|How old is the Universe?
|Question Date: 2003-03-20|
The universe is somewhere between 10 and 20
billion years old. This is a wide range and
scientists are working on getting a better answer.
If you do some research, you may be able to find a
more accurate answer than what I have given.
We think it is about 13 billion years old, but we
can't say for sure. We believe that it is older
than 10 or 11 billion years, but younger than 15
billion years. This is one of the biggest
questions of modern astronomy and cosmology!
The Big Bang created the universe 14 billion years
ago, so it would be impossible to see anything
farther than 14 billion light years away, because
nothing existed- not even space or time. The most
distant thing we can see is the fading fireball of
the Big Bang itself, a bit less than 14 billion
light years away. We can't see the first instant
of the Big Bang, because the universe was too hot
and dense- it only became transparent when it
cooled to a few thousand degrees. We see the
fireball in any direction we look, because the Big
bang occurred everywhere- even here. This is
because space itself has expanded. At the time of
the Big Bang, space was a single point, so
everywhere in the universe was all the same place
(sounds like a garbled sentence- but the wording
is correct!) The expansion of space has
"redshifted" the fireball far down the
electromagnetic spectrum- down past red and infra
red, all the way to microwaves- so its now called
the "cosmic microwave background". Redshifting is
similar to the reduction of a sound's pitch as the
source speeds away from you. If not for this
phenomenon the fireball would still be bright,
like a sun covering the entire sky. Nothing in
space could be colder than the fireball, so the
temperature of space would be a few thousand
degrees. Thanks to the extreme redshift, we
receive only a small fraction of the fireball's
original heat. It is possible for objects in dark,
empty space to cool down to about -415 degrees
Fahrenheit, or 5 degrees above absolute zero. This
is the temperature of space!
As you can probably imagine, this is a hard number
to measure, and I don't entirely understand how it
is done. However, I've heard that astronomers
think the universe is 11.2-20 billion years old.
This is a question that is guaranteed to create
lots of argument,even among scientists. Current
cosmology models place the age at between13 and 15
billion years old. By this measure, the sun is a
youngster at4.5 billion years old. This age is
determined by measuring the rate of expansion of
the visible universe and extrapolating back to the
when it started expanding (the big bang). This
time agrees fairly well with the age as determined
by the oldest stars, using models of stellar aging.
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