Nature abhors a vacuum

Meaning: Empty spaces become filled very quickly.

Note: nature (noun) = the force that we regard as controlling the physical world, plants, animals etc | abhor (verb) = detest; hate | vacuum (noun) = a space with nothing in it (not even air or gas)

Origin: Aristotle (ancient Greek philosopher and scientist, 384-322BC) first suggested that "nature abhors a vacuum" to explain why water pumps worked (an astute if not totally accurate observation).