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**from the centre of the earth by choosing the centre of the earth to be at zero potential. Here**

*R+h***is the radius of the earth and**

*R**is*

**h****not**very small wrt to

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- Thread starter Pratik Saha
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sophiecentaur

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That's a very bad place to take your reference from because the GPE is proportional to 1/r and it is indeterminate (aka -Infinity) for r=0. The normal reference for GPE in general is Infinity (for which the GPE reference is 0 (1/∞) or Mean Sea Level when you are doing calculations on Earth.by choosing the centre of the earth to be at zero potential

If you are going below that level then the GPE would be negative but no problem.

Google Gravitational Potential and all the common formulae (mgh etc.) can be found along with interesting reading.

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jbriggs444

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That is correct for an idealized Earth with all of its mass concentrated in the center (and maybe a thin shell we can stand on at 6000 km radius).That's a very bad place to take your reference from because the GPE is proportional to 1/r and it is indeterminate (aka -Infinity) for r=0.

For a realistic Earth, using a zero point at the center is still a poor choice because we have no highly accurate way of measuring potential difference between here and there. By contrast, we do have accurate measurements for the potential difference between here and infinity.

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sophiecentaur

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Yes but how would we calibrate our Earthbound measuring machines without still referring to some 'standard' measurement point on Earth? Most space navigation problems get away with a reference at infinity but most Earthbound problems are solved by assuming a spherical Earth and then applying some correction to the value of g if necessary. Where is your 'here'?By contrast, we do have accurate measurements for the potential difference between here and infinity.

Both approaches have their place, I think.

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jbriggs444

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I am not a metrologist. I suspect that your point is entirely correct and that "the geoid" is used as the operational standard rather than "infinity" for many purposes.Yes but how would we calibrate our Earthbound measuring machines without still referring to some 'standard' measurement point on Earth?

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Thanks a lot! I was thinking the same bc the answer would come same btw 2 points in however reference I take it, but not to mention that calculation would be a bit hectic to formulate coz the visualization of such case is indeed unusual...Hello and welcome to PF

That's a very bad place to take your reference from because the GPE is proportional to 1/r and it is indeterminate (aka -Infinity) for r=0. The normal reference for GPE in general is Infinity (for which the GPE reference is 0 (1/∞) or Mean Sea Level when you are doing calculations on Earth.

If you are going below that level then the GPE would be negative but no problem.

Google Gravitational Potential and all the common formulae (mgh etc.) can be found along with interesting reading.

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Thanks a lot to everyone for sharing their opinion on this topic!!! :)

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