Relativity: Massless particles and photons

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Discussion Overview

The discussion revolves around the nature of massless particles, particularly photons, and their relationship to mass and the speed of light. Participants explore concepts related to relativistic mass, the existence of massless particles, and the properties of photons in the context of physics.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants assert that if a particle moves at the speed of light, it becomes massless, while others argue that particles are either massless or massive and do not change their mass based on speed.
  • There is contention regarding the existence of massless particles, with some claiming that massless particles have no practical existence, while others reference the Standard Model which includes massless particles like photons.
  • Participants discuss the relationship between mass and speed, with one participant stating that a massive particle cannot travel at the speed of light and that relativistic mass approaches infinity as speed approaches light speed.
  • Confusion arises over the claim that photons are heavier than electrons, with multiple participants correcting this misunderstanding by stating that photons are massless.
  • One participant suggests that the understanding of these concepts may require revisiting foundational ideas, indicating a need for clarification on several points raised in the discussion.

Areas of Agreement / Disagreement

Participants express multiple competing views on the nature of massless particles and the implications of speed on mass. There is no consensus on the existence of massless particles or the interpretation of relativistic mass.

Contextual Notes

Some statements made by participants rely on specific interpretations of physics concepts, and there are unresolved assumptions regarding the definitions of mass and the implications of traveling at the speed of light.

sunmoon
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I f a particle starts moving with the velocity of light it becomes massless.But practically a massless particle has no existence.Again one of the main constituents of light is photon,then is it a massless particle?But I know electron has the least mass in this world and photon is heavier than it.So I am totally confused.
 
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sunmoon said:
I f a particle starts moving with the velocity of light it becomes massless.
It does not.
Particles are either massless, then they always travel at the speed of light, or they are not, then they never do that.
sunmoon said:
But practically a massless particle has no existence.
"Existence" can have philosophical issues, but I think light clearly exists.
sunmoon said:
Again one of the main constituents of light is photon
It is not a constituent. Light can be described with the concept of photons.
sunmoon said:
But I know electron has the least mass in this world
It does not. Neutrinos are lighter. And massless particles are even lighter of course, this includes the photon.
 
sunmoon said:
I f a particle starts moving with the velocity of light it becomes massless.But practically a massless particle has no existence.Again one of the main constituents of light is photon,then is it a massless particle?But I know electron has the least mass in this world and photon is heavier than it.So I am totally confused.

Hi there you have miss understood the equation if a particle travell with speed of light then its mass would become infinity remember the equation

M'= Mo/(√1- V2/C2)
 
Suraj Nehra said:
Hi there you have miss understood the equation if a particle travell with speed of light then its mass would become infinity remember the equation

That is still misleading... Keep in mind that no massive particle can travel with the speed of light...
If you take the limit of the velocity going to c, then you have that the relativistic mass (M' you wrote) goes to infinity, and not the rest (invariant) mass, which we call the mass of a particle.
The relativistic mass is more like the total energy of your particle (contains also the kinetic energy) and that's why the energy is written as E= m_0 \gamma (= m_{rel}).
 
sunmoon said:
I f a particle starts moving with the velocity of light it becomes massless.

You have an error in cause-and-effect here. A particle doesn't become massless when it "starts moving with the velocity of light". It is either massless, or it isn't! If it is massless, then it will move at c. It doesn't become massless when it reaches c.

But practically a massless particle has no existence.

Says who? What natural law are you using here to claim that there are no massless particle, especially when the Standard Model of elementary particle says that there is? Be very careful, on this forum, about espousing your personal beliefs, especially when it is glaringly wrong! Read the PF Rules!

Again one of the main constituents of light is photon,then is it a massless particle?

It is not the "main constituents", it is the ONLY constituent! Light is not made up of anything else.

But I know electron has the least mass in this world and photon is heavier than it.So I am totally confused.

Where did you get that a photon is "heavier" than an electron? It is difficult to answer your question when you are already asking us to explain it based on your faulty understanding. A photon is NOT heavier than an electron, as far as having a mass is concerned. A photon is massless. Period!

Maybe you need to start reexamining one conjecture at a time! Every single sentence that you posted here is faulty! Start from the beginning, and you might learn something without asking if you start reading our FAQ first, because I have a strong feeling a lot of your wrong understanding can be corrected by at least a couple of our FAQs.

Zz.
 
ZapperZ said:
Maybe you need to start reexamining one conjecture at a time! Every single sentence that you posted here is faulty! Start from the beginning, and you might learn something without asking if you start reading our FAQ first, because I have a strong feeling a lot of your wrong understanding can be corrected by at least a couple of our FAQs.

Says the person who have contributed in writing many parts of those FAQs o0) I can feel you there...
 

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