In a recent Big Bang Theory episode, Stephen Hawking defeats Sheldon
at Words with Friends, and jokes that Sheldon is like a black hole
because he “sucks”.
There’s really no such thing as “sucking”. Liquid travels up a straw
because you create a partial vacuum by “sucking”, so the stronger air
pressure outside the straw pushes the liquid up the straw, until the
force of gravity balances the difference in air pressure you’ve
created by “sucking” (this is also how barometers work).
Of course, Dr Hawking knows this and was just joking.