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Return to Genesis of Eden?
Is the Universe alive?
John
Gribbin New Scientist Jan 94
NOBODY would argue that human beings appeared out of nothing.
We are complex creatures, and could not have arisen “just
by chance” out of a brew of chemicals, even in some warm
little pond of the kind envisaged by Charles Darwin. Simpler kinds
of living organisms came first, and it took hundreds of millions
of years of evolution on Earth to progress from single-celled
life forms to complex organisms like ourselves. Could something
similar have happened with the Universe? It is a large complex
system which, some cosmologists argue, cannot have appeared by
chance. Simpler universes came first, they say, and it may have
taken hundreds of millions of universal generations to progress
to a universe as complex as our own. Lee Smolin, professor of
physics at the Center for Gravitational Physics and Geometry at
the Pennsylvania State University, is a leading proponent of this
idea, which also takes on board notions about baby universes developed
by Andrei Linde of the Lebedev Physics Institute in Moscow and
Stephen Hawking of the University of Cambridge. One of the jumping
off points for such speculation is that the Universe we see around
us seems to be in a very peculiar state, not “typical”
of the way a universe might be expected to emerge from a big bang.
According to the basic laws of physics, universes should be much
smaller and shorter-lived.
The puzzle has become more pressing as evidence has mounted
that the Universe really did emerge from a big bang some 15 billion
years ago. The evidence suggests that the Universe was born out
of a singularity-a point of infinite density occupying zero volume-and
that in the first split second the tiny seed containing all the
mass and energy in the observable Universe went through a period
of exponential expansion, known as inflation.
The key feature of inflation is that it stretches space-time-the
three dimensions of space together with time-by a very large amount,
smoothing out any irregularities that are present. Think of the
difference between the wrinkled skin of a dry prune and the smooth
surface of the same prune when it has absorbed its fill of water,
then picture how smooth the skin of the prune would be if it were
inflated to the size of the Earth, and you get some idea of how
the process works. But cosmic inflation happened on a much smaller
scale, and had ended by the time the Universe reached the size
of a grapefruit. Around this time, matter was distributed evenly-but
not perfectly evenly. There were small irregularities, or clumps
of matter. Once inflation slowed, these clumps had enough gravity
to gather other matter around them. Since then, more leisurely
inflation has taken 15 billion years to expand the grapefruit
to its present size, with the clumps of matter yielding galaxies,
stars-and people. At first sight, there is no obvious reason why
the inflation process should have gone on for just long enough
and at just the right rate to produce a Universe in which stars
and galaxies could form. A shorter, less intense burst of inflation
would have left the matter too jumbled up, and the proto-universe
in danger of quickly recollapsing back into a singularity. A longer,
stronger burst of inflation would have spread the stuff of the
proto-universe so thin that no stars and galaxies could ever form.
Goldilocks effect
This problem of fine-tuning is generally regarded as the biggest
difficulty with inflation. It is essentially an example of the
Goldilocks effect: why is inflation, like so many other properties
of the Universe, “just right” to allow our Universe
to exist. But the fine-tuning problem can be resolved by taking
on board the idea that the Universe itself is alive and has evolved.
A key feature of the argument is that the birth of the Universe-an
outburst from a singularity-is essentially a mirror image of the
collapse of a massive object into a black hole, which is an implosion
towards a singularity. it is 30 years since Roger Penrose, now
at the University of Oxford, and Hawking established that the
equations describing the big bang expansion of the Universe are
precisely the time-reverse of the equations describing the collapse
of a black hole. But it was only in the 1980s that cosmologists
realised that our Universe may contain so much material, most
of it in the form of invisible, dark matter, that one day die
enormous gravitational force would first halt the present expansion
and then reverse it, making the Universe collapse back into a
singularity that is a mirror image of the one that gave it birth.
At about the same time, relativists realised that there is nothing
to stop the material that falls into a singularity in our three
dimensions of space and one of time from being shunted through
a kind of space-time warp and emerging as an expanding singularity
in another set of dimensions-another space-time. Mathematically,
this “new” space-time is represented by a set of four
dimensions, just like our own, but with all the dimensions at
right angles to all the familiar dimensions of our own space-time.
