what is the nature of a photon ?

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Offline percepts

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what is the nature of a photon ?
« on: 07/03/2013 04:32:05 »
Just asked this on radio five live but ran out of time and didn't get to the bottom of it.

I keep hearing that light is massless which confuses me. So my question is:

Is a photon an actual partical which travels through space or does it only exist at the point of detection. i.e. when it hits something. Further more, if light is massless then that would imply that the electromagnetic waves passing through space don't have any energy if einsteins theory e = mc^2 is applicable to them. Unless my basic understanding of physics is completely wrong then that can't be the case which is why I have to ask how can light be massless or is this statement just being used to state the case at the point of detection. i.e. the residue of the electromagnetic wave hitting something is what we call a photon and has no mass but does have energy?

thanks

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Offline JP

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Re: what is the nature of a photon ?
« Reply #1 on: 07/03/2013 14:40:02 »
Just asked this on radio five live but ran out of time and didn't get to the bottom of it.

I keep hearing that light is massless which confuses me. So my question is:

Is a photon an actual partical which travels through space or does it only exist at the point of detection. i.e. when it hits something. Further more, if light is massless then that would imply that the electromagnetic waves passing through space don't have any energy if einsteins theory e = mc^2 is applicable to them. Unless my basic understanding of physics is completely wrong then that can't be the case which is why I have to ask how can light be massless or is this statement just being used to state the case at the point of detection. i.e. the residue of the electromagnetic wave hitting something is what we call a photon and has no mass but does have energy?

thanks

Good questions.  I'll try to answer them in order:
1) In quantum mechanics, "particle" means something different than a little tiny packet of something that moves through space along well-defined trajectories.  A photon is a particle in the quantum sense, in that it's the smallest piece of energy you can extract from an electromagnetic wave.  At a detector, it also interacts at a point.  It is not particle-like in a classical sense in that when it travels from point A to point B it does so in a wavey way that's spread out over all space, not along a single trajectory.

2) The actual equation for a particle is not necessarily E=mc2, but rather E2=m02c4+(pc)2, where p is momentum.  There are two important issues in this equation: first, m0 represents what's called the invariant mass of a particle, which for photons is zero.  (Defining mass usually leads to a debate on this forum, since there are several possible definitions in relativity, but invariant mass is usually what physicists mean when they say the mass of a photon is zero).  In this case, E2=(pc)2, and a photon does have momentum, so there's no problem.

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Offline evan_au

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Re: what is the nature of a photon ?
« Reply #2 on: 07/03/2013 14:55:05 »
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if light is massless then that would imply that the electromagnetic waves passing through space don't have any energy

Quote
The Planck constant was first described as the proportionality constant between the energy (E) of a photon and the frequency (v) of its associated electromagnetic wave. This relation between the energy and frequency is called the Planck relation:

    E = hv    (see http://en.wikipedia.org/wiki/Planck_constant)

So a photon traveling through space does have energy, provided its frequency > 0 (ie not red-shifted into oblivion).
When the photon strikes an an object, that energy typically drives an electron into a higher orbit, which can trigger chemical reactions, generate electricity in a solar cell, cause the object to get hot, etc.

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Offline Pmb

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Re: what is the nature of a photon ?
« Reply #3 on: 07/03/2013 15:31:19 »
Quote from: percepts
I keep hearing that light is massless which confuses me.
There has been a debate on the definition of mass for several decades. What has happened is that particle physicists, the major ďusersĒ of special relativity, who study the intrinsic properties of particles only speak of whatís called the rest mass aka proper mass aka invariant mass of the particle. This is the mass you know from Newtonian mechanics. However those physicists who arenít particle physicists but who specialize only in relativity more often seem to use the term to refer to what is called the ďinertial massĒ of a particle (a more complete name of what you know of from Newtonian mechanics). Cosmologists have their own ideas too since they use mass densities. When it comes to more complex systems, i.e. macroscopic bodies and bodies under stress, the simple notion of invariant/proper mass is insufficient.

