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The Big BAng was NOT a Fireworks Display!
Written by Sten Odenwald
Copyright (C) 1997
Published in the Washington Post Horizon education supplement on May 1
4, 1997.
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The Big Bang wasn't really big. Nor was it really a bang. In fact, the
event that created the universe and everything in it was a very diffe
rent kind of phenomenon than most people--or, at least, most nonphysic
ists--imagine.
Even the name "Big Bang" originally was a put-down cooked up by a scie
ntist who didn't like the concept when it was first put forth. He favo
red the idea that the universe had always existed in a much more digni
fied and fundamentally unchanging, steady state.
But the name stuck, and with it has come the completely wrong impressi
on that the event was like an explosion and that the universe is expan
ding today because the objects in it are being flung apart like fragme
nts of a detonated bomb.
Virtually every basic aspect of this intuitive image for the Big Bang
(we ARE stuck with the name) is incorrect. To understand why, you need
to understand Albert Einstein's general theory of relativity. Or, at
least, you need to have a sense of it. That may sound daunting, but ge
neral relativity is the most revolutionary scientific advance of the 2
0th century, and we all ought to acquire some feeling for it before th
e century ends.
After all, it's been 82 years since Einstein put forth his theory. It'
s been tested in scores of experiments and has always passed with flyi
ng colors and is now firmly established as our premier guide to unders
tanding how gravity operates. Moreover, it is part of the foundation o
f Big Bang cosmology. And it is because of general relativity that we
know the Big Bang was (and is, for the event is still going on) nothin
g like an explosion.
Albert Einstein developed general relativity in order to make his famo
us theory of special relativity include the effects of gravity. It is
a better way than Sir Isaac Newton's of understanding how gravity work
s. Like a hungry amoeba, general relativity ( or just GR for short) ha
d absorbed both Einstein's newly-minted special relativity and Newton'
s physics, giving us the means to replicate ALL of the predictions fro
m these two great theories, while extending them into unfamiliar realm
s of experience. One of these realms was the Black Hole. The other was
the shape and evolution of the universe itself.
Big Bang cosmology says that the universe came into existence between
10 to 20 billion years ago, and that from a hot dense state has been e
xpanding and cooling ever since, remains unassailable. Yet, Big Bang c
osmology is vulnerable. It is based on GR being accurate over an enorm
ous range of scales in time and space. Just how good is general relati
vity? So far, GR has made the following specific predictions:
1...The entire orbit of Mercury rotates because of the curved geometry
of space near the sun. The amount of 'perihelion shift' each century
was well known at the time Einstein provided a complete explanation fo
r it in 1915.
2...Light at every frequency can be bent in exactly the same way by gr
avity. This was confirmed in the 1919 Solar Eclipse for optical light
using stars near the Sun's limb, and in 1969-1975 using radio emission
s from star-like quasars also seen near the limb of the Sun. The defle
ction of the light was exactly as predicted by GR.
3...Clocks run slower in strong gravitational fields. This was confirm
ed by Robert Pound and George Rebka at Harvard University in 1959, and
by Robert Vessot in the 1960's and 70's using high-precession hydroge
n maser clocks flown on jet planes and on satellites.
4...Gravitational mass and inertial mass are identical. Most recently
in 1971, Vladimir Braginsky at Moskow University confirmed GRs predict
ion of this to within 1 part in a trillion of the exact equality requi
red by GR.
5...Black holes exist. Although these objects have been suspected to e
xist since they were first introduced to astronomers in the early 1970
's, it is only in 1992 that a critical acceptance threshold was crosse
d in the astronomical community. It was then that Hubble Space Telesco
pe observations revealed monstrous, billion-sun black holes in the cor
es of nearby galaxies such as Messier 87, Messier 33 and NGC 4261.
6...Gravity has its own form of radiation which can carry energy. Russ
el Hulse and Joseph Taylor in 1975 discovered two pulsars orbiting eac
h other, and through careful monitoring of their precise pulses during
the next 20 years, confirmed that the system is loosing energy at a r
ate within 1 percent of the prediction by GR based on the emission of
gravitational radiation.
7...A new force exists called 'gravito-magnetism'. Just as electric an
d magnetic fields are linked together, according to GR, a spinning bod
y produces a magnetism-like force called gravitomagnetism. GR predicts
that rotating bodies not only bend space and time, but also make empt
y space spin. A NASA satellite called Gravity Probe B will be launched
in the next few years to see whether this effect exists. This is a ki
ller. If it is not found, GR is mortally wounded despite its long stri
ng of other successes.
8...Space can stretch during the expansion of the universe. This was c
onfirmed by Edwin Hubble's detection of the recession of the galaxies
ca 1929. More recently in 1993, Astronomer Kenneth Kellerman confirmed
that the angular sizes of distant radio sources shrink to a minimum t
hen increase at greater distances exactly as expected for a dilating s
pace. This is not predicted by any other cosmological model that does
not also include the dilation of space as a real, physical phenomenon.
We have now boxed ourselves into a corner. If we accept the successes
of GR, we are forced to see the world and the cosmos through its eyes,
and its eyes alone, since it is the theory which satisfies all known
tests to date.