Every singularity, on this picture, has its own set of spacetime
dimensions, forming a bubble universe within the framework of
some “super” space-time, which we can refer to simply
as “superspace”. One way to picture what this involves
is to use the analogy between the three dimensions of expanding
space around us and the two-dimensional expanding surface of a
balloon steadily filling with air. The analogy is not with the
volume of air inside the balloon, but with the expanding skin
of the balloon ' stretching uniformly in two dimensions but curved
around upon itself in a closed surface. Imagine a tiny pimple
forming on the surface of the balloon, a small piece of the stretching
rubber that gets pinched off and starts to expand in its own right.
It develops into a bubble, attached to the original balloon by
a tiny, narrow throat-the black hole. And this new bubble can
expand away happily in its own right to become as big as the original
balloon, or even bigger, without the skin of the original balloon
(the original universe) being affected. There can be many bubbles
growing out of the skin (the space-time) of the original universe
in this way at the same time, all interconnected by a system of
black hole “throats' referred to as wormholes or tunnels.
And new bubbles can grow out of each new universe, ad infinitum,
Instead of the collapse of a black hole representing a one-way
journey to nowhere, Hawking, Linde and Smolin and others suggest
that it is a one-way journey to somewhere-to a new expanding universe
in its own set of dimensions. The dramatic implication is that
many, perhaps all the black holes that form in our Universe may
be the seeds of new universes. And, of course, our own Universe
may have been born in this way out of a black hole in another
universe. What's more, it turns out that the fact that the Universe
seems to be so efficient at the job of making stars and fuming
them into black holes means that it is also efficient at making
more universes. This is a spectacular shift of viewpoint, and
most cosmologists are still struggling to come to grips with it.
If one Universe exists, then it seems that there must be many-very
many, perhaps even an infinite number of universes. Our Universe
has to be seen as just one component of a vast array of universes,
a self-reproducing system connected only by the tunnels through
space-time, which in this view are perhaps better regarded as
cosmic umbilical cords that join a baby universe to its parent.
But there is still a puzzle of why inflation should have just
the right strength to lead to a universe like our own. The “natural”
size for a universe is down in the subatomic region, on the scale
of the Planck length, IO^-35 of a metre, the smallest “distance”
that can exist. This is where evolution comes in. The key element
that Smolin has introduced is the idea that every time a black
hole collapses into a singularity and a new baby universe is formed
with a new space-time, the laws of physics that are bom with it
are slightly different. The force of gravity, for example, may
be a little stronger -or weaker-in the baby universes than in
the parent. The process, he argues, resembles the way mutations
provide the variability among organic life forms on which natural
selection can operate.
Each baby universe, says Smolin, is not a perfect replica of
its parent but a slightly mutated form. The original, natural
state of a baby universe may indeed be to expand out to a few
times the Planck length, before collapsing once again. But if
the random changes in the workings of the laws of physics the
mutations-happen to allow a little bit more inflation, a baby
universe will grow a little larger. If it becomes big enough,
it may separate into two or more different regions that each collapse
to make a new singularity and thereby trigger the birth of another
generation of universes. Those new universes will also be slightly
different from their parents. Some may lose the ability to grow
much larger than the Planck length, and will fade back into the
quantum realm. But some may have a little more inflation still
than their parents, growing even larger, producing more black
holes and giving birth to more baby universes in their turn. The
number of new universes that are produced in each generation will
be roughly proportional to the volume of the parent universe.
“The essential point,” says Smolin, “is that the
universes that reproduce the most successfully by leaving the
largest number of progeny dominate the ensemble after many generations.”
