Found ‘Em!

Credit: BICEP2 Collaboration

Swirly B-mode pattern.  Credit: BICEP2 Collaboration

Researchers on the BICEP2 project in Antarctica celebrated yesterday. And it wasn’t because of St. Patrick’s Day.

The researchers say they’ve found the first direct evidence of gravitational waves. Physicist Albert Einstein theorized about them more than a century ago. However, no one has directly seen them.

When I wrote about gravity for ODYSSEY last year, physicist Xavier Siemens at the University of Wisconsin-Milwaukee compared gravitational waves to light waves. Shaking around an electric charge generates light, he told me. “When you shake around a mass, you generate a wave of gravity.”

So why were researchers looking for gravitational waves with a microwave telescope in Antarctica? After all, it’s cold year round and pizza delivery is sparse.

“The South Pole is the closest you can get to space and still be on the ground,” explained John Kovac of the Harvard-Smithsonian Center for Astrophysics in a press release announcing the discovery. “It’s one of the driest and clearest locations on Earth, perfect for observing the faint microwaves from the Big Bang.”

Gravitational waves squeeze space as they move, and that distortion causes patterns in the cosmic microwave background. That’s a faint glow of electromagnetic radiation left over from the Big Bang.

Scattering causes the glow to become polarized. Polarization restricts a wave’s vibrations in whole or in part.

Researchers expected gravitational waves would cause polarized microwaves to have a certain type of swirly pattern. And they found it.

“The swirly B-mode pattern is a unique signature of gravitational waves because of their handedness,” Chao-Lin Kuo at Stanford University noted in the press release. Just as your thumbs point in one direction or another, handedness of a wave tells whether its pattern goes to the left or right.

“This is the first direct image of gravitational waves across the primordial sky,” Kuo added.

The researchers hadn’t expected the signal to be as strong as it was, however.

“This has been like looking for a needle in a haystack, but instead we found a crowbar,” Clem Pryke of the University of Minnesota noted in the press release.

Finding evidence of gravitational waves helps confirm physicists’ ideas about what gravity is made of. More importantly, it also acts as confirmation of the Big Bang and the rapid expansion of the early universe.

If further work confirms the discovery, it could open a “new chapter in astronomy, cosmology and physics,” reports the journal Nature.


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