So, how should we think about the Big Bang? Our mental 'fireworks' ima
ge of the Big Bang contains these basic elements: 1) A pre-existing sk
y or space into which the fragments from the explosion are injected; 2
) A pre-existing time we can use to mark when the explosion happened;
3) Individual projectiles moving through space from a common center; 4
) A definite moment when the explosion occurred; and 5) Something that
started the Big Bang.
All of these elements to our visualization of the Big Bang are complet
ely false according to GR!
Preexisting Space?
There wasn't any!
The mathematics of GR state specifically and unambiguously that 3-dime
nsional space was created at the Big Bang itself, at 'Time Zero', alon
g with everything else. It was a 'singular' event in which the separat
ions between all particles everywhere, vanished. This is just another
way of saying that our familiar 3-dimensional space vanished. Theorist
s studying various prototypes for the Theory of Everything have only m
odified this statement somewhat. During its earliest moments, the univ
erse may have existed in a nearly incomprehensible state which may hav
e had more than 4 dimensions, or perhaps none at all. Many of these th
eories of the earliest moments hypothesize a 'mother space-time' that
begat our own universe, but you cannot at the same time place your min
ds eye both inside this Mother Spacetime to watch the Big Bang happen,
and inside our universe to see the matter flying around. This is exac
tly what the fireworks display model demands that you do.
Preexisting Time?
There wasn't any of this either!
Again, GR's mathematics treats both space and time together as one obj
ect called 'space-time' which is indivisible. At Time Zero plus a mome
nt, you had a well defined quantity called time. At Time Zero minus a
moment, this same quantity changed its character in the mathematics an
d became 'imaginary'. This is a mathematical warning flag that somethi
ng dreadfully unexpected has happened to time as we know it. In a famo
us quote by Einstein, "...time and space are modes by which we think a
nd not conditions in which we live". Steven Hawking has looked at the
mathematics of this state using the fledgling physics of Quantum Gravi
ty Theory, and confirms that at the Big Bang, time was murdered in the
most thorough way imaginable. It may have been converted into just an
other 'timeless' dimension of space...or so the mathematics seems to s
uggest.
Individual objects moving out from a common center?
Nope!
GR says specifically that space is not a passive stage upon which matt
er plays out its dance, but is a member of the cast. When you treat bo
th galaxies and space-time together, you get a very different answer f
or what happens than if you treat them separately, which is what we in
stinctively always do. Curved space distorts the paths of particles, s
ometimes in very dramatic ways. If you stepped into a space ship and t
ried to travel to the edge of the universe and look beyond, it would b
e impossible. Not only could you not reach a supposed "edge" of the un
iverse no matter how long or how fast you traveled, in a closed univer
se, you would eventually find yourself arriving where you departed. Th
e curvature of space would bring you right back, in something like the
way the curvature of Earth would bring you home if you flew west and
never changed course. In other words, the universe has no edge in spac
e. There is nothing beyond the farthest star.
As a mental anchor, many have used the expanding balloon as an analogy
to the expanding universe. As seen from any one spot on the balloon's
surface, all other spots rush away from it as the balloon is inflated
. There is no one center to the expansion ON THE SURFACE of the balloo
n that is singled out as the center of the Big Bang. This is very diff
erent than the fireworks display which does have a dramatic, common ce
nter to the expanding cloud of cinders. The balloon analogy, however,
is not perfect, because as we watch the balloon, our vantage point is
still within a preexisting larger arena which GR says never existed fo
r the real universe.
The center of the Big Bang was not a point in space, but a point in ti
me! It is a center, not in the fabric of the balloon, but outside it a
long the 4th dimension...time. We cannot see this point anywhere we lo
ok inside the space of our universe out towards the distant galaxies.
You can't see time afterall! We can only see it as we look back in tim
e at the ancient images we get from the most distant objects we can ob
serve. We see a greatly changed, early history of the universe in thes
e images but no unique center to them in space.
It is at this point that common sense must give up its seat on the bus
, and yield to the insights provided by GR. And it is at precisely thi
s point that so many non-physicists refuse to be so courteous. And who
can blame them? But there's more to come.
Projectiles moving through space?
Sorry!
GR again has something very troubling to say about this. For millions
of years we have learned from experience on the savanas of the African
continent and elsewhere, that we can move through space. As we drive
down the highway, we have absolutely no doubts what is happening as we
traverse the distance between landmarks along the roadside. This know
ledge is so primal that we are incapable of mustering much doubt about
it. But science is not about confirming our prejudices. It's about re
vealing how things actually are.
What if I told you that you could decrease the distance from your hous
e and the Washington Monument by 'standing still' and just letting spa
ce contract the distance away? GR predicts exactly this new phenomenon
, and the universe seems to be the only arena we know today in which i
t naturally occurs. Like spots glued to the surface of the balloon at
eternally fixed latitude and longitude points, the galaxies remain whe
re they are while space dilates between them with the passage of time.
There is no reason at all we should find this kind of motion intuitiv
e.