The Universe within
The end product should be not one but many universes, an about
as big as it is possible to get while still being inside a black
hole and in which the parameters of physics are such that the
formation of stars and black holes is favoured. Our Universe exactly
matches that description. This explains the otherwise baffling
mystery of why the Universe we live in should be “set up”
in what seems, at first sight, such an unusual way. Just as you
would not expect a random collection of chemicals suddenly to
organise themselves into a human being, so you would not expect
a random collection of physical laws emerging from a singularity
to give rise to a Universe like the one we live in. Smolin has
stopped short of suggesting that the Universe is alive. But heredity
is one of the defining attributes of life, and Smolin suggests
that universes pass on their characteristics to their offspring
with only minor changes, just as people pass on their characteristics
to their children with only minor changes. Universes that are
successful in evolutionary terms are the ones that leave the most
offspring. Provided that the random mutations are indeed small,
there will be a genuinely evolutionary process favouring larger
and larger universes. Smolin's ideas are far from being accepted.
One criticism is his assumption that the physical laws a universe
is born with will be only slightly different from those of its
parent; they could equally be very different or the same. “I
don't go along with all the details of Smolin's argument,”
says Paul Davies of the University of Adelaide, “but it's
a welcome new way of looking at the old problem of why the Universe
is as it is.” Before Charles Darwin and Alfred Wallace came
up with the idea of evolution, many people believed that the only
way to explain the existence of so unlikely an organism as a human
being was by supernatural intervention. The apparent unlikelihood
of the Universe has similarly led some people to suggest that
the big bang may have resulted from supernatural intervention.
Even respectable cosmologists such as Davies and Frank Tippler
of the University of New Orleans talk of the new cosmology as
revealing “the mind of God” at work. But if Smolin is
right, there is no longer any basis for invoking the supernatural.
We live in a Universe which is exactly the most likely kind of
universe to exist if there are many living universes that have
evolved in the same way that living things on Earth have evolved.
In the Beginning 24 Jan 98
New Scientist
COULD the Universe have been its own mother? Two physicists
in New Jersey say that this may be a more satisfying way of explaining
the origin of the Universe than any alternatives dreamt up so
far. Physicists have huge problems trying to work out how the
Universe got going (“The day time began”, New Scientist,
29 April 1996, p 30). Some say the question of what happened before
the beginning of time, space and matter is like asking what is
south of the South Pole. Others argue that the Universe has existed
forever, or somehow popped into existence out of nothing. “We
suggest that the Universe emerged from something rather than nothing-and
that that something was itself,” says Richard Gott III of
Princeton University in New Jersey. This strange suggestion is
a spin-off from the theory of inflation which purports to describe
what happened immediately before the big bang. In inflation an
unusual state of the vacuum grows rapidly and exponentially One
version is “chaotic inflation”, suggested by Andrei
Linde of Stanford University in California, in which inflating
regions spawn others of their kind. “These are baby universes
which bud off from the Universe like the branches of a tree,”
says Gott. Gott and his colleague Li-Xin Li say it's possible
that a branch of spacetime could loop backwards to rejoin the
tree trunk. “Such a thing is possible because Einstein's
general theory of relativity permits closed time-like currents
- loops of time”, says Gott. Gott and Li found that a time
loop could have existed before the big bang without violating
any laws of physics. Space would have been in a loop of time,
perpetually recreating itself. If so, the Universe could be viewed
as having given birth to itself. Gott says that asking what the
first event in the Universe was becomes meaningless. “Every
event in the Universe could have an event preceding it,”
he says. One consequence of the idea is a natural explanation
for the so-called arrow of time. Theories of general relativity
and electromagnetism do not rule out the idea that waves can affect
events that occurred in the past. For instance, they do not forbid
light from travelling back in time. Yet in our Universe light
always travels with us into the future. The reason, say Gott and
Li, has to do with what would happen to waves that regressed in
time in the kind of universe they envisage. “They would travel
back to the epoch of the time loop and circle forever, constantly
reinforcing each other,” says Gott. Such a universe could
not exist, Gott concludes, because the time loop would quickly
become unstable. “This whole area of cosmology is incredibly
speculative,” comments Astronomer Royal Martin Rees at the
University of Cambridge. “But I think this is a fascinating
contribution.” Gott and Li say that they have only begun
to explore their idea and much more work needs to be done. Their
results have been submitted to the J Phys Rev D. Marcus Chown
N
In the Beginning/2 NS 25 April 1998
A discrepancy in the size of primordial fluctuations has been
found in the extrapolation of galaxy clusters back to the primordial
distribution of matter. An apparent preponderance of clusters
300 million light years across was found by Subir Sarkar, suggesting
there may be an imprint of the complex phase transition accompanying
inflation.
