Sunday, March 16, 2014

Have Physicists Finally Detected Gravitational Waves? (via io9)

From the io9 Space page, the has been an announcement of an impending announcement, i.e., today it was announced that there will be a press conference tomorrow by the Harvard-Smithsonian Center for Astrophysics. The speculation is that they may announce having discovered gravitational waves (the last predicted by unseen element in Einstein's General Theory of Relativity).

Have physicists finally detected gravitational waves?


Mika McKinnon

The Harvard-Smithsonian Center for Astrophysics has news so big it announced that it would announce something. The press conference will stream live tomorrow at noon, but cosmologists everywhere are gossiping about what that news could be. The leading theory: Scientists have detected gravitational waves, in what would be a landmark discovery for the field of physics.

Gravitational waves are the last chunk of Einstein's General Theory of Relativity that was predicted but not yet observed. If gravitational waves have been observed, it most likely was done by the Background Imaging of Cosmic Extragalactic Polarization (Bicep) telescope at the south pole. It stared at the cosmic microwave background radiation from 2003 to 2008, but it takes a long time to process and analyze the data when looking for a faint signal in a lot of noise.

2007 photograph of telescopes at the Dark Center at the Amundsen-Scott South Pole Station. From top to bottom, the partly-buried AST/RO, QUaD, Viper, and finally BICEP and SPT at the bottom. Image credit: Robert Schwarz
The Bicep mission page describes anticipated gravitational waves as faint, polarized, and distorted by gravitational lensing of objects between us and the cosmic microwave background radiation. They released a video of their observations in 2008. The colour scale adjusts throughout the movie to highlight temperature fluctuations of both the cosmic microwave background radiation, and the galactic plane:


Why look at the cosmic microwave background radiation for signs of gravitational waves? Because an infinitesimal moment after the universe started — 10-34 seconds after the big bang — we think it went through an inflationary period. If it did, that inflation could have amplified gravitational waves to such an extent that we can actually detect them. This would not only fill in that last missing chunk of things predicted by General Relativity that we haven't seen yet, but also offer a glimpse into the primeval universe. They won't be insta-proof that inflationary theory is correct, but they would rule out some cyclic theories for the origin of the universe.

Some pre-announcement articles are already mixing up very common gravity waves with gravitational waves. To differentiate, I'll pass things off to an exasperated Dr. Katherine Mack:

Katie Mack @AstroKatie GRAVITY WAVES are a fluid dynamics thing; we see them all the time: http://en.wikipedia.org/wiki/Gravity_wave … GRAVITATIONAL WAVES are ripples in spacetime. 
15 Mar  

People use "gravity waves" to mean "gravitational waves" constantly, so probably any clarification is a lost cause, but had to say it.

Gravity waves are common phenomena in both the ocean and the sky, as seen in this MODIS image. Read more about them at the Earth Observatory.
As for the press conference, I'm already bracing for disappointment. "Breaking news! We'll have breaking news for you on Monday!" announcements produce so much hype that the actual discovery probably won't live up to expectations. I'm not the only one feeling that way — the Guardian ran an entire piece interviewing cautiously excited cosmologists warning that the observations would need to be highly robust if they're going to be momentous.
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