The Physical Review Letters paper has free access. http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.116.061102 -- Gene From: Warren D Smith <warren.wds@gmail.com> To: math-fun@mailman.xmission.com Sent: Thursday, February 11, 2016 12:06 PM Subject: [math-fun] Gravitational waves found news media now onto it: https://www.washingtonpost.com/news/speaking-of-science/wp/2016/02/11/cosmic... https://www.theguardian.com/science/2016/feb/11/gravitational-waves-discover... http://www.bbc.com/news/science-environment-35524440 "The published paper names a staggering 1,004 individual authors... It was a clear, compelling signal of two black holes coalescing, LIGO scientists said. It lasted less than half a second... These black holes were each approximately the diameter of a major metropolis. They orbited one another at a furious pace at the very end, speeding up to about 75 orbits per second -- warping the space around them like a blender cranked to infinity -- until finally the two black holes became one... LIGO scientists said they are analyzing additional data from the observational run lasting from September to early January, and that they may find other signs of black hole mergers. One candidate for such an event, picked up in October, is still being analyzed, they said... One of the two black holes had a mass about 36 times greater than our sun. The other registered at 29 solar masses. Both were rather massive as black holes go -- 10 solar masses is more typical...the resulting black hole was not the 65 solar masses you'd expect from basic arithmetic, but only 62. The rest was converted to energy that radiated across space in a grand gravitational burp...That burp first reached the LIGO facility in Louisiana, then the one in Washington state just 7 milliseconds later. The sequence is important, as it allowed physicists to chart the black-hole collision back to somewhere in the southern sky. And the incredibly brief time delay supports something that theorists have long believed about gravitational waves: They move at the speed of light...LIGO is still only about a third as sensitive as it is designed to be, and improvements in coming months should let it pick up signals from deeper regions of space, the scientists said." The paper is in PHYSICAL REVIEW LETTER and something also is in SCIENCE magazine: http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripple... https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102
From which we find: Incredibly, these two black holes are believed to have been 1.3 billion light years away... the signal hit us on 14 September 2015... the wave stretched space around here by about 1 part in 10^21, "making the entire Earth expand and contract by 1/100,000 of a nanometer... The oscillation emerged at a frequency of 35 cycles per second, or Hertz, and sped up to 250 Hz before disappearing 0.25 seconds later. The increasing frequency, or chirp, jibes with two massive bodies spiraling into each other. The 0.007-second delay between the signals in Louisiana and Washington is the right timing for a light-speed wave zipping across both detectors... Comparison with computer simulations reveals that the wave came from two objects 29 and 36 times as massive as the sun spiraling to within 210 kilometers of each other before merging. Only a black hole... can pack so much mass into so little space, says Bruce Allen, a LIGO member at the Max Planck Institute for Gravitational Physics in Hanover, Germany. The observation provides the first evidence for black holes that does not depend on watching hot gas or stars swirl around them at far greater distances. 'Before, you could argue in principle whether or not black holes exist,' Allen says. 'Now you can't.... For a tenth of a second [the collision shined] brighter than all of the stars in all the galaxies. But only in gravitational waves [not in any other kind of radiation].' Kip Thorne: 'It is by far the most powerful explosion humans have ever detected except for the big bang'."
Rainer Weiss says this is the first test of GR in highly nonlinear regime and it passed with flying colors. You can actually listen to an audio recording of the signal -- better listen carefully, it is near my perception threshold -- here: https://soundcloud.com/emily-lakdawalla _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun