Why is the force of gravity lower on the moon than on earth?
An Olympic Games held on the Moon, if that were possible, would produce some remarkable results. High jumpers would soar six times as high, broad jumpers would leap much farther, shot putters and hammer throwers would hurl their missiles astonishing distances. All this would result from the fact that gravity on the Moon is only one-sixth of that on Earth. Thus, a 6-kg (13-lb) bag of potatoes bought in an earthly market would weigh only 1 kg (about 2 lb) on the Moon.
In 1665, the 23-year old Isaac Newton first explained the force of gravity, and drew up a mathematical formula, known as Newton’s laws, by which we can calculate gravitational pull on the Moon’s surface or elsewhere. Newton explained that all objects exert the force of gravity. The attraction between two bodies, such as the Moon and the Earth, depends on their mass the greater their mass, the stronger the attraction and also on their distance apart, measured from the centre of each body.
Newton’s laws still work extremely well, and are used in guiding spacecraft. As Apollo 8 headed towards the Moon and came under the influence of its gravitational pull, astronaut Bill Anders commented, ‘I think Isaac Newton is doing most of the driving now.’
A spacecraft falling towards the Moon would take longer and not hit so hard as one dropping to Earth. The Moon’s mass is much less than that of the Earth’s. For one thing, the Moon is much smaller only about one quarter of the Earth’s diameter of 12 800 km (8000 miles). Also, the Moon is made of lighter material. On average, a cubic centimetre (0.06 cu in) of rock from the Moon weighs only 3.3 grams (0.1 oz) compared with 5 5 grams (0.2 oz) for a cubic centimetre of Earth.
For these reasons, gravity on the Moon is much less than that on Earth, both of which Newton’s laws enable us to calculate precisely.
In 1665, the 23-year old Isaac Newton first explained the force of gravity, and drew up a mathematical formula, known as Newton’s laws, by which we can calculate gravitational pull on the Moon’s surface or elsewhere. Newton explained that all objects exert the force of gravity. The attraction between two bodies, such as the Moon and the Earth, depends on their mass the greater their mass, the stronger the attraction and also on their distance apart, measured from the centre of each body.
Newton’s laws still work extremely well, and are used in guiding spacecraft. As Apollo 8 headed towards the Moon and came under the influence of its gravitational pull, astronaut Bill Anders commented, ‘I think Isaac Newton is doing most of the driving now.’
A spacecraft falling towards the Moon would take longer and not hit so hard as one dropping to Earth. The Moon’s mass is much less than that of the Earth’s. For one thing, the Moon is much smaller only about one quarter of the Earth’s diameter of 12 800 km (8000 miles). Also, the Moon is made of lighter material. On average, a cubic centimetre (0.06 cu in) of rock from the Moon weighs only 3.3 grams (0.1 oz) compared with 5 5 grams (0.2 oz) for a cubic centimetre of Earth.
For these reasons, gravity on the Moon is much less than that on Earth, both of which Newton’s laws enable us to calculate precisely.
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