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Name: Liu J.
Status: student
Age: 15
Location: N/A
Country: N/A
Date: 4/12/2004


Question:
What is the cosmic background radiation? Is this like the 'barrier' of the universe?


Replies:
It is, sort of, but edge of time, not space. Not the present edge of space, but the beginning edge of time. Cosmic background radiation is though to be the last faint remaining heat-glow we see from the "big bang" when the universe was very small and all hot. This light has sailed around everywhere for billions of years, always getting cooler and fainter. It was there before all the stars and galaxies, so now it looks like it comes from "behind" them all. Remember, because of the limited speed of light, the farther away we see, the older the scene is.

We cannot see any "edge of space" anywhere around us. Seems like the universe is only about 15 billion years old, but it is bigger than light can cross in that time. I think we are not sure about all this yet. Debate is ongoing, and mixed up with "missing mass / dark matter" questions. Just like there are not enough dinosaur bones to be sure of everything, there are not enough space-objects visible at the farthest reaches of sight.

Think of it this way: Suppose you close your eyes and try to "see" by shooting a squirt-gun in various directions around the room and listening for the splatter when it hits. Your water stream always arcs downwards due to gravity. In a big room, all you will ever "see" is the floor. And even that, only to about 30 feet away. In a large enough room, you could have problems figuring out of walls even exist, let alone how big the room is.

Well, our "sight-lines" always slant backwards in time (1 year of time, for each light-year of distance), because the speed of light is limited. So, far enough away, all we can see is the beginning of time. If there is one. Kind of looks like there is.

So far, our universe is very good at not showing any "barriers" other than the speed of light and maybe the big bang.

Jim Swenson



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