for National Geographic News
Dark energy, a mysterious force proposed more than a decade ago to explain why the universe is flying apart at an increasingly faster clip, is no longer necessary.
That's the conclusion of a controversial new theory that shows how the accelerated expansion of the universe could be just an illusion.
In a new study, two mathematicians present their solutions to Einstein's field equations of general relativity, which describe the relationship between gravity and matter.
The work suggests that our home galaxy sits inside a vast region of space in which there's an unusually low density of matter due to a post-big bang wave that swept through the universe.
From our viewpoint, other galaxies outside this region appear to have moved farther away than expected, when really they're right where they should be.
"If correct, these solutions can account for the anomalous accelerated expansion of galaxies without dark energy," said study team member Blake Temple of the University of California, Davis.
Other experts call the attempt to excise dark energy from models of the universe "commendable." But the same scientists note that the new theory could violate a cornerstone of modern cosmology, which would make dark energy's demise very hard for astronomers to accept.
Dark Energy Alternative
Until 1998 astronomers had thought that gravity should be slowing down the cosmic expansion triggered by the big bang.
That year two independent teams announced data showing that the universe's expansion is speeding up.
Both teams saw that light from distant supernovae appears much fainter than expected—suggesting that the explosions are farther away than they should be if the universe is being driven by the pull of gravity alone.
To explain this observation, astronomers started to entertain the idea of dark energy, a universal repulsive force that is pushing apart the very fabric of space-time.
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