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What is gravity?

PHYSICAL WORLD: Students from Ross Intermediate asked this question

This is a very deep question. The best answer comes from Einstein’s general theory of relativity which says that the force of gravity cannot be distinguished from the force which you feel when being accelerated. In a lift you feel momentarily heavier as the lift accelerates upwards and you feel lighter as it starts to drop. In practice, all bodies (that is all materials) attract one another – this is the force of gravity. Unless the body is very large however you will not feel this force. The force that holds you on the ground comes from the attraction exerted by the Earth on your body.

Our expert

Professor John Harvey anwered this question. He is a Fellow of Royal Society Te Apārangi, which means he’s one of the top experts in his field of photonics and optics. John started the University of Auckland Laser Lab in the early 80′s and has been CEO of Southern Photonics since its inception in 2001.

For more information visit:  http://www.southernphotonics.com/about-us/prof-john-harvey/