As of something gently rapping, rapping at LIGO’s door."
First some background. LIGO is the facility, next door to The Engineer's nuclear plant, that measures gravitational waves from space - which was first posited by Albert Einstein re his theory of special relativity in 1905. The first gravitational wave was heard here in 2015 and finally proved Einstein's theory. Needless to say we were all excited around here.
And then one day there came another sound.... tap, tap, tap. What is that?!?!? Aliens?
Turns out the frost build up on the cooling system for the apparatus was appealing to the ravens in the summer heat. So they tap, tap, tapped it off the pipes for some refreshment.
"Altering the setup to prevent ice buildup now keeps the ravens from tapping, evermore."