What happens to gravity in one dimension of space?

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Discussion Overview

The discussion explores how gravity would behave in one-dimensional space, comparing it to its behavior in two, three, and four dimensions. Participants examine various mathematical formulations and implications of gravity in this hypothetical scenario.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that in one dimension, gravity could be expressed as F=x/r^-1, leading to the conclusion that gravity would become stronger with distance, potentially indicating a repulsive force.
  • Another participant points out a missing integer in the initial reasoning, prompting a reevaluation of the formula.
  • A subsequent reply proposes that gravity in one dimension could be represented as F=x, implying that distance would not affect the gravitational force.
  • Another participant introduces the idea that the gravitational force could be expressed as f(r) = xln(r), suggesting that gravity would increase with distance until a certain point, after which it would become repulsive.
  • One participant asserts that gravity does not change with distance in one-dimensional space, referencing Laplace's equation and the resulting gravitational potential.
  • Another participant reiterates the same point about Laplace's equation, leading to a question of whether their previous understanding was incorrect.

Areas of Agreement / Disagreement

Participants express differing views on how gravity behaves in one-dimensional space, with no consensus reached. Some argue that gravity does not change with distance, while others propose varying models that suggest it could either increase or remain constant.

Contextual Notes

There are unresolved assumptions regarding the definitions and implications of gravity in one dimension, as well as the mathematical steps leading to different conclusions.

KeplerJunior
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I recently heard that it was found how gravity would behave in different dimensions of space. Apparently, while in our 3 dimensions of space gravity is F= x/r^2, in 4 dimensions it would be F=x/r^3, so it would be weaker, and in 2 dimensions it would be F=x/r so it would be stronger.What it didn't say was what would happen in 1 dimension, it follows from the above that it would be F=x/r^-1, which simplifies to F=xr, which would indicate that gravity would get stronger as you went further away from the object. Is this what would happen? And if so does that mean gravity would become a repulsive force?
 
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You skipped over a key integer. Hint: What integer is between -1 and +1?
 
Oh of course, so would it just be x/r^0 so x/1, so x. So then distance wouldn't change anything in 1 dimension
 
KeplerJunior said:
I recently heard that it was found how gravity would behave in different dimensions of space. Apparently, while in our 3 dimensions of space gravity is F= x/r^2, in 4 dimensions it would be F=x/r^3, so it would be weaker, and in 2 dimensions it would be F=x/r so it would be stronger.What it didn't say was what would happen in 1 dimension, it follows from the above that it would be F=x/r^-1, which simplifies to F=xr, which would indicate that gravity would get stronger as you went further away from the object. Is this what would happen? And if so does that mean gravity would become a repulsive force?

Um, actually, the integer x/r dr is xln(r). Which means the equation of gravity in one dimension would be:

f(r) = gravitational force = xln(r). So gravity would according to this increase with increased distance, something I find hard to believe. It means the further you are away, the stronger it'd pull, well until you get to a distance of 0, then it starts to push you away again... because ln(r)<0 if r<1. This is something similar to strong force, it's repulsive at a certain closeness, but if they stray too for from each other it becomes a very strong attractive force.
 
Last edited:
I thought that gravity did not change with distance in 1 dimensional space?
 
It doesn't. Laplace's equation in one dimension for the gravitational potential exterior to a point mass is simply ##\frac{\mathrm{d} ^2 \varphi}{\mathrm{d} x^2} = 0## so ##\varphi = Ax + B## and ##g = - \frac{\mathrm{d} \varphi}{\mathrm{d} x} = -A##.
 
WannabeNewton said:
It doesn't. Laplace's equation in one dimension for the gravitational potential exterior to a point mass is simply ##\frac{\mathrm{d} ^2 \varphi}{\mathrm{d} x^2} = 0## so ##\varphi = Ax + B## and ##g = - \frac{\mathrm{d} \varphi}{\mathrm{d} x} = -A##.

So I was wrong?
 

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