There is a write up on the mass of a photon here
http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/photon_mass.html

I myself have researched this subject and written extensively on it. Please see
http://arxiv.org/abs/0709.0687
http://home.comcast.net/~peter.m.brown/sr/inertial_mass.htm
http://home.comcast.net/~peter.m.brown/sr/invariant_mass.htm
http://home.comcast.net/~peter.m.brown/sr/long_trans_mass.htm


Quote from: percepts
So my question is:

Is a photon an actual partical which travels through space or does it only exist at the point of detection. i.e. when it hits something.
A photon is referred to as a ďparticleĒ but itís a quantum mechanical particle, not a classical particle. When one detects a photon one finds it located at a single place and not spread all over the place like a wave. However there are wave properties of a photon since a beam of photons will interact with each other even when the photons arrive at the detectors one at a time! Itís a complex issue as you can imagine.

The most general thing used to describe matter is the stress-energy-momentum tensor. I've discussed the inertia of stress in that paper above which is on an archive at Cornell University. Enjoy! Please let me know if the above links are useful. If not then I'll keep that in mind when/if I modify them.

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Offline lightarrow

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Re: what is the nature of a photon ?
« Reply #4 on: 08/03/2013 13:55:25 »
Further more, if light is massless then that would imply that the electromagnetic waves passing through space don't have any energy if einsteins theory e = mc^2 is applicable to them.
E = mc2 should be used only by vaccinated, adult, well knowledged in physics people. Popular books which use it improperly shoud be burned...  [:)]
That equation is WRONG in your case.
It is correct only for STATIONARY BODIES.
Is light stationary? Of course not.

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Offline lightarrow

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Re: what is the nature of a photon ?
« Reply #5 on: 08/03/2013 13:57:03 »
Is a photon an actual partical which travels through space or does it only exist at the point of detection. i.e. when it hits something.
Define "particle". After your answer, my reply will show you that the question was not trivial.

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Offline lightarrow

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Re: what is the nature of a photon ?
« Reply #6 on: 08/03/2013 14:05:45 »
There has been a debate on the definition of mass for several decades. What has happened is that particle physicists, the major ďusersĒ of special relativity, who study the intrinsic properties of particles only speak of whatís called the rest mass aka proper mass aka invariant mass of the particle. This is the mass you know from Newtonian mechanics.
You compute that light has zero mass with newtonian mechanics? Or, maybe, with classical electrodynamics (Mxwell's theory)? And what about the *quantum* object "photon"? Still newtonian mechanics?

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Offline JP

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Re: what is the nature of a photon ?
« Reply #7 on: 08/03/2013 15:05:46 »
Matt Austern expresses this entire argument nicely in two equations in the Baez link posted above:

E = mrelc2   
and
E2 = p2c2 + mrest2c2 .         

Obviously a photon has non-zero energy, and from the first equation, mrel is therefore non-zero for a photon.
The second equation does allow mrest to be zero for a photon, and there are good reasons for it to be zero in quantum mechanics. 

So how can one of these masses be zero and the other non-zero for a photon?  They represent two different physical quantities.  The reason they're both sometimes confusingly called "mass" is that for macroscopic objects moving at non-relativistic speeds (when you can use classical mechanics), both definitions reduce to the same thing that Newton would have called simply "mass."

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Offline percepts

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Re: what is the nature of a photon ?
« Reply #8 on: 09/03/2013 01:19:57 »
Thanks all for replies. I begin to understand.

