover sheet page 65
C)
Introduction
Scientific
revolutions, almost by definition, defy common sense.
If all our common-sense notions about the universe were
correct, the science would have solved the secrets of the universe thousands of
years ago. The purpose of science is to peal back the layer of the appearance of
objets to reveal their underlying nature. In fact, if appearance and essence
were the same thing, there would be no need for science.
Perhaps the most deeply entrenched common-sense notion
about our world is that it is three dimensional. It goes without saying that
length, width, and breadth suffice to describe all objects in our visible
universe. Experiments with babies and animals have shown that we are born with
an innate sense that our world is three dimensional. But to record all events in
the universe, we need another dimension. If we include time as another
dimension, then four dimensions are sufficient. No matter where our instruments
have probed, from deep within the atom to the farthest reaches of the galactic
cluster, we have only found evidence for these four dimensions.
Time is a very
complex dimension. So not only in science, thus also in common usage, time is
hard to understand. There are so many possible meanings
implied.
If you just say the word time when you enter
different situations, it depends on which room you have entered. When you enter
a restaurant, you will receive the time of the time zone you are right now,
which is the usual answer. But there are many different answers possible. Like
if you enter a soccer stadion. Everybody will yell at you the score, how much
time there is left, and to shut up. If you sit in a plane, and you ask the
captain will tell you several times you haven`t even thought of: The time of
your arrival and departure in the time zone you left and will arrive, how long
your flight was since now and how long it will take in miles per hour or km per
second. Which speed the plain in that moment has, and which average speed it
needs for take off or landing. If you enter a fast-food restaurant and you just
ask "time?", you will hear how long it takes to finish the fries or the burger.
If you are in a university and you ask for "time?", the answer depends again in
what room you are. In the dorms you will get a tired "too late" or a curse like
"damn it! I`m late." as answer. On the foodcourt a hectically "just five more
minutes" is the usual answer. And during a physics class, the answer is a long
precise definition of time.
What time really
is, nobody truly can tell, but scientists try their hardest to find answers to
their unanswered questions. In this Special Topic "Time" I would like to give an
idea of the momentary situation science is now, and show some possible answers
from some of the brightest minds of mankind.
But also scientists do not agree in every respect. They
try to fit all their observations in formulas they again try to combine all to
get a unifying theory about the smallest and the largest things in our universe
we live in.
The aim of science is to penetrate into smaller and
bigger dimensions and not to stop until humankind has a complete theory of all
forces and particles that appear in nature.
Like Thomas H. Huxley once said,
The known is finite, the unknown infinite;
intellectually we stand on an islet in the midst of an illimitable ocean of
inexpl- icability. Our business in every generation is to reclaim a little more
land.
On the next pages I would like to give an easy
understandable, brief description of what time is considered to be and want to
try to uncover some secrets of Time
1) Time is an
Arrow
Seeing Things Different
Before the 20th century, Newton`s laws
belonged to the basis of physics. But at the end of the 19th century
there were discovered two conflicts, with thermodynamics and electro-magnetism,
that ultimately led to the formulation of first the theory of relativity and
then the quantum theory. Einstein told us that space and time were part of a
four-dimensional space-time and both relative. He was the first to count these
to physics instead of accepting it as simply “existing”. When it was
later discovered that the universe is expanding, scientists quickly realised
that everything had to start existing at a certain point in the past, known as
the “Big Bang”.
At the Big Bang the universe`s density was infinite.
Under such conditions all the laws of science, and therefor all ability to
predict the future, would break down. If there were events earlier than this
time, then they could not affect what happens at the present time. Their
existence can be ignored because it would have no observational consequences.
One may say that time had a beginning at the big bang, in the sense that earlier
times simply would not be defined.
We are creatures in time and this has a very great
effect on how we think about time and the temporal aspect of what is
real.
The psychological time is very much different from the
physical one. It seems that we are not able to perceive too short events, and
that our brain manipulates our perceptions before they become conscious. Based
on experiments, psychologists therefore suggest that our consciousness is a
whole bunch of parallel processes.
People seem to sense time in a very subjective way, a
fact that is in conflict with an universal time. In other cultures, like the
Aborigines, there is not even a clear distinction between past, present and
future. But the latter vanished in physics too, with the invention of
relativity.
Many religions and philosophers believe in a cyclic
time, and they are consistent with some scientific theories. Laplace first
realised that when everything is predictable, knowledge of the moment is enough
to know the situation in every moment, also in the future, thus making time
obsolete.
With the laws of thermodynamics physicists then realised
that the universe is developing towards maximal entropy, or chaos. This made the
perpetuum mobile impossible and put an end to Newton`s linear time. It also
brought an arrow of time into physics. Based on Boltzmann´s work
Poincaré then proved the possibility of a cyclic universe, but with
cycles being incredibly long.
Religions like to believe in creation, which cannot be
proven to be wrong. The P`an Ku myth of China`s third century describes the time
before creation like that:
In the beginning, was the great cosmic egg. Inside the
egg was chaos , and floating in chaos was P ` an Ku, the divine
Embryo.
In India`s ninth century, the Mahapurana, one of the
most important books was written. In this book, the beginning of time is
described as follows:
If God created the world, where was He before
Creation?... Know that the world is uncreated, as time itself is, without
beginning and end.
It is not entirely impossible that we all live only
since some minutes ago, created with memories of past times. Seen out of this
respect, the flow of time can never be proven, and
time itself may as well be an illusion.
The increase of disorder or entropy with time is one
example of what is called an arrow of time, something that distinguishes the
past from the future, giving a direction to time. There are at least three
different arrows of time.
First, there is the thermodynamic arrow of time, the
direction of time in which disorder or entropy increases. Then, there is the
psychological arrow of time. This is the direction in which we feel time passes,
the direction in which we remember the past but not the future. Finally, there
is the cosmological arrow of time. This is the direction of time in which the
universe is expanding rather than contracting.
The psychological arrow is essentially the same as the
thermodynamic arrow, so that the two would always point in the same
direction.
The no boundary proposal for the universe predicts the
existence of a well defined thermodynamic arrow of time because the universe
must start off in a smooth and ordered state. And the reason why we observe this
thermodynamic arrow to agree with the cosmological arrow is that intelligent
beings can exist only in the expanding phase of our universe.
However, a strong thermodynamic arrow is necessary for
intelligent life to operate. In order to survive, human beings have to consume
food, which is an ordered form of energy, and convert it to heat which is a
disordered form of energy. Thus intelligent life could not exist in a
contracting phase of the universe. This is the explanation of why we observe
that the thermodynamic and cosmological arrows of time point in the same
direction.
The contracting phase will be unuitable because it has
no strong thermodynamic arrow of time.
Some scientists interpose a fourth arrow, an arrow that
helps to explain the causal asymmetry. We use "cause" to mark the earlier and
"effect" to mark the later of a pair of events which are related this way.
Cause-effect relation is itself asymmetric - that is, that causes and effects
can be distinguished in some way.
Scientists are everything else but the same opinion in
which direction they themselves should research to find answers to the questions
the arrows and the asymmetry of time pose to us. In the respect of the
increasing disorder in the course of time, James Thurber was right as he
said:
"It is better to know some of the
questions than all of the answers."
Because the more answers we find the more questions
arise.
Summary
Up to the beginning of our century people believed in an
absolute time.
Newton considered time to be moving like a straight
arrow, which unerringly flies forward toward its target. Nothing could deflect
or change the course of this arrow once it was shot. Einstein, however,
abandoned the idea of an absolute time and showed that time was more like a
mighty river, moving forward but often meandering through twisting valleys and
plains created through matter on a space-time surface. The presence of matter or
energy might momentarily shift the direction of the river, but overall the
river`s course was smooth: It never abruptly ended or jerked
backward.
However, successors like Kurt Gödel or Louis
Tamburino showed that the river of time could be smoothly bent backward into a
circle. Rivers, after all, have eddy currents and whirlpools. In the main, a
river may flow forward, but at the edges there are always side pools where water
flows in a circular motion.
2) Relativity
of Time
Newton`s laws of motion put an end to the idea of
absolute position in space. The theory of relativity put an end to the idea of
absolute time, so any observer can work out precisely what time and position any
other observer will assign to an event, provided he knows the other observer`s
relative velocity. (they are related)
Nowadays we use just this method to measure distances
precisely, because we can measure time more accurately than length. In effect,
the meter is defined to be the distance travelled by light in vacuum in
0.000000003335640952 seconds, as measured by a caesium clock. So, we must accept
that time is not completely separate from and independent of space, but is
combined with it to form an object called space-time. (more
later)
The Beginning
I want to know how God created this world. I am not
interested in this or that phenomenon. I want to know His thoughts, the rest are
details.
Albert Einstein
When Einstein was born, Newton`s theory led to absurd
results for the movement of light, leading him to postulate the relativity of
time and to set the speed of light as the highest one possible.
Early on in physics, scientists invented an ether to
explain the characteristics of light. But Michelson and Morley proved this idea
ultimately wrong. This led Einstein to the idea that neither space nor time are
fixed. His theory of relativity has been proved often since, as an example with
the help of pulsars, and turned out to be right. The speed of light being the
absolute top causes time dilatation effects, which allow us to observe myons.
But this effect also causes the twin paradoxon, which is absolutely possible on
closer examination, and it puts an end to a definite present.
This paradoxon is one of the best known world-wide. It
describes twins, one staying on earth the other twin making a journey in a
rocket travelling with a velocity near the speed of light. They were exactly the
same age when the brother departs but when he comes back after 50 years, the
brother that stayed is older than the one that went with the rocket. For the one
that lived on earth all the time, 50 years had gone by, whereas for the other
one in the rocket, just 5 or 10 or 13 years had passed. (dependent on the
velocity he travelled)
It is not that the one in the rocket lived 50 years and
got only 13 years older; He lived just 13 years in the rocket. For him and all
the watches on board only 13 years passed. And for his brother and all the
watches placed on earth 50 years passed. Both of them are
right.
That time is not a constant but dependent on the
velocity of the system in which it is measured, is an assumption of Albert
Einstein. Meanwhile there are very exact atomic clocks that proof his assumption
as true.
Einstein`s idea was that if the speed of light appeared
the same to every observer, no matter how he was moving, another factor has to
be variable, what led him to the theory of relativity. And this factor is the
velocity with which time goes by, to say, time itself. Out of this thought
follows that clocks, carried by different observers, would not necessarily
agree.
Seen from an observer outside of the moving system, this
interesting effect in the flow of time is called time dilatation. The nearer to
the speed of light you get, the slower time goes by.
If an object moves with 100% lightspeed, time would
stand still; and the mass would get infinite. That is the reason why travelling
with speed greater than the one of light is impossible. The spaceship would have
to get through the barrier of infinite mass and no time passing by, the
so-called light barrier. The second problem is the slightest problem for the
person travelling in the rocket. For his point of view the flow of time is
constant all the journey long! He just would not find the same persons he left
when he comes back. They will all be dead since millions of
centuries.
So if one does not like his century, travelling near the
speed of light would offer a realistic possibility to jump into the next without
a worth mentioning loss of time.
In this respect the advertisement slogan of
Swatch, now seen from another background, gets a completely new
meaning:
"Time is what you make of
it!"
It`s all Relative
Both Aristotle and Newton believed in absolute time.
That is, they believed that one could unambiguously measure the interval of time
between two events, and that this time would be the same whoever measured it,
provided they used a good clock. Time was completely separate from and
independent of space. This is what most people would take to be the common-sense
view. However, we have had to change our ideas about space and time. Although
our apparently common-sense notions work well when dealing with things like
apples and planets that travel comparatively slowly they do not work at all for
things moving at or near the speed of light.
Einstein had worked as a patent officer in Berne, in
Switzerland, to earn a living and pay for his academic work while he wrote up
his ideas about the laws of physics. In doing this he was rapidly becoming known
as the visionary scientist of his time. His first major work was published in
1905, the first of two Theories of Relativity. It is called special Relativity;
and the later theory, published in 1915, is called General Relativity. The
fundamental postulate, we recall from our time at school, was that the laws of
science should be the same for all freely moving observers, no matter what their
speed. Both deal with the way an observer and the event he or she observes are
related; Special Relativity essentially spells out what happens when there is a
constant movement linking the event and the observer, and General Relativity
brings in gravity. It also suggests what happens as the speed of any movement
increases or decreases. The idea included also the speed of light: all observers
should measure the same speed of light, no matter how fast they are moving. This
simple idea has some remarkable consequences which I will describe later
on.
They are both still very difficult theories to
understand fully, but they are nevertheless widely acknowledged as the ideas
which placed Einstein on the scientific world stage. Einstein did not set out
specifically to explain the nature of time or the universe, but his theories
inevitably interested many scientists, because he was in effect rewriting the
laws of physics which had been left unchallenged since the time of
Newton.
Einstein argued that the laws of physics must be the
same, from whatever position they happened to be observed. This idea stemmed
from the insight that the same event can appear different to two different
observers, depending on their relative positions.
Several day-to-day examples have been suggested to help
illustrate the point. One that most of us have experienced at some time or
another is when two trains stop alongside each other in a railwaystation. You
can be sitting on one train, looking out of the window at the other train, when
it seems to move off. For a second or two you are not sure whether it has in
fact started to move, or whether it is your own train which is moving off. All
you know is that one train must be moving relative to the other; hence
Relativity.
Now imagine a situation where one observer is on board a
train another is on a railway station platform as the train rushes by. A cup on
a table in front of the man on the train will appear to stay 60 centimetres in
front of him. So, from his point of view, it will not be moving. However, to the
man on the platform who watches the passing carriage windows, the cup will be
seen to rush past at great speed as the train hurtles through the
station.
Einstein`s great insight was that the laws of physics
had to be rewritten in such a way that the laws of motion would be recognised as
being consistent. They would have no account for related concepts such as
acceleration and momentum, which were involved in these apparently different
views of the cup. And this meant understanding the nature of time and space, and
how they affect things.
After all, what causes two different views of the cup
are the different positions of the observers relative to the cup in time and
space. One is travelling through time and space alongside the cup, so that its
relative position is always 60 centimetres in front of him; it stays in his
field of vision as long as they are both travelling through time and space in an
identical fashion. The other observer is, by comparison, stationary in time and
space relative to the moving cup, so that it comes into and moves out of his
field of vision in a very short time.
