Is the Photon Mass Really Zero or Does It Have a Finite Value?

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Discussion Overview

The discussion centers on the mass of the photon, exploring whether it is truly zero or if it possesses a finite value. Participants engage with concepts from relativity, energy, and the implications of massless particles, with references to both theoretical and experimental perspectives.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants assert that the photon has zero mass, citing its properties and the implications of Einstein's relativity.
  • Others express skepticism about the idea of a massless photon, suggesting that its energy, calculated as h x λ, implies a small but finite mass.
  • One participant references Einstein's equation E = mc², arguing that it applies to mass-energy conversion in nuclear reactions, which raises questions about the mass of photons.
  • Another participant corrects a claim regarding the applicability of E = mc² to photons, stating that the complete form of the equation includes momentum and that photons possess momentum despite having no mass.
  • Some participants discuss the implications of massless particles, suggesting that if photons were truly massless, they would travel at infinite speed, which contradicts observed phenomena.
  • There are mentions of misleading information from YouTube videos, with suggestions to seek more reliable sources for understanding particle physics.

Areas of Agreement / Disagreement

Participants generally disagree on the mass of the photon, with some supporting the idea of zero mass and others proposing that it has a small, finite mass. The discussion remains unresolved with multiple competing views present.

Contextual Notes

Some claims rely on interpretations of Einstein's equations and the definitions of mass and energy, which may not be universally accepted. The discussion also touches on the limitations of popular science media in conveying complex physics concepts.

vijayst
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Photon is the sub-atomic particle that light is made of. The properties of Photon:
Mass = 0, Charge = 0, Spin = 1.

According to Einstein's relativity, light travels fastest at 300,000 km / sec. When any other object travels at the speed of light, the universe shrinks to zero distance. But, we know that it takes 8.3 minutes for light from the sun to reach earth. So, even for sun light, the universe does not shrink to zero.

I find it hard to believe that photon has no mass. The energy of a photon is h x λ (Planks constant multiplied by Frequency) is roughly 10-20 Joules, small but finite.

According to Einstein, E = mc2. In a nuclear reaction, the mass lost is converted to energy which is carried by photon. Consider a hypothetical experiment, where photon is converted to a truly mass-less energy "particle". In the experiment, the mass of a photon is converted to pure energy. In short, the mass of the photon is lost. The lost mass is equivalent to the energy calculated by Planks formula (proportional to its frequency). So, the mass of a photon is 10-36 (small but finite).

If there was a mass-less particle, it would travel at infinite speed and can move from one end of the universe to the other end of the universe in zero time. For a truly mass-less particle, the universe would truly shrink to zero.
 
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vijayst said:
But, we know that it takes 8.3 minutes for light from the sun to reach earth. So, even for sun light, the universe does not shrink to zero.

You seem to be working in the frame of a photon. This is not possible in physics.

I find it hard to believe that photon has no mass. The energy of a photon is h x λ (Planks constant multiplied by Frequency) is roughly 10-20 Joules, small but finite.

According to Einstein, E = mc2.

This is not the actual formula. The formula is fine for slow moving objects, but not for things like photons.

If there was a mass-less particle, it would travel at infinite speed and can move from one end of the universe to the other end of the universe in zero time. For a truly mass-less particle, the universe would truly shrink to zero.

This is completely false and contrary to mainstream physics. Please do not write things like that.

Some things to read:
https://www.physicsforums.com/showthread.php?t=511175
https://www.physicsforums.com/showthread.php?t=511173
https://www.physicsforums.com/showthread.php?t=511170
https://www.physicsforums.com/showthread.php?t=512541
 
Last edited by a moderator:
vijayst said:
According to Einstein, E = mc2.

The full form of the equation is e2 = m2c4 + p2c2, where p = the momentum of the an object. Photons do not have mass, but they do possesses momentum. So even when the mass is zero, you still have a finite amount of energy.

You can check that here: http://en.wikipedia.org/wiki/Photon#Physical_properties
 
Thank you, micromass, Drakkith. It is 17 years since I last read a formal textbook in physics. I recently got interested in Particle Physics. One of the YouTube video misled me to come to the above conclusions.

As you rightly pointed out, I should have warned the reader that I was trying to prove a claim.
 
vijayst said:
One of the YouTube video misled me to come to the above conclusions.

You better avoid youtube videos and watch some nice lectures. Sometimes, youtube videos tend to mislead others
 
vijayst said:
Photon is the sub-atomic particle that light is made of. The properties of Photon:
Mass = 0, Charge = 0, Spin = 1.

According to Einstein's relativity, light travels fastest at 300,000 km / sec. When any other object travels at the speed of light, the universe shrinks to zero distance. But, we know that it takes 8.3 minutes for light from the sun to reach earth. So, even for sun light, the universe does not shrink to zero.

I find it hard to believe that photon has no mass. The energy of a photon is h x λ (Planks constant multiplied by Frequency) is roughly 10-20 Joules, small but finite.

According to Einstein, E = mc2. In a nuclear reaction, the mass lost is converted to energy which is carried by photon. Consider a hypothetical experiment, where photon is converted to a truly mass-less energy "particle". In the experiment, the mass of a photon is converted to pure energy. In short, the mass of the photon is lost. The lost mass is equivalent to the energy calculated by Planks formula (proportional to its frequency). So, the mass of a photon is 10-36 (small but finite).

If there was a mass-less particle, it would travel at infinite speed and can move from one end of the universe to the other end of the universe in zero time. For a truly mass-less particle, the universe would truly shrink to zero.

You should phrase your statements as questions. That way it doesn't sound like you think you understand something that you really don't.
 
adjacent said:
You better avoid youtube videos and watch some nice lectures. Sometimes, youtube videos tend to mislead others

I vote for less avoidance and more participation so that more people are exposed to real Science. Granted, it can seem an often thankless "job" but it's difficult to argue that it is ignore-worthy.
 

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