Dr. Hannah Fry examines the science of size in this two-part documentary.
In this opening episode, she asks if bigger is better. How would life on Earth cope if the planet was twice the size it normally is? What would a human look like if they were 15ft tall? How do the largest animals in the world survive, and what happened to the big animals that have now gone extinct?
Size Matters is on BBC Four at 21.00.