More support for the existence of dark energy

The case for dark energy is looking stronger, thanks to new results from the recently-installed Wide Field Camera 3 instrument aboard the Hubble Space Telescope. Dark energy has been hypothesized as the mysterious force causing the expansion of the universe to speed up, but competing models suggest other reasons for the accelerated expansion. A leading competitor is a bubble model that suggests our Milky Way galaxy sits at the center of a relatively sparse region of the universe, and the resulting weaker gravity is causing our local “bubble” to expand more rapidly than the universe as a whole. However, astrophysicists at the Space Telescope Science Institute claim that refined measurements made with the WFC3 have ruled out the bubble model, which predicts a different expansion rate than what is observed.

There are philosophical objections to the bubble model, as well. Ever since Copernicus put forth his Sun-centered model of the solar system, scientists have tended to reject the notion that we occupy any special place in the universe. A model that requires Earth-observers to be at the center of a cosmic bubble makes us a little too special for comfort for most scientists. This alone doesn’t disprove the model (we must never be locked into a conclusion by our philosophy), but it can certainly offer guidance. Adam Riess, head of the research team publishing the new results, comments,

“I know that a lot of people have not taken that theory very seriously because of a major problem with it,” he said. “We tend to believe theories where we don’t live in any special place in the universe. That would be very strange – why should we be in a special place?”

Now that scenario is even less likely to be true, Riess said.

“But on the other hand, dark energy’s pretty weird too,” he said.

Every revolutionary idea in science seems weird at first. If the dark energy model survives the rigors of scientific testing, people a hundred years from now probably won’t find it any weirder than we find the electromagnetic theory of light.

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