is photon considered matter?

- ghazi

is photon considered matter?

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- anonymous

Of course not. Surely you know this?

- Xishem

Nope. Matter must have mass, and photons are massless!

- anonymous

Well...that's a little complicated. It kind of depends on what you mean by "matter." If you mean "stuff that exists," then, yes, electromagnetic radiation is a peculiar kind of matter that has energy, momentum, spin -- but zero rest mass. It certainly exists.
But you might also mean by "matter" is "stuff that exists and has a rest mass greater than zero" in which case photons do not qualify. I'm not sure what you'd call them in that case. You probably need to make a special category.
It's tempting often to call photons "energy," but that is not correct. Energy is a property of substances, like mass or charge, and is not itself a substance. A photon *has* energy, just like a speeding bullet -- it is not energy itself.

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## More answers

- anonymous

YES PHOTONS ARE MATTER

- anonymous

YES PHOTONS HAVE MASS

- anonymous

It is called the motion-mass because photons only EXIST while moving

- anonymous

AND it can be measured and even USED FOR ROCKET PROPULSION. There is this principle of Solar Sail (you can easily google up tons and tons of articles on both the theory and the engineering required for solar sails)

- anonymous

Summary:
1 Photon IS matter
2 Photons have mass
3 It can be measured AND used for rocket propulsion

- ghazi

@carl_pham that's why i am confused....actually if you consider definition of entropy it says photon is the ultimate elementary particle and for more info because of what i am confused is here http://xian.name/en/articles.htm and if it is matter..then i'll have some new deductions.... @Mikael Impressive thank you...i'll have to go through your points

- anonymous

@ghazi - one more point, which is also relevant here. There MATTER particles which ARE matter and have almost NO mass - the neutrino-s (not the sopranos , the Neutrinos).
They also are matter.

- anonymous

You can calculate mass of photon using de broglie wavelength equation

- anonymous

use wavelength of visible light

- ghazi

exactly neutrinos are mass less but still considered as matter....hmm.something can be done on a new concept....de broglie equation fails for photon

- anonymous

lol .. :p

- anonymous

Well I think the most EN-LIGHTENING way (Pun INTENDED) to compute photon mass is by Einstein's equation E = mc^2

- anonymous

\[{\E_{ph}} = h \nu\]

- anonymous

Then \[{\m_{ph}}*c^2 = h\nu\]

- ghazi

@vikrantg4 de broglie said that it's the only case of photon where he was compelled to consider dual behavior and ....he was forced to consider frequency.....although he found it difficult to correlate dual behaviour for light

- anonymous

oh.. i am new to this topic.. :P

- ghazi

okay..that's fine...

- anonymous

The whole point of MELTING-TOGETHER of notions of energy and matter was from TWO directions" De Broglie showed that being a particle is not necessarily different from being a wave (so particulate matter and wave-like energy are same) and Albert Einstein

- anonymous

showed that HAVING AN ENERGY is equivalent to HAVING a mass (this statement is INDEPENDENT of De Broglie's revelation)

- anonymous

Aaa-nd you are welcome to become my "fan" , which i think is well deserved here

- anonymous

Thx and mutually

- ghazi

i went through the model of wolf...but that's far away from particle nature..so i am still struggling to classify photon....i guess i'll do it soon ....but your stuff was really helpful...and try to go to the link i've mentioned

- anonymous

1 Photons actually exist as space-localized WAVEPACKET form - so they have fuzzy kind of "size' or "extent"

- anonymous

2 There are research articles of the last 15 years on the actual EXACT wavefunction of the photon. You can look them up in scholar.google.com

- ghazi

what you believe? is it considered matter?? or not?

- anonymous

@ghazi of course it is matter. If you want my intuition , then the more fundamental "thing" is Energy. Protons, neutrons, photons, electrons - all of them are actually "made of" energy tightly woven into kind of granny's wool filament yarn ball

- anonymous

and some honorable mention is in order here, me-thinks

- ghazi

exactly ....most fundamental of all is energy

- anonymous

Photon is both matter and wave,the best thing about it is it can exist both as matter and wave(light).simple example are electrons.

- anonymous

@ghazi your linked article, by Mr. Xian, is unreadable garbage. If it confuses you, that is probably a good sign -- a sign that you understand some physics.

- ghazi

@Carl_Pham it is an open platform....and everyone has got logic..to put in front of us ...so that's what Mr. Xan has done...it has some logic

- anonymous

Logic is not the problem. Astrology, voodoo, and the Greek pantheon of gods are all logical, too. The missing ingredient is a sound grounding in empirical fact. Without a close connection to measured fact, logic is just a way of going wrong with confidence.

