What cause gravity to act like a magnet ? what is the reason for that?


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Ray  Dart Profile
Ray Dart answered

This is a simple question, but the answer could make several pages. If you take Einstein's hypothesis. Mass (the "cause" of gravity) bends space (or more accurately "spacetime"). The act of "falling" is merely travelling along "straight" paths in a space that is fundamentally curved. (Take a look at the "equivalence principle" - there's a good wiki page.) This is the relativistic model.

Planck and other "quantum people" hypothesise that gravity is caused by the exchange of subatomic particles (gravitons). This is part of quantum theory.

Newton just assumed that the force exists, rather like magnetism, he explained how it worked (so well, in fact that it approximates VERY closely to the relativistic model, despite being fundamentally flawed). He didn't bother to try to explain what it was.

We know that the first two theories cannot really co-exist, although some, like Steven Hawking are trying to combine them in the "Grand Unified Theory".

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Gokul Krishna
Gokul Krishna commented
Thank you sir for your answer, does this force(magnetic force due to gravity) can be felt, when 2 objects are holded tightly for some duration and release slowly.
Ray  Dart
Ray Dart commented
Hey G. There is always apparent attraction between two objects that have mass. The problem is detecting it.

When calculating the "force" (bad word, I know) of gravity, they originally used a Scottish Mountain, Schiehallion, as their "source" of mass.
It's a big mountain (in UK terms) but its gravitational effect was difficult to measure compared with the Earth it stands upon. (They managed it though! - Either Charles Mason or Jeremiah Dixon, who went on to establish the Mason-Dixon line in the US was one of the surveyors/physicists working on this project, I cannot remember which - I must be getting old.)

Henry Cavendish, an oddball British scientist, used much smaller equipment than a mountain to make the same calculation. His calculations, made at the end of the 18th century, have hardly been bettered.

There was a standing joke about an English footballer, Frank Lampard, who got a bit overweight, that he was able to tie up a number of defenders as they were naturally attracted to him by force of gravity.

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