Gauging the mass of a black hole is tricky, but astronomers have devised multiple methods to measure the heft of these ...

It is tempting to think that some materials are always heavier than other materials. For example, someone might say that metal is heavier than air. But it depends on how much of each material there is ...

Weight is the force acting on an object due to gravity - it has the unit newtons (N) and acts towards the centre of a gravitational field. So weight is a gravitational force on an object that has mass ...