Inflation and Cosmology ```Name: Mike Status: other Grade: other Location: N/A Country: N/A Date: 4/2/2005 ``` Question: 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? Replies: 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. Vince Calder Click here to return to the Astronomy Archives

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