Written by: Stephen Hsu
Primary Source: Information Processing
Live-blogging the LIGO announcement of detection of gravity waves. Detection of an event in 2015 (initial science run of advanced LIGO) is good news for the future use of gravity waves as an astrophysical probe — it suggests a fairly high density of NS-NS, NS-BH, and BH-BH binaries in the universe. Each time astronomers have developed a new probe (radio waves, x-rays, etc.) they have discovered new cosmic phenomena. The future is promising!
Techno-pessimists should note that detecting gravity waves is much, much harder than landing on the moon. LIGO measured a displacement 1/1000 of a neutron radius, in a noisy terrestrial background, accounting even for quantum noise.
https://www.ligo.caltech.edu/: 9/14/15 detection of BH-BH (~ 30 solar masses) merger at distance 1.3 Gy. The energy in the gravitational wave signal was ~3 solar masses!
Here is the paper http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102
When I was an undergraduate, I toured the early LIGO prototype, which was using little car shaped rubber erasers as shock absorbers. Technology has improved since then, and the real device is much bigger.
Kip Thorne (from whom I learned General Relativity) has been one of the driving forces behind the effort to detect gravity waves for over 40 years. The picture below was taken during a conference in Eugene back in 2005.