What things can inspire your enthusiasm?
Challenges, both physical and mental. Nothing beats the feeling of looking back at something great that you have achieved, such as a sporting success or a task which you were able to complete successfully.
One day you wake up and find you can do anything you want to do. What's the first thing you'll do?
A lavish breakfast, ideally with friends, and then board a plane and travel around the whole world.
What have you always really wanted to know?
Everything about the theory of relativity. Time and space fascinate me because they are intangible, but very powerful.