Far out cosmology: LIGO and BICEPS2 differ (Introduction)

by David Turell , Thursday, January 14, 2016, 19:53 (3234 days ago) @ David Turell

BICEPS2 looks for primordial waves from the Big Bang. LEGO looks for current waves from collisions between massive objects like black holes:-http://www.scientificamerican.com/article/not-all-gravitational-waves-are-created-equal/?WT.mc_id=SA_DD_20160114-"LIGO searches for powerful gravitational waves created by some of the most violent events in the cosmos, such as collisions between black holes or dense objects called neutron stars. “They're looking for the most cataclysmic events you could imagine happening in our galaxy or nearby galaxies,” says Lawrence Krauss, a physicist at Arizona State University in Tempe who is not involved in the experiment and tweeted about his excitement over the rumors. “The mass is so great in such a small area that the gravitational fields are strong enough that most of the energy of the collision would be emitted in the form of gravitational waves.”-"Gravitational waves are a prediction of Albert Einstein's general relativity, which explained that gravity results from a curvature in spacetime. Whenever mass moves through space it warps the geometry of the universe around it, causing other nearby traveling masses to move along curving paths.-***-"The gravitational waves LIGO is looking for are thought to arise every so often in the modern universe around us. BICEP2, on the other hand, targets primordial gravitational waves born in the very early universe. Based at the South Pole, BICEP2 studies the cosmic microwave background (CMB) light released just some 380,000 years after the big bang and looks not for the waves themselves but for a signature they might have left in the light. The telescope is searching for imprints in the CMB of gravitational waves that might have been created if the universe ballooned rapidly in size immediately after its birth, as predicted by a theory called inflation. According to inflation, tiny random quantum fluctuations in spacetime would have stretched along with the universe, producing gravitational waves that would have left polarization—that is, a special orientation of the light waves—in the CMB.-***-"A discovery of either primordial or contemporary gravitational waves would be a major breakthrough, but for different reasons. “The gravitational waves that BICEP2 was trying to detect would have been a signal from the very early universe,” says Marc Kamionkowski, an astrophysicist at Johns Hopkins University who predicted in 1997 how primordial gravitational wave imprints could be found. The discovery would have offered proof for inflation theory and could have revealed details about how the first moments of cosmic history played out. LIGO's gravitational waves, if they are real, would probe how gravity works in extreme objects such as neutron stars and black holes, where current physics theories break down. And whereas BICEP2 seeks imprints on the CMB light created by gravitational waves, LIGO is aiming to directly detect the waves themselves, which would be a first.-Comment: Discovery of both types would confirm Einstein's space-time gravity theory and also inflation theory with solid evidence.