Far out cosmology: LIGO finds waves? Yes!!! (Introduction)

by David Turell , Thursday, February 11, 2016, 19:42 (3206 days ago) @ David Turell

More commentary on the discovery:-http://www.scientificamerican.com/article/not-all-gravitational-waves-are-created-equal/?WT.mc_id=SA_IDR_20160211-"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. “Every time I move my arms my body is changing the curvature of space around me, which produces a ripple in spacetime,” Krauss says. “It's just that those gravitational waves are so small” they are imperceptible. LIGO uses detectors in Louisiana and Washington State to search for tiny differences in the time it takes light to travel down perpendicular pathways. The pathways are the same length but if a gravitational wave passed by, it would stretch spacetime in one direction, causing only one of the two pathways to expand and thus inducing a minute difference in the travel time for the light. “They have to measure a path difference smaller than one one-hundredth of a proton,” Krauss says. “It's amazing they can do that.”-"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. In April 2015 the team announced, to much fanfare, that they had discovered this polarization. But later studies revealed that what they saw is most likely contamination from nearby dust in our galaxy.-***-"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 Again, wow!