is the center of the Universe?
Here, there, and everywhere.
by Paul Doherty, Exploratorium Teacher Institute
When astronomers look at distant galaxies to determine how fast they're moving, it looks like they're all moving away from us. Does that mean we're at the center of the universe? Well, no. It turns out that every point in the universe sees itself as the center! You can show yourself why with this activity.
- Use your mouse to drag the top (blue circle) layer randomly over the bottom one, the difference between the two is hard to see. But if you place the top layer so that one of its dots lines up with the same dot on the bottom layer, you'll notice a pattern: it looks like the dot you've chosen is the center of the expansion.
- Now choose a different dot on the top layer and line it up with its corresponding dot on the bottom layer. Once again, the universe seems to expand around that position. This will be true of any point you choose in our model universe. No matter where you are, it looks like the universe is expanding away from you!
What's going on?
The top layer (the universe today) was made by enlarging the bottom layer (the universe 1 billion years ago) by 5% percent. That means every space on the top layer is enlarged by 5 percent. The real universe is the same: in a billion years all of the spaces between galaxy clusters has expanded by about 5 percent. Viewed from any point, the universe seems to be expanding about that point.
© 2001 Exploratorium