Picture of the Universe

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Dick Jacobson
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Joined: Fri Jun 04, 2004 9:21 pm
Location: Cottage Grove, MN

Picture of the Universe

Post by Dick Jacobson »

How would you depict the entire universe on one piece of paper? Check out the October issue of Astronomy magazine. In the center is a remarkable four-page foldout that tries to picture everything in the universe, or rather the portion of the universe that is detectable from Earth. (The entire universe is estimated to be at least 1000 times larger in volume, and may be infinite.) The vertical scale is logarithmic, increasing by a factor of 10 for each 1.46 inches. At the bottom is the inner core of the Earth. The cosmic microwave background is at the top. On this scale, the nearest stars are near the middle of the chart. The planets are about 1/4 of the way up from the bottom, and the Local Group of galaxies are about 3/4 of the way up. The top 1/8 or so shows the sponge-like pattern of galaxies and quasars as revealed by the Sloan Digital Sky Survey.

The bottom of the chart is arbitrarily set at 1000 kilometers from the center of the Earth. Of course, they could have continued arbitrarily far downward, to the nucleus of the atom that happens to be at the exact center of the Earth and so on. But what do we know of what's down there? Is there anything more interesting than a white-hot hunk of iron? The deepest feature we know about (correct me if I'm wrong, geologists) is the boundary between the solid and liquid core at a little over 1000 kilometers.

If Einstein was right and no information can travel faster than light, we will never be able to extend the top of the chart very much. Maybe gravitational radiation, once we are able to detect it, will allow us to push our knowledge out a bit further. Maybe some day we'll have a rock-solid theory of cosmology that lets us confidently portray unobservable parts of the universe.

Copernicus would probably be displeased with this diagram since it seems to show the Earth at the center of the universe. But when you think about it, the Earth really is at the exact center of the portion of the universe that is observable from Earth (duh)!

Anyway, I think this is a really interesting diagram and is well worth the price of the magazine. I hope they publish a larger poster-sized version of it. The remainder of the magazine contains some articles about cosmology that are interesting but, to my point of view, rather superficial. They tried to over-simplify a very big and complicated subject.
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