Day #5, Tuesday, January 28, 1997: The goal today is to explore the
question "From where did
we come?" The answer is that the universe was born out of
The start of our quest for our origins is in the discovery in
1929 by Edwin Hubble that galaxies are moving away from us. Except
for members of our "local group" of galaxies, lying
within a few million light years from us, every galaxy in the
.and we mean every one
is moving away from
us as though we suffered from a severe case of cosmic body odor.
The further a galaxy is from us, the faster is it moving away.
One of Hubble's startling discoveries was that the speed of recession
increases directly proportional to distance. A galaxy that is
twice as far as another is traveling twice as fast; one that is
100 time more distant is traveling 100 time faster! Very strange!
This proportionality of velocity and distance is known as the
Hubble relationship and can be written V=Hxd, where V is velocity,
H is the so-called Hubble constant, and d is distance.
An even stranger feature of this relationship is that at a sufficiently
great distance from the earth, galaxies should be moving at the
speed of light. IMPOSSIBLE As far as we know, nothing in our universe
can travel faster than light. The distance at which galaxies would
be traveling at light speed is about 15 billion light years. No
galaxy can exist beyond it for it would be traveling faster than
light, and could not be inside our universe.
Space ends thus at a distance of 15 billion light years. So too
does time end, 15 billion years in the past.
Since we travel back in time as we move out in space, the edge
of space is also the edge of time. Our universe can not be older
than 15 billion years; we and everything within our universe were
born 15 billion years ago.
What was the universe like at that time? IT WAS SMALL. AND HOT
We can imagine traveling backward in time like running a movie
backward. In the smaller universe, the same amount of matter and
energy was concentrated in smaller amounts of space, and therefore
the energy density would have been larger and the temperature
would have been higher. Smaller and smaller as we go into the
past: hotter, hotter, and hotter. Our average temperature of the
universe is now 2.7 degrees above absolute zero. At the earliest
time we can imagine, the temperature was 1032 K; that
time corresponds to the end of Primordial Chaos, which was 10-43
seconds after creation. At that time, the average density
of tèe universe was astonishingly high, 1092
grams per cubic centimeter.
At earlier times, the universe was totally chaotic. Space and
time were so chaotic, that there was no sequence of time or organization
of space. The universe at that time was too young for messages
traveling at the speed of light to move from one particle to another,
and all was therefore in darkness and ignorance: no gravity, There
was soo much chaos that there was NO PHYSICS, and that is chaotic,
believe me. Because of this layer of primordial chaos (extending
from time=0 to 10-43 seconds) around the actual moment
of creation, we can never explore the actual moment of creation
with our physics. It will remain forever outside of our ability
to explore, The instant of creation is like what ever lies beyond
the edge of space: FOREVER UNKNOWN.
This very early universe, which was incredibly small and incredibly
hot, is what we mean by the BIG BANG: immense temperatures and
densities that could not be contained and exploded. In that explosion
chaos was converted to order.
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