Planck Length & Singularity: Point or Sphere?

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Discussion Overview

The discussion revolves around the nature of the Planck length and its implications for the concept of singularities and point particles in physics. Participants explore whether entities like electrons or singularities can be considered true points or if they must be represented as spherical volumes with a diameter of the Planck length. The conversation touches on theoretical implications, speculative ideas in quantum gravity, and the validity of Planck units.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant suggests that since the Planck length cannot be further subdivided, it implies that point particles like electrons must be spherical volumes rather than true points.
  • Another participant counters that the assertion of Planck length as the smallest unit is speculative and lacks empirical evidence, emphasizing the challenges in probing such small scales.
  • A different participant acknowledges the established nature of the Planck constant and questions the validity of the equations leading to Planck units, seeking clarification on their implications.
  • Some participants argue that while the equations for Planck units are valid, this does not necessarily mean they represent the smallest possible sizes of physical entities.
  • It is noted that a black hole singularity is not a point in space but rather a moment in time, challenging the notion of singularities as point-like entities.
  • One participant reflects on the implications of an electron having a diameter equal to the Planck length, questioning the interpretation of such a size.

Areas of Agreement / Disagreement

Participants express differing views on the implications of the Planck length and the nature of singularities and point particles. There is no consensus on whether Planck units represent the smallest possible sizes or how to interpret singularities in this context.

Contextual Notes

Participants highlight the speculative nature of current understanding regarding Planck length and its implications, as well as the limitations in probing such small scales. The discussion also reflects on the definitions and interpretations of singularities in black holes.

jnorman34
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TL;DR
Does the concept of “Planck length” imply that a singularity (or any other “point” particle) is not actually a “point”?
Since Planck length is a distance unit of space-time which cannot be further subdivided, would that not imply that an electron, or singularity, or any other point particle cannot actually be a “point”, but must rather be a spherical volume with a Planck length diameter?
i realize this may well be a naive question based on my poor understanding of so many fundamental concepts. Thank you.
 
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jnorman34 said:
Planck length is a distance unit of space-time which cannot be further subdivided

We don't know that this is true. It is a common speculation in quantum gravity, but it's just a speculation. We have no evidence to back it up, and no feasible way of getting any for the foreseeable future, since it would require probing length scales 20 orders of magnitude smaller than the smallest ones we can probe today.
 
Thanks Peter - as I understand it, the Planck constant is well established, and Planck length, Planck time, etc are derived directly from the Planck constant. Is there any reason to question the validity of the equations that lead to these Planck units?
 
jnorman34 said:
Is there any reason to question the validity of the equations that lead to these Planck units?

No, but there is also no reason to think of Planck units as the smallest of anything. The Planck resistance is 30 ohms.
 
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jnorman34 said:
Is there any reason to question the validity of the equations that lead to these Planck units?

No, but the Planck units having particular values is not the same as those values being the smallest possible sizes of things.
 
jnorman34 said:
singularity, or any other point particle
Also worth noting is that a black hole singularity isn't a point in space anyway. A Schwarzschild black hole's singularity is a moment in time (despite a lot of popsci descriptions).
 
jnorman34 said:
Since Planck length is a distance unit of space-time which cannot be further subdivided, would that not imply that an electron, or singularity, or any other point particle cannot actually be a “point”, but must rather be a spherical volume with a Planck length diameter?

If an electron had a diameter of the Planck length, then its radius would be half the Planck length. Hmm?
 
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