The Big Bang
 Q: Can you give a succinct explanation of the Big
Bang Theory? Specifically, how is it possible that
all of the atoms of all of the matter in the Universe
were squeezed together into a tiny point, which
then exploded?
A cloud in the Pleiades star cluster, illuminated by starlight from the nearby star, Merope. [NASA and the Hubble Heritage Team, George Herbig and Theodore Simon
(Institute for Astronomy, University of Hawaii)]
A: That's one good question. Before we get into an
answer, though, let's clear up a common
misconception. The Universe did not start from a
single point.
"The Big Bang was an explosion of space (with
matter carried along), not stuff exploding from a point
into space," says Dr. Michael S. Turner, Chair of the
Department of Astrophysics at the University of
Chicago in recent email.
According to Einstein's general relativity theory, the
Big Bang event was the creation of matter, energy, space, and time. So, Einstein's theory says
there is no such thing as "before" the Big Bang. The Big Bang created space and time itself.
You ask, how could all the matter in the Universe be squeezed together into such a patch and
then explode? Your question addresses the instant of the Big Bang: Time Zero. Our present
theory doesn't cover that early a time: only right after the Big Bang instant.
At time 10^-43 seconds, all matter that we see today occupied a space about one millimeter
across, the distance across the head of a pin. How could everything in the Universe be squeezed
into such a space? "At this time, matter consisted of its most elemental pieces--the quarks and
leptons--which are point-like [in size]", says Turner.
Quarks are too small for us to measure using existing accelerator and experimental methods, so
theorists treat them as point particles. As an upper limit, which physicists determined
experimentally: they must be less than 10^-18 meters.
That's our answer with the best theory we now have: Right after the Big Bang, all matter could
fit within a grain of sand because it was essentially dimensionless: point elements.
Further Surfing:
Cosmology: A research briefing, National Research Council, Board on Physics and Astronomy
Theoretical Astrophysics and Cosmology, University of Chicago
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