by Dennis Overbye
New York Times
May 22, 2001
What was God doing before he created the world?
The philosopher and writer (and later saint)
Augustine posed the question in his "Confessions" in the fourth
century, and then came up with a strikingly modern answer: before
God created the world there was no time and thus no "before."
To paraphrase Gertrude Stein, there was no
Until recently no one could attend a lecture on astronomy and ask
the modern version of Augustine's question - what happened
before the Big Bang? - without
receiving the same frustrating answer, courtesy of Albert Einstein's
general theory of relativity, which describes how matter and energy
bend space and time.
If we imagine the universe shrinking backward, like a film in
reverse, the density of matter and energy rises toward infinity as
we approach the moment of origin.
Smoke pours from the computer, and space and time
themselves dissolve into a quantum "foam."
"Our rulers and our clocks break," explained Dr.
Andrei Linde, a cosmologist at Stanford University. "To ask what
is before this moment is a self-contradiction."
But lately, emboldened by progress in new theories
that seek to unite Einstein's lordly realm with the unruly quantum
rules that govern subatomic physics - so-called
quantum gravity - Dr. Andrei
Linde and his colleagues have begun to edge their speculations
closer and closer to the ultimate moment and, in some cases, beyond
Some theorists suggest that the Big Bang was not so much a birth
as a transition, a "quantum leap" from some formless era
of imaginary time, or from nothing at all. Still others are
exploring models in which cosmic history begins with a collision
with a universe from another dimension.
All this theorizing has received a further boost of sorts from
recent reports of ripples in a diffuse radio glow in the sky,
thought to be the remains of the Big Bang fireball itself.
These ripples are consistent with a popular theory,
inflation, that the universe
briefly speeded its expansion under the influence of a violent
antigravitational force, when it was only a fraction of a fraction
of a nanosecond old. Those ripples thus provide a useful check on
Any theory of cosmic origins that does not explain
this phenomenon, cosmologists agree, stands little chance of being
Fortunately or unfortunately, that still leaves room for a lot of
"If inflation is the dynamite behind the Big
Bang, we're still looking for the match," said Dr. Michael
Turner, a cosmologist at the University of Chicago. The only
thing that all the experts agree on is that no idea works - yet.
Dr. Michael Turner likened cosmologists to
jazz musicians collecting themes that sound good for a work in
"You hear something and you say, oh yeah, we want
that in the final piece."
One answer to the question of what happened before
the Big Bang is that it does not matter because it does not affect
the state of our universe today.
According to a theory known as eternal inflation, put
forward by Dr. Linde in 1986, what we know as the Big Bang was only
one out of many in a chain reaction of big bangs by which the
universe endlessly reproduces and reinvents itself.
"Any particular part of the universe may die, and
probably will die," Dr. Linde said, "but the universe as a whole
Dr. Linde's theory is a modification of the inflation
theory that was proposed in 1980 by Dr. Alan Guth, a
He considered what would happen if, as the universe
was cooling during its first violently hot moments, an energy field
known as the Higgs field, which interacts with particles to give
them their masses, was somehow, briefly, unable to release its
Space, he concluded, would be suffused with a sort of latent energy
that would violently push the universe apart. In an eyeblink the
universe would double some 60 times over, until the Higgs field
released its energy and filled the outrushing universe with hot
Cosmic history would then ensue...
Cosmologists like inflation because such a huge outrush would have
smoothed any gross irregularities from the primordial cosmos,
leaving it homogeneous and geometrically flat. Moreover, it allows
the whole cosmos to grow from next to nothing, which caused Dr. Guth
to dub the universe "the ultimate free lunch."
Subsequent calculations ruled out the Higgs field as the inflating
agent, but there are other inflation candidates that would have the
More important, from the pre-Big-Bang perspective,
Dr. Linde concluded, one inflationary bubble would sprout another,
which in turn would sprout even more. In effect each bubble would be
a new big bang, a new universe with different characteristics and
perhaps even different dimensions.
Our universe would merely be one of them.
