- #1
DaveC426913
Gold Member
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I am trying to explain to someone why there is still gravitational time dilation at the centre of the Earth.
(Not to over-tax the rubber sheet analogy, but...)
When we sketch a gravity well, we show a curve that starts out nearly flat, then curves away from the flat plane, until it reaches the centre of the mass. At that point, it is parallel with flat space, but not in the flat space plane. i.e. Y has a non-zero, negative value, yet a slope of zero.
So, the y-axis in this diagram does not represent gravitational force experienced , since otherwise it should a y=0.
So, how do we describe the gravitational state of the small area at the bottom of this well?
More to the point, how do I convince my colleague that, at that point - though gravitational forces are cancelled, they are not ... zero? And that GR time dilation applies here?
What is the term? Gravitational potential?
(Not to over-tax the rubber sheet analogy, but...)
When we sketch a gravity well, we show a curve that starts out nearly flat, then curves away from the flat plane, until it reaches the centre of the mass. At that point, it is parallel with flat space, but not in the flat space plane. i.e. Y has a non-zero, negative value, yet a slope of zero.
So, the y-axis in this diagram does not represent gravitational force experienced , since otherwise it should a y=0.
So, how do we describe the gravitational state of the small area at the bottom of this well?
More to the point, how do I convince my colleague that, at that point - though gravitational forces are cancelled, they are not ... zero? And that GR time dilation applies here?
What is the term? Gravitational potential?