Whoops apocalypse NS 9 May 1998
A certain class of supersymmetric theories suggests further
Higgs fields could turn on at arbitrary times, causing abrupt
changes in physics like those which accompanied symmetry-breaking
and cosmic inflation. Fortunately the probability of this happening
in the universes lifetime is slight or negligible.
The Day Time Began
Paul Davies New Scientist 27 Apr 96
Can science explain how the universe began? Such questions
have provoked an angry and passionate response from many quarters.
Religious people tend to see the claim as a move to finally abolish
God the Creator. Atheists are equally alarmed, because the notion
of the Universe coming into being from nothing looks suspiciously
like the creation, ex nihilo of Christianity. The general sense
of indignation was well expressed by writer Fay Weldon. “Who
cares about half a second after the big bang,” she railed
in 1991 in a scathing newspaper attack on scientific cosmology.
“What about the half a second before?” What indeed.
The simple answer is that, in tile standard picture of the cosmic
origin, there was no such thing as the half-second before.
To see why, we need to examine this standard picture in more
detail. The first point to address is why anyone believe, the
Universe began at a finite time. How do we know it hasn't been
around forever? Most cosmologists reject this alternative because
of the severe problem of the second law of thermodynamics. Applied
to the universe as a whole, this law states that the cosmos is
in a one-way slide towards disorder, or entropy. Irreversible
changes, such as the gradual consumption of fuel by the Sun and
stars, ensure that the Universe must eventually “run down”
and exhaust its supplies of useful energy. lt follows that the
Universe cannot have been drawing on this finite stock of useful
energy for all eternity.
Body of evidence
Direct evidence for a cosmic origin in a big bang comes from
three observations. The first, and most direct, is that the Universe
is still expanding today. The second is the existence of a pervasive
heat radiation that is neatly explained as the fading afterglow
that accompanied the big bang. The third strand of evidence is
the relative abundances of the chemical elements, which can be
correctly accounted for in terms of nuclear processes in the hot
dense phase that followed the big bang. But what caused the big
bang to happen? Where is the centre of the explosion? Where is
the edge of the Universe? Why didn't the big bang turn into a
black hole?
Though they seem pertinent, they are in fact based on an entirely
false picture of the big bang. To understand the correct picture,
it is first necessary to have a clear idea of what the expansion
of the Universe entails. Contrary to popular belief, it is not
the explosive dispersal of galaxies from a common centre into
the depths of a limitless void. The best way of viewing it is
to imagine the space between the galaxies expanding or swelling.
The idea that space can stretch, or be warped, is a central prediction
of Einstein's general theory of relativity, and has been well
enough tested by observation for all professional cosmologists
to accept it. According to general relativity, space-time is not
a static arena, but an aspect of the gravitational field. This
field manifests itself as a warping, or curvature, of space-time
geometry, and when it comes to the large scale structure of the
Universe, such a warping occurs in the form of space being stretched
with time. A helpful, albeit two-dimensional, analogy for the
expanding Universe is a balloon with paper spots stuck to the
surface. As the balloon is inflated so the spots, which play the
role of galaxies, move apart from each other. Note that it is
the surface of the balloon, not the volume within, that represents
the three-dimensional Universe. Now, imagine playing the cosmic
movie backwards, so that the balloon shrinks rather than expands.
If the balloon were perfectly spherical (and the rubber sheet
infinitely thin), at a certain time in the past the entire balloon
would shrivel to a speck. This is the beginning. Translated into
statements at)out the real Universe, I am describing an origin
in which space itself comes into existence at the big bang and
expands from nothing to form a larger and larger volume. The matter
and energy content of the Universe likewise originates at or near
the beginning, and populates the Universe everywhere at all times.
Again, I must stress that the speck from which space emerges Is
not located in anything. lt is not an object surrounded by emptiness.
