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# Describe how a mass creates a gravitational field in the space around it watch

1. Describe how a mass creates a gravitational field in the space around it
2. Bowling ball on a trampoline analogy: the bowling ball is a heavy object and the trampoline is the fabric of space.

(despite that the reason the bowling ball sinks is because of gravity, it works pretty well)
3. I would also like to know an exam style answer for this
4. Unless you're taking General Relativity, there is no description of how this happens. In Newtonian mechanics, it's simply stated that gravitational fields are produced by the presence of a mass, and acts upon other masses; which isn't so helpful as it amounts to the answer of "why?" being "Because it's there".

In the case of Relativity, the 'bowling ball on a trampoline' is the analogy most commonly seen. A lot of people dislike it because they feel it tries to describe gravity, with gravity; but personally I think it's a good analogy, since the sheet only shows the curvature of one plane (and probably not correctly) while gravity helps to show how the curvature in general causes the path of an object to change. Mass causes curves in space-time, and other masses travel along locally straight paths in this curved space. This is hard to think about since all your intuition and experience of space is Euclidean, whereas all this takes place in Riemannian geometry (and that's far more complicated than euclidean!). I like to think about this as how/why light cannot escape black holes, even though it's massless. Black holes create such a strong gravitational field, that the curviness of space is so great, that when light enters it travels (from an outside perspective; the light itself will think it's moving in a straight line) around these curves, and cannot escape from the black hole because none of the curves it has to travel along will lead out of it.
5. (Original post by FireGarden)
Unless you're taking General Relativity, there is no description of how this happens. In Newtonian mechanics, it's simply stated that gravitational fields are produced by the presence of a mass, and acts upon other masses; which isn't so helpful as it amounts to the answer of "why?" being "Because it's there".

In the case of Relativity, the 'bowling ball on a trampoline' is the analogy most commonly seen. A lot of people dislike it because they feel it tries to describe gravity, with gravity; but personally I think it's a good analogy, since the sheet only shows the curvature of one plane (and probably not correctly) while gravity helps to show how the curvature in general causes the path of an object to change. Mass causes curves in space-time, and other masses travel along locally straight paths in this curved space. This is hard to think about since all your intuition and experience of space is Euclidean, whereas all this takes place in Riemannian geometry (and that's far more complicated than euclidean!). I like to think about this as how/why light cannot escape black holes, even though it's massless. Black holes create such a strong gravitational field, that the curviness of space is so great, that when light enters it travels (from an outside perspective; the light itself will think it's moving in a straight line) around these curves, and cannot escape from the black hole because none of the curves it has to travel along will lead out of it.
you explained that so well! very insightful
6. For A level , the field 'explanation' runs something like this.

The mass creates a gravitational field
The field spreads out into the space around it at the speed of light.
When the field 'reaches' another mass, it creates an attractive force on the mass.
7. (Original post by teachercol)
For A level , the field 'explanation' runs something like this.

The mass creates a gravitational field
The field spreads out into the space around it at the speed of light.
When the field 'reaches' another mass, it creates an attractive force on the mass.
Spent so long trying to find a good, simple explanation, thanks!
8. Take in consideration, space is warped, then time will be more or less in certain areas of space.
And space is warping most or all of the time.

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