Gravitational Waves Have Been Detected For the First Time!

February 11, 2016 | Joanne Kennell

Two merging black holes emit gravitational waves
Photo credit: C. Henze/NASA Ames Research Center

This is monumental!

Rumors about the detection of gravitational waves have been floating around for months, and finally, these rumors were addressed in a press conference this morning and also in a peer-reviewed paper no online in Physical Review Letters.

Drum roll… gravitational waves have officially been detected!  

This is a point in our history just as monumental as Galileo looking into the sky with a telescope for the first time!

On September 14, 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) observatories, located in Louisiana and Washington, recorded a signal at nearly the same time.

After months of checking, rechecking, and analysing the data, researchers are finally convinced that what they saw were gravitational waves.

Gravitational waves are dynamical perturbations in the fabric of spacetime — they stretch space in one direction, and compress it in another.

The gravitational waves measured were produced by two colliding black holes 1.3 billion years ago.  The signal had a very specific characteristic — as time went forward, the frequency went up — exactly what is expected for two large objects merging.

LIGO interferometer detectors are L-shaped, 4 kilometers long on each side and composed of lasers that go back and forth between mirrors, so that any gravitational waves passing through these lasers would distort spacetime.

These detectors measure the vibrations in spacetime in a way that allows us to hear them, and on September 14, 2015, researchers heard the characteristic chirp that had been predicted to indicate the merger of black holes. But a lot more can be learned from these measured waveforms.  For example, the frequency of the wave can indicate the masses of the initial black holes and the mass of a newly merged one, while the amplitude of the wave can tell us how far away it is.

Amazingly, this technology will allow us to hear things that we expect, but also things that we never expected.  This is a very exciting time.

Read more about gravitational waves and What It Means for Science If Gravitational Waves Have Been Detected.

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