It is the origin of space itself, infinitely compressed. Note
that the speck does not sit there for an infinite duration. It
appears instantaneously from nothing and immediately expands.
This is why the question of why it does not collapse to a black
hole is irrelevant. Indeed, according to tile theory of relativity,
there is no possibility of the speck existing through time because
time itself begins at this point. This becomes the most difficult
and most critical aspect of the big bang theory. The notion that the physical universe came into existence with time and not in
time has a long history, dating back to St. Augustine in the fifth
century. But it took Einstein's theory of relativity to give the
idea scientific respectability. The key feature of the theory
of relativity is that splice and time are part of the physical
Universe, and not merely an unexplained background arena in which
the Universe happens. Hence the origin of the physical Universe
must involve the origin of space and time too. But where could
we look for such an origin? Well, the theory of relativity requires
space and time to possess a variety of edges, technically known
as singularities. One type of singularity exists in the centre
of a black hole. Another corresponds to a past boundary of space
and time at the big bang. The idea is that, as you move backwards
in time, the Universe becomes more and more compressed and the
curvature or warping of space-time escalates without limit, until
it becomes infinite at a singularity. Very roughly, it resembles
the apex of a cone, where the fabric of the cone tapers to an
infinitely sharp point and ceases. lt is here that space and time
begin. Once this idea is accepted, it is immediately obvious
that the question “What happened before the big bang?”
is meaningless. There was no such epoch as “before the big
bang”. Because time began with the big bang. Unfortunately,
the question is often answered with the bald statement “There
was nothing before the big bang”, and this has caused yet
more misunderstandings. Many people interpret “nothing”
in this context to niean empty space, but as I have been at pains
to point out, space did not exist either prior to tile big bang.
Absolutely nothing
Perhaps “nothing” here means something more subtle,
like pre-space, or some abstract state from which space emerges?
But again, this is not what is intended by the word. As Stephen
Hawking has remarked, the question 'What lies north Of the North
Pole?” can also be answered by “nothing”. not because
there is some mysterious land of nothing there but simply because
the region referred to does not exist. It is not merely physically,
but also logically, non-existent. So too with the epoch before
the big bang, In my experience, people get very upset when told
this. They think they have been tricked, verbally or logically.
They suspect that scientists can't explain the ultimate origin
of the Universe and are resorting to obscure and dubious concepts
like the origin of time merely to befuddle their detractors. The
mind-set behind such outraged objection is understandable: our
brains are hard wired for us to think in terms of cause and effect.
Because normal physical causation takes place within time with
effect following cause, there is a natural tendency to think of
a chain of causation stretching back in time, either without any
beginning, or else terminating in a metaphysical First Cause,
or Uncaused Caused, or Prime Mover. But cosmologists now invite
us to contemplate the origin of the Universe as having no prior
cause in the normal sense, not because it has an abnormal or supernatural
prior cause but because there is simply no prior epoch in which
a preceding causative agency-natural or supernatural-can operate.
Nevertheless cosmologists have not explained the origin of the
Universe by the simple expedient of abolishing any preceding epoch.
After all, why should time and space have suddenly “switched
on”? The latest thinking is that this spontaneous origination
of time and space is a natural consequence of quantum mechanics.
Quantum mechanics is the branch of physics that applies to atoms
and subatomic particles, and it is characterised by Heisenberg's
uncertainty principle, according to which sudden and unpredictable
fluctuations occur in all observable quantities. Quantum fluctuations
are not caused by anything – they are genuinely spontaneous and
intrinsic to nature at its deepest level.
Impossible predictions
For example, take a collection of uranium atoms suffering radioactive
decay due to quantum processes in their nuclei. There will be
a definite time period, the half-life, after which half of the
nuclei present should have decayed. But according to Heisenberg
it is not possible, even in principle, to predict when a given
nucleus will decay. If you ask, having seen a particular nucleus
decay, why the decay event happened at that moment rather than
some other, there is no deeper reason, no underlying set of causes,
that explains it. It just happens. The key step for cosmogenesis
is to apply this same idea not just to matter, but to space and
time as well. Because space-time is an aspect of gravitation,
this entails applying quantum theory to the gravitational field
of the Universe. The application of quantum mechanics to a field
is fairly routine for physicists, though it has to be said that
there are special technical problems associated with the gravitational
case that have yet to be satisfactorily resolved (“Can gravity
take a quantum leap?', 10 September 1994, p 28). The quantum theory
of the origin of the Universe therefore rests on shaky ground.
