What is the actual size of a photon?

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Discussion Overview

The discussion centers around the concept of the size of a photon, exploring various interpretations and implications of this idea within quantum mechanics and general relativity. Participants examine the relationship between photons and their wavelengths, the implications of point particles, and the relevance of Schwarzschild radius in defining size.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants suggest that photons are point particles in quantum mechanics, implying they have no spatial extension.
  • Others propose that the size of a photon could be related to its wavelength, suggesting that the natural size of a photon is approximately equal to its wavelength.
  • There is a discussion about the Schwarzschild radius, with some arguing it sets a fundamental limit on how much mass/energy can be packed in space, while others question its relevance to the physical size of a photon.
  • Some participants express skepticism about the notion of point particles and the associated infinities, suggesting that the concept of size should be measured in bits rather than traditional spatial dimensions.
  • A few participants mention the classical electron radius as a potential measure, but emphasize that the figure of interest should be the radius for matter distribution.
  • There are conflicting views on whether it is valid to consider the size of a photon in the context of squeezing it into a black hole, with some arguing against this approach.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the size of a photon, with multiple competing views and interpretations remaining throughout the discussion. The relationship between quantum mechanics and general relativity, particularly regarding the concept of size, is contested.

Contextual Notes

Limitations include unresolved definitions of "size," dependence on interpretations of quantum mechanics, and the implications of theoretical constructs like Schwarzschild radius and point particles. The discussion reflects a variety of assumptions and perspectives without definitive conclusions.

  • #31
ansgar said:
E = mc^2 is not valid for a photon...

E^2 = (mc^2)^2 + (pc)^2

or did you mean that m = m_0 x Gamma ?

then Gamma = infinity for photons...

sorry dmtr, there is something strange going on here :(

and what is a CS grad?

Computer science graduate. Read "complete failure in physics".

Yes. E^2 = (mc^2)^2 + (pc)^2. But m = 0. So E = pc.
Now I'm trying to calculate the equivalent increase of the mass of the black hole (assuming I throw that photon into it), AFAIK I can use the mass-energy equivalence principle - E = mc^2 for that.
 
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  • #32
The OP appeared to have not participated in this thread beyond the first post. As has been pointed out, this has been discussed already many times before, and a link to one of them has been provided.

How this thread has somehow meandered into a black hole is beyond me.

Zz.
 

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