The correct answer is, "When covered by
LIQUID sufficient to reduce the coefficient...
The Big Bang Theory Season 2, Episode 5
The world's most boring LIQUID
and the world's most boring vegetable,
The Big Bang Theory Season 10, Episode 13
my original theory that space time
was like a super-cooled LIQUID,
The Big Bang Theory Season 9, Episode 18
How about a LIQUID cooler?
A little aquarium pump here.
The Big Bang Theory Season 1, Episode 2
Floating in a warm pool
of LIQUID
The Big Bang Theory Season 12, Episode 19