None. Bill Gates will just redefine Darkness® as the industry standard.
or
A comb.
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They turn from notating nuclear spins to notating unclear puns.
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His son, because he's a little Bigger!
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Three:
One to write the light bulb removal program,
one to write the light bulb insertion program, and
one to act as a light bulb administrator to make sure nobody else tries to change the light bulb at the same time.
or