Why do we get moonquakes?

And it's sort of that snap backing and that gives us what we call a spacequake.

When the earthquake happens is completely random.

It's the subject to very many bad disaster films.

Hello and welcome to the Supermassive podcast from the Royal Astronomical Society with me,

science journalist Izzy Clark and astrophysicist

Dr Becky Smethurst. Yeah, hold on tight because this month we're covering shaky ground.

This episode is all about quakes, whether that's on Earth with earthquakes or other planets entirely.

And even on our pal of the moon. Yeah, moonquakes. Do you know what? I'm looking forward to getting into that later because it's just something that we bypass all the time. But anyway, Dr. Robert Massey, the deputy director of the Royal Astronomical Society, is here too. So, Robert, can you give us a basic definition of a quake? Is there one?

Yeah, as basic as I can. So the British Geological Survey has a handy definition

that it describes it's a sudden release of energy in the Earth's crust, in this case,

leading to waves, radiating outwards and shaking the ground. Now, we see about,

or we detect about two or three hundred moderate quakes each year, even in the UK, although only a small number are actually strong enough to be felt about 10% of those. I have to say that I know quite a lot of people who felt earthquakes in the UK, but I'm not one of them. I've slept for them. I've been at my desk, you know, when an earthquakes happened, just didn't notice, you know. Yeah, it's like,

it just doesn't happen for me. The only thing I remember about when earthquakes hit in the UK

is all the news stories that are like, my wheelie bin fell over. Yes. Well, yeah, exactly. My windows

vibrated, yeah, which is pretty much as it's as strong as it gets. I mean, my wife actually felt

quite a strong earthquake in Athens back in 1999. Then that was known by those of us who saw the total of solar eclipse that year because it was around the same time. But not that there's a connection. But, you know, as an example of someone, I do know people who felt them. Just doesn't include me. I felt one. It was actually when I was observing. So I was using the Caltech submilometer observatory, which no longer exists, sadly. But it's on top of Mount O'Kahe in Hawaii, which is obviously quite a geologically active place. But we were in this telescope that the whole control room moves with the telescope as you move the telescope to look at something else. So we just felt the shift and we thought it was like, you know, like the tracking on the

telescope catching up or something, like the dome catching up with the tracking.

And then we were looking at all these tables swaying like rhythmically and repeatedly.

And we were like, was that an earthquake?

And then we realized the telescope was not pointing where it was supposed to be pointing anymore.

So we realised that an earthquake hit.

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