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How the Universe Expands
Large-Scale StructureSome months ago, I read an article on astronomy in the New York Times that changed my whole concept of what the universe is like.
Let me start by explaining what I knew previously. First, there's the solar system, consisting of the sun, the planets, and whatnot. Next, there's the galaxy—the sun is one of the zillion stars that make up the galaxy, and lies near the edge of one of the spiral arms. (According to Principles of Astronomy, the actual number of stars is on the order of 100 billion.) After that, there are other galaxies. On the one hand, the galaxies can be thought of as organized into clusters of galaxies, and superclusters of clusters, presumably with some nice fractal structure. On the other hand, the galaxies (and hence the clusters and superclusters) can also be seen to be organized in other ways, the most notable example being the wall of galaxies known as the “great wall”.
That was as much as anyone knew, because every time we became able to observe at greater distances, we saw new and different things.
Now I can tell you about that article. A new survey of distant galaxies had been performed, with the following result.
… it confirmed a fundamental assumption about the birth of the universe: that cosmic structures have a maximum size, a limit called the “end of greatness.”
That, by itself, wouldn't have done much for me; what really did it was the picture, a plot in which each point represented an entire galaxy of stars. I found the same picture online, in a press release from the survey group.
It may be that “continents” is the correct imagery, but to me the pictures, and the name “great wall”, suggest something else: a big mess of soap bubbles all stuck together, with the galaxies being the soap film.
@ October (2000)