In spite of these technical obstacles, one may say quite generally
that once space and time are made subject to quantum principles,
the possibility immediately arises of space and time “switching
on”, or popping into existence, without the need for prior
causation, entirely in accordance with the laws of quantum physics.
The details of this process remain both subtle and contentious,
and depend to some extent on the interrelationship between space
and time. Einstein showed that space and time are closely interwoven,
but in the theory of relativity they are still distinct. Quantum
physics introduces the new feature that the separate identities
of space and time can be “smeared” or “blurred”
on an ultramicroscopic scale. in a theory proposed in 1982 by
Hawking and American physicist Jim Hartle, this smearing implies
that, closer and closer to the origin, time is more and more likely
to adopt the properties of a space dimension, and less and less
likely to have the properties of time. This transition is not
sudden, but blurred by the uncertainty of quantum physics. Thus
time does not switch on abruptly in Hartle and Hawking's theory,
but it emerges continuously from space. There is no specific first
moment in which time starts, but neither does time extend backwards
for all eternity (see Diagram p 34). Unfortunately, the topic
of the quantum origin of the Universe is fraught with confusion
because of the publicity given to a preliminary, and in my view
wholly unsatisfactory theory of the big bang based on an instability
of the quantum vacuum. According to this alternative theory, first
noted by Edward Tryon in 1973, space and time are eternal, but
matter is not. lt suddenly appears in a pre-existing and unexplained
void due to quantum vacuum fluctuations. In such a theory, it
would indeed involve a serious misnomer to claim that the Universe
originated from nothing: a quantum vacuum in a background space-time
is certainly not nothing.
Law unto itself
However, if there is a finite probability of an explosive appearance
of matter, it should have occurred an infinite time ago. In effect,
Tryon's theory and others like it run into the same problem of
the second law of thermodynamics as most models of an infinitely
old Universe. it will be obvious from what I have said that the
attempt to explain the origin of the Universe is based on an application
of the laws of physics. This is normal in science: one takes the
underlying laws of the Universe as given. But when tangling with
ultimate questions, it is only natural that we should also ask
about the status of these laws. One must resist the temptation
to imagine that the laws of physics, and the quantum state that
represents the Universe, somehow exist before the Universe. They
don't any more than they exist north of the North Pole. In fact,
the laws of physics don't exist in space and time at all. They
describe the world, they are not “in” it. However, this
does not mean that the laws of physics came into existence with
the Universe. If they did-if the entire package of physical Universe
plus laws just popped into being from nothing then we cannot appeal
to the laws to explain the origin of the Universe. So to have
any chance of understanding scientifically how the Universe came
into existence, we have to assume that the laws have an abstract
eternal character. The alternative is to shroud the origin in
mystery and give up. It might be objected that we haven't finished
the job by baldly taking the laws of physics as given. Where did
those laws come from? And why those laws rather than some other
set? This is a valid objection. I have argued that we must eschew
the traditional causal chain and focus instead on an explanatory
chain, but inevitably we now confront the logical equivalent of
the First Cause-the beginning of the chain of explanation. In
my view it is the job of physics to explain the world based oii
lawlike principles. Scientists adopt differing attitudes to
the metaphysical problem of how to explain the principles themselves.
Some simply shrug and say we must just accept the laws as a brute
fact. Others suggest that the laws must be what they are from logical necessity. Yet others say there exist many worlds, each with differing laws, and that only a small
subset of these universes possess the rather special laws needed
if life and reflective beings like ourselves are to emerge. Some
sceptics rubbish the entire discussion by claiming that the
laws of physics have no real existence anyway-they are merely
human inventions designed to help us make sense of the physical
world. It is hard to see how the origin of the Universe could
ever be explained with a view like this.
