The Hubble Expansion

Red Dots (0.5MB)

This movie shows "rubber sheet" model of an expanding Universe. The Universe is a rubber sheet, and the galaxies are red dots pasted on to the surface of that rubber sheet. As the Universe expands, the dots get farther from each other.

Red & Blue Dots (0.6 MB)

Just like the last movie, except that a blue dot is left behind from where the red dot started. The end state gives you a nice visual description of a uniform expansion. One can see two things. First, from the point of view of the galaxy at the center of the expansion, the expansion looks the same in all directions. Second, the rate at which a galaxy moves away is proportional to its distance. (Two galaxies over, over the time of the animation the galaxy has moved about one dot-width farther away. Four galaxies over, it has moved about two dot-widths farther away.)

Red & Blue Dots Redux (0.6 MB)

So why are we so lucky as to be at the center of the cosmological expansion? The answer is, we are at the center, but we aren't so lucky; everybody is just as much at the center. This movie does the same expansion as the last two, stretching the rubber sheet, but rather than lining it up on a galaxy in the center, it lines up the before and after states on a galaxy down and to the right.

This movie was made entirely in the Gimp (using a Gimp-Perl plugin to render the dots in appropriate places).

These movies emulate a demonstration that Saul Perlmutter does in public lectures using two transparencies (one filled with red dots, one with blue dots).

This work is licensed under a Creative Commons License.

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