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Gravitational Waves

This article appeared in the February 28, 2016 edition of the Davis Enterprise.


By Vinita Domier

Special to the Enterprise


Exactly a century after Albert Einstein predicted the existence of gravitational waves (GWs) in his revolutionary General Relativity theory, scientists from the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced on February 11, 2016, the detection of ripples in spacetime emanating from two massive black holes orbiting and then violently colliding into each other at a distance of 1.3 billion light years from Earth.


The incredibly small GW signal, GW150914, was detected on September 14, 2015, by both LIGO Livingston Observatory (in Louisiana) and LIGO Hanford Observatory (in Washington) within 10 milliseconds of each other. The 200-millisecond signal’s frequency increased from 35 Hz to 150 Hz, producing a characteristic audible ‘chirp’ when converted to sound waves (human audible range is 20-20,000 Hz).


The detection of GW150914 is a momentous and history-making event as it is the first time a GW has been directly detected, and the existence and merger of binary black holes has been directly confirmed. GWs emanating from a binary pulsar, PSR 1913+16, (discovered in 1974) were indirectly inferred because the pulsar’s orbital distance from its companion neutron star is steadily decreasing, due to loss of energy to GWs, at a rate in accordance to Einstein’s General Relativity theory.


GWs are analogous to electromagnetic waves (EMWs) in many ways. Both self-propagating waves radiate from the source, carrying energy and momentum in all directions, at the maximum speed c approximately 3.00X108 m/s (speed of light in a vacuum). Their amplitudes attenuate with increasing distance of detector and source, and their frequencies are redshifted or blueshifted due to the relative velocities of source and detector.


GWs are another tool to study the cosmos, though they are extremely difficult to detect because the ripples in spacetime are smaller than the size of a proton by the time they reach Earth. Thus far, astronomers have studied the universe by ‘seeing’ EMWs that travel at the speed of light but can get reflected or absorbed by intervening matter. Now they will be able to learn more about the universe by ‘hearing’ GWs that also travel at the speed of light but pass through intervening matter virtually unchanged. Phenomena that don’t radiate EMWs, like the interiors of black holes and the universe immediately after the Big Bang, can potentially be observed using GWs.


Join the Davis Astronomy Club on Saturday, February 27, starting at 7pm at the Explorit Science Center (3141 5th Street, Davis) when we will discuss gravitational waves and how they are detected. Everyone is invited to the free meeting indoors, followed by a star party outdoors (weather permitting).



Explorit’s coming events:


  • Explorit’s Exploration Gallery is open to the public every Wednesday, Saturday and Sunday, 1:00-5:00 p.m. and every Friday, 3:00-6:00 p.m.  Admission is $5.00 per person; Explorit members, teachers and children 2 and under are free. Come check out the new Nano Mini Exhibition!
  • Exporit’s next free evening lecture is Thursday March 3, 7 p.m. “Blue-Green Algae: The Good, The Bad, and The Deadly!” by Dr. Annaliese Franz and Dr. Bob Poppenga at DMG MORI 3805 Faraday Ave., Davis.


Explorit Science Center is located at 3141 5th St. For more information call (530) 756-0191 or visit, or “like” us on Facebook at

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