How far is infinity?

 

The size of infinity is a vexed topic. "An infinite distance" is an important concept in gravitational fields because it is the point of zero gravitational potential. This is because Newton's Law of Gravitation, which is an inverse square law, shows that the force of gravitational attraction is zero at an infinite distance from the Earth. It is then impossible to store gravitational potential energy by doing work against gravitational attraction. So to find the distance to infinity, one way is to hang a mass on a spring balance and travel outwards until the reading says zero. The distance will be finite and will actually be based on the resolution of the spring balance. Hence different spring balances would give different infinities!