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Offline Pmb

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Re: what is the nature of a photon ?
« Reply #9 on: 09/03/2013 02:15:42 »
There has been a debate on the definition of mass for several decades. What has happened is that particle physicists, the major ďusersĒ of special relativity, who study the intrinsic properties of particles only speak of whatís called the rest mass aka proper mass aka invariant mass of the particle. This is the mass you know from Newtonian mechanics.
You compute that light has zero mass with newtonian mechanics? Or, maybe, with classical electrodynamics (Mxwell's theory)? And what about the *quantum* object "photon"? Still newtonian mechanics?
I was referring to luxons i.e. particles which have a rest frame or travel at v << c. In any case Newtonian (inertial) mass is define as the m in p = mv. Same in relativity. I gave those links above so as to explain all of this in excrutiating detail. Anybody who reads those should pretty much be an expert on the subject by the time they're finished reading all of them.
« Last Edit: 09/03/2013 03:14:00 by Pmb »

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Offline Pmb

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Re: what is the nature of a photon ?
« Reply #10 on: 09/03/2013 02:17:00 »
Matt Austern expresses this entire argument nicely in two equations in the Baez link posted above:

E = mrelc2   
and
E2 = p2c2 + mrest2c2 .         

Obviously a photon has non-zero energy, and from the first equation, mrel is therefore non-zero for a photon.
The second equation does allow mrest to be zero for a photon, and there are good reasons for it to be zero in quantum mechanics. 

So how can one of these masses be zero and the other non-zero for a photon?  They represent two different physical quantities.  The reason they're both sometimes confusingly called "mass" is that for macroscopic objects moving at non-relativistic speeds (when you can use classical mechanics), both definitions reduce to the same thing that Newton would have called simply "mass."
It's also because they are affected by gravity and generate a gravitational field.

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Offline Pmb

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Re: what is the nature of a photon ?
« Reply #11 on: 09/03/2013 02:49:41 »
Quote from: lightarrow
That equation is WRONG in your case.
It is correct only for STATIONARY BODIES.
Is light stationary? Of course not.
Yeah, but as you very well know, whether it's right or wrong is a matter of what the definition of m is. If m is proper mass then it's wrong. If it's inertial mass then it's right.
« Last Edit: 09/03/2013 03:12:30 by Pmb »

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Offline lightarrow

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Re: what is the nature of a photon ?
« Reply #12 on: 09/03/2013 12:18:03 »
There has been a debate on the definition of mass for several decades. What has happened is that particle physicists, the major ďusersĒ of special relativity, who study the intrinsic properties of particles only speak of whatís called the rest mass aka proper mass aka invariant mass of the particle. This is the mass you know from Newtonian mechanics.
You compute that light has zero mass with newtonian mechanics? Or, maybe, with classical electrodynamics (Mxwell's theory)? And what about the *quantum* object "photon"? Still newtonian mechanics?
I was referring to luxons i.e. particles which have a rest frame or travel at v << c.
?? What do you mean?
Luxons don't have a rest frame and travel at c:

http://en.wikipedia.org/wiki/Massless_particle
Quote
In any case Newtonian (inertial) mass is define as the m in p = mv. Same in relativity. I gave those links above so as to explain all of this in excrutiating detail. Anybody who reads those should pretty much be an expert on the subject by the time they're finished reading all of them.
I wrote that comment on your post because I had the ... subtle feeling that you tried to suggest to people that invariant mass is a less modern concept than relativistic mass  [:)]
I believe it's the opposite...
« Last Edit: 09/03/2013 12:21:12 by lightarrow »

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Offline Pmb

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Re: what is the nature of a photon ?
« Reply #13 on: 09/03/2013 16:41:40 »
Quote from: lightarrow
What do you mean?
Luxons don't have a rest frame and travel at c:
Sorry. I meant tardyons.

Quote
http://en.wikipedia.org/wiki/Massless_particle
Quote
In any case Newtonian (inertial) mass is define as the m in p = mv. Same in relativity. I gave those links above so as to explain all of this in excrutiating detail. Anybody who reads those should pretty much be an expert on the subject by the time they're finished reading all of them.
I wrote that comment on your post because I had the ... subtle feeling that you tried to suggest to people that invariant mass is a less modern concept than relativistic mass  [:)]
I believe it's the opposite...
We've already discussed that subject to death so I won't go there. Sorry.