- ghazi

hmm

- anonymous

Of course it is matter, anything that has a mass and occupies space in the universe is matter. Sometimes books give wrong and outdated stuff. Physics is a dynamic subject, things keep on changing here, you need to keep yourself updated

- anonymous

You are not entirely correct. Fields are NOT matter. But they DO occupy space.

- anonymous

but they donot have mass!

- Xishem

Neutrinos aren't considered massless. They are thought to have mass, but have never been measured accurately because the mass is so small.
Having no mass and having almost no mass are not -- at all -- the same thing.

- anonymous

1 You cannot have ANY particle without motion mass.
2 And Israel , haveri - fields have energy in volume of space. It (this energy content) gravitates to other bodies. For all purposes energy IS mass

- anonymous

I feel the need to speak up if only due to the general consensus of this conversation.... photons have no mass. Period. They are massless particles. Your idea of "motion mass" is meaningless. Either something has rest mass or it does not. The fact that photons have momentum does not imply that they are massive.
Secondly, according to the standard model, they are not particles of matter. Photons mediate the electromagnetic force, and as such they are gauge bosons, not matter particles. There is a distinction between elementary matter particles (quarks and leptons) and force mediators (photons, gluons, W and Z bosons).

- anonymous

Jemurray, my understanding wasn't nearly as sophisticated as yours, but the way I understood it is, simply because something can be mathematically treated as a particle, doesn't mean it has mass. An electron BEHAVES like a wave when bound to an atom and it BEHAVES like a particle once unbound. That alone doesn't tell you if it has mass.
My understanding is that there are two measures of mass: inertial mass - resistance to change in velocity and gravitational mass - the attraction between two massive bodies.
Another piece is that if two things have mass, they will have the interaction that we would expect when they collide - they will deflect off one another. Photons, however, are still waves in some sense. If their path of collision is orthogonal, they will have no interaction. They will pass through one another. If their path is not orthogonal relative to one another they will interfere, either increasing or decreasing the intensity of the wave.

- ghazi

@Jemurray3 what that mediator is ?? and i would suggest that photon is a particle which is a packet of energy (quanta) and it shows dual behaviour and also i would also suggest that photon is an elementary particle and most the fundamental particle of all .....also you can't compare it with gluons and bosons...

- anonymous

You're right. The fact that photons can be treated as particles does not mean that they have mass. It would obviously cause problems in classical physics, but with relativistic quantum mechanics it can be incorporated rather easily.
You're also correct in that those are the two measures of mass -- in Einstein's General Relativity, his equivalence principle says that these two things are equivalent.
And yes, it is also true that photons do not interact with one another, so if you had two beams at right angles there would never be any scattering from photon-photon collision.
@ghazi I agree up to "the most fundamental of all .... also you can't compare to gluons and bosons".
Why on earth not? Gluons are force - mediators, like photons, and photons themselves are bosons.

- ghazi

gluons are responsible for hooking energy but photons act as energy carrier..so both are different... and what is the ultimate answer
is photon considered matter?? YES or NO

- anonymous

They both mediate forces, is all I mean. Virtual photons are responsible for all electromagnetic interaction, be it attractive or repulsive. And if you define matter as something with mass, then no. If you define matter as something made up of quarks and leptons (as is generally the case), then NO.
Also I should point out that E = mc^2 does not mean that having energy is equivalent to having mass. That is a fundamental misunderstanding of Einstein's work. Given the full equation
\[E^2 = (pc)^2 + (mc^2)^2 \]
We find that the square of the total energy is the sum in quadrature of the energy due to momentum and the energy due to rest mass.
E = mc^2 means that energy can transform into matter or vice versa, but they are NOT the same thing AT ALL.

- ghazi

when you say energy due to rest mass....how come you apply it for photon?? photon has got no mass

- anonymous

That's true. So that part is zero. In the case of a photon,
\[E = pc \]
or
\[p = \frac{E}{c} = \frac{h\nu}{c} = \frac{h}{\lambda} \]
reproducing the de Broglie relation.

- ghazi

well when i use \[\lambda=\frac{ h }{ m*c }\] in this case lambda would be infinite? isn't it?

- anonymous

No, because relativistic momentum is not just p = mv.

- ghazi

hmm...seems a point in it...i forgot that

- anonymous

Relativistically,
\[ p = \gamma mv = \frac{mv}{\sqrt{1-\frac{v^2}{c^2}}} \]
This works for massive particles, but for massless particles, it seems to vanish unless v = c, in which case this expression is not well-defined.

- ghazi

in case of photon it seems unaccepted but yea i agree with the proof of E= mc^2

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