Einstein developed mathematical equations to describe
these kinds of relationships. Taken together, they defined the nature of time
and space; and they had momentaneous consequences for cosmologists. To begin
with, it emerged that time and space were mathematically one and the same thing.
And, as a consequence, Newton`s explanation of gravity had to be totally
revised, accurate as it seemed to be.
But more to this in the next chapter about `Space and
Time`.
Contemporary physics states that no object should be
able to travel faster than the speed of light
c = 299`792`458 metres per
second.
Although the value of c appears enormous when compared
with conventional travelling speeds, it suggests a limit which renders a
practical realisation of interstellar travel improbable. Whereas another planet
in our solar system is reachable within minutes or at least hours at the speed
of light, a journey to the nearest star system Alpha Centauri would already
demand a travelling time of several years (4,2 Light-years). Surely, the
question remains: Are faster-than-light speeds possible? At the present time
most scientists believe that the correct answer should be "no". However, it has
to be emphasised that there is no definite proof for this claim. Actually,
whether superluminal speeds are possible in principle depends on the real
structure of the space-time continuum. (more later)
This book shows what would happen if time was no longer
an arrow but anything else. There are several examples of different kinds of
appearances of time like being like a stream of water, a circle or even parted
in regions where in each time runs at a different speed.
It is a fiction book, endearingly short, airy and
irrational, in simple and beautiful language. The science is gentle and it is
cast in language to bring the flush of envy to any one of the many famous
writers alive today who has coaxed himself into the delusion that scientists
cannot write. It is a celebration of a world in which time does not march
brutally through people`s lives, but rather skips and gambles, forever quirky
and unpredictable. Lightman is exploring fiction`s deep space, taking us further
than we are used to being taken.
The setting of the story is located in Berne, in
Switzerland.
In this book Alan Lightman describes the dreams of
Albert Einstein, a young patent clerk had between 14th April 1905 and 28th June
1905. Although the characters and situations in this book are entirely imaginary
and bear no relation to any real person or actual happening, it is a
breathtaking synthesis of science and imagination.
One witnesses Einstein`s dreams of new worlds:
extraordinary visions of the effect on people`s lives when the direction and the
flow of time changes to circular or flows backwards, slows down or takes the
form of a nightingale.
In all dreams there are given examples, of how life
changes when time is different, and most of them play in Berne, the city
Einstein used to live.
The whole book is a flashback that starts after Einstein
has finished his work. He reflects back on his time of creating the new theory
of time. This ends two hours later. In those two hours Einstein reflects on the
past several months, where he had many dreams about time. The book describes
some of the dreams and tells the reader that those have taken hold of his
research.
Out of many possible natures of time, imagined in as
many nights, one seems compelling. Not that the others are impossible. The
others might exist in other worlds.
The result of all those dreams was the special theory of
relativity. It was a completely new point of view. Although it cost Einstein a
lot of energy, he believed that it was worth it. The picture of time that got
its final shape while it was dreaming, was so obvious, so clear to him. Other
people might also have such visions, but Einstein had the ability to write it
down as a physical concept.
New Findings
The essence of Einstein`s equations is that the matter
and energy content of an object determines the amount of curvature in the
surrounding space and time.
The question whether the speed of light is a true
physical limit has no definite answer yet. It depends on the real structure of
space-time. If there is an absolute time preserving causality (by preventing
time-travel paradoxes), then faster-than-light speeds - and even
faster-than-light travel - are possible, at least in principle. On the other
hand, if superluminal processes are to be discovered, then absolute time
will
probably have to be reintroduced in physics. Although
the theory of special relativity states against absolute time and superluminal
phenomena, it does it not by proof, but only by assumption.
Are there indications that absolute time and
faster-than-light processes
exist ? My opinion is "yes" !
The theory of relativity does not make faster-than-light
moving completely impossible, it only forbids the crossing of the light barrier,
thus principally allowing tachyons that always move faster than light, but are
not manipulatable by us. Based on the equivalency principle and the Doppler
effect Einstein concluded that also gravity influences light, putting an end
even to sub-atomic perpetuum mobiles.
Another example where particles can travel faster than
light is given in the quantum theory. There exists a phenomenon called the
tunnel effect. It turned out that it is impossible to measure the length of the
tunnelling time. Some other experiments also showed that one cannot determine
which way a photon has taken in an experiment. The photons even seemed to
communicate to each other faster than light! Quantum theory therefore proposes
the concept of multiple realities.
General Relativity
In 1949, Einstein was concerned about a discovery by one
of his close colleagues and friends, the Viennese mathematician Kurt Gödel.
Gödel found a disturbing solution to Einstein`s equation that allowed for
violation of the basic tenets of common sense: His solution allowed for certain
forms of time travel. For the first time in history, time travel was given a
mathematical foundation.
If one followed the path of a particle in a Gödel
universe, eventually it would come back and meet itself in the past. He wrote,
"By making a round trip on a rocket ship in a sufficiently wide curve, it is
possible in these worlds to travel into any region of the past, present, and
future, and back again."
His solution let time bend into a circle, called a
closed timelike curve (CTC).
Einstein`s equations, in some sense, were like a Trojan
horse. On the surface, the horse looks like a perfectly acceptable gift, giving
us the observed bending of starlight under gravity and a compelling explanation
of the origin of the universe. However, inside lurk all sorts of strange demons
and goblins, which allow for the possibility of interstellar travel through
wormholes and time travel. (more later)
The price we had to pay for peering into the darkest
secrets of the universe was the potential downfall of some of our most commonly
held beliefs about our world - that its space is simply connected and its
history is unalterable.
But the question still remained: Could these CTCs be
dismissed on purely experimental grounds, as Einstein did, or could someone show
that they were theoretically possible and then actually build a time
machine?
3) Space and
Time
Because of the non-existence of an absolute rest, the
lack of an absolute position in space and time is explained !
A Brief History of
Time[2]
"A Brief History of Time" is a book that tries to
explain the main theories of today physics in a quite "non-technical" language
so everybody can understand them. This book starts at the beginning of science
with the Greek philosopher Aristotle and goes on until the youngest theories
about our universe like the superstring-theory which needs
10dimensions.
We go about our daily lives understanding almost
nothing of the world. We give little thought to the machinery that generates the
sunlight that makes life possible, to the gravity that glues us to an Earth
that would otherwise send us spinning off into space, or to the atoms of which
we are made and on whose stability we fundamentally depend. Except for children,
few of us spend much time wondering why nature is the way it is; where the
cosmos came from, or whether it was always here; if time will one day flow
backward and effects precede causes; or whether there are ultimate limits to
what humans can know. Was there a beginning of time? Could time run backwards?
Is the universe infinite or does it have boundaries? These are just some of the
questions considered in an internationally acclaimed masterpiece which begins by
reviewing the great theories of the cosmos from Newton to Einstein, before
diving into the secrets which still lie at the heart of space and
time.
This book tries to answer at least some of these
questions that can be answered now. To get some answers we can only follow the
theories of Stephen Hawking, which are very good explained in his
best-seller.
Sinking into space-time
As I already mentioned, Einstein developed mathematical
equations to define the nature of time and space. These equations had momentous
consequences for cosmologists. To begin with, it emerged that time and space
were mathematically one and the same thing. And, as a consequence, Newton`s
explanation of gravity had to be totally revised, accurate as it seemed to be.
Einstein argued that two objects do not directly attract each other as Newton
has thought; rather, each of the two objects affects time and space, and any
gravitational effects are a consequence of this. That was the moment when he
found out that space and time are warped.
If this concept is difficult to grasp, imagine a heavy
object (such as a cannon ball), representing the sun, being placed in the middle
of a taut rubber sheet [{ einfügen Bild in files }], creating a cone-shaped
dent all around it - rather reminiscent of the surface of a vortex of swirling
water rushing down a plunge hole.
Einstein argued that whenever something heavy bent
space-time like this, it would naturally affect the path of anything lighter
travelling nearby. So a smaller ball representing the Earth or one of the other
planets could be rolled across the stretched rubber sheet representing
space-time, towards the dent around the cannon ball sun.
If it was travelling too slowly, it would fall directly
into the dent and quickly reach the surface of the sun (just like Newton`s apple
falling to the surface of the Earth). If it was travelling too fast, it would
have its path deflected towards the cannon ball sun, but would only dip into the
dent then climb out of the other side, before continuing on its journey. But at
just the right speed, the small planet ball would be going fast enough not to
fall right into the dent, but too slowly to escape it completely. With nothing
else to stop it or slow it down, it would find its level on the `side` of the
dent in space-time, rather like a motorcycle stunt rider going round and round
the `wall of death`. It would have found its static orbit around the
sun.
The mathematical formula of Einstein could apart from
even describe the orbit of Mercury, what was not possible with Newton`s rather
simpler equation. This was impressive evidence that Einstein`s theory was
correct, or at least an improvement on Newton`s explanation of gravity. It was
natural for physicists to begin to think: if it fits in with Einstein`s
theories, it is probably going to be true.
It was while studying these equations of Einstein`s that
Lemaître, a priest and Belgium`s most famous astronomer, discovered
something which really excited him. One of the consequences of Einstein`s maths
was that the universe was not static; it was dynamic.
It is simply enough to see why. If time and space are
`dented` by anything with mass, then, as one body passes another, it will be
drawn closer to it.
If the universe is static, then all objects will
eventually be drawn to each other; all mass will congregate together at the
bottom of the largest dent in space and time.
This was the same problem which had worried Newton when
he came up with his theory of gravity; how could all the matter in the universe
still be widely spread out after billions of years? Why hadn`t it been pulled
together by gravity into one conglomerate lump? But, whereas Newton`s idea had
confined itself to the attraction of objects, Einstein`s theory involved the
mathematics of how space and time change when an object with mass affects them.
Thus Newton`s system had no way for the coming together of all objects to be
avoided but Einstein`s maths did. Einstein needed space and time to be able to
change in the presence of mass. So space and time had to be dynamic, rather than
static.
Consequently, space-time, and so the universe, could not
remain still; and if it had to change it could only really get bigger or
smaller. Hence it ought to be gently expanding or contracting.
It is gravity that governs and shapes the large-scale
structure of the universe and thus even time.
The laws of gravity were incompatible with the view held
until quite recently that the universe is unchanging in time: the fact that
gravity is always attractive implies that the universe must be either expanding
or contracting.
According to general theory of relativity, there must
have been a state of infinite density in the past, the big bang, which would
have been an effective beginning of time. (Scientists today generally agree on
an age of the universe of about 13 billion years.)
Similarly, if the whole universe recollapsed, there must
be another state of infinite density in the future, the big crunch, which would
be an end of time. Even if the whole universe did not recollapse, there would be
singularities in any localised regions that collapsed to form black holes. These
singularities would be an end of time for anyone who fell into the black
hole.
In every case there are certain locations in space that
effect time, seen from an different, innocent, and independent
observer.
Schwarzschild calculated a solution to Einstein`s
equations where the time dilatation is infinite from a certain radius on, out of
which evolved the idea of black holes. Wheeler found out that
Schwarzschild´s solution included a singularity, but also proved its
possibility. (The first black hole was found in 1964 in the system Cygnus
X-1.)
Hubble proved the even expanding of space, which allowed
to calculate the Big Bang. Einstein therefore introduced a new term into his
theory of relativity, the “cosmic term”, which he later thought of
as his biggest error, because it would have caused the universe to become
unstable.
In the search for “theories of everything”,
which try to unite relativity and quantum mechanics, the possibility of a cosmic
term returned.
When scientists like Stephen Hawking combine quantum
mechanics, with general relativity, there seems to be a new possibility for him
that did not arise before: that space and time together might form a finite,
four-dimensional space without singularities or boundaries, like the surface of
the earth but with more dimensions. It seems that this idea could explain many
of the observed features of the universe, such as its large-scale uniformity and
also the smaller-scale departures from homogeneity, like galaxies, stars, and
even human beings. It could even account for the arrow of time that we
observe.
At the end of A Brief History of Time Stephen
Hawking concludes that, if we do discover a complete theory that could describe
everything, its basic principles and implications should in time be
understandable by everyone. And once we all understand the true nature of the
universe, we all, philosophers, scientists and just ordinary people, can take
part in the discussion of the question of why it is that we and the universe
exist. Should we ever resolve this question, he suggests, it will be `the
ultimate triumph of human reason - for then we would know the mind of
God`.
Perhaps, for many of us, that challenge will seem a step
too far. There are millions of us who have never before got close to discovering
the nature of the universe. We may just have not tried; more likely we were
convinced that it was beyond our limited capacity to
understand.
But I think that our opinion is changing. Changing
towards knowing more and more about the world and universe we live in. And that
is the reason for me to belief that in no way research in this field will find a
sudden end.
Already Yogi Berra said :
“It ain’t over till
it’s over”
I think that these concepts will come to seem as natural
to the next generation as the idea that the world is round. Imaginary time is
already a commonplace of science fiction. But it is more than science fiction or
a mathematical trick. It is something that shapes the universe we live
in.
An example of how the human race could cope with the
progress made in all scientific directions is given in Star Trek. It shows how
much we know already and how much we will be able to do with our knowledge in
the near future.
- The Physics of Star
Trek[3]
It is a popular science book, trying to tell most modern
science in a simple language. " The Physics of Star Trek" is a book to be read
many times as long it is up-to-date with our time (till we cross the milky ways
of our and other galaxies). It offers a lot of exotic science to anyone who
wants to make a small investment of imagination. Perhaps accidentally, Krauss
also does a useful job in explaining some important physics, using Star Trek as
a pop culture example: the physics of Newton, Einstein and Stephen Hawking all
figure in the highly successful analysis. It is a book on physics, but it is
written in such a spirit of fun, it might even make you want to watch Star Trek.
This book is fun, and Mr. Krauss has a nice touch with a tough subject. Krauss
is smart, but speaks and writes the common tongue.
In this entertaining book the physics professor Lawrence
Krauss looks at how the imaginary science of the Star Trek universe stacks up
against the real thing. Krauss speculates on the possibility of alien life,
touching on whether any kind of life is such an improbable phenomenon.
There are impressively clear explanations of difficult
and up-to-date concepts in information theory, quantum mechanics, particle
physics, relativity, mechanics and cosmology. The book goes where not even the
show`s laudable tradition of scientific evangelism has gone
before.