"If it starts, this process can keep happening
forever," Dr. Linde explained. "It can happen now, in some part
of the universe."
The greater universe envisioned by eternal inflation
is so unimaginably large, chaotic and diverse that the question of a
beginning to the whole shebang becomes almost irrelevant.
For cosmologists like Dr. Guth and Dr. Linde, that is
in fact the theory's lure.
"Chaotic inflation allows us to explain our world
without making such assumptions as the simultaneous creation of
the whole universe from nothing," Dr. Linde said in an e-mail
Questions for Eternity -
Trying to Imagine the Nothingness
Nevertheless, most cosmologists, including Dr. Guth and Dr. Linde,
agree that the universe ultimately must come from somewhere, and
that nothing is the leading candidate.
As a result, another tune that cosmologists like to hum is
Heisenberg's uncertainty principle,
one of the pillars of this paradoxical world, empty space can never
be considered really empty; subatomic particles can flit in and out
of existence on energy borrowed from energy fields.
Crazy as it sounds, the effects of these quantum
fluctuations have been observed in atoms, and similar fluctuations
during the inflation are thought to have produced the seeds around
which today's galaxies were formed.
Could the whole universe likewise be the result of a quantum
fluctuation in some sort of primordial or eternal nothingness?
Perhaps, as Dr. Turner put it, "Nothing is unstable."
The philosophical problems that plague ordinary quantum mechanics
are amplified in so-called quantum cosmology. For example, as Dr.
Linde points out, there is a chicken-and-egg problem.
Which came first: the universe, or the law governing
Or, as he asks,
"If there was no law, how did the universe
One of the earliest attempts to imagine the
nothingness that is the source of everything came in 1965 when Dr.
John Wheeler and Dr. Bryce DeWitt, now at the
University of Texas, wrote down an equation that combined general
relativity and quantum theory.
Physicists have been arguing about it ever since.
Wheeler-DeWitt equation seems to
live in what physicists have dubbed "superspace," a sort of
mathematical ensemble of all possible universes, ones that live only
five minutes before collapsing into black holes and ones full of red
stars that live forever, ones full of life and ones that are empty
deserts, ones in which the constants of nature and perhaps even the
number of dimensions are different from our own.
In ordinary quantum mechanics, an electron can be thought of as
spread out over all of space until it is measured and observed to be
at some specific location. Likewise, our own universe is similarly
spread out over all of superspace until it is somehow observed to
have a particular set of qualities and laws.
That raises another of the big questions:
Since nobody can step outside the universe, who
is doing the observing?
Dr. Wheeler has suggested that one answer to that
question may be simply us, acting through quantum-mechanical acts of
observation, a process he calls "genesis by observership."
"The past is theory," he once wrote.
"It has no existence except in the records of the
present. We are participators, at the microscopic level, in
making that past, as well as the present and the future."
In effect, Dr. Wheeler's answer to Augustine is that
we are collectively God and that we are always creating the
Another option, favored by many cosmologists, is the so-called many
worlds interpretation, which says that all of these possible
universes actually do exist.
We just happen to inhabit one whose attributes are
friendly to our existence.
The End of Time - Just
Another Card in the Big Deck
Yet another puzzle about the Wheeler-DeWitt equation is that it
makes no mention of time.
In superspace everything happens at once and forever,
leading some physicists to question the role of time in the
fundamental laws of nature.
In his book "The
End of Time," published to coincide with the millennium,
Dr. Julian Barbour, an independent physicist and Einstein
scholar in England, argues that the universe consists of a stack of
moments, like the cards in a deck, that can be shuffled and
reshuffled arbitrarily to give the illusion of time and history.
The Big Bang is just another card in this deck, along with every
other moment, forever part of the universe.
"Immortality is here," he writes in his book.
"Our task is to recognize it."
Dr. Carlo Rovelli, a quantum gravity theorist
at the University of Pittsburgh, pointed out that the Wheeler-DeWitt
equation doesn't mention space either, suggesting that both space
and time might turn out to be artifacts of something deeper.
