You're listening to Brains on from MPR News and Southern California Public Radio.

We're serious about being curious.

I'm Molly Bloom.

Have you ever wondered what's beyond the edge of the universe?

Or maybe a better question?

Is there even an edge of the universe?

And what does it mean that the universe is expanding?

We're about 15 seconds into this episode and my brain already hurts from thinking about

these big questions.

So it's a good thing that we have help.

Today we're going to be listening in on a conversation between two very smart people

who are wrestling with these very big and very mind-blowing questions.

The first is an astrophysicist.

Hi, my name is Katie Mack.

I am a theoretical astrophysicist and I study the early universe and dark matter and stuff like that.

And I live in Melbourne, Australia, and I work at the University of Melbourne.

And the second is thea Hutchins.

Hi, my name is Thea.

I'm nine years old and I live in Sydney, Australia.

Thea wrote what is perhaps our favourite email that has ever been written to brains on.

I don't understand how the universe can be expanding into nothing.

Like, what is the nothing that the universe is going into?

...