Gravitational Attraction of a Massive Particle

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Discussion Overview

The discussion centers on the equations governing the gravitational attraction of a massive particle, such as a proton, particularly when it is traveling at near light speed. The scope includes theoretical aspects of gravitational fields, the limitations of current understanding in quantum gravity, and the mathematical frameworks involved.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant inquires about the equations for gravitational attraction of a massive particle at relativistic speeds.
  • Another participant questions the inquirer's level of understanding in physics and mathematics.
  • A participant notes that current knowledge does not allow for a clear understanding of the gravitational field around single particles due to the absence of a working quantum theory of gravity.
  • It is suggested that undergraduate-level algebra and calculus are insufficient for grasping the equations of General Relativity (GR), which require knowledge of differential geometry and tensor calculus.
  • A participant mentions that while all objects are affected by gravity, measuring a "gravitational field" is not straightforward, particularly for moving masses.
  • Another participant introduces the concept of measuring the tidal gravitational field of a moving particle and references the Aichelburg-Sexl solution, which resembles a plane wave similar to electromagnetic waves.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the mathematical requirements for discussing gravitational attraction at relativistic speeds, and there is no consensus on the feasibility of measuring gravitational fields for single particles.

Contextual Notes

The discussion highlights limitations in current theoretical frameworks, particularly the lack of a quantum theory of gravity and the complexity of the mathematics involved in GR.

GuyWQuestion
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I was wondering what equations govern calculating the gravitation attraction of a massive particle (say a proton) traveling at near light speed? Thanks!
 
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What is your current level of understanding of physics and mathematics?
 
Lets go with college level Algebra, but I've taken college level Calculus, just don't remember most of it.
 
Okay. Just to be precise, we don't know how the gravitational field looks around single particles because we don't have a working quantum theory of gravity yet. We can say quite a bit about more massive objects though.

Unfortunately, college undergraduate level algebra and calculus is insufficient in order to understand the equations of GR, the matematical framework for which is differential geometry and tensor calculus. As such, giving you the equations immediately would be meaningless. I suggest you take a look at Prof. Susskind's video lecture series on GR, which is available fo free on youtube;

Here is the link to the Special Relativity lecture series:
General relativity lecture series:
 
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Because all objects are affected by gravity, we can't actually measure a "gravitational field" in the same sense that we can measure , say, an electric field. In some specialized circumstances we can work around this lack of a reference particle that would be "unaffected by gravity", but the case of a moving mass isn't one of those special circumstances.

What we could measure, in principle, is the tidal gravitational field of a moving particle - the accelerations induced in nearby test particles relative to each other. Unfortunately, the detailed presentation on it gets rather technical. It's known as the Aichelburg - Sexyl solution, and in general terms, it looks like a plane wave, similar to the electromagnetic case, which behaves in a similar manner.
 

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