What is the actual size of a photon?

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The discussion centers on the size of a photon, with participants debating its nature as a point particle in quantum mechanics, which implies it has no spatial extension. The conversation touches on concepts like the Schwarzschild radius and classical electron radius, suggesting these relate to fundamental limits on mass and energy density. Participants argue about the appropriate way to conceptualize the "size" of a photon, with some proposing that it should be measured in terms of the smallest aperture it can pass through without distortion. The complexities of quantum gravity and the limitations of current theories are acknowledged, highlighting the ongoing debate in physics regarding the nature of particles and their sizes. Ultimately, the discussion reflects the intricate relationship between quantum mechanics and general relativity.
  • #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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