"If we take general relativity seriously," he
said, "we have to learn to do physics without time, without
space, in the fundamental theory."
While admitting that they cannot answer these
philosophical questions, some theorists have committed pen to paper
in attempts to imagine quantum creation mathematical rigor.
Dr. Alexander Vilenkin, a physicist at Tufts University in
Somerville, Mass., has likened the universe to a bubble in a pot of
boiling water. As in water, only bubbles of a certain size will
survive and expand, smaller ones collapse.
So, in being created, the universe must leap from no
size at all - zero radius, "no space and no time" - to a radius
large enough for inflation to take over without passing through the
in-between sizes, a quantum-mechanical process called "tunneling."
Dr. Stephen Hawking, the Cambridge University cosmologist and
best-selling author, would eliminate this quantum leap altogether.
For the last 20 years he and a series of
collaborators have been working on what he calls a "no boundary
proposal." The boundary of the universe is that it has no boundary,
Dr. Hawking likes to say.
One of the keys to Dr. Hawking's approach is to replace time in his
equations with a mathematical conceit called imaginary time; this
technique is commonly used in calculations regarding black holes and
in certain fields of particle physics, but its application to
cosmology is controversial.
The universe, up to and including its origin, is then represented by
a single conical-shaped mathematical object, known as an
instanton, that has four spatial
dimensions (shaped roughly like a squashed sphere) at the Big Bang
end and then shifts into real time and proceeds to inflate.
"Actually it sort of bursts and makes an infinite
universe," said Dr. Neil Turok, also from Cambridge University.
"Everything for all future time is determined, everything is
implicit in the instanton."
Unfortunately the physical meaning of imaginary time
is not clear. Beyond that, the approach produces a universe that is
far less dense than the real one.
The Faith of Strings -
Theorists Bring on the 'Brane' Worlds
But any real progress in discerning the details of the leap from
eternity into time, cosmologists say, must wait for the formulation
of a unified theory of quantum gravity that succeeds in marrying
Einstein's general relativity to quantum mechanics - two views of
the world, one describing a continuous curved space-time, the other
a discontinuous random one - that have been philosophically and
mathematically at war for almost a century.
Such a theory would be able to deal with the universe
during the cauldron of the Big Bang itself, when even space and
time, theorists say, have to pay their dues to the uncertainty
principle and become fuzzy and discontinuous.
In the last few years, many physicists have pinned their hopes for
quantum gravity on string theory, an ongoing mathematically
labyrinthean effort to portray nature as comprising tiny wiggly
strings or membranes vibrating in 10 or 11 dimensions.
In principle, string theory can explain all the known (and unknown)
forces of nature. In practice, string theorists admit that even
their equations are still only approximations, and physicists
outside the fold complain that the effects of "stringy physics"
happen at such high energies that there is no hope of testing them
in today's particle accelerators.
So theorists have been venturing into cosmology,
partly in the hopes of discovering some effect that can be observed.
The Big Bang is an obvious target. A world made of little loops has
a minimum size. It cannot shrink beyond the size of the string loops
themselves, Dr. Robert Brandenberger, now at Brown, and Dr.
Cumrun Vafa, now at Harvard, deduced in 1989.
When they used their string equations to imagine
space shrinking smaller than a certain size, Dr. Brandenberger said,
the universe acted instead as if it were getting larger.
"It looks like it is bouncing from a collapsing
In this view, the Big Bang is more like a
transformation, like the melting of ice to become water, than a
birth, explained Dr. Linde, calling it,
"an interesting idea that should be pursued."
Perhaps, he mused, there could be a different form of
space and time before the Big Bang.
"Maybe the universe is immortal," he said. "Maybe
it just changes phase. Is it nothing? Is it a phase transition?
These are very close to religious questions."
Work by Dr. Brandenberger and Dr. Vafa also explains
how it is that we only see 3 of the 9 or 10 spatial dimensions the
theory calls for.
