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Bill1939's avatar

Can a photon be smaller than a Planck sphere?

Asked by Bill1939 (7195 points ) April 12th, 2014

Since a photon particle exists in the physical universe it seems to me that it could not be smaller than a Planck sphere, which would have a diameter of one Planck length. Viewing “Cosmos” number five I learned that an electron, while remaining within its fixed orbital, travels a distance greater than the circumference of its orbit. This led me to imagine that the surface of a Planck sphere could have movement without leaving the sphere’s area. In this way the sphere could have an electromagnetic vibration and could be a photon. Any thoughts about my conjecture?

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9 Answers

cazzie's avatar

The planck length is 1.616 X 10–35 meters long. Now…. a photon is a conundrum because it seems to have mass, but acts like a wave (pure energy). From what I understand of the facts, photons take up even less space than a planck. Again, this is really unprovable ideas of quantum physics and I haven’t studied quite enough. I’ll see if BBE can weigh in on this with how he understands it as a PhD of physics.

flutherother's avatar

I can’t imagine a Planck sphere with a diameter of one Planck length. If there is no dimension smaller than the diameter in what dimension does the sphere curve? Does this make sense?

jerv's avatar

I think that there is enough leeway in the phrase “exists in the physical universe” as it pertains to subatomic particles that a truly accurate answer to this question may alter our understanding of the universe. The fact that we have yet to definitively figure out photons reinforces that belief.

Dan_Lyons's avatar

Photons are the part part of light that is a particle. What is the part of light which acts like a wave?

cazzie's avatar

OK.. I did some reading. Photons have no set size because their planck length can be infinitely small or large, depending on their wavelength. That make sense, right? Also, their size can be altered simply by our perception, Doppler effect, say if we are travelling towards them, they will appear to be smaller.

Now, I think what you want to read about is Compton wavelength. Here:

Theoretically, a photon can not be smaller than the size of its gamma wave. That makes sense too, but not something that has been proven.

Bill1939's avatar

@cazzie thanks for the link. I am trying to absorb the ideas expressed in digital wave theory. I may lack sufficient intellect to grasp it fully. However, this will not stop me from trying. The concept of a Planck Instance is particularly appealing as well as the idea that the distance between them is a determinant of the frequency of a photon. That a photon particle only exists at Planck Instances seems analogous the presence of electrons at fixed orbitals. Thanks again.

cazzie's avatar

Sure. Also, I just ran my post by BBE and he said, “not bad”. So I guess I understood what I read well enough.

physitron's avatar

This may help. The beginning of understanding about Planck units is to grasp what the Planck length is. This was derived by Planck and published in 1905 as a relationship between three constants: Gravity, the speed of light and the Planck reduced constant, h bar. The equation is

Planck L = square root of (h bar X G/c cubed)

When the units of the constants are put in, we get the Planck length.

The Planck time is the time it takes light to travel one Planck length. Although the Planck volume is calculated in CODATA as a square with the Planck length as one side, people who work in this area often calculate the Planck volume as a sphere. We don’t worry about whether or not you can stack spheres the same way you can stack little squares. Just as you can imagine the little round bags we call “protons” to be stretchable bags that contain quarks, we can image that Planck spheres (sometimes called “particles”) can spontaneously assume different shapes. Also,a photon cannot be smaller (that is, could not have a MEASURABLE wavelength smaller) than a Planck sphere because the Planck length (the diameter of the sphere) is, by definition, the smallest space-time phenomenon measurable.

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