
Oh, GRAVITY, thou art a heatless bitch.
The Big Bang Theory Season 1, Episode 2

Besides disrupting the local GRAVITY field.
The Big Bang Theory Season 1, Episode 6

And, of course, it's Gravity Probe B.
The Big Bang Theory Season 1, Episode 13

Yes, and he never unified GRAVITY
with the other forces.
The Big Bang Theory Season 4, Episode 22

I don't know. In space you couldn't even
toss me a pen, and that was in zero GRAVITY.
The Big Bang Theory Season 8, Episode 3