'We Don't Planet' Episode 8: Gravitational Waves

When Albert Einstein first began developing what would eventually become the theory of general relativity, he probably wasn’t suspecting the full implications of what his explanation of gravity would entail. Perhaps most surprisingly, but discovered by Einstein himself, is that gravity makes waves. These waves travel at the speed of light, and are created anytime there’s an asymmetry in the gravitational interaction of two bodies. This situation is very common in the universe, so gravitational waves should be sloshing around the Earth constantly.

Gravitational waves are literally waves of space-time, so as they pass through an area, they alternatively stretch and squeeze objects. Imagine being pulled and squished like a piece of silly putty — the alternating action of gravity as the wave passes through does pretty much the same thing.

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But gravity is by far the weakest force, and gravitational waves are a small perturbation on top of it, so it took 100 years to finally detect them with the LIGO (Laser Interferometer Gravitational-Wave Observatory) instrument in the fall of 2015. And the waves LIGO detected were from a truly impressive event: the merger and coalescence of two black holes, each weighing in at dozens of solar masses. Even then, the confirmed gravitational waves barely nudged the sensitive LIGO apparatus by less than the width of an atom.

"We Don't Planet" is hosted by Ohio State University astrophysicist and COSI chief scientist Paul Sutterwith undergraduate student Anna Voelker. Produced by Doug Dangler, ASC Technology Services. Supported by The Ohio State University Department of Astronomyand Center for Cosmology and AstroParticle Physics. You can follow Paul on Twitterand Facebook.

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Paul Sutter
Space.com Contributor

Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron Institute in New York City. Paul received his PhD in Physics from the University of Illinois at Urbana-Champaign in 2011, and spent three years at the Paris Institute of Astrophysics, followed by a research fellowship in Trieste, Italy, His research focuses on many diverse topics, from the emptiest regions of the universe to the earliest moments of the Big Bang to the hunt for the first stars. As an "Agent to the Stars," Paul has passionately engaged the public in science outreach for several years. He is the host of the popular "Ask a Spaceman!" podcast, author of "Your Place in the Universe" and "How to Die in Space" and he frequently appears on TV — including on The Weather Channel, for which he serves as Official Space Specialist.