4) To Build a Time
Machine
The First Thoughts
Since ever, humans wanted to change the past and know
about the future. Just to know the results of a bet of tomorrow today or to mend
a decision, made in the past.
Since it was not possible for scientists to build
machines to look or travel through time, it was the duty of science fiction
authors to speculate about possible ways, how a time machine would look and work
like.
It is a science fiction novel about the Victorian
future which is more than a fantastical yarn. It raises chilling questions about
progress, social orders, so called civilisation and the ultimate fate of the
world. It tells the story from the present until the end of our sun-system, a
cold, almost lifeless earth with a dying sun.
Wells wrote this novel mainly because Charles Darwin
published and proved his theory of Evolution, which was the greatest scientific
rumpus since the trial of Galileo.
It is a story about evolution brought to the reader as
an adventure of an old scientist, who has invented a time machine. Although
Wells doesn’t tell the reader the names of the Victorian scientist and the
Narrator, he creates a personal relationship with the reader, which is very
difficult and proves again that H.G.Wells is one of the best
writers.
The Time Traveller lives in a house in London, in
Richmond. In the cellar he has his laboratory, his workshop. The Time Traveller
shows his disbelieving dinner guests a device he claims is a Time
Machine.
He tries to convey his dinner guests that he found a
machine to interrupt the floating time stream an though have the possibility to
move through time as one wants.
In real time a week later the dinner guests visit the
Time Traveller again, but instead of a settled old man they find him raged,
exhausted and garrulous. The tale he tells is of the year 802,701 AD of life as
it is lived on exactly the same spot, what once had been London. He has visited
the future, he has encountered the future -race -elfin, beautiful, vegetarian,
helpless, leading a life of splendid idleness.
But this is not the only race, these are not our only
descendants. In the tunnels beneath the new Eden there lurks another life
form.
The end of the book is open because the Time Traveller
disappears in front of the eyes of the Narrator and hasn’t come back for
three years although he said he’ll need only half an hour for his
journey.
Can we go back in time?
Like the protagonist in H.G. Wells`s The Time
Machine, can we spin the dial of a machine and leap hundreds of thousands of
years to the year 802,701? Or, like Michael J. Fox, can we hop into our
plutonium-fired cars and go back to the future?
The possibility of time travel opens up a vast world of
interesting possibilities. With time travel, we could go back to our youth and
erase embarrassing events from our past, choose a different mate, or enter
different careers; or we could even change the outcome of key historical events
and alter the fate of humanity.
For example, in the climax of Superman, our hero
is emotionally devasted when an earthquake ravages most of California and
crushes his lover under hundreds of tons of rock and debris. Mourning her
horrible death, he is so overcome by anguish that he rockets into space and
violates his oath not to tamper with the course of human history. He increases
his velocity until he shatters the light barrier, disrupting the fabric of space
and time. By travelling at the speed of light, he forces time to slow down, then
to stop, and finally to go backward, to a time before Lois Lane was crushed to
death.
This trick, however, is clearly not possible. Although
time does slow down when you increase your velocity, you cannot go faster than
the speed of light ( and hence make time go backward ) because special
relativity states that your mass would become infinite in the process. Thus the
faster-than-light travel method preferred by most science fiction writers
contradicts the special theory of relativity.
Einstein himself was well aware of this
impossibility.
Most scientists, who have not seriously studied
Einstein`s equations, dismiss time travel as poppycock, with as much validity as
lurid accounts of kidnappings by space aliens. However, the situation is
actually quite complex.
To resolve the question, we must leave the simpler
theory of special relativity, which forbids time travel, and embrace the full
power of the general theory of relativity, which may permit it. General
relativity has much wider validity than special relativity. While special
relativity describes only objects moving at a constant velocity far away from
any stars, the general theory of relativity is much more powerful, capable of
describing rockets accelerating near supermassive stars and black holes. The
general theory therefor supplants some of the simpler conclusions of the special
theory. For anyone who has seriously analysed the mathematics of time travel
within Einstein`s general theory of relativity, the final conclusion is,
surprisingly enough, far from clear.
Proponents of time travel point out that Einstein`s
equations for general relativity do allow some forms of time travel. They
acknowledge, however, that the energies necessary to twist time into a circle
are so great that Einstein`s equations break down. In the physically interesting
region where time travel becomes a serious possibility, quantum theory takes
over from general relativity.
Einstein`s equations state that the curvature or bending
of space and time is determined by the matter-energy content of the universe. It
is, in fact, possible to find configurations of matter-energy powerful enough to
force the bending of time and allow for time travel.
However, the concentrations of matter-energy necessary
to bend time backward are so vast that general relativity breaks down and
quantum corrections begin to dominate over relativity. Thus the final verdict on
time travel cannot be answered within the framework of Einstein`s equations,
which break down in extremely large gravitational fields, where we expect
quantum theory to become dominant. But quantum corrections, in turn, may
actually close the opening of the wormhole, making travel through the gateway
impossible.
This is when the ten dimensional hyperspace theory can
settle the question. Because both quantum theory and Einstein`s theory of
gravity are united in ten dimensional space, scientists expect that the question
of time travel will be settled decisively by the hyperspace theory. But
wormholes and dimensional windows which could be used for time travel might only
be understood completely when one incorporates the full power of the hyperspace
theory.
Because of this reason it will take some time until
enough scientists can research in this direction and decide whether these
wormholes are physically relevant or just another crazy idea.
However, the most bizarre consequence of wormholes is
that physicists can not only show that wormholes allow for multiply connected
spaces, but that they allow for time travel as well. This is the most
fascinating, and speculative, consequence of multiply connected universes. (more
later)
Problem: Time Travel
If what one does could be predicted, then the fact of
making that prediction could change what happens. It is like the problems one
would get into if time travel were possible. If you see what is going to happen
in the future, you could change it. But that action would change the odds. One
only has to see Back to the Future to realise what problems could
arise.
The peculiar risk lies in the possibility of the time
traveller finding some substance in the space which he, or the machine,
occupies. As long as the traveller travels through time at a high speed, this
scarcely matters, but to come to a stop would involve the jamming of him,
molecule by molecule into whatever lies in his way. That would result in a far
reaching explosion and would blow him and the apparatus out of all possible
dimensions into the `Unknown`.
Here one could raise the question weather air or water
is also a substance which leads to an explosion or if these substances are
exceptions because of their low density. Another interesting case that could
happen would be if a feather is just gliding through the air, exactly at the
place in space where the time traveller stops. When he stops and the feather is
exactly under his nose, he will sneeze. When he stops and it is there where his
lounges are, he will cough it up. But what will happen when the feather is there
where his leg or head is going to be?
Avoidable but risky problems are also posed by time
paradoxes, but more to this later on.
Another risk is that you never know the exact situation
in which you stumble in stopping the machine. At your destination a suddenly
appearing earthquake could surprise and kill you without giving you a chance to
flee through time in the last moment.
In the movie Time Cop one of the greatest risks
is described very vivid. The same object cannot exist in the same place, at the
same time! It would erase itself out of the universe. From that time on it would
stop to exist as matter.
But already while the time traveller is making or
entering the machine, he has to accepted these possibilities as unavoidable
risks, some of the risks a time traveller has to take.
To understand the problem with time travel, it is first
necessary to classify the various paradoxes. In general, most can be broken down
into one of two principal types:
1. Meeting your parents before you are
born
2. The man with no past
The first type of time travel does the most damage to
the fabric of space-time because it alters previously recorded events. For
example, remember that in Back to the Future, our young hero goes back in
time and meets his mother as a young girl his age, just before she falls in love
with his father. To his shock and dismay, he finds that he has inadvertently
prevented the fateful encounter between his parents. To make matters worse, his
young mother has now become amorously attracted to him! If he unwittingly
prevents his mother and father from falling in love and is unable to divert his
mother`s misplaced affections, he will disappear because his birth will never
happen.
The second paradox involves events without any
beginning. For example, let`s say that an impoverished, struggling inventor is
trying to construct the world`s first time machine in his cluttered basement.
Out of nowhere, a wealthy, elderly gentleman appears and offers him ample founds
and the complex equations and circuitry to make a time machine. The inventor
subsequently enriches himself with the knowledge of time travel, knowing
beforehand exactly when stock-market booms and busts will occur before they
happen. He makes a fortune betting on the stock-market, horse races, and other
events. Decades later, as a wealthy, ageing man, he goes back in time to fulfil
his destiny. He meets himself as a young man working in his basement, and gives
his younger self the secret of time travel and the money to exploit it. The
question is: Where did the idea of time travel come from?
My favourite time travel paradox is one of the second
type. It was cooked up by Robert Heinlein in his classic short story All You
Zombies--.
A baby girl is mysteriously dropped off at an orphanage
in Cleveland in 1945. "Jane" grows up lonely and dejected, not knowing who her
parents are, until one day in 1963 she is strangely attracted to a drifter. She
falls in love with him. But just when things are finally looking up for Jane, a
series of disasters strike. First, she becomes pregnant by the drifter, who then
disappears. Second, during the complicated delivery, doctors find that Jane has
both sets of sex organs, and to save her life, they are forced to surgically
convert "her" to a "him." Finally, a mysterious stranger kidnaps her baby from
the delivery room.
Reeling from these disasters, rejected by society,
scorned by fate, "he" becomes a drunkard and drifter. Not only has Jane lost her
parents and her lover, but he has lost his only child as well. Years later, in
1970, he stumbles into a lonely bar, called Pop`s Place, and spills out his
pathetic story to an elderly bartender. The sympathetic bartender offers the
drifter the chance to avenge the stranger who left her pregnant and abandoned,
on the condition that he join the "time travellers corps." Both of them enter a
time machine, and the bartender drops off the drifter in 1963. The drifter is
strangely attracted to a young orphan woman, who subsequently becomes
pregnant.
The bartender then goes forward 9 months, kidnaps the
baby girl from the hospital, and drops off the baby in an orphan age back in
1945. Then the bartender drops off the thoroughly confused drifter in 1985, to
enlist in the time travellers corps. The drifter eventually gets his life
together, becomes a respected and elderly member of the time travellers corps,
and then disguises himself as a bartender and has his most difficult mission: a
date with destiny, meeting a certain drifter at Pop`s place in
1970.
The question is: Who is Jane`s mother, father,
grandfather, grandmother, son, daughter, granddaughter, and grandson? The girl,
the drifter, and the bartender, of course, are all the same
person.
And the reason why it is my favourite is because it
makes your head spin, especially if you try to untangle Jane`s twisted
parentage. If You draw Jane`s family tree, we find that all the branches are
curled inward back on themselves, as in a circle. You will come to the
astonishing conclusion that she is her own mother and father! She is an entire
family tree unto herself.
Creating the Impossible?
Special warpings of space-time would make time
travelling possible. In warped space-time also wormholes are possible, although
all current models require exotic matter, to say imaginary matter, to generate
negative pressure and so negative gravity.
Using Einstein`s equations, it is perfectly possible to
predict changes to the shape of space and time which would affect us in ways we
have so far found no way to experience - like time warps.
Most people imagine the universe to be a bit like an
ever-inflating balloon, with us somewhere inside it. But perhaps the balloon is
hardly inflated at all, and is instead a loose and flexible bag. Perhaps we are
inside a universe where time and space can be so bent and flexed that the
balloon can be folded back on itself. Eventually two parts of the outer skin
could somehow get close enough to each other to be linked by wormholes - strange
tunnels through space and time through which we might one day be able to move
from one end of the universe to the another.
-
Multiply Connected
Universes
Multiply connected is the opposite to simply connected
what means, that our windows and doorways are not entrances to wormholes
connecting our home to a far-away universe.
Although the bending of our universe in an unseen
dimension has been experimentally measured, the existence of wormholes and
whether our universe is multiply connected or not is still a topic of scientific
controversy.
Many physicists, who once thought multiply connected
spaces in which regions of space and time are spliced together, are now
seriously studying multiply connected worlds as a practical model of our
universe.
These models are the scientific analogue of Alice`s
looking glass. When Lewis Carroll`s White Rabbit falls down the rabbit hole to
enter Wonderland, he actually falls down a wormhole.
One can visualise a wormhole as the tube between two
sheets of paper, connected through holes.
If you fall into the wormhole, you are instantly
transported to a different region of space and time. Only by retracing your
steps and falling back into the wormhole can you return to your familiar
world.
- Time Travel and Baby
Universes
Although wormholes provide a fascinating area of
research, perhaps the most intriguing concept to emerge from this discussion is
the question of time travel.
Wormholes may connect not only two distant points in
space, but also the future with the past.
Since travel through the wormhole is nearly
instantaneous, one could use the wormhole to go back in time. Unlike the machine
portrayed in H.G.Wells`s The Time Machine, however, which could hurl the
protagonist hundreds of thousands of years into England`s distant future with
the simple twist of a dial, a wormhole may require vast amounts of energy for
its creation, beyond what will be technically possible for centuries to
come.
Another bizarre consequence of wormhole physics is the
creation of "baby universes" in the laboratory. We are, of course, unable to
re-create the Big Bang and witness the birth of our universe. However, a few
years ago some physicists of the Massachusetts Institute of Technology shocked
many physicists, when they claimed that the physics of wormholes may make it
possible to create a baby universe of our own in the laboratory. By
concentrating the intense heat and energy in a chamber, a wormhole may
eventually open up, serving as an umbilical cord connecting our universe to
another, much smaller universe. If possible, it would give a scientist an
unprecedented view of a universe as it is created in the
laboratory.
One could then find out how the starting conditions of a
universe look like; if time is already one of those conditions or if it is just
a product, created by chance.
- Evading
the Light Barrier
When Carl Sagan wrote a novel called Contact, he
wanted to make his book as scientifically accurate as possible and though wrote
to the well known physicist Kip Thorne weather there was any scientifically
acceptable way of evading the light barrier.
Sagan`s request piqued Thorne`s intellectual curiosity.
A serious request that demanded a serious reply. Fortunately, because of the
unorthodox nature of the request, Thorne and his colleagues approached the
question in a most unusual way: They worked backward. Normally,
physicists start with a certain known object and then solve Einstein`s equation
to find the curvature of the surrounding space.
