Week 3: Gravitational waves

Yesterday, a breakthrough was announced in astrophysics: the first detection of gravitational waves. Gravitational waves were initially predicted by Einstein's theory of general relativity, but they hadn't been detected until September 2015. Their detection provides strong support for general relativity, as well as providing an avenue for studying the universe that is fundamentally different from just using electromagnetic radiation. I think this is probably the aspect of this discovery that I am most excited about--just last week I was wondering what telescopes would be like if they functioned less like the human eye, and using gravity as an observational tool could play that role. (Was I in on the discovery? Was it just coincidence? The mystery continues...)

Essentially what happened was that two black holes, one 36 times and one 29 times the mass of the Sun, collided and released 3 times the Sun's mass in pure energy. Remember, \(E=mc^2\) (another shout-out to Einstein), so this is a lot of energy--50 times the power of everything else in the visible universe, in fact. This energy was released largely in the form of gravitational waves, which is why LIGO (Laser Interferometer Gravitational Wave Observatory) was able to detect them, even though the event occurred 1.3 billion light years away (and therefore 1.3 billion years ago). The video below is a visualization of the two black holes orbiting each other and finally colliding. This video is in fact in slow motion--the actual event happened in just tenths of a second, with the black holes reaching half the speed of light in their orbit.

While this has been the most impressive signal received so far, there were a couple of smaller signals received during the 5 month detecting period. This is pretty cool because it means that the technology is working and that events are happening in the universe that are within our threshold of detection. It'll be really exciting to see how this can be used to advance our understanding of gravity, general relativity, and the universe as a whole.




Sources
https://www.ligo.caltech.edu/video/ligo20160211v3
http://gizmodo.com/physicists-are-freaking-out-about-gravitational-waves-a-1758605484
http://www.nytimes.com/2016/02/12/science/ligo-gravitational-waves-black-holes-einstein.html?_r=0
https://en.wikipedia.org/wiki/General_relativity#Gravitational_wave_astronomy
http://apod.nasa.gov/apod/ap160212.html