Tony Munden, of Dunedin, asks :-

What is gravity? How does it work and where does it come from?

Jenni Adams, a physicist at the University of Canterbury, responded.

We don't know. To produce a fundamental answer to your question would earn a Nobel prize!

We do know that gravity is a force that attracts two masses together. The gravitational force depends on the masses of the bodies and the distance between their centres. For example, an object on the surface of the Earth experiences a force of attraction nearly six times more than it would on the surface of the Moon. That is why astronauts on the Moon can jump higher than they can on Earth.

Newton made a basic contribution to physics when he showed, in 1665, that the force which holds the Moon in its orbit is the same force which makes an apple fall.

Einstein suggested an alternative theory to that of Newton. He proposed the idea that gravitation is due to a curvature (or shape) of space that is caused by the masses. Actually space and time are entangled so the curvature to which Einstein referred is really a curvature of spacetime, the combined four dimensions of our universe. The predictions made from Newton's theory and Einstein's theory are so close that we cannot tell the difference for many experiments we do on Earth. However light from distant stars passing near the Sun has its path bent slightly because of the curvature of space there, an effect called gravitational lensing. Observation of this effect helped confirm Einstein's theory.

Many physicists believe that one day Einstein's theory will be superseded by a quantum theory of gravity. In such theories gravitation is attributed to the actions of a type of fundamental particle called a graviton. This would bring gravity into line with modern theories of the electromagnetic and nuclear forces. The ultimate goal for many physicists is to continue the unification of seemingly unrelated phenomena and provide a theory which unifies all the forces.

Who knows, it might be someone who is now at a New Zealand school who one day gains international fame by formulating the correct theory.