Raj: You can't let this stop you. Almost any scientific advancement can be used for destructive purposes.
Amy: It's true. Even Einstein's theory of relativity was later applied to the development of nuclear weapons.
Penny: E equals MC squared. Yeah. E is for energy, M for mass, and C for the speed of light.
Amy: How do you know that?
Penny: Oh, Leonard mumbles it when he wants sex to last longer.