New calculations have just been completed that show the rate of expansion for the universe. By zeroing in on the rate, the Hubble Constant, these calculations hammer another nail the casket of a quirky little idea called Void Theory.
Image: Nasa STS-103
In the late nineties, physicists noticed that distant supernovas were dimmer than they should have been. After some observation, some debate, and a lot of thinking, they came up with a reason for this. The universe was expanding. The problem was, something had to be making it expand. This something was dubbed 'dark energy', and it sounded like a truckload of hooey. It was a mysterious force that was a little like gravity, only repulsive instead of attractive. It didn't seem to fit into any coherent mathematical models. It just - was there, shoving the universe asunder. The farther apart two astronomical bodies were, the quicker they moved away from each other.
Dark energy seemed preposterous, until someone came up with a competing theory that just happened to overturn everything astronomy took for granted since Copernicus. There was a time that the earth was considered the center of the universe. Then it got knocked out of the way by the sun, and ever since then the astronomer's mantra was, "We are nothing special." The part of the universe the earth resides in can't be any different than any other part. It's not unique, or remarkable, or even out of the ordinary. Void Theory contradicts all that. Instead of sitting in a typical part of the universe, the earth sits in an unusually empty part; a void. The universe isn't expanding due to some mysterious force. It's just that when light comes from a denser part of the universe and trips across the void, it is altered to make it look like the universe is expanding. Since this exansion is the same when observed from any part of the earth, the earth has to be roughly at the center of this void. Suddenly, the observable universe is geocentric again.
Void Theory was met with skepticism from the beginning. Over time, more and more evidence has built up against it. The distribution of the background radiation left over from the big bang put a big dent in the theory, as did the apparent rate at which the universe appeared to be expanding. It was considered too fast to support void theory. But since the measured rate had a significant margin of error, the Void Theory struggled along. The latest study has put a bullet in its head. The Hubble Constant - the expansion rate - has been calculated with a three percent margin of error. The constant is 73.8 kilometers per second per megaparsec. A parsec is 3.26 light-years, and a megaparsec is a million parsecs. Every added 3.26 million parsecs between two objects adds 73.8 kilometers per second on to the speed at which they're receding from one another. That, apparently, is too fast for Void Theory to catch up. The universe is not avoiding the earth, and dark energy wins the day.
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Via Science News, New Scientist, and Universe Today.