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Saturday, February 13, 2016

WHAT ARE GRAVITATIONAL WAVES?


I like to think that I know a little bit about everything.  But GRAVITATIONAL WAVES?    Supposedly, GWs are ripples in the fabric of space and time.  Huh?  They occur when, for example, two black holes merge, as above.  The size of the ripple?  Perhaps a small fraction of the diameter of a subatomic particle:
  • If you place 10 billion atoms side by side, that would be about one meter.  Incidentally, as this is Saturday, if you took a second for each number, it would take you more than 300 years to count up to 10 billion.
  • An electron is a large subatomic particle, but has only one-thousandth the mass of a typical atom.
So how do you measure anything that tiny?  Well, you build giant lasers, place them in  a tunnel between two high precision mirrors, one in Louisiana (Livingston) and the other in the state of Washington (Hanford), and call the system the Laser Interferometer Gravitational-Wave Observatory, or LIGO.  There is no tunnel connecting the two sites.  Each has up to five interferometers in an L-shaped ultra high vacuum chamber.  

The logic is that if gravitational waves arrive, they would be traveling at the speed of light, and as the sites are separated by 1865 miles, the initial detection should be followed ten milliseconds later at the second location.  There are, too, listening posts around the world.

Damn thing was able to measure trees being logged in Louisiana and earthquakes in Washington.  That was between 2002 and 2010, when the systems were shut down to improve the technology by a sensitivity factor of four.

It was a century ago that Albert Einstein postulated these ripples in his general theory of relativity.  Then in 1993 Russell Hulse and Joseph Taylor of Princeton University were awarded a Nobel Prize for discovering a pulsar, opening up the study of gravitation.

Founded in 1992 by Kip Thorne of Caltech and Rainer Weiss of MIT, they convinced the National Science Foundation (largest one project ever) and equivalents in the UK, Germany and Australia, to spend a bit more than billion dollas, got 900 scientists from the world over involved and enlisted 44,000 active Einstein@Home users to help.  
  • At 09.51 UTC on 14 September 2015 LIGO detected the merging of two black holes, each 30 times the mass of our Sun, which occurred 1.3 billion light years ago.
  • Just two days ago, 11 February 2016, LIGO announced the first observation of this gravitational wave.
Some say this find is bigger than the confirmation of the God Particle, or Higgs Boson.

Here is where I am again somewhat confused.  First, while, of course, confirmation must be verified, there is said to be less than a one to 3.5 million chance that they were wrong.  But what are the odds that during this recent period of LIGO capability, they would detect something that instantly occurred 1.3 billion years ago?  Unless similar events occur with regularity, and it must, because they expect several detections per month.

Another analogy is that gravitational waves finally have added the sound track to silent movies.  In the future, not only will you be able to view the awesomeness of the Universe, but hear the chirps.

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