A philospher, a physicist and a mathematician are about to jump off a bridge.
First the philosopher goes. He stands up on the guard rail, proclaims that life has no intrinsic meaning, accepts his fate and jumps. He hits the lake bellow and dies
Next the mathematician climbs on the guard rail. He tries to calculate his speed at impact, the angle at which he’ll hit the water, the odds of surviving and finally jumps. He hits the water but at a crooked angle and brakes his legs, he had an error in estimation.
Finally the physicist goes. He tries to calculate the gravitational acceleration, the aerodynamics and final velocity of his body, the forces at impact etc. After a while he’s ready and climbs the guard rail. As he jumps he starts flying upwards… he mistook the sign of gravity.