Could Zero Distance Create Infinite Gravitational Force?

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Discussion Overview

The discussion centers around the concept of gravitational force between objects at very small distances, particularly questioning whether zero distance could lead to infinite gravitational force. Participants explore the implications of classical mechanics and quantum effects in this context.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant suggests that if the separation between two objects is zero, the gravitational force should be infinite due to the division by r in the gravitational force equation.
  • Another participant counters that while the distances are small, the masses involved are also tiny, resulting in a small gravitational force overall.
  • A participant questions the magnitude of the gravitational force between their foot and the ground, implying it should be large due to contact.
  • It is noted that the gravitational force between extended masses requires consideration of the distance between their centers of mass, which remains significant.
  • One participant raises the idea that classical mechanics may break down at quantum levels when discussing forces at very small distances.
  • Another participant reiterates that only a few atoms are in contact with the ground, suggesting that not all mass contributes to the gravitational force at such scales.
  • A later reply states that Newton's Law of gravitation breaks down at small distances, indicating a transition to quantum effects, and similarly, Newton's Laws of motion break down at relativistic speeds.

Areas of Agreement / Disagreement

Participants express differing views on the implications of gravitational force at small distances, with no consensus on whether classical mechanics adequately describes these scenarios or if quantum mechanics must be invoked.

Contextual Notes

Limitations include the assumptions about the applicability of classical mechanics at small scales and the definitions of mass and distance in the context of gravitational interactions.

schaefera
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If the separation between two objects (say, me and my chair) is zero, shouldn't the gravitational force between those two objects be infinite because in the equation for force you divide by r?

And I understand that the centers of my atoms are not literally touching the chair, so maybe the separation is miniscule... but as they get so close that they are only TINY distances apart, the gravitational force should at least APPROACH infinity? But this seems to defy logic...
 
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They are tiny distances apart but the mass of those atoms is also tiny and the gravitational constant is also tiny, so you get a tiny number.
 
Ok well take the mass of my foot and the mass of the ground with which it is in contact. Shouldn't this be a magnificentally large force?
 
The gravitational force between two extended (not point) masses is
\frac{GmM}{r^2}.

where r is the distance beween their center of masses. For your body and the earth, that is a very large distance.

If you want to calculate forces between, say, atoms that are very close together then you have to deal with those very, very small masses at very small distances.
 
So would this be an example of the equations of classical mechanics breaking down when you get to quantum levels?
 
schaefera said:
Ok well take the mass of my foot and the mass of the ground with which it is in contact. Shouldn't this be a magnificentally large force?

No, only a few atoms are close to the ground, the rest aren't.
 
It's simple: Newton's Law for gravitation brakes down when you look at very small distances. Greetings! you're entering the realm of Quantum effects.
As do Newton's Laws of motion brake down when you travel at velocities close to the speed of light. Say hello the world of Relativity! :)
 

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