Professor Geraint Lewis, astrophysicist at University of Sydney, takes up the challenge to explain a proposed theory of everything in the time it takes to ride an elevator from ground floor to penthouse.

Bitcoin and Blockchain. You've heard of them. But what do the words actually mean? Can you define blockchain? We've challenged a computer science expert to do just that, in the time it takes to ride an elevator.

What happened before the big bang? How can something come from nothing? We've challenged a physicist to explain the origins of our universe in one elevator ride. Good luck Dr Julian Berengut, from University of NSW.