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New findings on dark energy back discarded Einstein theory

Scientists have found that dark energy, the force thought to be accelerating the expansion of the universe, may be doing the same thing to local groups of galaxies. That bolsters Einstein's idea of a 'cosmological constant.'

This Dec. 16, 2008 file photo, shows the galaxy cluster Abell 85, located about 740 million light years from Earth. Galaxy clusters are the largest collapsed objects in the Universe and are ideal for studying the properties of dark energy, the mysterious form of repulsive gravity that is driving the accelerated expansion of the Universe.


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Ten years ago, astronomers made the stunning discovery that the universe is expanding at a faster rate than it should, given the amount of matter the cosmos contains. Scientists named the driving force behind the unexpected acceleration dark energy.

Now a team of astronomers is reporting observations showing that this mysterious force not only works on cosmic scales spanning billions of light years. It's also affecting members of the Milky Way's local group of galaxies.

That strongly suggests that dark energy's effects are constant over time and space, arguing in favor of Albert Einstein's original notion of a cosmological constant that prevented the universe from ultimately collapsing under its own gravity, the team says. Einstein ultimately discarded the idea as his biggest blunder.

In principle, mutual gravity binds the 30-odd galaxies in the Milky Way’s local group together. But the team found that dark energy is driving the group's most distant galaxies away from the group, in the same way it does on vastly larger scales.

"We have an outflow that is consistent on the scale of millions of light years with the value of the dark energy that's obtained by studying galaxies billions of light years away," says University of Alabama astronomer Gene Byrd, a member of the team. He described the results at a briefing today at the American Astronomical Society's winter meeting in Washington.

Einstein's 'blunder'

Einstein was convinced the universe was static, neither expanding nor contracting. Yet his theory of general relativity implied that gravity from all the matter in the universe should cause it to contract. So he introduced the idea of a cosmological constant, a repulsive force that canceled out the contraction. He later discarded the in large part because astronomer Edwin Hubble discovered that the universe was in fact expanding and not static.


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