Gravitational Wave Background: A Very Simple Explanation

 By now you’ll have seen the news about the ground-breaking discovery of a low-frequency gravitational wave background caused—scientists think—by the supermassive black holes that orbit each other for a short while before merging.

We’re told this is big news—a new window to the universe, no less—but to many it will seem both complex and have little meaning to our lives. A tempting conclusion, but this really is incredible—and it’s worth five minutes of your time.

Here’s everything you need to know about the gravitational wave background in simple language:

Gravitational Waves Explained

A gravitational wave is a ripple in space-time caused by a violent event somewhere in the universe. They were predicted by Albert Einstein’s theory of general relativity in 1916. That theory posits that gravity is a symptom of spacetime being warped, twisted and curved by the presence of massive objects, such as stars and planets. However, it also predicted that massive accelerating objects would disrupt space-time in waves traveling out into the universe, in all directions, at the speed of light. The 2016 detection of gravitational waves proved that prediction when Laser Interferometer Gravitational-Wave Observatory (LIGO) physically sensed gravitational waves generated by two colliding black holes 1.3 billion light-years away.

What’s now been discovered is a cosmic background—a web—of long-wavelength gravitational waves. They’re thought to come from supermassive black hole binaries—two supermassive black holes orbiting each other.

A black hole is a region in space where gravity is so intense that nothing can escape—even light. A supermassive black hole weighs billions of times the mass of our sun.

How This Discovery Came About

It’s not just what we know, but how we know it that makes astronomy such a fascinating subject. For the gravitational wave background, that goes double.

Let’s start with a really simple visualization.

Imagine the universe as a lake with kayakers rhythmically paddling around it. Two motor boats are going around in a circle, following each other and sending out ripples that cause the kayaks to wobble—and the kayakers’ rhythmic paddling to be slightly altered. Now have dozens of pairs of speed boats all doing the same thing.

This is akin to what the scientists have seen. They monitored the light from 25 pulsars, the cores of dead stars that rotate every millisecond, sending out highly predictable radio signals. Astronomers call them cosmic clocks. They’re the kayakers’ paddles—and astronomers have noticed slight variations in their rhythms that reveal a web of ripple-like disruptions.

The speed boats, of course, are the supermassive black holes orbiting each other, creating the ripples. What the scientists want to do next is to trace these cosmic ripples—each of which carries information about their origins and clues about the nature of gravity itself—back to the supermassive black hole binaries they’re searching for.

After all, astronomers have yet to confirm the existence of a single supermassive black hole binary.

International Conference on Gravitational Waves

visit:gravity.sfconferences.com

Nomination link:https://x-i.me/granom

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