Early in time the strings, they showed, could wrap
around space and strangle most of the spatial dimensions, keeping
them from growing.
In the last few years, however, string theorists have been
galvanized by the discovery that their theory allows for membranes
of various dimensions ("branes"
in string jargon) as well as strings.
Moreover they have begun to explore the possibility
that at least one of the extra dimensions could be as large as a
millimeter, which is gigantic in string physics. In this new
cosmology, our world is a three-dimensional island, or brane
floating in a five- dimensional space, like a leaf in a fish tank.
Other branes might be floating nearby.
Particles like quarks and electrons and forces like
electromagnetism are stuck to the brane, but gravity is not, and
thus the brane worlds can exert gravitational pulls on each other.
"A fraction of a millimeter from you is another
universe," said Dr. Linde. "It might be there. It might be the
determining factor of the universe in which you live."
Worlds in Collision - A New
Possibility Is Introduced
That other universe could bring about creation itself, according to
several recent theories.
One of them, called branefall, was developed
in 1998 by Dr. Georgi Dvali of New York University and Dr.
Henry Tye, from Cornell. In it the universe emerges from its
state of quantum formlessness as a tangle of strings and cold empty
membranes stuck together.
If, however, there is a gap between the branes at
some point, the physicists said, they will begin to fall together.
Each brane, Dr. Dvali said, will experience the looming
gravitational field of the other as an energy field in its own
three-dimensional space and will begin to inflate rapidly, doubling
its size more than a thousand times in the period it takes for the
branes to fall together.
"If there is at least one region where the branes
are parallel, those regions will start an enormous expansion
while other regions will collapse and shrink," Dr. Dvali said.
When the branes finally collide, their energy is
released and the universe heats up, filling with matter and heat, as
in the standard Big Bang.
This spring four physicists proposed a different kind of brane clash
that they say could do away with inflation, the polestar of Big Bang
theorizing for 20 years, altogether.
Dr. Paul Steinhardt, one of the fathers of
inflation, and his student Justin Khoury, both of Princeton,
Dr. Burt Ovrut of the University of Pennsylvania and Dr.
Turok call it the
ekpyrotic universe, after the Greek
word "ekpyrosis," which denotes the fiery death and rebirth of the
world in Stoic philosophy.
The ekpyrotic process begins far in the indefinite past with a pair
of flat empty branes sitting parallel to each other in a warped
five-dimensional space - a situation they say that represents the
simplest solution of Einstein's equations in an advanced version of
The authors count it as a point in their favor that
they have not assumed any extra effects that do not already exist in
"Hence we are proposing a potentially realistic
model of cosmology," they wrote in their paper.
The two branes, which form the walls of the fifth
dimension, could have popped out of nothingness as a quantum
fluctuation in the even more distant past and then drifted apart.
At some point, perhaps when the branes had reached a critical
distance apart, the story goes, a third brane could have peeled off
the other brane and begun falling toward ours. During its long
journey, quantum fluctuations would ripple the drifting brane's
surface, and those would imprint the seeds of future galaxies
all across our own brane at the moment of collision.
Dr. Steinhardt offered the theory at an astronomical
conference in Baltimore in April.
In the subsequent weeks the ekpyrotic universe has been much
discussed. Some cosmologists, particularly Dr. Linde, have argued
that in requiring perfectly flat and parallel branes the ekpyrotic
universe required too much fine-tuning.
In a critique Dr. Linde and his co-authors suggested a modification
they called the "pyrotechnic universe."
Dr. Steinhardt admitted that the ekpyrotic model started from a very
specific condition, but that it was a logical one. The point, he
said, was to see if the universe could begin in a long-lived
quasi-stable state "starkly different from inflation." The answer
His co-author, Dr. Turok, pointed out, moreover, that
inflation also requires fine-tuning to produce the modern universe,
and physicists still don't know what field actually produces it.
"Until we have solved quantum gravity and
connected string theory to particle physics none of us can claim
victory," Dr. Turok said.
In the meantime, Augustine sleeps peacefully...