However, Thorne and his colleagues started with a rough
idea of what they want to find. They wanted a solution to Einstein`s equations
in which a space traveller would not be torn apart by the tidal effects of the
intense gravitational field. They wanted a wormhole that would be stable and not
suddenly close up in the middle of the trip. They wanted a wormhole in which the
time it takes for a round trip would be measured in days, not millions or
billions of earth years, and so on. In fact, their guiding principle was that
they wanted a time traveller to have a reasonably comfortable ride back through
time after entering the wormhole. Once they decided what their wormhole would
look like, then, and only then, did they begin to calculate the amount of energy
necessary to create such a wormhole.
They did not care if the energy requirements were well
beyond twentieth-century science. To them, it was an engineering problem for
some future civilisation actually to construct the time machine. They wanted to
prove that it was scientifically feasible, not that it was economical or within
the bounds of present-day earth science.
Much to their delight, they soon found a surprisingly
simple solution that satisfied all their rigid constrains. It was not a typical
black hole solution at all. They christened their solution the "transversible
wormhole," to distinguish it from the other wormhole solutions that are not
transversible by spaceship.
They were so excited by their solution that they wrote
back to Sagan, who incorporated some of their ideas in his novel. (and this year
in the identically named film Contact.)
Scientists are not quite sure what happens inside a
black hole. There are solutions of the equations of general relativity that
would allow one to fall into a black hole and come out of a white hole somewhere
else. A white hole is the time reverse of a black hole. It is an object that
things can come out of but nothing can fall into. The white hole could be in
another part of the universe. This would seem to offer the possibility of rapid
intergalactic travel. The trouble is it might be too rapid. If travel through
black holes were possible, there would seem nothing to prevent you from arriving
back before you set off. You could then do something, like kill your mother
before you were born. You must then cease to exist. But if you cease to exist,
you could not have gone back and killed your mother. But if you didn`t kill your
mother, then you have not ceased to exist. To put it another way: if you exist,
then you cannot exist, while if you don`t exist, you must
exist.
This is the most famous paradox to be found in both
science fiction and physics. (It belongs to the first type)
Perhaps fortunately for our survival ( and that of our
mothers), it seems that the laws of physics do not allow such time travel. What
seems to happen is that the effects of the uncertainty principle would cause
there to be a large amount of radiation if one travelled into the past. This
radiation would either warp space-time so much that it would not be possible to
go back in time, or it would cause space-time to come to an end in a singularity
like the big bang or the big crunch. Either way, our past would be save from
evil-minded persons.
But the best evidence that time travel is not possible,
and never will be, is that we have not been invaded by hordes of tourists from
the future.
But, are we alone?
I)
Conclusion
Why it
matters
In what sense do
these issues matter? Why shouldn`t we ignore the view from nowhen, and go on in
physics, philosophy, and ordinary life just as we always have? After all, we
cannot actually step outside time, in the way in which we can climb a tree to
alter our viewpoint. Isn`t it better to be satisfied with the viewpoint we
have?
We cannot step outside time, but we can try to
understand how the way in which we are situated within time comes to be
reflected in the ways in which we talk and think and conceptualise the world
around us. What we stand to gain is a deeper understanding of ourselves and of
what is external to us. This is a reflective kind of knowledge: we reflect on
the nature from the standpoint from within, and thereby gain some sense, a
sense-from-within, of what it would be like from without.
If the reflexivity were viscous the whole project would
be self-defeating, but is it vicious? Our understanding seems to be enhanced,
not overturned. With each advance comes a new picture of how the world would
look like from nowhere, and a new appreciation of the limits of our own
standpoint.
Our culture has been as surely shaped by the miracles of
modern physics as it has by any other human intellectual endeavour. And while it
is an unfortunate modern misconception that science is somehow divorced from
culture, it is, in fact, a vital part of what makes up our civilisation. Our
explorations of all dimensions of the universe, represent some of the most
remarkable discoveries of the human intellect, and it is a pity that they are
not shared among as broad an audience as enjoys the inspiration of great
literature, or painting, or music.
The campaign for a view from nowhen is a campaign for
self-improvement, and not a misguided attempt to do the impossible. It promises
only to enhance our understanding of ourselves and our world, and not to make us
gods.
A proof for this kind of argumentation is the increasing
number of still present a new question: Why is the future so different from the
past? Why does the past affect the future and not the other way round? The
universe began with the Big Bang - will it end with a `Big
Crunch`?
To try to answer these questions we adopt some "world
picture." Each answer and each new theory we humans find, lets us feel that
mankind could bring the world totally under his control. But until now, none of
the known theories results in a completely determined picture of our
universe.
This paper presents an innovative and controversial view
of time and contemporary physics. I especially pondered on time in space, the
paradoxes of time and time travel to throw a fascinating new light on some of
the great mysteries of the universe and to give all the readers the opportunity
to look at the world from a fresh perspective.
II)
Glossary
big bang: The singularity at the beginning of the
universe.
big crunch: The singularity at the end of the
universe.
black hole: A region of space-time from which
nothing, not even light, can escape, because gravity is so
strong.
Chandrasekhar limit: The maximum possible mass of
a stable cold star, above which it must collapse to a black
hole.
cosmological constant: A mathematical device used
by Einstein to give space-time an inbuilt tendency to expand.
event: A point in space-time, specified by its
time and place.
field: Something that exists throughout
space-time, as opposed to a particle that exists at only one point at a
time.
general relativity: Einstein`s theory based on
the idea that the laws of science should be the same for all observers, no
matter how they are moving. It explains the force of gravity in terms of the
curvature of a four-dimensional space-time.
grand unified theory: A theory that unifies the
electromagnetic strong and weak forces.
imaginary time: Time measured using imaginary
numbers.
light cone: A surface in space-time that marks
out the possible directions for light rays passing through a given
event.
light-second (light-year): The distance travelled
by light in one second (year).
no boundary condition: The idea that the universe
is finite but has no boundary (in imaginary time).
primordial black hole: A black hole created in
the very early universe.
quantum mechanics: The theory developed from
Planck`s quantum principle and Heisenberg`s uncertainty
principle.
singularity: A point in space-time at which the
space-time curvature becomes infinite.
space-time: The four-dimensional space whose
points are events.
special relativity: Einstein`s theory based on
the idea that the laws of science should be the same for all freely moving
observers, no matter what their speed.
III)
Bibliography
|
Nr.
|
Titel
|
Autor
|
Publishing Company
|
|
|
|
|
|
1)
|
A Brief History of Time
|
Stephen W. Hawking
|
Rowohlt
|
|
2)
|
The Time Machine
|
H. G. Wells
|
Everyman - JM Dent
|
|
3)
|
Einstein`s Dreams
|
Alan Lightman
|
Sceptre
|
|
4)
|
Hyperspace, a scientific odyssey through the 10th
dimension
|
Michio Kaku
|
Oxford University Press
|
|
5)
|
Black Holes and Baby Universes
|
Stephen W. Hawking
|
Bantam Books
|
|
6)
|
Time’s Arrow and Archimedes’
Point
|
Huw Price
|
Oxford University Press
|
|
7)
|
The Physics of Star Trek
|
Lawrence M. Krauss
|
Flamingo
|
|
8)
|
Why aren`t Black Holes Black?
|
Robert M. Hazen
|
Anchor Books
|
|
9)
|
Stephen Hawking`s Universe
|
David Filkin
|
BBC
|
|
10)
|
Multimedia Encyclopedia CDv1.5
|
Encyclopedia
|
Software Toolworks
|
|
11)
|
Encarta 95 CD
|
Lexicon
|
Microsoft
|
V)
Bookreports
i) Einstein`s Dreams page 30
ii) The Time Machine page 37
iii) A Brief History of Time page
45
iiii) The Physics of Star Trek page
61
Marcus Meisel,8C
Einstein`s Dreams by Alan
Lightman
Author:
"Einstein`s Dreams" was written by
Alan Lightman, who was born in Memphis, Tennessee, in 1948 and was
educated at Princeton and at the California Institute of Technology. He has
written for Granta, Harper`s, The New Yorker, and The New York Review
of Books.
His previous books include "Time Travel and Papa Joe`s Pipe
", "A Modern-Day Yankee in a Connecticut Court ", "Origins ", "Ancient Light ",
"Great Ideas in Physics ", and "Time for the Stars ".
"Einstein`s Dreams " is his first work of fiction. He
teaches physics and writing at the Massachusetts Institute of Technology and
currently directs the MIT programme in writing and humanistic
studies.
Published
:
It´s a Sceptre Book,
published by Hodder and Stoughton in Great Britain in 1994. It was first
published in Great Britain in 1993 by Hodder and Stoughton, a division of Hodder
Headline PLC.
Type of
book:
It is a fiction book,
endearingly short, airy and irrational, in simple and beautiful language. It is
an accomplished first novel and a beautiful book. The science is gentle and it
is cast in language to bring the flush of envy to any one of the many famous
writers alive today who have coaxed themselves into the delusion that scientists
cannot write. "Einstein`s Dreams " is the sort of book to be read many times and
hored and treasured for bleak times and empty spaces.
" A joy to read. It is a celebration of a world in which
time does not march brutally through people`s lives, but rather skips and
gambols, forever quirky and unpredictable" - The Times
"Original, beautifully written... light, amusing, fresh... a
bit of scintillating intellectual daring" - The Observer
"Lightman is exploring fiction`s deep space, taking us
further than we are used to being taken. It is payful, poignant, intimate...
cool, languid, intelligent and quotable.Lightman writes movingly and with great
precision"-The Sunday
TimesSubject:
The setting of the story is located in
Bern in Switzerland.
In this book Alan Lightman describes the dreams of Albert
Einstein, a young patent clerk, which he had between 14th April 1905 and 28th
June 1905. Although the characters and situations in this book are entirely
imaginary and bear no relation to any real person or actual happening, it is a
breathtaking synthesis of science and imagination.
One witnesses Einstein`s dreams of new worlds: extraordinary
visions of the effect on people`s lives when the direction and the flow of time
changes to circular or flows backwards, slows down or takes the form of a
nightingale.
The whole book is a flashback that starts after Einstein has
finished his work. He reflects back on his time of creating the new theory of
time. This ends two hours later. In those two hours Einstein reflects on the
past several months, where he had many dreams about time. Most of the dreams
take place in Berne, where Einstein lives, while he is dreaming. So in each
dream a typical situation out of everyday life of the dream persons, is
described. The book describes some of the dreams and tells the reader that those
have taken hold of his research.
Out of many possible natures of time, imagined in as many
nights, one seems compelling. Not that the others are impossible. The others
might exist in other worlds.
The most important
persons:
Einstein: a young, 26 years
old patent clerk in Berne, dreaming about time while he is discovers a new
theory of time. Already this year, he has completed his Ph.D. thesis, finished
one paper on photons and another on Brownian motion. The current project
actually began as an investigation of electricity and magnetism, which, Einstein
suddenly announced one day, would require a reconception of
time.
Besso: a close friend to
Einstein. They have known each other since their student days in Zürich,
and still meet to talk and dine. He is married.
a typist: she has already typed
several of his personal papers for him in her spare time. She likes
Einstein.
Plot
synopsis:
It is six o`clock in the
morning and Einstein has finished with his new theory of time, which he will
mail to the German journal of physics that day. It cost him a lot of strength
and energy, but now he has finished. But not completely. While he waits for the
typist in the patent office in Berne he works in, he begins to reflect on the
dreams he had.
14th April 1905
Suppose time is a circle, bending back on itself. The world
repeats itself precisely, endlessly. Every movement and thought, every flapping
of a butterfly`s wing, each touch, each smile, every kiss, every birth and every
word will be repeated an infinite number of times. But how would humans living
in such a world know that nothing is temporary, that everything happened and is
going to happen again and again?
There are some few people in every town, who, in their
dreams, are vaguely aware that all has occurred in the past. These are the
people with unhappy lives who fill up the vacant streets with their moans at
night. They are unable to rest because they have the knowledge that they cannot
change a simple action or mistake they or anyone else has made.
16th April 1905
In this world time is like a flow of water. Now and then,
some cosmic disturbance will cause a rivulet of time to turn away from the
mainstream, to make connection backstream.
When this happens, birds, soil, people caught in the
branching tributary find themselves suddenly carried to the past. Persons who
have been transported back in time are easy to identify because of their fear
that any change they make in the past, could have drastic consequences for the
future.
There is an example given, of such a traveller from the
future. She huddles in a corner, creeps across the street and cowers in another
darkened spot. For if she makes the slightest alteration in anything, she may
destroy the future. Like kicking up dust while she crossed the street just as
Peter Klausen is making his way to the apothecary in Berne on Spitalgasse this
afternoon of 16th April 1905. Klausen hates to have his clothes
sullied. If dust messes his clothes, he will stop and brush them off, regardless
of waiting appointments. If Klausen is sufficiently delayed, he may not buy the
ointment for his wife, who has been complaining of leg aches for weeks. In that
case, Klausen´s wife, in a bad humour, may decide not to make the trip to
Lake Geneva .
And if she does not go to Lake Geneva on June 23rd, 1905,
she won´t meet a Catherine d`Épinay walking on the jetty of the east
shore and will not introduce Mlle. d`Épinay to her son Richard. In turn,
Richard and Catherine will not marry on 17th December 1908, will not give birth
to Friedrich on 8th July 1912. Friedrich Klausen will not be father to Hans
Klausen on 22nd August 1938, and without Hans Klausen the European Union of 1979
will never occur.
The woman from the future knows the Klausen story and a
thousand other stories, waiting to unfold, dependent on the birth of children
and the movement if people in the streets.
19th April 1905
In this world time has three dimensions, like space.
Just as an object may move in three perpendicular
directions, corresponding to horizontal, vertical, and longitudinal, so an
object may participate in three perpendicular futures. Each future moves in a
different direction of time.
Each future is a real one. At every point of decision the
world splits into three worlds, each with the same people but with different
fates for these people. In time, there are an infinity of
worlds.
24th April 1905
There are two times at the same time. There is a mechanical
time and there is a body time. The first is like a pendulum that swings back and
forth, regularly and without anything disturbing it. The second wriggles like a
bluefish in a bay. It makes up its mind as it goes along.
All people who are convinced that mechanical time does not
exist, never look at a clock. They eat when they are hungry, sleep, whenever
they want and go to their jobs, whenever they wake from their sleep. The others
live like machines, they think their bodies don´t exist. They rise at seven
a.m., eat their lunch at noon, supper at six, and make love between eight and
ten at night.
You can live in either time, but not in both times. Each
time is true, but the truths are not the same.
