Mass, Light Speed, and the Mystery of Photons Explained

[bluecap]

A particle without mass is supposed to travel at speed of light.

But isn't it that a photon has no mass but has relativistic energy.. therefore why does it travel at speed of light.. or perhaps if a photon had no relativistic energy.. it would travel a bit faster than the current lightspeed?

 

[Orodruin]

There is no such thing as "relativistic energy". There is energy. It is unclear why you think it would travel faster than the speed of light. A massless particle can have a kinetic energy and it travels at the speed of light, there is no contradiction in that.

 

[lekh2003]

It is unclear why you think it would travel faster than the speed of light.

OP is under the assumption that the "relativistic energy" from photons can be traded for a little extra speed.

Needless to say, OP is incorrect. Your question is based on assumptions that are incorrect.

 

[bluecap]

There is no such thing as "relativistic energy". There is energy. It is unclear why you think it would travel faster than the speed of light. A massless particle can have a kinetic energy and it travels at the speed of light, there is no contradiction in that.

Can a massless particle be without any kinetic energy... and does it still travel at the speed of light?

 

[lekh2003]

Can a massless particle be without any kinetic energy... and does it still travel at the speed of light?

Massless particles are very different from normal particles. Their kinetic energy is often not related to speed directly, but instead to wave-like properties such as frequency.

 

[bluecap]

Massless particles are very different from normal particles. Their kinetic energy is often not related to speed directly, but instead to wave-like properties such as frequency.

Ok.. is there a massless particle without any frequency?

 

[lekh2003]

Ok.. is there a massless particle without any frequency?

No no that's not how it works. A photon is known to have more energy when it has a higher frequency. It doesn't work like you think it might.

You can't have zero frequency, it just gets very small.

 

[Orodruin]

Note that the energy is not something that is inherent for a type of particle. You can have a photon of any energy, it will still travel at the speed of light. The energy will also depend on the reference frame, the same photon will have different energies in different frames.

 

[bluecap]

No no that's not how it works. A photon is known to have more energy when it has a higher frequency. It doesn't work like you think it might.

You can't have zero frequency, it just gets very small.

I know the Planck quanta thing and the history of the quantum.. but I forget.. why is it in the form of frequency and waves as in wave function or even in the Hilbert space formulation which still has frequency aspect .. couldn't a particle instead have 0 and 1 as output instead of a frequency/wave. In the dark matter sector.. couldn't the particle have other modes besides frequency/waves?

 

[Dale]

Can a massless particle be without any kinetic energy... and does it still travel at the speed of light?

Such a particle would not be able to interact with anything. It would be undetectable by any means. It may as well not exist.

 

[Khashishi]

Can a massless particle be without any kinetic energy... and does it still travel at the speed of light?

If a massless particle had no kinetic energy, it would have no energy at all, and it would be literally nothing. So, no, massless particles aren't allowed to have no kinetic energy.

There is an equation which connect mass, energy, and momentum.
$E^2 = m^2 c^4 + p^2 c^2$
Massless particles (m=0) still have momentum, so all of their energy is due to momentum. It's all kinetic energy.

 

[jerromyjon]

why is it in the form of frequency and waves as in wave function

I think the wave function "waves" aren't directly related to the electromagnetic radiation "waves" like it appears you think. The photon is quite literally electromagnetic energy as it exists exclusively as waves of alternating potential.

The energy will also depend on the reference frame, the same photon will have different energies in different frames.

I understand this pretty well, but then would it be logical to think there would indeed be a frame where a photon has zero energy? Or now I'm thinking the only frame that would be is one comoving with the photon, where it would never reach you to be measured... sorry if that makes no sense!

 

[jbriggs444]

but then would it be logical to think there would indeed be a frame where a photon has zero energy?

No. You can find frames where the energy is smaller than any chosen threshold. But you cannot find a frame in which it is zero. There is no such thing as a frame of reference that is co-moving with a photon.

 

[Orodruin]

No. You can find frames where the energy is smaller than any chosen threshold. But you cannot find a frame in which it is zero. There is no such thing as a frame of reference that is co-moving with a photon.

To expand a little bit on this, if the light wave has frequency $f_0$ in one inertial frame it will have energy
$$
f = f_0 \sqrt{\frac{c-v}{c+v}}
$$
in an inertial frame moving in the same direction with speed $v$. This is just the formula for relativistic Doppler shift. Since $v < c$ for all observers, you can never find an observer for whom $f = 0$. However, you can get an arbitrarily small $f$ by just solving for $v$ in terms of that $f$ and $f_0$ in the Doppler shift formula.

 

[bluecap]

I think the wave function "waves" aren't directly related to the electromagnetic radiation "waves" like it appears you think. The photon is quite literally electromagnetic energy as it exists exclusively as waves of alternating potential.

I'm also referring to other particles besides photons. I want to know if other particles can exhibit unique modes (akin to the photon electromagnetic energy) like perhaps exhibiting 0 and 1 in the dark matter sector. Remember we can't detect any particles whether WIMPS or normal Axions so could it have non-wave or based on non-frequency modes.. what other modes in a particle can impart momentum without having any frequency?

I understand this pretty well, but then would it be logical to think there would indeed be a frame where a photon has zero energy? Or now I'm thinking the only frame that would be is one comoving with the photon, where it would never reach you to be measured... sorry if that makes no sense!

 

[Vanadium 50]

Bluecap, I've read that three times and can't make head or tail of it. Can you rewrite it?

 

[bluecap]

Bluecap, I've read that three times and can't make head or tail of it. Can you rewrite it?

I mean, there is a difference between a photon and electron.. a photon has inherent electromagnetic field while an electron has wave function.. I want a list of complete of article properties so I can know if there is another kind besides it having electromagnetic or wave function and what are the possibilities that are theoretically possible but haven't been detected yet and they trying to detect it (for example in the dark matter sector)...

 

[jerromyjon]

I mean, there is a difference between a photon and electron

Is there a difference between two photons and an electron?

 

[jerromyjon]

I want a list of complete of article properties so I can know if there is another kind besides it having electromagnetic or wave function and what are the possibilities

Sounds to me like you've seen all there is known to be and somehow you think there's more, yes, something is missing.

 

[Drakkith]

I mean, there is a difference between a photon and electron.. a photon has inherent electromagnetic field while an electron has wave function..

They're different particles with different properties, so that's the distinction between them. The photon is the quanta of the electromagnetic field while the electron is the quanta of the electron field (no, that's not the electric field). All particles are quantized excitations of their respective fields in quantum field theory and all use the same mathematical and theoretical framework to describe their behaviors. Also, photons do not have an "inherent EM field" unless you mean what I've put here.

I want a list of complete of article properties so I can know if there is another kind besides it having electromagnetic or wave function

I assume you're asking for "particle properties", in which case you can add mass, electric charge, spin, color charge, isospin, and several others to your list.

and what are the possibilities that are theoretically possible but haven't been detected yet and they trying to detect it (for example in the dark matter sector)...

I think you're trying to ask questions that are a little outside of your knowledge range right now. Try to understand what we already know about the fundamental interactions between particles before trying to ask about theoretical possibilities. Right now you're asking questions which don't make any sense and are difficult to answer, since understanding the answers themselves require some of that prerequisite knowledge.