What It Means for Science If Gravitational Waves Have Been Detected

February 10, 2016 | Joanne Kennell

gravitational waves
Photo credit: ESO/L. Calçada (CC BY 4.0)

Einstein predicted their existence over 100 years ago.

The National Science Foundation (NSF) will update the world tomorrow (February 11) at 10:30 a.m. EST on their efforts to detect gravitational waves, and it is important to know what detecting these elusive waves means for science.  Just a hint… it’s huge!

Gravitational waves are ripples in space-time, and they were predicted to exist by Einstein’s theory of general relativity over 100 years ago.  The theory states that objects like black holes and neutron stars warp space-time, and when two of these giant objects collide, these distortions ripple outward at the speed of light.

SEE ALSO: Wrinkles in Space-Time: The Quest to Detect Gravitational Waves

Although scientists are fairly certain that these events happen, the waves have never been directly measured.  However, tomorrow’s announcement may change things.

NSF uses the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO), which consists of twin giant detectors — one in Louisiana, and the other in Washington, to detect ripples in space-time.  Gravitational waves are often compared to sound, meaning gravitational wave telescopes allow scientists to “hear” phenomena at the same time light-based telescopes “see” them.

So, if scientists have in fact detected these waves, it could answer some fundamental questions in the field of astrophysics according to Davide Castelvecchi’s paper published in Nature.

Do Black Holes Exist?

The signal from LIGO is rumored to have been produced by two merging black holes.  The power of the gravitational waves emitted during this sort of event can briefly be stronger than all the stars in the observable universe combined.

A black hole merger occurs when two black holes start to spiral towards each other, radiating energy as gravitational waves, and producing a characteristic sound called a chirp.  Clearly, detecting a black hole merger is confirmation that black holes really do exist and that they merge as predicted.

Do Gravitational Waves Travel at the Speed of Light?

Physicists have long theorized that gravity is transmitted by particles called gravitons.  If they are like photons, the particles that transmit light, and also have no mass, then gravitational waves should travel at the speed of light — matching predictions.

However, if LIGO and Virgo (a smaller version of LIGO in Italy) were to detect gravitational waves, and they took slightly longer to arrive than the bursts of gamma rays, then gravitons have a slight mass.  This would have substantial consequences for fundamental physics.

Is Space-Time Made of Cosmic Strings?

Cosmic strings are hypothetical defects in the curvature of space-time.  Researchers have predicted that these strings occasionally develop kinks, and when one of these kinks snaps, it releases a burst of gravitational waves which detectors could measure.

Are Neutron Stars Rugged?

Neutron stars are remnants of bigger stars that collapsed due to their own weight — becoming so dense that all their electrons and protons fuse into neutrons.  Although the physics behind their formation is not well understood, gravitational waves could provide some insight.

For example, although neutron stars are almost perfectly round, researchers have theorized that there could be “mountains” — just a few millimeters high — making the stars slightly asymmetrical.  Since these stars spin very fast, any asymmetries would deform space-time, producing a continuous gravitational wave signal.

What Makes Stars Explode?

Astrophysicists think the process that forms black holes and neutron stars also powers a common type of supernova explosion, known as Type II.  Listening to gravitational wave bursts from real supernova, and determining how loud and frequent the bursts are, could help provide some answers.

How Fast is the Universe Expanding?

The continuous expansion of the universe means that distant objects are getting further and further away — making them look redder than they really are because the light they emit stretches as it travels.  Cosmologists estimate the rate of the universe’s expansion by comparing the redness of galaxies with how far away they are, but it is an imperfect technique.

However, gravitational wave detectors measure the loudness of a signal, meaning they can reveal not only how far away a merger occurred, but also the direction that it came from — leading to a more accurate measurement of the universe’s expansion.

So many opportunities!

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