If space is stretching like this, where do the brand new millions of c
ubic light years come from, from one moment to the next? The answer in
GR is that they have always been there. To see how this could happen,
I like to think of the shape of our universe as a "Cosmic Watermellon
". The fact that this is only the shape for a 'closed' finite universe
is only a technicality. Finite watermellons are also cheaper to buy t
han infinite ones.
GR predicts the entire past, present and future of the universe all at
once, and predicts its entire 4-dimensional shape. As we slice the 4-
dimensional, Cosmic Watermellon at one end of the cosmic time line, we
see 3-dimensional space and its contents soon after the Big Bang. At
the other end of the Cosmic Watermellon in the far future, we see the
collapse of space and matter just before the Big Crunch. But in betwee
n, our slices show the shape of space (closed, spherical volumes) and
the locations of galaxies ( at fixed locations) as space dilates from
one extreme to the other.
As a particular slice through an ordinary watermellon, we see that its
meat has always been present in the complete watermellon. The meat is
present as a continuous medium, and we never ask where the meat in a
particular slice came from. Cosmologically, GR ask us to please think
of 3-dimensional space in the same way. Space, like the meat of the wa
termellon, has always existed in the complete shape of the universe in
4-dimensions. But it is only in 4-dimensions that the full shape of t
he universe is revealed. It is a mystery why our consciousness insists
on experiencing the universe one moment at a time, and that is why we
end up with the paradox of where space comes from. There really is no
paradox at all.
Space is not 'nothing' according to Einstein, it is merely another nam
e for the gravitational field of the universe. Einstein once said, "Sp
ace-time does not claim existence on its own but only as a structural
quality of the [gravitational] field". If you could experimentally tur
n-off gravity with a switch, space-time would vanish. This is the ulti
mate demolition experiment known to physics for which an environmental
impact statement would most certainly have to be filed.
The gravitational field at one instant is wedded to itself in the next
instant by the incessant quantum churnings of the myriad of individua
l particles that like bees in a swarm, make up the gravitational field
itself. In this frothing tumult, the gravitational field is knit toge
ther, quantum by quantum, from perhaps even more elemental building bl
ocks, and it is perhaps here that we will find the ultimate origin for
the expansion of the universe and the magical stretching of space. We
hope the much anticipated Theory of Everything will have more to say
about this, but to actually test this theory may require technologies
and human resources that we can only dimly dream of.
Was there a definite moment to the Big Bang?
GR is perfectly happy to forecast that our universe emerged from an in
finite density, zero-space 'Singularity' at Time Zero, but physicists
now feel very strongly that this instant was smeared out by any number
of quantum mechanical effects, so that we can never speak of a time b
efore about 10^-43 seconds after the Big Bang. Just as Gertrude Stein
once remarked about my hometown, Oakland, California that "There is no
'There' there", at 10^-43 seconds, nature may tell us that before the
Big Bang, "There was no 'When' there" either. The moment dissolves aw
ay into some weird quantum fog, and as Steven Hawking speculates, time
may actually become bent into a new dimension of space and no longer
even definable in this state. Ordinary GR is unable to describe this c
ondition and only some future theory combing GR and quantum mechanics
will be able to tell us more. We hope.
Something started the Big Bang!
At last we come to the most difficult issue in modern cosmology. In th
e fireworks display, we can trace the events leading up to the explosi
on all the way back to the chemists that created the gunpowder and wra
pped the explosives. GR, however, can tell us nothing about the equiva
lent stages leading up to the Big Bang, and in fact, among its stronge
st statements is the one that says that time itself may not have exist
ed. How, then, do we speak or think about a condition, or process, tha
t started the whole shebang if we are not even allowed to frame the ev
ent as "This happened first...then this...then kerpowie!"? This remain
s the essential mystery of the Big Bang which seems to doggedly transc
end every mathematical description we can create to describe it.
All of the logical frameworks we know about are based on chains of eve
nts or states. All of our experiences of such chains in the physical w
orld have been ordered in time. Even when the mathematics and the theo
ry tell us 'What happened before the Big Bang to start it?' is not a l
ogical or legitimate question, we insist on viewing this as a proper q
uestion to ask of nature, and we expect a firm answer. But like so man
y other things we have learned this century about the physical world,
our gut instincts about which questions ought to have definite answers
is often flawed when we explore the extreme limits to our physical wo
rld.
I wrote this essay before seeing the new IMAX file at the Air and Spac
e Museum 'Cosmic Journey", by far one of the nicest and most heroic mo
vies of its kind I had ever seen. But of course it showed the Big Bang
as a fireworks display. No matter. It doesn't take a rocket scientist
to accept the fact that the Big Bang was a spectacular moment in hist
ory. What is amazing is that the daring audacity of humans may have de
mystified some of it, and revealed a universe far stranger than any co
uld have imagined.
Still, we are haunted by our hunches and intuitions gathered over mill
enia, and under circumstances far removed from the greater physical wo
rld we are now exploring. No wonder it all seems so alien and maddenin
gly complex.
--
浪子无家，寻梦天涯
※ 来源:．月光软件站 http://www.moon-soft.com．[FROM: 202.106.15.80]
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