
The wheel was a great idea.
Relativity was a great idea.
The Big Bang Theory Season 1, Episode 7

...of the equations of general RELATIVITY
and hydrodynamics...
The Big Bang Theory Season 6, Episode 24

Just explaining the theory of RELATIVITY.
The Big Bang Theory Season 6, Episode 5

When Einstein came up
with special RELATIVITY...
The Big Bang Theory Season 3, Episode 14

...with general RELATIVITY
than does string theory.
The Big Bang Theory Season 2, Episode 2