Relativity: Massless particles and photons

In summary, the conversation discusses the concept of massless particles and their existence, specifically in relation to light and the photon. It is clarified that a particle does not become massless when it reaches the speed of light, it is either massless or not. The idea that a massless particle has no existence is questioned, as the Standard Model of elementary particles includes massless particles. It is also corrected that the photon is not a constituent of light, but rather the only constituent. The belief that a photon is heavier than an electron is also addressed and corrected. The suggestion to start reexamining one's understanding and reading the FAQ section on the topic is given.
  • #1
sunmoon
4
0
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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  • #2
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.
 
  • #3
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)
 
  • #4
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 [itex]E= m_0 \gamma (= m_{rel})[/itex].
 
  • #5
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.
 
  • #6
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...
 

FAQ: Relativity: Massless particles and photons

1. What is the theory of relativity?

The theory of relativity is a scientific theory developed by Albert Einstein in the early 20th century. It explains the relationship between space and time, and how they are affected by the presence of matter and energy.

2. What are massless particles?

Massless particles are particles that have no rest mass, meaning they do not have any physical substance or material. The most well-known example of a massless particle is the photon, which is the fundamental particle of light.

3. How are massless particles and photons related to relativity?

According to the theory of relativity, the speed of light is constant and the same for all observers, regardless of their relative motion. This means that massless particles, such as photons, must also travel at the speed of light, and their behavior is governed by the principles of relativity.

4. Can massless particles have energy?

Yes, even though massless particles do not have any rest mass, they can still have energy. This is because energy and mass are equivalent, as stated in Einstein's famous equation E=mc². Photons, for example, have energy in the form of their frequency and wavelength.

5. How does the theory of relativity impact our understanding of the universe?

The theory of relativity has had a significant impact on our understanding of the universe. It has helped us to understand the fundamental principles of space and time, and has led to groundbreaking discoveries in fields such as cosmology, astrophysics, and particle physics. It has also played a crucial role in the development of technologies such as GPS and nuclear energy.

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