It Turned Out The Universe Was Expanding After All

Almost a century ago, a lot of scientists didn't want to believe that the universe was expanding, because that might imply that there was a moment of creation. They ended up being proved wrong. That doesn't prove there's a God, of course, but it's still an interesting story, as discussed in the continuation of this posting.

For a long time, many scientists tended to assume that the universe was eternal and static. This may have come from a science vs. religion mindset. Some scientists refused to consider any theory that might involve the universe having an origin, because that would imply that it might have had a creator.

In 1915, Einstein published his Theory of General Relativity. He had developed some mathematical equations relating to the curvature of a four-dimensional space-time. Those equations had some solutions which indicated that the universe was either expanding or contracting. Einstein didn’t like that idea, so he added a fudge factor to the equations to eliminate that possibility. The fudge factor was called the cosmological constant.

But not everyone assumed that the universe was eternal and static. Georges Lemaître was a Belgian astronomer who had a PhD from MIT; he also happened to be a Roman Catholic priest. Lemaître suggested that the universe was indeed expanding, and that the expansion had started out when the universe was like a primordial atom.

Lemaître's primordial-atom theory wasn’t a very popular theory with astronomers, who were largely still hooked on the static-universe assumption. Einstein rejected LeMaitre’s idea, although he later came around. Science values real-world data very highly, however. More data kept coming in from people doing observations. Some astronomers had observed that the light from distant galaxies was “red-shifted.” This is the Doppler effect that we can see in everyday life.

(The Doppler shift is like being stopped at a railroad crossing. The train is coming. The engineer in the locomotive is blowing the whistle. As the locomotive moves past you, you’ll hear the pitch of the whistle drop slightly. That's the Doppler effect. Astronomers were noticing the same thing in the light that they were getting from distant stars -- the “pitch” or “tone” of the light from the stars was lower than they expected, and this was true no matter what direction one looked.)

This red-shifting of starlight from every direction suggested that galaxies are moving away from each other. The only logical explanation was that the universe itself is expanding. Suppose that you put small dots of white paint onto a balloon, and then blow the balloon up. Every dot will move away from every other dot. That’s what astronomers were observing.

Edwin Hubble, for whom the Hubble Space Telescope is named, figured this out. He based his conclusion on his own work and on earlier red-shifting observations by Vesto Slipher at the Lowell Observatory in Arizona. (See the Web page Evolution of Modern Cosmology for more background information about red-shifting.)

The implication was that the universe was indeed smaller in the past. This was quite a revolutionary idea. It led eventually to the Big Bang theory - about which more in a later blog posting.