One of your BBC programs begins with a lovely moment where you examine the beauty of a snowflake.

The inspiration for that came from the 17th century and an incredible work called The Six-Cornered Snowflake by (Johannes) Kepler. It is absolutely brilliant. It's considered the first book to ever describe the structure of crystals or snowflakes, and I would recommend it to anyone and everyone.

A courtier is charged by his king to bring the most valuable gift he can find that is close to nothing. So the courtier considers some water, some dust and then the snowflake. "I'll give you the most valuable gift, which is the closest thing to nothing I can find," he says. Kepler is a great genius, with the most amazing mind. Every single question he asks about the universe so long ago is correct.

Do you think of space as having dimensions we can't conceive of yet?

There are plenty of theories of extra dimensions and we do experiments to find them. Interestingly, one of the ideas about why gravity is so weak is because it has to deal with other dimensions, where other forces don't.

What would you say is people's biggest misconception about space?

It's not a misconception, exactly, but a lot of people can't come to terms with what it means to be human without considering the universe. So if there's anything that surprises me about some people, it is that they don't really care. But as long as enough people do, we're okay. I remember people used to say to the famous US cosmologist Carl Sagan, "Look at those lights in the sky." And he'd say, "They're more than lights, kids - they're worlds."