In my experience, almost all physicists who work on fundamental
problems accept that the laws of physics have some kind of independent
reality. With that view, it is possible to argue that the laws
of physics are logically prior to the Universe they describe.
That is, the laws of physics stand at the base of a rational explanatory
chain in the same way that the axioms of Euclid stand at the base
of the logical scheme we call geometry. Of course, one cannot
prove that the laws of physics have to be the starting point of
an explanatory scheme, but any attempt to explain the world rationally
has to have some starting point, and for most scientists the laws
of physics seem a very satisfactory one. in the same way, one
need not accept Euclid's axioms as the starting point of geometry;
a set of theorems like Pythagoras's would do equally well. But
the purpose of science (and mathematics) is to explain the world
in as simple and economic a fashion as possible, and Euclid's
axioms and the laws of physics are attempts to do just that. in
fact, it is possible to quantify the degree of compactness and
utility of these explanatory schemes using a branch of mathematics
called algorithmic information theory. Obviously, a law of physics
is a more compact description of the world than the phenomena
that it describes. For example, compare the succinctness of Newton's
laws with the complexity of a set of astronomical tables for the
positions of the planets. Although as a consequence of Godel's
famous incompleteness theorem of logic, one cannot prove a given
set of laws, or mathematical axioms, to be the most compact set
possible, one can investigate mathematically whether other logically
self-consistent sets of laws exist. One can also determine whether
there is anything unusual or special about the set that characterises
the observed Universe as opposed to other possible universes.
Perhaps the observed laws are in some sense an optimal set, producing
maximal richness and diversity of physical forms. It may even
be that the existence of life or mind relates in some way to this
specialness. These are open questions, but I believe they forin
a more fruitful meeting ground for science and theology than
dwelling on the discredited notion of what happened before the
big bang.
World Without End New Scientist
27 Apr 96 Gabrielle Walker
TRY asking a bunch of cosmologists about the origin of the
Universe, and it's hard to get a clear answer. “The Universe
didn't start. It's infinite.” says British cosmologist Fred
Hoyle. “It's an open question.” says Steven Weinberg,
Nobel prize-winning particle physicist from the University of
Texas. “It's up in the air.” says Paul Steinhardt from
Pennsylvania State University. co-developer in the 1980s of a
key theory about the early Universe. “It must have had a
beginning,” says cosmologist Alexander Vilenkin of Cruft,
University in Massachusetts. The standard big-bang model is agreed
say Roger Penrose and everything else is embellishments and flights
of fancy. So what gives? Well, Hoyle is convinced that the big
bang is a myth, and that the Universe is eternal, with matter
continuously created at the centres of galaxies. But virtually
everyone else is happy with the big bang model. at least as far
back as the early stages of the Universe. Says Weinberg, “We
are in an expanding Universe which at one time, before any of
the stars or galaxies formed was very hot and dense. I don't think
there', any serious argument that in that sense there was a big
bang, and the part of the Universe that we live in had a start.
gut beyond that we really don't know.” To try to trace the
history of the Universe back to its origin, cosmologists picture
the expansion running backwards to a point where the Universe
was almost unimaginably small and dense. The first problem they
meet. when they do this. is that the concept of time comes apart
in their hands. The reason is that at the so-called Planck scale
(a mere IO^-35 metres), Two theories begin to clash. Einstein's
smooth, large-scale, classical theory of gravity makes no provision
for the fuzzy, indeterminate quantum theory of tiny particles.
and all bets are off. “Questions about what happened before
what begin to lose meaning says Steinhardt “Before only makes
sense if there is a sensible time ordering to things, and that
notion breaks down at the Planck scale.” Weinberg agrees:
“Any description that tries to go to earlier times has to
give up the idea of time. It's no longer a meaningful concept.”
