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Asked by anon-276414 to William, Christopher on 13 Jan 2021.
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William Smith answered on 13 Jan 2021:
Most of my knowledge of gravity comes from my hobby: rock climbing which is kind of like a fight between gravity and the climber 🙂
More seriously, gravity does actually come into my work in a roundabout sort of way…
If you have a photograph of a scene and you would like to work out exactly where the camera was positioned (i.e. where the photograph was taken from and how the camera was oriented), then it’s helpful to know which way is “down” – i.e. in which direction gravity is pulling. In modern cameras and phones, this is recorded via something called an accelerometer which is very helpful.
But even in old images we might be able to use information in the image to work out which way is down. For example, if something is hanging freely (like the end of a rope) it will be pointing down. Or if there is a manmade building, the walls are usually parallel with gravity. If the photos were taken from an aeroplane, the motion of the plane is an interaction between air resistance and gravity, again this can be modelled.
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Comments
Graham commented on :
I don’t know much about gravity except that the gravitational attraction between the Earth and the Moon causes tides. The loss of energy from tides makes the Earth rotate more slowly and move away from the Moon by almost 4 cm per year. That does not sound like much but over millions of years, it adds up. A billion years ago, the Moon was much closer, a day lasted only 18 hours, and the Moon looked much bigger in the sky. It is only today that the Sun and the Moon appear to be the same size in the sky.
Kirstie commented on :
All I know about gravity is that it means it hurts when you fall over!! 🙂
Michael commented on :
Gravity is an interesting force…it is the only fundamental force that is always attractive (the weak, strong and electromagnetic forces can also be repelling) and so when you bring enough bits of dust together their mutual gravitational attraction can build a planet.
Gravity is the warping of space-time by bodies with a large mass (like the sun) which gives the gravitational “attraction” between the sun and the earth. However, an atomic level understanding of gravity still eludes us and finding that would be rather awesome!
Gravitational waves are produced when two black holes collide (check out the LIGO work) and we measure this on earth allowing now to do gravitational astronomy.
A rather important phenomenon, crucial for the universe and life on earth (tides for example), but we are still a long way from really understanding it