Is it possible to use Newton's Law of Gravity AND Einstein's Theory of Gravity?

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Discussion Overview

The discussion revolves around the compatibility and application of Newton's Law of Gravity and Einstein's Theory of Gravity, particularly in the context of calculating gravitational forces between two masses. Participants explore whether Einstein's theory can be applied to a specific gravitational calculation and the implications of using both theories in different energy regimes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant poses a question about calculating the gravitational force between two masses using Einstein's theory, seeking clarification on the methodology.
  • Another participant asserts that Newton's gravity is a low-energy limit of Einstein's gravity, suggesting that using Newton's formula inherently involves Einstein's theory.
  • A request for examples of high-energy limits is made, along with a query about the additional information needed for calculations using Einstein's framework.
  • It is noted that Einstein's equations do not calculate force but instead describe the curvature of space-time, indicating a fundamental difference in approach compared to Newton's law.
  • A follow-up question arises regarding the calculation of curvature experienced by each mass, implying a need to consider the distortions caused by both masses.
  • One participant mentions the bending of light as a practical example of applying Einstein's theory, referencing a book that discusses this topic.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of Newton's and Einstein's theories for gravitational calculations. While some suggest a seamless integration of both theories, others emphasize the distinct nature of Einstein's approach, leading to an unresolved discussion regarding their compatibility in practical scenarios.

Contextual Notes

Participants highlight the limitations of applying Newton's law in high-energy contexts and the need for additional information when using Einstein's equations, which may not directly yield force calculations.

Who May Find This Useful

This discussion may be of interest to those studying gravitational theories, physics students exploring the relationship between classical and modern physics, and individuals curious about the implications of general relativity in practical calculations.

studentxlol
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to answer this question:

Q) A mass of 100kg is 50m away from a mass of 250kg (from centre of masses). Calculate the gravitational force of attraction between both point masses.

Could I use Einstein's theory of gravity to answer this question using the information given. If so, how would I go about doing it?
 
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Since Newton's gravity is just a low-energy limit of Einstein gravity, you technically are using Einstein gravity when you compute [itex]F = {{GmM}\over{r^2}}[/itex] :D
 
Pengwuino said:
Since Newton's gravity is just a low-energy limit of Einstein gravity, you technically are using Einstein gravity when you compute [itex]F = {{GmM}\over{r^2}}[/itex] :D

Ok. Give me an example of a high-energy limit and what extra information I need to calculate using Einstein's formula.
 
studentxlol said:
to answer this question:

Q) A mass of 100kg is 50m away from a mass of 250kg (from centre of masses). Calculate the gravitational force of attraction between both point masses.

Could I use Einstein's theory of gravity to answer this question using the information given. If so, how would I go about doing it?
Einstein's equations don't calculate force. They describe the shape of space-time. Objects move along geodesics of the space-time. No force.
 
So you would actually have to calculate the curvature felt by each object, which would be a kind of sum of the distortions from each mass?
 
khemist said:
So you would actually have to calculate the curvature felt by each object, which would be a kind of sum of the distortions from each mass?
Yes. Probably the easiest calculation is the bending of light as it grazes the sun. There is an excellent book about this and very easy to read. "The Einstein theory of Relativity" by Lieber and Lieber.
 

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