Glimmers of hope for reconciling relativity and quantum theory
come from an idea called superstrings-in which all matter is made
up of tiny 10-dimensional strings. Although we appear to live
in a Universe with just four dimensions, three for space and one
for time, the theory goes that the other dimensions present are
curled up so tightly that we can't detect them directly. But this
cause, even greater problems, because at the Planck Scale the
tightly curled extra dimension, become significant. “You
go back in time and it looks like you're heading towards a singularity
and all of a sudden-wham-physics changes because all those extra
dimensions that you weren't aware of suddenly come into Play.”
says Steinhardt. It is usually easy to tell time and space apart.
But, says Steinhardt, “When you unwrap the extra dimensions.
you don't know what they'll be like lt may be that you even have
two time-like: coordinates, or more.” The idea of before
and after would then be been shakier. How the Universe could appear
from nothing in the first place? In 1982, Vilenkin came up with
the idea that the universe literally tunneled its way into existence,
something allowed by quantum theory but impossible on an everyday
large scale. In the classical world, it you have a heavy object
lying in a dip it will need a push to climb over hie edge and
roll down the other side. But in the quantum world, there is a
small, but non-zero probability that the object can simply tunnel
to the other side of the dip without any outside help. The only
condition is that it does not gain any energy in the process.
So how does this relate to the Universe? Well, say you start with
nothing at all-not even space or time. Presumably the total energy
of this system would be zero. Is it possible to make a Universe
of space, time and matter whose total energy is still zero? The
answer is yes. “You can't create something out of nothing,”
says Vilenkin. “But the Universe is an exception. Gravitational
energy is negative and matter energy is positive. In a closed
Universe, one where if you keep going in one direction you come
back to the same point-the negative energy of gravity exactly
cancels the positive energy of matter, so the total energy is
zero.” In the classical picture, the Universe cannot appear
out of nothing because it is forbidden to adopt a certain range
of sizes. But in quantum theory, the Universe can tunnel through
this size barrier, and appear spontaneously with a size greater
than the critical value.
Can we ever know if the universe began at a single point or
has simply been going on forever. There is yet another complication
which may make the whole question academic. lt stems from an idea
called inflation, first developed in the early 1980s to solve
some vexing problems with the standard big bang model. In its
earliest versions. inflation theory stipulated that. immediately
after the big bang, the Universe suddenly ballooned, increasing
its diameter by more than a trillion trillion times in just a
tiny fraction of a second. After this, the Universe switched to
a noninflationary phase, and expanded at a more sedate rate. But
in the mid 1980s. cosmologist Andrei Linde at Stanford University
realised that such a system would be self-replicating. Once you
kicked it off with a big bang, it would go on forever. Even when
most of the Universe had moved out of the inflationary phase,
Linde reasoned, tiny fluctuating regions would still be capable
of undergoing inflation. These would then go from being infinitesimal
regions to sizable chunks of Universe in a split second, and
would themselves go on to spawn new patches of Universe and so
on. In each case, once inflation was over, the patch would evolve
according to standard big bang theory. If this is true, the whole
Universe could be made up of a huge number of expanding patches which
could be quite different from our own. The problem is that we
can never know. “We are removed be a tremendous distance
from regions that underwent a different history.” says Steinhardt.
“Inflation casts a pall on things because it makes the part
of the Universe we see so infinitesimal compared to the entire
Universe, and perhaps not even representative. We will never be
able to see the edge of the patch we live in, and this puts us
beyond the ability to be able to probe things through observations.”
What's more, an eternal. self-replicating Universe may not even
need a big bang. Vilenkin says he has proved in a theorem that
the inflationary Universe must have had an origin, but Linde is
skeptical. He thinks it likely but unproved that there was an
initial big bang from which all of the “pretty big bangs”
came. However, he adds that the question is so far removed from
our experience that it is irrelevant: “Say you have an infinite
number of bubbles, all producing new ones. You live in one of
these bubbles and you look at the point the bubble -as formed.
For all practical purposes that's the beginning of your Universe.”
Because there are infinitely many such bubbles, we have no reason
to believe that ours is the first, or even the hundredth. It's
more likely, says Linde, that our own personal big bang is actually
a pretty insignificant one. way down the list from the one that
set the Universe going.