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Offline lightarrow

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Re: what is the nature of a photon ?
« Reply #14 on: 09/03/2013 19:54:32 »
Quote from: lightarrow
That equation is WRONG in your case.
It is correct only for STATIONARY BODIES.
Is light stationary? Of course not.
Yeah, but as you very well know, whether it's right or wrong is a matter of what the definition of m is. If m is proper mass then it's wrong. If it's inertial mass then it's right.
Are you sure? Which is the transverse relativistic mass of a photon?

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Offline percepts

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Re: what is the nature of a photon ?
« Reply #15 on: 09/03/2013 22:55:37 »
Just asked this on radio five live but ran out of time and didn't get to the bottom of it.

I keep hearing that light is massless which confuses me. So my question is:

Is a photon an actual partical which travels through space or does it only exist at the point of detection. i.e. when it hits something. Further more, if light is massless then that would imply that the electromagnetic waves passing through space don't have any energy if einsteins theory e = mc^2 is applicable to them. Unless my basic understanding of physics is completely wrong then that can't be the case which is why I have to ask how can light be massless or is this statement just being used to state the case at the point of detection. i.e. the residue of the electromagnetic wave hitting something is what we call a photon and has no mass but does have energy?

thanks

Good questions.  I'll try to answer them in order:
1) In quantum mechanics, "particle" means something different than a little tiny packet of something that moves through space along well-defined trajectories.  A photon is a particle in the quantum sense, in that it's the smallest piece of energy you can extract from an electromagnetic wave.  At a detector, it also interacts at a point.  It is not particle-like in a classical sense in that when it travels from point A to point B it does so in a wavey way that's spread out over all space, not along a single trajectory.

2) The actual equation for a particle is not necessarily E=mc2, but rather E2=m02c4+(pc)2, where p is momentum.  There are two important issues in this equation: first, m0 represents what's called the invariant mass of a particle, which for photons is zero.  (Defining mass usually leads to a debate on this forum, since there are several possible definitions in relativity, but invariant mass is usually what physicists mean when they say the mass of a photon is zero).  In this case, E2=(pc)2, and a photon does have momentum, so there's no problem.
Thanks for this reply which puts it in simplistic terms that even I can begin to understand.

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Offline Pmb

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Re: what is the nature of a photon ?
« Reply #16 on: 10/03/2013 03:56:00 »
Quote from: lightarrow
Are you sure? Which is the transverse relativistic mass of a photon?
Yes. I'm sure. I'm confused as to why you don't know the answer. It's pretty trivial. I think you forgot to put on your thinking cap. :) Tardyons, such as electrons can be defelcted so that they accceleratet transverse to their direction. Since a photon can't be deflected it travels in a straight line so that the transverse mass is zero. The same holds for the longitudinal mass, it's zero too. What isn't zero is the relativistic mass defined as the m in p = mv by hypothesis this is a conserved quantity.
« Last Edit: 10/03/2013 04:05:05 by Pmb »

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Offline lightarrow

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Re: what is the nature of a photon ?
« Reply #17 on: 10/03/2013 16:18:14 »
Quote from: lightarrow
Are you sure? Which is the transverse relativistic mass of a photon?
Yes. I'm sure. I'm confused as to why you don't know the answer. It's pretty trivial. I think you forgot to put on your thinking cap. :) Tardyons, such as electrons can be defelcted so that they accceleratet transverse to their direction. Since a photon can't be deflected
Why a photon can't be deflected?
Quote
it travels in a straight line so that the transverse mass is zero. The same holds for the longitudinal mass, it's zero too. What isn't zero is the relativistic mass defined as the m in p = mv by hypothesis this is a conserved quantity.
Let's say that you are right about relativistic mass of a photon: the formula E = mc2, with m as the relativistic mass, is correct for photons only, not for tardyons.

