The cosmic web is kind of like the skeleton of the universe.

The clustriest of clusters and the voidiest of voids is the things that come to mind, right?

If you get things that challenge that, well, then we just rethink the physics.

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

science journalist Izzy Clark and astrophysicist Dr. Becky Smethurst. This month we're untangling

the cosmic web, not the James Webb space telescope, but the large scale structure of the universe.

What do we know about it? And what can it tell us?

Yeah, I just thought it was about time we got into something really complicated because we'd

just be taking a bit too easy with all this planetary science on our tour of the solar system.

Well, is your head not hurt very recently busy when you've been recording?

No, I'm due another headache, so here we go.

As always, Dr. Robert Massey, the deputy director of the Royal Astronomical Society, is here.

So, Robert, how would you describe the cosmic web?

Because it might not be something that everyone is familiar with.

So let's begin this brain stretch right now.

Exactly. Brain stretch, headache, questions I struggle to answer. You know, everything

it makes a good supermassive episode. The good questions. Exactly. The good questions. Yeah.

So look, I mean, if you take a kind of casual look at the sky, a very quick glance up, you

think, okay, randomly distributed stars. But even in our own galaxy, you look a bit longer, you see the band of the Milky Way, so you can quite easily deduce there's some structure in the way the stars are distributed. And if you look on a much bigger scale, if you map galaxies on a huge scale, and you do that in 3D, then it turns out they're grouped into these huge clusters, and those clusters are on these filaments of this giant web, and there are these filaments and voids, and that's the sort of bubbly structure of the universe on the biggest scale. And we didn't know about it until the 1980s, because that was when we got better telescopes, and we were able to measure those distances more reliably and push them out further than before. And those galaxies, the galaxies like the one we live in, they're concentrated into these huge clusters. They tend to be concentrated along the nodes or the knots and strands of the web. And they're around voids where there are far fewer of them. And these are really big. These are billions of light years across. So they're certainly the biggest structures in the whole universe. So understandably there's a lot of interesting understanding things on the biggest scales. Yeah, I like to joke that, you know, instead of like turtles all the way down, it's just filaments all the way. It's exactly, filaments, bubbles. So whether you describe it as, I don't know, soap or spongy or something like that. Yeah, I've always looked at it as like a big sponge, right?

And I like how you were saying, you know, we didn't discover this to the 80s

because we almost couldn't zoom out far enough to see it, right? Cheers, Robert. We'll catch up with you later in the show for some more questions and this month's Stargazing Tips. So buckle up, everyone. the mind stretching continues

because we're going to dive into the world of cosmology.

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