Evan Pederson's Profile

Scientists first detected the acceleration by noting that distant supernovae seemed to be moving away from us faster than they should be.

One type of supernova (called Type Ia) is a useful distance indicator, because the explosions always have the same intrinsic brightness.

Since light gets dimmer the farther it travels, that means that when the supernovae appear faint to us, they are far away, and when they appear bright, they are closer in.

But if we happened to be in a portion of the universe with less matter in it than normal, then the space-time around us would be different than it is outside, because matter warps space-time.

Light travelling from supernovae outside our bubble would appear dimmer, because the light would diverge more than we would expect once it got inside our void.

One problem with the void idea, though, is that it negates a principle that has reigned in astronomy for more than 450 years: namely, that our place in the universe isn't special.

When Nicholas Copernicus argued that it made much more sense for the Earth to be revolving around the sun than vice versa, it revolutionized science.

Since then, most theories have to pass the Copernican test. If they require our planet to be unique, or our position to be exalted, the ideas often seem unlikely.

"This idea that we live in a void would really be a statement that we live in a special place," Clifton told SPACE.com. "The regular cosmological model is based on the idea that where we live is a typical place in the universe. This would be a contradiction to the Copernican principle."

Clifton, along with Oxford researchers Pedro G. Ferreira and Kate Land, say that in coming years we may be able to distinguish between dark energy and the void.

They point to the upcoming Joint Dark Energy Mission, planned by NASA and the U.S. Department of Energy to launch in 2014 or 2015.

The satellite aims to measure the expansion of the universe precisely by observing about 2,300 supernovae.

The scientists suggest that by looking at a large number of supernovae in a certain region of the universe, they should be able to tell whether the objects are really accelerating away, or if their light is merely being distorted in a void.

The new study will be detailed in an upcoming issue of the journal Physical Review Letters.