26th April 1905
This is an odd world. Everybody lives on Dome, the
Matterhorn, Monte Rosa, and other high ground. No one would buy or build a home
elsewhere.
And all this because some time in the past, scientists
discovered that time flows more slowly the further from the centre of the earth.
The effect, produced by the rotation of the earth , is minuscule, but it can be
measured with extremely sensitive instruments. Once the phenomenon was known,
the people got anxious to stay young and moved to the mountains. To get the
maximum effect, they have constructed their houses on stilts.
Height has become status. In time people have forgotten the
reason why higher is better. Nevertheless, they continue to live on the
mountains. They tolerate cold, thin air and discomfort for staying
younger.
28th April 1905
Time is visible in all places. Clock towers, wristwatches,
church bells divide years into months, months into days, days into hours, hours
into seconds, each increment of time marching after the other imperfect
succession.
In this world a second, is a second. Time is equal for all,
it´s an infinite ruler.
Time is absolute. A world in which time is absolute, is a
world of consolation. For while the movements of people are unpredictable, the
movement of time is predictable.
3rd May 1905
Consider a world in which cause and effect are
erratic.
Sometimes the first precedes the second, sometimes the
second the first.
Or perhaps cause lies forever in the past while effect in
the future, but future and past are entwined.
It is a world of impulse. It´s a world of sincerity.
It´s a world in which every word spoken speaks just to that moment, every
glance given, has only one meaning, each touch has no past or no future, each
kiss is a kiss of immediacy.
4th May 1905
In this world, time does pass, but little happens. Just a s
little happens from year to year, little happens from month to month, day to
day.
If time and the passage of events are the same, then time
moves barely at all. If time and events are not the same, then it is only people
who barely move. If a person holds no ambitions in this world, he suffers
unknowingly. If a person holds ambitions, he suffers knowingly, but very
slowly.
8th May 1905
The world will end on 26th September 1907. Everyone knows
it. In Berne, it is just as in all cities and towns. One year before the end,
schools close their doors. Why learn for the future, with so brief a future?
One month before the end, businesses close. What need is
there for commerce and industry with so little time left? People are not afraid
. They sit and sip coffee and talk easily of their lives. What is there to fear
now?
One day before the end the streets swirl in laughter.
Neighbours who have never spoken greet each other as friends. What do their past
stations matter? In a world of one day they are equal.
One minute before the end of the world everyone in Bern
gathers on the grounds of the Kunstmuseum. No one moves. No one
speaks.
In the last seconds, it is as if everyone has leaped off
Topaz Peak, holding hands. The end approaches like approaching ground. Cool air
rushes buy, bodies are weightless. The silent horizon yawns for miles. And
below, the vast blanket of snow hurtles nearer and nearer to envelope this
circle of pinkness and life.
There are a lot more dreams described, and in each dream
time has a completely different character and behaviour.
Here are some other examples:
Each village is fastened to a different time and this is
because the texture of time is not smooth but it happens to be
sticky.
In another dream the passage of time brings increasing
order. If time is an arrow, that arrow points toward order.
This book is about the things in life, life, and the humans
living in the world. But not only a simple description of their places ,
behaviours or themselves, it is a description of what happens to them if time
has another appearance as we know it.
If there is a world with a centre of time, the time would
stand still in the centre. The further one moves away, the faster time goes by.
Or imagine a world without any time at all. There would be only
images.
A world without memory, as a world in which time flows not
evenly but fitfully also occurs in Einstein`s dreams. As a consequence of the
fitful flow of time, the people receive fitful glimpses of their
future.
In another dream all the buildings are built on wheels and
race through the cities. Instead of standing still they move fast. Everybody is
fixed on speed and this only because some time in the past scientists discovered
that time passes more slowly for people in motion. Thus everyone travels at a
high velocity, to gain time.
In other worlds the time runs backwards, or the lifetime is
compressed to the space of one turn of the earth on its axis, or that time is a
sense some people have, and some not.
There are some interludes between these chronologically
ordered dreams in which the real time and though Einstein`s actions in real
live, like meetings with his best friend Besso are described. In such meetings
they talk about Einstein`s progress with his work, but the reader also gets a
glimpse of Einstein`s lifestyle in Berne.
Other dreams are about worlds where people live forever, or
that time is not a quantity but a quality so that it exists but cannot be
measured, or about a world without future where no person can imagine the
future.
In another dream, time is a visible dimension which
everybody is able to use like all the other dimensions in space, or in another
world, time is not continuos, its a local phenomenon. This world is split up in
zones of time.
In another dream there is a world where every moment of time
is determined.
Other examples of the behaviour of time in the worlds of
Einstein`s dreams are a world in which time is like the light between two
mirrors, a world of countless copies, or a world in which time is a nightingale.
For everyone who catches a nightingale, time stands still.
This was the last dream of Einstein before he finished his
"Special Theory of Relativity".
Ideas, opinions and
comments:
This is my favourite book. As I read the book
the first time, I was able to understand the meaning of everything what was
written, but as I read it the second time, I could enter the plot and really
live in the thoughts of Einstein. It was such a fantastic and extraordinary
experience, to be relaxed and excited the same time while reading this book. I
truly can recommend this book to any person who want`s to get a short but deep
insight in the thoughts of a genius. It will be an enlarging
experience.
Marcus Meisel,7C
The Time Machine by
H.G.Wells
Author:
"The Time Machine" was written by
H.G.Wells, who was born in Bromley, Kent in 1866, to a working class
family. His mother worked as a maid and housekeeper.
After working as a draper’s apprentice and
pupil-teacher, he won a scholarship to the ”Normal School of
Science” in South Kensington, where he began to write. The first published
work appeared in May 1887 in the Science Schools Journal -”A Tale of the
Twentieth Century”. After his studies he worked in poverty in London as a
cramer and published his first book ”A Textbook of Biology” (1893),
which was to remain in print for over forty years. Wells had been in print as a
professional writer, since 1891 when the FORTNIGHTLY REVIEW published his
article ”The Rediscovery of the Unique”. He lived on his writing in
those times. But not until he published his first novel ”The Time
Machine” (1895) did his literary career start.
H.G.Wells died in London, on 13th August 1946 at
the age of 79 years, after having survived the First and Second World
War.
Published
:
It´s an EVERYMAN Book,
published by J.M.Dent, and edited by John Lawton in 1995. It was first published
on paperback by J.M.Dent in Everyman’s Library 1935.The first publication
as book was 1895 by Heinemann in Britain and in the USA by
Holt.
Type of
book:
It is a science fiction
novel about the Victorian future which is more than a fantastical yarn. It
raises chilling questions about progress, social orders, so called civilisation
and the ultimate fate of the world. It tells the story from the present until
the end of our sun-system, a cold, almost lifeless earth with a dying
sun.
Wells wrote this novel mainly because Charles Darwin
published and proved his theory of Evolution, which was the greatest scientific
rumpus since the trial of Galileo. Although the theory shocked society, and
Wells had created another ”prove” with ”The Time
Machine”, he got positive critics like:
”The Time Machine - considered by the majority of
scientific readers to be Mr. Wells’s best work” - Nature
Magazine.
”The Time Machine - A new thing under the sun” -
The Daily Chronicle.
Subject:
It´s a story about evolution
brought to the reader as an adventure of an old scientist, who has invented a
time machine. Although Wells doesn’t tell the reader the names of the
Victorian scientist and the Narrator, he creates a personal relationship with
the reader, which is very difficult and proves again that H.G.Wells is one of
the best writers.
The Time Traveller lives in a house in London, in Richmond.
In the cellar he has his laboratory, his workshop, where he invents a miniature
and a full- size time machine. The Time Traveller shows his disbelieving dinner
guests a device he claims is a Time Machine.
In real time a week later the dinner guests visit the Time
Traveller again, but instead of a settled old man they find him raged, exhausted
and garrulous. The tale he tells is of the year 802,701 AD of life as it is
lived on exactly the same spot, what once had been London. He has visited the
future, he has encountered the future -race -elfin, beautiful, vegetarian,
helpless, leading a life of splendid idleness.
But this is not the only race, these are not our only
descendants. In the tunnels beneath the new Eden there lurks another life
form.
The end of the book is open because the Time Traveller
disappears in front of the eyes of the Narrator and hasn’t come back for
three years although he said he’ll need only half an hour for his
journey.
The most important
persons:
The Time Traveller:
He is an old but lively grey-eyed man who usually has
a pale face. He is very learned and wise. The Time Traveller is as reliable as
all inventors of new things that weren’t proved properly. He thinks un-
happily of the Advancement of Mankind, and sees in the growing pile of
civilisation only a foolish heaping that must inevitably fall back upon and
destroy its makers in the end.
The Narrator: He
is one of the most constant guests of the Time Traveller. He is a young man, who
believes the Time Traveller because of the things he saw ( the flowers, the Time
Traveller disappearing). But he also has his own point of view of the future.
For him future is still black and blank - is a vast ignorance, lit at a few
casual places by the memory of the Time Traveller’s
story.
A Psychologist: He always tries
to destroy a theory with facts that are universally accepted.
A Medical Man: He is a very
realistic thinking man. He trusts his eyes but doesn’t make premature
decisions.
A Provincial Mayor: He
doesn’t really understand the matters of science, but tries hard to do
so.
Filby: He is an argumentative
person with red hair.
A Very Young Man: Smokes
cigars, is very young and gullible
A Journalist: He thinks the
same as the Editor.
A Editor: He believes that the
Time Traveller is only an old man who made ”telling fantastic
stories” to his aim.
A Silent Man: plays his part
perfectly. Silent in action and sound.
The Eloi and the
Morlocks: Those were the two species that
resulted from the evolution of man. Those two were now in the year 802,701 AD
sliding down towards, or had already arrived at, an altogether new relationship.
The Eloi who were the Upperworld people, might once have been the favoured
aristocracy, and the Morlocks, their mechanical servants. But that had been long
ago. The Eloi, like Carlovingan kings, had decayed to a mere beautiful futility.
They still possesed the earth on sufferance, since the Morlocks, subterranean
for innumerable generations, had come at last to find the daylight surface
intolerable.
In contrast to the Upper-worlders, to whom fire is a novelty
to watch and play with, the Morlocks fear any light because their eyes were that
sensible that they could see under the surface of earth.
Weena: One of the
Eloi women. She fell in love with the Time Traveller because he saved her life.
Weena had the oddest confidence in the Time Traveller. She followed him
everywhere he went and tried to delight him when he got upset. The Eloi feared
the darkness like the Morlocks the light but nevertheless Weena followed the
Time Traveller into the darkness. After one week queer friendship for about a
week, during a journey, the Time Traveller and Weena got attacked by
Morlocks and Weena died.
All characters are only related to one another because of
their meetings with the Time Traveller.
Plot
synopsis:
The action of the book plays in two main settings. One is
the house of the Time Traveller in the Victorian age. The other one is on
exactly the same place, on an area from Richmond until Wimbledon (in London),
but in the year 802701, where everything but-physical rules-has changed. The
action, if one sees it in the perspective of the Time Traveller, is strictly
chronological, but in the view of all other involved persons in real time, the
action has a long and exact foreshadowing.
The novel is gradually built up. It starts with an open
beginning, where the Time Traveller, Provincial Mayor, Very Young Man,
Psychologist, Filby and the Narrator discuss the existence and nature of a
fourth dimension. The Time Traveller explains, that he found out that the fourth
dimension, time, is only another dimension of space. He also tries to convey to
the dinner guests that man is only able to move in two dimensions without
technical help (like a balloon as technical help for the third dimension,
heighth). He compares time with some sort of gravitation which limits our
movements up or down. The Timetraveller visualises with that example, if it is
like that, that it is possible, with technical help, to interrupt the floating
time stream, or even move through time as one wants. To prove that to his
guests, he experiments with a miniature time machine and shows his guests his
lifework, the full-size version of the nearly completed Time
Machine.
After a week real time, the Psychologist, Medical Man,
Journalist, Editor, Silent Man and Narrator gather at the Time
Traveller’s. As they can’t find him, they start to eat dinner. When
he suddenly appears, dishevelled and lame, he washes himself, eats dinner and
begins his story.
There is one disruption in the tale of the Time Traveller in
chapter seven while he puts the flowers of Weena on the table. This should be a
significant sign for the reader that there were two actions at the same time.
And that the Time Traveller is only telling a story which is told like a very
long direct speech. Except for that very long direct speech the whole book is
narrated like a diary by the Narrator who is not named.
”At ten o’clock this day, real time,...”
the Time Traveller begins his hardly believable story about his journey. He
tells about his sensations as he travelled through time, that one gets a bit
sick of it, that years pass like seconds for him,... and he tells about the
risks of time travelling.
The peculiar risk lies in the possibility of him finding
some substance in the space which he, or the machine, occupies. As long as he
travels through time at a high speed, this scarcely matters, but to come to a
stop would involve the jamming of him, molecule by molecule into whatever lies
in his way. That would result in a far reaching explosion and would blow him and
the apparatus out of all possible dimensions into the Unknown.
But already while he was making the machine, he accepted it
as an unavoidable risk, one of the risks a man has to take.
When continuing the story, the Timetraveller says that when
he halted, he saw some creatures, friendly, smiling, human, vegetarian, but
degenerated. Their behaviour was comparable to children’s, not to
adult’s. He says that he had dined with the creatures he met and comments
on their nature and way of life. Eg. that they spoke a very sweet and liquid
tongue. They didn’t know what fear during sunshine was, their hair, which
was uniformly curly, came to a sharp end at the neck and check, their mouths
were small, with bright red, rather thin lips and their eyes were large and
mild,... etc.
The Time Traveller considers how the world of his own time
could have changed to that in which he finds himself after the journey. After
dinner he discovered that his machine had disappeared. He met Weena. In the
early dawn of one night he caught a glimpse of creatures other than those he
first met and concluded that there were two distinct peoples, those who lived
above ground, and those who existed below.
Convinced the under-world creatures which he named Morlocks
had hidden his machine, the Time Traveller descended to their underground caves
but had to escape, empty- handed.
But that action was not useless. From that moment on he knew
that the Morlocks feared light and the Eloi, like he named the upperworlders,
feared the dark. He considered the relationship between the two races and
realised that the once- subservient Morlocks now dominated the Eloi. So he took
Weena to explore a large place , which had been a museum in former
times.
