Ever since the days of the ancient Greeks, scientists have struggled to understand the universe. And over the centuries, we have managed to come up with various theories to explain the different forces that shape our world.  Newton gave us a theory of gravity; Maxwell gave us electromagnetism; Einstein gave us relativity; Planck and others gave us quantum theory. But now physicists are searching for a simple, elegant theory that combines and explains all the other theories together. A Theory of Everything. A theory so simple, it will fit on a T-shirt.  That's the subject of a new book by Canadian science writer Dan Falk. It's called Universe on a T-Shirt and it's published by Penguin.