Although astronomers understand what the universe
was like just a few seconds after the Big Bang, no one yet knows
what happened at the instant of the Big Bang - or what came before.
What powered the Big Bang? Where did all the stuff in the universe
come from in the first place? What was the universe like just before
the Big Bang?
Scientists have developed a number of new ideas about what might
have powered the Big Bang. They are also creating bold new space
missions to test these ideas.
The leading idea is called the "inflationary universe" model.
The key assumption of this model is that just before the Big
Bang, space was filled with an unstable form of energy, whose
nature is not yet known. At some instant, this energy was transformed
into the fundamental particles from which arose all the matter
we observe today. That instant marks what we call the Big Bang.
A remarkable consequence of this model is that, if even a pinpoint
of space contained this primordial form of energy, then the pinpoint
of space would expand extremely rapidly and would bring into
existence more of the same kind of energy. In fact, all the
matter in the universe could have arisen from a bit of primordial
energy weighing no more than a pea. This amazing scenario is a
consequence of applying Einstein's theory of gravity to the inflationary
universe model. Thus the known laws of nature can in principle
explain where the matter and energy in the universe came from,
provided there was at least a tiny seed of energy to begin with.
A model is useful only if it makes predictions that can be tested
with evidence. The inflation model makes several testable predictions. One
of the most important is that the primordial energy would have
been "lumpy" - i.e., unevenly spread out in space - due
to a kind of quantum noise that arose when the universe was extremely
small. This pattern would have been transferred to the particles
that burst into existence during the Big Bang. As a result, the
matter that filled the universe then would not have been uniformly
spread out; some regions would have slightly more matter, some
slightly less. This lumpiness of the baby universe is fortunate
for us: Had the universe been uniformly filled with matter, then
stars and planets would never have formed. We wouldn't be here.
Evidence for the inflationary model of the universe.
the inflationary universe model is correct, then we should see
this lumpy pattern in the afterglow from the Big Bang. Astronomers
have observed exactly this predicted pattern, in a spectacular
picture of the Big Bang's afterglow, taken in 2003 by NASA's WMAP
space probe. The picture shows us what the universe
looked like about 300,000 years after the instant of the Big Bang.
The inflationary universe model is important because, for the
first time, it gives us a glimpse of how nature may have arranged
to create all the matter in the universe: only a tiny "seed" amount
of space and energy would have sufficed.
But what was this primordial form of energy? And where
did the "seed" of space and energy come from in the first
place? How did the universe as a whole begin? Explore more in the next