During the journey Weena put some flowers into his pocket.
While he tells the story he puts the flowers onto a table in his smoking room.
After a short break he continues and says that it was further than he thought.
With the darkness approaching, his and Weena’s fear of Morlocks grew. They
spended the night in safe. In the ruined museum the Time Traveller found
matches, camphor and a metal bar to use against the Morlocks as a
weapon.
As the Time Traveller and Weena returned from the museum,
they were forced by tiredness to rest in a forest. Although the Time Traveller
had set fire to the trees to fend off the Morlocks, the two were attacked and
Weena disappeared which gave the Time Traveller a keen stab of pain directly
into his heart. The Morlocks, however, were blinded by the raging
fire.
On the next day the Traveller returned to the Eloi and found
his time machine in a trap of the Morlocks, but he escaped through time. He went
on into the future. During his journey he recognised that the changing of day
and night got more slowly although he drove at a constant speed, which could
only mean, that the earth was spinning more and more slowly. He also saw that
the sun got bigger. When he stopped, he discovered a cold and almost lifeless
earth with a dying sun. That shocked him that much, that he returned immediately
into his own time, where he was greeted with scepticism.
As the Narrator visits the Time Traveller on the next day
again, he, the Time Traveller disappears with a camera in his Time
Machine.
In the Epilogue the Narrator reflects on what might have
befallen the Time Traveller, he also considers his own view of the future, as
black and blank as ever.
Ideas, opinions and
comments:
This book is very interesting because since I
was in Kindergarten, I wanted to build a Time Machine, so I really could easily
identify with the Time Traveller, as an excellent scientist and inventor. I
really enjoyed that science fiction novel because it is not that unrealistic,
how time works and what will happen to our earth. I think many writers of
science fiction novels have gathered material from the fairy- land of science,
and have used it in their construction of literary fabrics, but none have done
it more successful than H.G.Wells.
Marcus Meisel,8C
A Brief History
of
Time
by Stephen W. Hawking
Author:
"A Brief History of Time" was written
by Professor Stephen Hawking, who was born in Oxford, Great Britain, on
8th January 1942.
He studied physics at Oxford University and went on to
pursue his graduate studies at Cambridge. In his early twenties he was diagnosed
as having ALS (Amyotrophic Lateral Sclerosis), known in the UK as Motor Neurone
Disease. He holds Newton`s chair as Lucasian Professor of Mathematics at
Cambridge and is widely considered to be the greatest scientific thinker since
Newton and Einstein. In 1989 he received an Honorary Doctor of Science degree
from Cambridge University and was made a Companion of Honour.
Published
:
It´s a Bantam Books Book,
published by Bantam Press. It was first published by Bantam Books in 1988. "A
Brief History of Time" remained on The New York Times best-seller list for
fifty-three weeks; and in Britain, as of February 1993, it had been on The
Sunday Times list for 205 weeks. (At week 184, it went into the Guinness Book of
Records for achieving the most appearances on this list.) The number of
translated editions is now thirty-three.
Type of
book:
"A Brief History of Time" is a
book that tries to explain the main theories of today physics in a quite
"non-technical" language so everybody can understand them. Stephen also explains
also the basics to these theories so that the reader has to know almost nothing
about physics to understand them. This book starts at the beginning of science
with the Greek philosopher Aristotle and goes on until the youngest theories
about our universe like the superstring-theory which needs
10dimensions.
The book is divided into 11 chapters and 3 epilogues about
Einstein, Newton and Galileo Galilei. There is also a glossary that explains the
main technical verbs that are used in this book.
" This book marries a child`s wonder to a genius intellect.
We journey into Hawking`s universe, while marvelling at his mind " - Sunday
Times
Subject:
We go about our daily lives understanding
almost nothing of the world. We give little thought to the machinery that
generates the sunlight that makes life possible, to the gravity that glues us
to an Earth that would otherwise send us spinning off into space, or to the
atoms of which we are made and on whose stability we fundamentally depend.
Except for children few of us spend much time wondering why nature is the way it
is; where the cosmos came from, or whether it was always here; if time will flow
backward one day and effect precede causes; or whether there are ultimate limits
to what humans can know. Was there a beginning of time? Could time run
backwards? Is the universe infinite or does it have boundaries? These are just
some of the questions considered in an internationally acclaimed masterpiece
which begins by reviewing the great theories of the cosmos from Newton to
Einstein, before delving into the secrets which still lie at the heart of space
and time.
This book tries to answer this question, but a lot of these
questions can not be answered now and so we can only follow the theories of
Stephen Hawking, which are very well explained here.
The most important
persons:
Albert Einstein: He is a
German-born American physicist and Nobel laureate, best known as the creator of
the special and general theories of relativity and for his bold hypothesis
concerning the particle nature of light. He is perhaps the most well-known
scientist of the 20th century.
Einstein was born in Ulm on March 14, 1879. At the age of 12
he taught himself Euclidean geometry.
In 1902 he secured a position as an examiner in the Swiss
patent office in Bern. After 1919, Einstein became internationally renowned. He
accrued honours and awards, including the Nobel Prize in physics in 1922, from
various world scientific societies. His visit to any part of the world became a
national event.
When Hitler came to power, Einstein immediately decided to
leave Germany for the United States. He took a position at the Institute for
Advanced Study at Princeton, New Jersey. Einstein died in Princeton on April 18,
1955.
He often said, only the discovery of the nature of the
universe would have lasting meaning.
Galileo Galilei: Galileo was
born near Pisa, on February 15, 1564. He was a Italian physicist and astronomer,
who, with the German astronomer Johannes Kepler, initiated the scientific
revolution that flowered in the work of the English physicist Sir Isaac Newton.
Born Galileo Galilei, his main contributions were, in astronomy, the use of the
telescope in observation and the discovery of sunspots, lunar mountains and
valleys, the four largest satellites of Jupiter, and the phases of Venus. In
physics, he discovered the laws of falling bodies and the motions of
projectiles. In the history of culture, Galileo stands as a symbol of the battle
against authority for freedom of inquiry.
In 1589 he became professor of mathematics at Pisa. Only the
Copernican model supported Galileo`s tide theory, which was based on motions of
the earth. He discovered mountains and craters on the moon. He also saw that the
Milky Way was composed of stars. By December 1610 he had observed the phases of
Venus, which contradicted Ptolemaic astronomy and confirmed his preference for
the Copernican system.
He died in 1642.
Sir Isaac Newton: He was born
on January 4, 1643 at Woolsthorpe, near Grantham in Lincolnshire. He was an
English mathematician and physicist, considered one of the greatest scientists
in history, who made important contributions to many fields of science. His
discoveries and theories laid the foundation for much of the progress in science
since his time. Newton was one of the inventors of the branch of mathematics
called calculus. He also solved the mysteries of light and optics, formulated
the three laws of motion, and derived from them the law of universal
gravitation.
Later, in the summer of 1661, he was sent to Trinity
College, at the University of Cambridge. Newton received his bachelor`s degree
in 1665. He received his master`s degree in 1668.
Newton is probably best known for discovering universal
gravitation, which explains that all bodies in space and on earth are affected
by the force called gravity. He published this theory in his book Philosophiae
Naturalis Principia Mathematica in 1687. This book marked a turning point in the
history of science. Newton died in 1727.
Plot
synopsis:
In the introduction
Stephen Hawking explains that he left out all but one equation, the most famous
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found by Albert Einstein because someone told him every equation would halve the
sales of the book. He also describes how he got help from friends, who donated a
communication programme and a speech synthesiser to him, which in combination
with a small personal computer mounted on his wheelchair, allows him a better
communication than before he lost his voice.
In the beginning Hawking tells an anecdote on how a
well-known scientist once gave a public speech on astronomy and in the end an
old lady got up and said that he´d talked rubbish, because in reality the
world would be a flat plate supported on the back of a giant tortoise that
stands on the back of another tortoise and so on. He points out that most people
would find this picture rather ridiculous, but why do we think to know
better?
Only recent breakthroughs in physics suggest answers to our
questions about the history of the universe, which may seem as obvious as the
earth orbiting our sun, or as ridiculous as a tower of tortoises. Only time
(whatever that may be) will tell.
The Greek philosopher Aristotle was the first to point out
that earth was a round sphere. Nevertheless the Greek still believed in the
earth being the stationary centre of the universe. This idea was elaborated by
Ptolemy into a complete cosmological model, which was generally accepted and
adopted by the Christian church as the picture of the universe that was in
accordance with the Scriptures, for it had the great advantage that it left lots
of room outside the sphere of the fixed stars for heaven and
hell.
A simpler model suggesting that the sun was stationary at
the centre and the earth and the planets moved in circular orbits around the
sun, was proposed by Nicholas Copernicus. Nearly a century passed before this
idea was taken seriously by two astronomers, the German, Johannes Kepler and the
Italian, Galileo Galilei. Galileo observed the moons of Jupiter with a just
invented telescope, which was the deathblow to the old theory. An explanation
was provided only much later, in 1687, when Sir Isaac Newton published his
"Philosophiae Naturalis Principia Mathematica", probably the most important
single work ever published in the physical sciences. In there, he postulated the
law of universal gravitation and developed the complicated mathematics needed to
analyse the motions of planets and calculus.
The beginning of the universe has been discussed long then,
because according to religious traditions the universe started at a finite, and
not very distant time in the past. Nowadays we take it for granted that we live
in a lacy spiral disk galaxy and that there are many other galaxies more or less
like it in the universe. But early in our century not everyone accepted this
picture.
It was the American astronomer Edwin Hubble who, in the
1920s, showed that there are indeed many galaxies besides our own. It was Hubble
again who showed that distant galaxies, wherever you look, are all moving away
from us. In other words, the universe is expanding. The most helpful way to
think of the expansion of the universe is not as things rushing away from one
another but as space between them swelling. Imagine a balloon with dots on its
surface being inflated. When the balloon swells, the dots move
apart.
This discovery finally brought the question of the beginning
of the universe into the realm of science. If galaxies move apart from each
other, they used to be much closer together at some moment in the past, ten or
twenty thousand million years ago. They all have been in exactly the same place.
All the enormous amount of matter in the universe packed in a single point,
infinitely dense and infinitesimally small. Such a situation is called the "big
bang". One may say that time had a beginning at the big bang, in the sense that
earlier times simply would not be defined.
But this is not the only possible history of an expanding
universe.
The second chapter describes the non-existence of absolute
rest and therefore the lack of an absolute position in space and
time.
The fact that light travels at a finite, but very high,
speed ( 186,000 miles per second) was first discovered by the Danish astronomer
Roemer. He measured the motion of Jupiter and the eclipses of its moons. A
better theory of the locomotion of light did not come until the 19th
century when the British physicist Maxwell managed to unify the partial theories
that till then had been used to describe the forces of electricity and
magnetism. Maxwell`s theory predicted that radio or light waves should travel at
a certain fixed speed. In order to fit Newton`s theories he introduced a
substance called "ether" that was present also in empty space.
Finally in 1905 Albert Einstein came to the conclusion that
the whole idea of an ether was unnecessary, providing one was willing to abandon
the idea of absolute time. Based on this Einstein worked out first the special,
then the general theory of gravity, presenting the famous equation
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and the law that nothing can travel faster than the speed of
light.
The theory of relativity describes that any observer can
work out precisely what time and position any other observer will assign to an
event, provided he knows the other observer`s relative velocity. Nowadays we use
just this method to measure distances precisely, because we can measure time
more accurately than length. In effect, one meter is defined to be the distance
travelled by light in 0.000000003335640952 seconds, as measured by a caesium
clock.
So, we must accept that time is not completely separate from
and independent of space, but is combined with it to form an object called
"space-time".
Einstein spent several years attempting to find a theory of
gravity that would work with what he had discovered about light and motion at
near light speed. In 1915 he introduced the theory of general relativity where
he thinks of gravity not as a force acting between two bodies but in terms of
the shape, the curvature, of four-dimensional space-time itself. In general
relativity, gravity is the geometry of the universe. According to Einstein the
curvature is caused by the presence of mass. Every massive body contributes to
the curvature of space-time. Things going "straight ahead" in the universe are
forced to follow curved paths. Imagine a heavy object, such as a cannon ball,
representing the sun, being placed in the middle of a taut rubber sheet,
creating a cone-shaped dent all around it.
Einstein argued that whenever something heavy bent
space-time like this, it would naturally affect the path of anything lighter
travelling nearby. If you now try to roll a smaller ball representing the Earth
or one of the other planets across the stretched rubber sheet representing
space-time, it will certainly change direction slightly when it meets the dent
caused by the cannon ball sun.
It will probably do more than that: it may describe an
ellipse and roll back in your direction. Something like that happens as the
earth tries to continue in a straight line past the sun. The sun warps
space-time as the canon ball warps the rubber sheet. The earth’s orbit is
the nearest thing to a straight line in warped space-time. At just the right
speed, the small planet ball would be travelling fast enough not to fall right
into the dent, but too slowly to escape it completely. With nothing else to stop
it or slow it down, it would find its level on the `side` of the dent in
space-time.
The speed of light in space time can be seen like the
ripples that spread out on the surface of a pond when a stone is thrown in. The
ripples spread out as a circle that gets bigger as time goes on. If one thinks
of a three-dimensional model consisting of the two-dimensional surface of the
pond and the one dimension of time, the expanding circle of ripples will mark
out a cone whose tip is at the place and time at which the stone hit the water.
Similarly the light spreading out from an event forms a three-dimensional cone
in the four-dimensional space-time. This cone is called the future light cone of
the event. In the same way we can draw another cone, called the past light cone,
which is the set of events from which a pulse of light is able to reach the
given event.
Einstein’s theory predicts that not only planets, also
Photons are affected by the warp of space-time. If a light ray is travelling
from a distant star and its path takes it close to our sun, the warping of
space-time near the sun causes the path to bend inward towards the sun for a few
degrees. Perhaps the path of light bends in such a way that the light finally
hits the earth. Our sun is too bright for us to see such starlight; except
during an eclipse of the sun.
If we see it then and do not realise the sun is bending the
path of the stars light, we would get the wrong idea about which direction the
beam of light is coming from and where that star actually is in the sky.
Astronomers make use of this effect. They measure the mass of objects in space
by measuring how much they bend the paths of light from distant stars. The
greater the mass , the greater the bending.
