What are Gravitational Waves? Part 1– Astronomy

Gravitational waves: the hubbub around LIGO’s February announcement still hasn’t died down. The question isn’t even whether it will win the Nobel Prize, but which of its scientists it will be awarded to. But, what exactly are gravitational waves? What causes them and why are they such a big deal?




Let’s turn back the clock one hundred years. The year is 1914. A few months after Charlie Chaplin makes his film debut, Einstein comes up with the theory of General Relativity, which states that massive objects like stars or planets curve the very fabric of space and time. Smaller masses fall into this curved spacetime: this is what we call gravity.

Some regions of spacetime known as black holes are so dense that they exert gravity strong enough nothing, not even light, can escape.

If two black holes get too close to each other, they start exerting gravity on each other.The closer they get the faster they orbit until finally they collide. The energy emitted by this collision is massive- yet the signal it gives off are so weak by the time they reach the earth we’ve never been able to prove that these collisions happen.

That is, until a project known as LIGO, the Laser Interferometer Gravitational Wave Observatory, detected two black holes colliding. These black holes were roughly THIRTY TIMES the mass of the sun– each! At one point it even released more power than that released by all the stars in the universe — combined.

This collision was so huge and catastrophic that we could detect it from one billion light years away. What we heard were the “aftershocks” of the event: gravitational waves, ripples from massive objects accelerating that cause space to expand and contract.

Gravity is a weak force, and gravitational waves are nearly impossible to detect, since they are drowned out by other signals in the universe. However this collision was so strong, LIGO was able to “listen” to it happen.

Written by: Jessica Karch
Animated and illustrated by: Maxine Nelson
Narrated by: Ciara McGovern
Special thanks to Brian Dawes
Music Credit: “New Dawn”, Bensound.com