Hello and welcome to another bonus episode of the Supermassive podcast with me, science journalist Izzy Clark and as ever, Dr Robert Massey, the deputy director of the Royal Astronomical Society, is here too.

So after our astronaut special last time, we've got one more astronaut for you.

We'll hear from British European Space Agency astronaut, Rosemary Kugan, who is also an astrophysicist.

My goodness, they just never stop, do they, astronauts?

They're just such overachievers.

I will continually say that.

But this is also time for us to catch up on the supermassive mailbox. So, Robert, first up,

we have an email from John Hickson. And I'm going to paraphrase his question, which is about the

shape of the universe. So, Robert, is it curved? Is it flat? What shape is space? I'm glad you

paraphrase that, Izzy. The simple questions are always

great, aren't they? John, the short answer is that we think it's flat. Now, this is not an easy

concept in itself, as you have to imagine a universe sort of shaped beyond the three dimensions of space,

or four of you include time, and something that we don't experience that, you know, even if there

is that curvature, we wouldn't experience it on a local level, right?

So you're talking about very large scales.

And I was reading around this and I thought, well, actually, you know, the analogy is given that

if you think about a triangle on a flat piece of paper, okay, the angles add up to 180 degrees if you think back to your

GCSE maths course or O-level maths course if you're old enough. But if you curve that paper,

then the angle, the sum of the angles changes. If you draw a triangle on a sphere, for example,

it's more than 118. If it's negatively curved, it's like a saddle shape, then the total is less than 180.

So in a positively curved

universe in some kind of hypersphere, then in theory, light would eventually travel back more or less

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