Inflation and Cosmology
If all matter started at the one point with a big bang,
how does matter get so far apart that light takes billions of years to
get from there to here on Earth? I understand that the time light takes
to get here is similar to the age of the universe in some cases. Does
that mean the matter went in different directions at greater than the
speed of light relative to each piece of matter?
You need to re-picture your mental image of the "big bang". Your image
(which is very common) is that there was pre-existing space and the "big
bang" was like a fire cracker going off at some point in that space. That
is not the correct way to think about the "big bang". The actual correct
mental image is far less intuitive. The "big bang" CREATED SPACE AND
MATTER. There was no "over here" or "over there". No matter where you are
or I am in the Universe, everything else (on the large scale) is moving
away from you, and everything else (on the large scale) is moving away
from me (including you), because space is expanding away from both of us.
The common analogy used is the surface of a balloon. If you and I are dots
on the surface of the balloon, and the balloon is being blown up, all dots
on the balloon's surface are moving away from every other one because
"space" (the surface of the balloon) is being created everywhere in the
"balloon Universe" as the balloon expands. The theory of relativity
predicts, and all experimental observations to date confirm, that nothing
that transports information (matter, in this sense, is a type of
information) can travel faster than the speed of light, c ~ 3x10^8
meters/sec. Furthermore, the speed of light you measure somewhere in the
Universe is the same as the value I would measure somewhere else in the
Universe. What this means (and as non-intuitive as it seems) is that it
does not matter whether you and I are moving toward one another or away
from one another, if I send you a message (at the speed of light) your
measured value of 'c' will be the same no matter what our relative motion
is with respect to one another.
Now there are some unresolved issues with regard to the expansion of the
Universe. The first is the large scale structure of galaxies. You have no
doubt seen pictures of spiral-shaped galaxies. "Intuitively" one expects
that stars and matter should spin more slowly the further you move from the
center of the spiral. That is what happens in spiral motions we view (the
whirlpool formed by an emptying sink, a hurricane, etc.). However, for
galactic motion that is not happening. Somehow the outside parts of the
spiral is "keeping up with" the inner parts of the spinning galaxy. This can
be explained? if there is unobservable matter in the outer parts of the
spinning galaxy -- so called "dark matter". In addition, the expansion of
galaxies (on the large scale) seems to be accelerating faster than can be
accounted for by current cosmological models. There appears to be some sort
of unobserved "dark energy" driving galaxies apart faster than they "should
be". To make matters more humbling, the amount of "dark matter and dark
energy" needs to be about 90% of the matter and energy of the Universe. What
we are able to observe accounts for only about 10%. What this "dark stuff"
is no one knows.
There is another disturbing unresolved issue. The "standard model" of
the Universe predicts that there should be equal amounts of matter and
anti-matter (identical to matter but with the opposite charge). But this
anti-matter is missing. It "should" be easily observable when it reacts with
regular matter to produce characteristic energy:
E = m*c^2. This happens when anti-matter is created in the laboratory, but
it has not been observed astronomically. So, where is it? Where did it go?
Why is it not around? No one knows.
The bottom line is this. There is a lot we do not understand about the
Universe around us.
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Update: June 2012