What surprises you about ancient belief systems about the age of the universe?

The force it would take to accelerate an 900-kg car at the rate of 6m/s2

What do we mean by the event horizon of a black hole?

Suppose that a cylindrical tank 6 meters high with a radius of 2 meters is filled to the rim with water. the tank is buried so that the top of the tank is 1 meter below ground level. the space above the tank is not filled with water. calculate how much work needs to be done by a pump to pump the water out of the tank up to ground level. (the water weighs 9,800 newtons per cubic meter.)