Einstein made the revolutionary suggestion that gravity is
not a force like other forces, but is a consequence of the fact that space-time
is not flat, as had been previously assumed: it is curved, or warped, by the
distribution of mass and energy in it. Roger Penrose and Stephen Hawking showed
that Einstein`s general theory of relativity implied that the universe must have
a beginning and, possibly, an end.
Chapter three begins with the observation that even fixed
stars in fact change their position, and all visible to us are concentrated in
one band, which we call the Milky Way. Our modern picture of the universe dates
back to Hubble, who demonstrated that ours was not the only galaxy. There were
in fact many others, with a lot of empty space between them. We live in a galaxy
that is about one hundred thousand light-years across and is slowly rotating.
The stars in its spiral arms orbit around its centre about once every several
hundred million years. Our sun is just an ordinary, average-sized, yellow star,
near the inner edge of one of the spiral arms.
The characteristics of a stars, we get by observing the
spectra, which not only tells us the temperature, but also the elements it
consists of.
Friedmann started with two assumptions in his model:
1st: The universe looks much the same in whatever direction you look
(except for nearby things like our Solar System and the Milky Way);
2nd: The universe looks like this from wherever you are in the
universe.
Friedmann’s first assumption is fairly easy to accept.
The second isn’t. We do not have any scientific evidence for or against
it.
From these two ideas alone, Friedmann showed that we should
not expect the universe to be static. In fact, in 1922, several years before
Edwin Hubbell`s discovery, Friedmann predicted exactly what Hubble found! In
1965 two American physicists at the Bell Telephone Laboratories in New Jersey,
discovered the microwave background of the universe and thereby proved
Friedmann´s theories.
Although Friedmann found only one, there are in fact three
different kinds of models that obey Friedmann´s two fundamental
assumptions. In the first which Friedmann found, the universe is expanding too
slowly so that the gravitational attraction between the different galaxies
causes the expansion to slow down and eventually to stop. The galaxies then
start to move toward each other and the universe contracts until the big crunch.
In the second kind of solution, the universe is expanding so rapidly that the
gravitational attraction can never stop it, though it does slow it down a bit.
Finally, there is a third kind of solution, in which the universe is expanding
only just fast enough to avoid recollapse. However, the speed at which the
galaxies are moving apart gets smaller and smaller, although it never quite
reaches zero. Because of insufficient measuring methods and some uncertainty
about dark matter we cannot exactly figure out which Friedmann model describes
our universe. All the Friedmann solutions have the feature that at some time in
the past, the distance between neighbouring galaxies must have been zero. At
that time, which we call the big bang, the density of the universe and the
curvature of space-time would have been infinite. Because mathematics cannot
really handle infinite numbers, this means that the general theory of relativity
(on which Friedmann´s solutions are based) predicts that there is a point
in the universe where the theory itself breaks down. Such a point is an example
of what mathematicians call a singularity.
In 1965 the British mathematician and physicist Roger
Penrose discovered the existence of black holes, which also contain
singularities.
The idea, that stars may end up and can become a black hole,
is based on the gravitational effect of mass. Imagine a star that has ten times
the mass of the sun. The star’s radius is about 3 million kilometres,
about five times that of the sun. Escape velocity is about 1,000 kilometres per
second. Such a star has a life span of about a hundred million years. On one
side the sun has to fight against gravity: the attraction of every particle in
the star for every other. On the opposing side is the pressure of the gas in the
star. This pressure comes from heat released when hydrogen nuclei in the star
collide and merge to form helium nuclei what is called the fusion process. The
heat makes the star shine and creates enough pressure to resist gravity and
prevent the star from collapsing.
For a hundred million years this balance is held. Then the
star runs out of hydrogen that it could convert into helium. Some stars then
convert helium into heavier elements, but that gives them only a short
reprieve.
When there’s no more pressure to counteract gravity,
the star shrinks. As it does, the gravity on its surface becomes stronger and
stronger because the mass gets more and more compressed. It won’t have to
shrink to a singularity to become a black hole. When the 10-solar-mass
star’s radius is about 30 kilometres, escape velocity on its surface will
have increased to 300,000 kilometres per second, the speed of light. And out of
these facts rises the definition of a black hole: When light can no longer
escape the star is a black hole.
Stars with less than 8 solar masses probably don’t
shrink all the way to form black holes. Such stars are then called brown dwarfs.
The limit, beyond that a star can become a black hole, is called the
"Chandrasekhar limit".
Whether our star goes on shrinking to a point of infinite
density or stops shrinking just within the radius where escape velocity reaches
the speed of light, gravity at that radius is going to feel the same, as long as
the star’s mass doesn’t change. Escape velocity at that radius is
the speed of light and will stay the speed of light. Such a border of a black
hole is called "event horizon". Light coming from the star will find escape
impossible. Nearby beams of light from distant stars may curl around the black
hole several times before escaping or falling in.
A black hole, with its event horizon for an outer boundary,
is shaped like a sphere, or if it is rotating, a bulged-out sphere, a convex
lens. The event horizon is marked by the paths in space-time of rays of light
that hover just on the edge of that spherical area, not being pulled in but
unable to escape. Gravity at that radius is strong enough to stop their escape,
but just not strong enough to pull them back in. We can`t see them because the
photons of those rays can’t escape from that radius, they can’t
reach our retina.
General relativity predicts the existence of singularities,
but in the early 1960s only a few took this prediction seriously. Until Hawking
and Penrose showed that if the universe obeys general relativity, a star of
great enough mass undergoing gravitational collapse must form a
singularity.
Hawking realised that if he reversed the direction of time
so that the collapse became an expansion, everything in the theory would still
hold. If general relativity tells us that any star which collapses beyond a
certain point must end in a singularity, then it also tells us that any
expanding universe must have begun as a singularity therefore as a Friedman
model.
With newly developed mathematical techniques and other
technical conditions from the theorems that singularities must occur, Penrose
and Hawking at last proved that there must have been a big bang singularity
provided only that general relativity is correct and the universe contains as
much matter as we observe. It is perhaps ironic that now, having changed his
mind, Hawking actually is trying to convince other physicists that there was in
fact no singularity at the beginning of the universe - as you will see later, it
can disappear once quantum effects are taken into account.
The fourth chapter begins with the theory of determinism
proclaimed by the French scientist the Marquis de Laplace at the beginning of
the 19th century.
To avoid that a hot object, or body, such as a star, must
radiate energy at an infinite rate, the German scientist Planck suggested in
1900 that light, X rays, and other waves could not be emitted at an arbitrary
rate, but only in certain packets that he called quanta. 1926 another German
scientist, Heisenberg, formulated his famous uncertainty principle. In order to
predict the next position and velocity of a particle, one has to be able to
measure its present position and velocity exactly.
This led Heisenberg, Schrödinger, and Dirac to
reformulate mechanics into a new theory called quantum mechanics, based on the
uncertainty principle. It predicts a number of different possible outcomes and
tells us how likely each of these is. Quantum theory also led to the theory of
wave-particle duality.
The fifth chapter deals with elementary particles and the
forces of nature. Just thirty years ago, it was thought that protons and
neutrons were elementary particles, but experiments in which protons were shot
on one another at high speeds had shown that they were in fact made up of
smaller particles which were named quarks. There are different types of quarks:
there are thought to be at least six "flavours", which we call: up, down,
strange, charmed, bottom, and top. Each flavour comes in three "colours", red,
green, and blue. These colours and names are just a creative invention of
physicist, quarks are much smaller than the wavelength of visible light and so
do not have any colour in the normal sense.
A proton or neutron for instance, is made up of three
quarks, one of each colour. We can create particles made up of the other quarks,
but these all have a much greater mass and decay very rapidly into protons and
neutrons.
The wave-particle dualism leads to a characteristic of
particles, called spin. Since particles have no well-defined axis, the spin
really tells us what the particle looks like seen from different directions. A
particle of spin 0 is like a dot: it looks the same from every direction. A
particle of spin 1 has to be turned round a full revolution to look the same, a
particle of spin 2, half a revolution. But there are particles that do not look
the same if one turns them through just one revolution: you have to turn them
through two complete revolutions! Such particles are said to have spin ½.
All the known particles in the universe can be divided into two groups:
particles of spin ½, which make up the matter in the universe, and
particles of integer spin which give rise to forces between the matter
particles. The matter particles obey what is called Pauli´s exclusion
principle. This was discovered in 1925 by an Austrian physicist, Wolfgang
Pauli.
There exist just four groups of force-carrying particles.
You can sort them according to the strength of the force they carry and the
particles with which they interact. These four are: gravitational force,
electromagnetic force, weak nuclear force, and strong nuclear force. The last
three are combined into what is called a Grand Unified Theory (GUT), but these
contain a number of parameters whose values cannot be predicted from the theory.
That`s the reason why this theory is not the ultimate theory up to
now.
Till 1956 it was believed that the laws of physics obeyed
each of three separate symmetries called C, P, and T. The symmetry C(charge)
means that the laws are the same for particles and antiparticles. The symmetry
P(parity) means that the laws are the same for any situation and its mirror
image (the mirror image of a particle spinning in a right-handed direction is
one spinning in a left-handed direction). The symmetry T(time) means that if you
reverse the direction of motion of all particles and antiparticles, the system
should go back to what it was at earlier times; in other words, the laws are the
same in the forward and backward directions of time. However, in 1964 two
Americans, J. W. Cronin and Val Fitch proved this believe to be
wrong.
The sixth chapter gets a little bit more practical and
explains the mystery of black holes. In 1969 the term "black hole" was put into
the world by the American scientist John Wheeler as a graphic description of an
idea at least two hundred years old. Roemer´s discovery that light travels
at a finite speed meant that gravity might have an important effect on it,
following the wave-particle duality of quantum mechanics. However, a consistent
theory of how gravity affects light did not come along until Einstein proposed
general relativity.
The possible final states are "white dwarfs", neutron stars
or black holes. Chandrasekhar had shown that the exclusion principle could not
halt the collapse of a star more massive than the Chandrasekhar limit, but the
problem of understanding what would happen to such a star, according to general
relativity, was first solved by a young American, Robert Oppenheimer. He found
that at this singularity the laws of science and our ability to predict the
future would break down.
Anybody who remained far enough away of the black hole would
not be affected by this failure of predictability, because neither light nor any
other signal could reach him from the singularity.
There are some solutions of the equations of general
relativity in which occur so-called "wormholes". These are "highways" of
transport through space. You can get from one region of the universe to another
in no time at all. This would offer great possibilities for travel through space
and time, but unfortunately, it seems that these solutions may all be highly
unstable.
The extra attraction of a large number of black holes could
also explain why our galaxy rotates at the rate it does: the mass of the visible
stars is insufficient to account for this. We also have some evidence that there
is a much larger black hole, with a mass of about a hundred thousand times that
of the sun, at the centre of our galaxy.
As in the case of Cygnus X-1, a very possible candidate for
a black hole, the gas will spiral inward and will heat up. It will not get hot
enough to emit X-rays, but it could account for the very compact source of radio
waves and infrared rays that is observed at the galactic centre. It is thought
that similar but even larger black holes, with masses of about a hundred million
times the mass of the sun, occur at the centres of quasars. Matter falling into
such a supermassive black hole would provide the only source of power great
enough to explain the enormous amounts of energy that these objects are
emitting.
As the matter spirals into the black hole, it would make the
black hole rotate in the same direction, and though producing a magnetic field
like that of the earth. Very high energy particles would be generated near the
black hole by the in-falling matter. The magnetic field would be so strong that
it could focus these particles into jets ejected outward along the axis of
rotation of the black hole. Such jets are really observed in a number of
galaxies and quasars.
The seventh chapter is about light rays in the event
horizon. If the rays of light that form the event horizon can never approach
each other, the area of the event horizon might stay the same or increase with
time but it could never decrease - because that would mean that at least some of
the rays of light in the boundary would have to be approaching each other. In
fact, the area would increase whenever matter or radiation fell into the black
hole. The nondecreasing behaviour of a black hole`s area was very significant
for the behaviour of a physical quantity called entropy, which measures the
degree of disorder of a system. It is a matter of common experience that
disorder will tend to increase if things are left to
themselves.
This idea combined with the second law of thermodynamics,
leaded to a fatal law. If a black hole has entropy, then it ought also to have a
temperature! But a body with a particular temperature must emit radiation at a
certain rate. This radiation is required in order to prevent violation of the
second law. So black holes ought to emit radiation. But by their very
definition, black holes are objects that are not supposed to emit anything. It
therefore seemed that the area of the event horizon of a black hole could not be
regarded as its entropy.
But calculations showed that black holes in fact emitted
radiation. The spectrum of the emitted particles was exactly that which would be
emitted by a hot body, and the black hole was emitting particles at exactly the
correct rate to prevent violations of the second law.
So there occurred a new question: How is it possible that a
black hole appears to emit particles when we know that nothing can escape from
within its event horizon? The answer, quantum theory tells us, is that the
particles do not come from within the black hole, but from the "empty" space
just outside the black hole`s event horizon.
What we think of as "empty" space cannot be completely empty
because that would mean that all the fields, such as the gravitational and
electromagnetic fields, would have to be exactly zero. There must be a certain
minimum amount of uncertainty, or quantum fluctuations, in the value of the
field. One can think of these fluctuations as pairs of particles of light or
gravity that appear together at some time, move apart, and then come together
again and annihilate each other. These particles are virtual particles like the
particles that carry the gravitational force of the sun: unlike real particles,
they cannot be observed directly with a particle detector, but their indirect
effects, like small changes in the energy of electron orbits in atoms, can be
measured. And those measurements agree with the theoretical predictions with a
high accuracy.
Heisenberg`s uncertainty principle also predicts that there
will be similar virtual pairs of matter particles, such as electrons or quarks.
In this case one member of the pair will be a particle and the other an
antiparticle. Out of the reason that energy cannot be created out of nothing,
one of the partners in a particle/antiparticle pair will have positive energy,
and the other partner negative energy. The one with negative energy is condemned
to be a short-lived virtual particle because real particles always have positive
energy in normal situations. It must therefore seek out its partner and
annihilate with it. Normally, the energy of the particle is still positive, but
the gravitational field inside a black hole is so strong that even a real
particle can have negative energy there. If a black hole is present, it is
possible for the virtual particle with negative energy to fall into the black
hole and become a real particle or antiparticle. In this case it no longer has
to annihilate with its partner. Now there are two possibilities what could
happen: The second partner could also fall into the black hole and disappear
forever, or it might also escape from the black hole as a real particle or
antiparticle. To an observer at a distance, like us humans, it will appear to
have been emitted from the black hole. And this is the radiation we can
observe.
