Daniel Whiteson

If you have a gravitational wave passing through the universe and it passes between you and the pulsar, it's going to affect the pattern of the pulses, right?

You're going to see this blip, blip, blip, blip, blip, and one of them is going to be a little bit longer and the other one is going to be a little bit shorter.

So you can predict how a gravitational wave with a wavelength the size of the galaxy is going to affect how you see these incredible clocks that the universe has put everywhere.

And so if you make really careful measurements of all those pulsars, you can reverse engineer what happens to that gravitational wave.

And they've recently seen this a few years ago.

Really incredible pulsar timing arrays.

And this is what I mean by the ingenuity of experimental physicists.

You can't just build a device the size of the galaxy to measure these things.

You've got to figure out what's out there and how do we use it to reveal the truth to us.

That's brilliant.

It's brilliant stuff.

So since that worked, what did that mean?

Why was that so important?

What it means is that we learned that there are gravitational waves out there that are wavelength the size of the galaxy.

The gravitational wave detector we built on Earth, LIGO, it can see gravitational waves of a certain wavelength.

but it can't see the really, really big ones.

And that's the kind of thing that is going to tell us about the very early universe.

So right now they're just seeing, oh, there are gravitational waves out there with huge wavelength.

And it's kind of a noisy environment because anytime anything in the universe moves, it makes a gravitational wave, any acceleration.

I wave my hand, that's a gravitational wave.