'Accelerating universe' could be just an illusion

[Tenet Nosce]

'Accelerating universe' could be just an illusion

If true, theory would rid cosmology of its biggest headache — dark energy

Now, a new theory suggests that the accelerating expansion of the universe is merely an illusion, akin to a mirage in the desert. The false impression results from the way our particular region of the cosmos is drifting through the rest of space, said Christos Tsagas, a cosmologist at Aristotle University of Thessaloniki in Greece. Our relative motion makes it look like the universe as a whole is expanding faster and faster, while in actuality, its expansion is slowing down — just as would be expected from what we know about gravity.

In a series of papers over the past three years, Kashlinsky and his colleagues have shown that the huge region of space-time in which we live — a region at least 2.5 billion light-years across — is moving relative to the rest of the universe, and fast.

"My article discusses how observers living inside such a large-scale 'dark flow' could arrive at the (false) conclusion that the universe is accelerating, while it is actually decelerating," Tsagas told Life's Little Mysteries. In his paper, he illustrates that dark flow would cause the space-time within our moving bubble to expand faster than the space-time outside of it (which is not accelerating). Without considering the dark flow, but just knowing that light we observe from nearby galaxies left its source more recently than light from galaxies farther away, we get the false impression that the whole of space-time recently entered an accelerating phase.

In short, Tsagas' explains our observations of the expansion of space-time nearby and far away without invoking dark energy, or any other mysterious mechanism. According to Tsagas' work, the acceleration of the universe in our immediate vicinity is caused by its motion alone. The universe beyond our region isn't accelerating outward; rather, it is safely rolling to a stop.