One thing people often wonder about is; if gravity is always pulling then why doesn’t the Moon fall down and hit us? Newton worried about this too and that was when came up with his famous cannon ball analogy. I will not repeat it here but if you are interested click on the cannon ball analogy to read about Newton and his analogy. Actually the Moon does “fall” but because the Earth is like a giant ball whose surface is curved rather than flat and because the Moon is going so fast then when the moon falls it never hits the ground because the Earth curves away from the falling path before the Moon can hit it. The Moon is constantly being pulled towards the Earth and constantly misses Earth so its path forms an orbit around the Earth.

• The first flaw discovered is usually referred to as an “action at a distance” assumption. This means that Newton assumed that the gravitational force acted instantaneously no matter how far apart the two different bodies were. Experiments prove that nothing can travel faster than the speed of light so this had to be wrong. Various attempts were made to fix the theory but they were mathematically very complicated fixes and they were almost impossible to solve. Mathematicians call such problems “intractable” because you can only find approximate solutions not complete solution. Physicists call complete solutions a “closed form” solution.
• Since Newton’s time we have observed several discrepancies between measured data and Newton’s theory. The most famous of these discrepancies is a small discrepancy is in the orbit of the planet Mercury and the bending of light as a beam of light passes very near a large body like the Sun.
• Newton’s theory tells us how gravity works most of the time but it is inadequate to explain what and why gravity works.

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Tags: Physics, Science

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