Few things can make a newsroom full of journalists look up from their computers, but the sight of a guy using only suction cups to climb a 58-story skyscraper owned by a leading presidential candidate is one of them. (The promise of free food is another.)

Coverage of the unidentified man scaling the sheer, shiny walls of Trump Tower in Manhattan on Wednesday afternoon got some of our colleagues wondering: How does that even work?

So without further ado, a brief primer on suction.

A suction cup is a flexible, curved object — often made of plastic, but octopuses have natural ones — that, when pressed against a flat surface, pushes out all the air between the cup and the surface to create a vacuum. The pressure difference between the inside of the cup and the outside holds the cup in place.

That force is astonishingly powerful. The amount of weight a suction cup can hold is equal to the surface area of the cup multiplied by the pressure outside it (i.e., atmospheric pressure). All a climber needs to get up a wall is a few of those cups and a healthy faith in the power of physics.

If that fails, police told the Associated Press, air bags have been deployed on the street in case the climber falls.