Because of this radiation, the black hole therefore reduces
its mass, very slowly, but it does.
Moreover, the lower the mass of the black hole, the higher
its temperature. So, as the black hole loses mass, its temperature and rate of
emission increase, so it loses mass more quickly. What happens when the mass of
the black hole eventually becomes extremely small, is not quite clear, but the
most reasonable guess is that it would disappear completely in a huge final
burst of emission, equivalent to the explosion of millions of
H-bombs.
The eighth chapter is about the origin and fate of the
universe as general relativity predicts it and when quantum effects are taken
into account. Hawking first gives us an opportunity to think about the role the
church had played in the picture of the universe, and then goes on with new
theories science has uncovered.
We don´t yet have a complete and consistent theory that
combines quantum mechanics and gravity, but we are fairly certain of some
features that such a unified theory should have.
One is that it should incorporate Feynman´s proposal to
formulate quantum theory in terms of a sum over histories. In this approach, a
particle does not have just a single history, as it would in a classical theory.
Instead, it is supposed to follow every possible path in space-time, and with
each of these histories there are associated a couple of numbers, one
representing the size of a wave and the other representing its phase. The whole
thing works with probabilities of the sums of waves, associated with every
possible history that a particle has.
To avoid technical problems, one must add up the waves for
particle histories that are not in the "real" time that you and I experience but
take place in what is called imaginary time. Imaginary time may sound like
science fiction but it is in fact a well-defined mathematical concept. There are
special numbers, called imaginary, that, unlike ordinary numbers, give negative
numbers when multiplied by themselves. So for the purposes of the calculation of
Feynman`s theory, one must measure time using imaginary numbers, rather than
real ones. This has an interesting effect on space-time: the distinction between
time and space disappears completely.
A second feature that we believe must be part of any
ultimate theory, is Einstein`s idea that the gravitational field is represented
by curved space-time. When we apply Feynman´s sum over histories to
Einstein`s view of gravity, the analogue of the history of a particle is now a
complete curved space-time that represents the history of the whole
universe.
In the classical theory of general relativity, there are
many different possible curved space-times, each corresponding to a different
initial state of the universe. If we knew the initial state of our universe, we
would know its entire history!
Similarly, in the quantum theory of gravity, there are many
different possible quantum states for the universe. Again, if we knew how the
Euclidean curved space-times in the sum over histories behaved at early times,
we would know the quantum state of the universe now and in the
future.
In the classical theory of gravity, which is based on real
space-time, there are only two possible ways the universe can behave: either it
has existed for an infinite time, or else it had a beginning at a singularity at
some finite time in the past. In the quantum theory of gravity, a third
possibility arises. Because it is possible for space-time to be finite in extent
and yet to have no singularities that formed a boundary or edge. Space-time
would be like the surface of the earth, only with two more
dimensions.
The ninth chapter discusses the arrow of time and its
direction. There are at least three different arrows of time. First, there is
the psychological arrow of time. This is the direction in which we feel time
passes, the direction in which we remember the past but not the future. Then,
there is the thermodynamic arrow of time, the direction of time in which
disorder or entropy increases. Finally, there is the cosmological arrow of time.
This is the direction of time in which the universe is expanding rather than
contracting.
Chapter ten speculates about the unification of physics. To
remove infinities, one uses a process called renormalization, but this leads to
many errors conflicting with observation. The introduction of "supergravity"
caused problems, too. So, in 1984 there was a change of opinion in favour of
string theories. In these theories the basic objects are not particles, which
occupy a single point of space, but things that have a length but no other
dimension, like an infinitely thin piece of string. These strings may have ends
or they may join with themselves in closed loops. A particle occupies one point
of space at each instant of time. Thus its history can be represented by a line
in space-time, the "world-line". A string, on the other hand, occupies a line in
space at each moment of time. So its history in space-time is a two-dimensional
surface called the world-sheet. Any point on such a world-sheet can be described
by two numbers: one tells the time and the other the position of the point on
the string.
But, string theories seem to be consistent only if
space-time has either ten or twenty-six dimensions, instead of the usual four.
The suggestion is, therefore, that the other dimensions are curved up into a
space of very small size.
The eleventh, final chapter, tries to draw a conclusion. The
history of science (and time) is once again briefly summed up, and Stephen
Hawking ends with the hope of finally gain understanding of everything that
happens in our universe.
Ideas, opinions and
comments:
I liked this book
very much, for it is one of the very best I´ve ever read. Stephen Hawking
points out the most complicated scientific facts in an easily understandable and
very fascinating way. This book will attract the interest of any reader, and
probably everyone willing to think about it will have no problems to understand
it.
At the end I just want to mention that
Stephen`s book has sold 8 million copies world-wide and familiarised a whole
generation with complex but intensely exciting scientific theories. I think that
he has a very good ability to explain complicated things in an easy
understandable way. I really loved to read this book and I can only strongly
recommend this book to anyone!
Marcus Meisel,8C
The Physics
of
Star Trek
by Lawrence M. Krauss
Author:
"The Physics of Star Trek" was written
by Lawrence M. Krauss. He is Ambrose Swasey Professor of Astronomy and
Chairman of the Department of Physics at Case Western Reserve University. He is
the author of two acclaimed books, Fear of Physics: A Guide for the Perplexed
and The Fifth Essence: The Search for Dark Matter in the Universe,
and over 120 scienific articles. He is the recipient of several international
awards for his work, including the Presidential Investigator Award, given by
President Reagan in 1986. He lectures extensively to both lay and professional
audiences and frequently appears on radio and television.
Published
:
It´s a Flamingo Book, published
by HarperCollinsPublishers in 1997. It was first published in the USA by
Basic Books, a division of HarperCollinsPublishers in
1995.
It was first published in the UK by
HarperCollinsPublishers in 1996.
Type of
book:
It is a popular science
book, trying to tell most modern science in a simple language.
" The Physics of Star Trek" is a book to be read many times
as long it is up-to-date with our time (till we cross the milky ways of our and
other galaxies). It offers a lot of exotic science to anyone who wants to make a
small investment of imagination. Perhaps accidentally, Krauss also does a useful
job in explaining some important physics, using Star Trek as a pop culture
example: the physics of Newton, Einstein and Stephen Hawking all figure in the
highly successful analysis.
It is a book on physics, but it is written in such a spirit
of fun, it might even make you want to watch Star Trek.
"Always enlightening... this book is fun, and Mr Krauss has
a nice touch with a tough subject... Krauss is smart, but speaks and writes the
common tongue." - New York Times Book Review
" Entertaining and fascinating" - Manchester Evening
News
" A brilliant book" - Cambridge Evening
News
" Highly recommended" - SFX
Subject:
This entertaining book from the popular professor for
physics and astronomy at the Case Western University, Cleveland, Ohio deals with
the physical backgrounds of Star Trek and looks at how the imaginary science of
the Star Trek universe stacks up against the real thing. Krauss speculates on
the possibility of alien life, touching on whether any kind of life is such an
improbable phenomenon.
There are impressively clear explanations of difficult and
up-to-date concepts in information theory, quantum mechanics, particle physics,
relativity, mechanics and cosmology. The book goes where not even the show`s
laudable tradition of scientific evangelism has gone before.
The most important
persons:
This book is about science from the past through the present
into the future. Because of this enormous frame of time it is not possible to
give a brief description of every important scientist or character of the Star
Trek series.
Plot
synopsis:
In the foreword famous Lucasian Professor and one-time
Star Trek guest star Stephen Hawking points out that the main purpose of science
fiction is to expand the imagination of all people. He says that "Science
fiction suggests ideas that scientists incorporate into their theories". Star
Trek literally takes us “where no one has gone before”, and the
science fiction of today may become the science of tomorrow.
In the first four chapters the author takes us on a guided
tour through the history of physics, always with an eye on some Star Trek
adventures that fit to this special part of physics.
He starts with seventeenth-century mathematician and
physicist Isaac Newton, continues with Albert Einstein and Stephen Hawking until
he finally reaches Trek`s 24th century, with Data as the temporary
end of knowledge. A main objective of these first four chapters is
faster-than-light travel, called "warp drive" in Star Trek. Lawrence M. Krauss
notices that the authors of Star Trek had a brilliant imagination with the word
“warp”, because for almost all scientists warping space seems to be
the only possibility to move faster than light.
His next objective is the transporter, probably one of the
most fascinating technics in Star Trek. At the beginning he asks the question of
whether to transport atoms or Bits, because this has never become clear in Star
Trek until today. A big problem in dematerialising a man would be how to get rid
of the body. Following Einstein`s famous equation
Originaldokument enthält an dieser Stelle eine Grafik!
Original document contains a graphic at this position!
,
the atoms of only one man would transform to the energetic equivalent of about
one thousand hydrogen bombs. On the other hand, the energy needed to
dematerialise someone is gigantic, because to convert matter into energy you
have to heat it up to about 1000 billion degrees like in a fusion-reactor. To
"save" a human body on a hard disk of a computer you need to save the position,
kind and movement of every single atom in that moment. If you try to remember
only the position, you would need about 1028 Kilobytes of RAM for the
storage of a single human. Another question that rises at this point is if the
"soul" of someone is, or would be transported too. In addition, Heisenberg`s
uncertainty principle also sets limits for just scanning somebody. Based on
this, Krauss considers a transporter to beam someone, is nearly impossible to
realise.
Another problem for the Enterprise is the energy she needs
to survive and move through the universe. The engines of the Enterprise are
constructed to use anti-matter to produce energy. But the huge amounts needed
are much more than we can today even imagine to produce. One very informative
detail of this book is to reveal the formula for dilithium crystals: 2<5>6
dilithium 2<:>1 diallosilikat 1:9:1 heptoferranid. These dilithium
crystals are the most important part in a warp drive, and it seems that the
theoretical method could work with today`s understanding of nuclear
physics.
The next part of the Enterprise the author examines is the
so-called "holodeck". Though three dimensional touchable holograms are possible,
but this device suffers from the same problems as the transporter, the almost
infinite memorycapacity it would need.
A very interesting chapter is the one about the possibility
of extraterrestrial life, one of the most important points in Star Trek.
It´s a pity that this one allows only speculations until we have the first
contact to any kind of species of another planet (also in our own solar
system).
Near the end the author tells us about perspectives of
modern physics in connection with Star Trek, which is very interesting for
somebody with knowledge on these issues.
The last chapter then reveals the ten biggest mistakes in
the history of Star Trek. This starts with the fact that it is absolutely silent
in space, and goes on with the second fact, that an event horizon is a
mathematical border in which it is impossible to shoot a hole with a phaser.
Other funny mistakes are technical terms used in a wrong way. As an example, in
one episode the Enterprise is cleaned from Baryons. But the only Baryons are
protons and neutrons. If you clean a ship from them, there isn´t much
left... The last error is a very specialised one, because in one episode the
Neutrinos have a wrong spin. I guess that only a few people even know what
Neutrinos are.
The author ends with a quote from Gene Roddenberry: " The
human race is a remarkable creature, one with great potential, and I hope that
Star Trek has helped to show us what we can be if we believe in ourselves and
our abilities."
Ideas, opinions and
comments:
I liked this book because I am very interested
in physics, all the explained theories in this book and especially the future
of mankind. I was not a Star Trek freak before I read this book and I won`t get
one now, but I am sure I will watch more if I have more time.
It is generally very easy to read, but a few
parts are specialised. For that reason I would recommend a basic knowledge in
physics for reading this book.
[1] "Einstein`s Dreams" was written by
Alan Lightman, who was born in Memphis, Tennessee, in 1948 and was
educated at Princeton and at the California Institute of Technology. He has
written for Granta, Harper`s, The New Yorker, and The New York Review
of Books.
His previous books include "Time Travel and Papa Joe`s Pipe ", "A
Modern-Day Yankee in a Connecticut Court ", "Origins ", "Ancient Light ", "Great
Ideas in Physics ", and "Time for the Stars ".
"Einstein`s Dreams " is his first work of fiction. He teaches physics and
writing at the Massachusetts Institute of Technology and currently directs the
MIT programme in writing and humanistic studies.
[2] "A Brief History of Time" was written by
Professor Stephen Hawking, who was born in Oxford, Great Britain, on
8 th January 1942.
He studied physics at Oxford University and went on to pursue his graduate
studies at Cambridge. In his early twenties he was diagnosed as having ALS
(Amyotrophic Lateral Sclerosis), known in the UK as Motor Neurone Disease. He
holds Newton`s chair as Lucasian Professor of Mathematics at Cambridge and is
widely considered to be the greatest scientific thinker since Newton and
Einstein. In 1989 he received an Honorary Doctor of Science degree from
Cambridge University and was made a Companion of Honour.
[3]"The Physics of Star Trek" was written by
Lawrence M. Krauss. He is Ambrose Swasey Professor of Astronomy and
Chairman of the Department of Physics at Case Western Reserve University. He is
the author of two acclaimed books, Fear of Physics: A Guide for the Perplexed
and The Fifth Essence: The Search for Dark Matter in the Universe,
and over 120 scientific articles.
He is the recipient of several international awards for his work, including
the Presidential Investigator Award, given by President Reagan in 1986. He
lectures extensively to both lay and professional audiences and frequently
appears on radio and television.
[4] Herbert George Wells, "The Time
Machine" was written by H.G.Wells,who was born in Bromley, Kent in 1866,
to a working class family.His mother worked as a maid and housekeeper.
After working as a draper’s apprentice and pupil-teacher, he won a
schoolarship to the ”Normal School of Science” in South Kensington,
where he began to write.The first published work appeared in May 1887 in the
Science Schools Journal -”A Tale of the Twentieth Century”. After
his studies he worked in poverty in London as a cramer and published his first
book ”A Textbook of Biology” (1893), which was to remain in print
for over forty years. Wells had been in print as a professional writer, since
1891 when the FOTNIGHTLY REVIEW published his article ”The Rediscovery of
the Unique”. He lived on his writing in those times. But not until he
published his first novel ”The Time Machine” (1895) did his literary
career start.
H.G.Wells died in London, on 13th August 1946 at the age of 79
years, after having survived the First and Second World War.
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