Posts Tagged ‘gravity’


That is the sound of the gravitational waves hitting the LIGO detector. A chirp.

That is also the sound of the celebratory hurrah’s from the gravity community. We  finally have experimental (observational) confirmation to a prediction made by Einstein’s theory of general relativity 100 years ago.

The quest to hear gravitational waves started about 50 years ago by Webber and it is only now that enough sensitivity is available in the detectors to be able to hear the ripples of spacetime as they pass through the earth.

The particular event in question turned the equivalent of 3 solar masses into gravitational waves in a few seconds. This is much brighter in power than the brightest supernova. Remember that when supernova collapse, the light emitted from them gets trapped in the shells of ejected mater and the rise of the signal and afterglow is extended to months. This was brighter in energy than all the output of all the stars in the visible universe combined! The event of Sep. 14 2015 recorded the merger of two black holes of intermediate masses (about 30 solar masses each) about 1.3 billion lightyears away.

The official press release is here, the PRL paper is here.

The New York times has a nice movie and article to mark this momentous scientific breakthrough.

Congratulations to the LIGO team.


Usual caveat: Now we wait for confirmation, yadda yadda.






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So I have been pondering about Newton lately. Mostly because I heard various stories that might be apocryphal. I could not find a reference to them, but they strike me as being true. There is a legend about apples falling on Isaac Newton’s head as a story of how he discovered the law of gravitation…


Alas, Newton discovers too late that one should not exchange apples and moons.

Alas, Newton discovers too late that one should not exchange apples and moons.

Of course, this is probably just a fancy legend concocted after the facts to paint a more romantic picture of the discovery. What is true however, is that Newton had some hint of using a central force to explain the motion of the planets from Hooke. However Hooke could not solve the problem, and Newton had to invent calculus and differential equations to really solve this problem.


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