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Offline simplified

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Re: what is the nature of a photon ?
« Reply #18 on: 10/03/2013 17:01:54 »
Relativistic mass should be = general mass - gravitational mass
Because gravitational mass is constant for any observer,it is not relativistic.

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Re: what is the nature of a photon ?
« Reply #19 on: 10/03/2013 22:39:58 »
Hmm :)

We're of two minds there. Relativistic gravitational mass just mean that you change your coordinate system. If you fall with the gravity, the gravity disappear for you. If a floor stops you, you find it to come back. That's how we define it as 'relativistic', meaning that it depends on you, relative it, as well as mass. If gravity was a substance then you could say you are co moving with it in a free fall. But it is no substance I know how to define, and if it also can 'distort' a space, what substance would it be?
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Re: what is the nature of a photon ?
« Reply #20 on: 10/03/2013 22:59:46 »
A correction. Shouldn't have used  'Relativistic gravitational mass', it's better to just call it 'gravity' because putting those words together it becomes a 'energy density'. When you get up to relativistic speeds that 'energy density' created will bend a space a according to relativity. Although you could read that as changing your 'coordinate system' too it becomes extremely tricky. If you look at particle accelerators they create particles of more mass than the two colliding on a daily basis, using a acceleration.
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Re: what is the nature of a photon ?
« Reply #21 on: 11/03/2013 01:30:29 »
Quote from: lightarrow
Why a photon can't be deflected?
First off Iím restraining my discussion to special relativity (SR). In SR there is nothing that interacts with a photon that can deflect it. As I recall it, and I may e wrong, I donít consider Compton scattering to be deflecting the photon since a photon is destroyed when it hits the electron and a new one produced. Otherwise the photon canít be deflected as an electron is i.e. via the electric field. No such field for deflecting photons exit that Iím aware of,


 
Quote from: lightarrow
Let's say that you are right about relativistic mass of a photon: the formula E = mc2, with m as the relativistic mass, is correct for photons only, not for tardyons.
That is incorrect. Some people even define relativistic mass as m = E/c2.

It can be shown that if p = mv where m = relativistic mass then it can be shown that E = mc[sup[2[/sup]. Iíve derived that relationship here - http://xxx.lanl.gov/abs/physics/0308039

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Offline simplified

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Re: what is the nature of a photon ?
« Reply #22 on: 11/03/2013 13:44:48 »
Hmm :)

. If you fall with the gravity, the gravity disappear for you.
No,that doesn't.Gravity increases my energy.

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Re: what is the nature of a photon ?
« Reply #23 on: 11/03/2013 15:46:47 »
Well, We're in a gravitational field now, on Earth. And as long as you feel gravity acting on you, you can be seen as accelerating relative it, at one G, according to relativity, and also as I think. Now assume that we 'push' Earth a little, accelerating this little planet :) to then stop accelerating it. Will the light bulb inside a house now become slightly more blue shifted, as it gained a new 'relative motion', which also is a uniform motion, equal to the uniform motion before the acceleration?
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Re: what is the nature of a photon ?
« Reply #24 on: 11/03/2013 15:52:29 »
But yes, assuming that gravity only has to do with mass and accelerations you might formulate it that way, with a question mark regarding the way gravity at large is presumed to act in space.. But, to use it you need that floor, and that is frames of reference.

Or maybe not thinking some more. If we take planets of different mass we can define each one as 'accelerating' 'differently. Will now a same light bulb, blue or redshift, depending on what planet you connect it? Or will it present you with a same 'energy' locally measured?

After all, if you accept that you're not 'at rest' with the gravitational field, while being 'at rest' with the surface of a planet, different mass should make a difference? (If that formulation would be correct.)
=

Locally meaning you being 'at rest' with the light bulb, in each case, as being in a 'black box scenario' on that surface.

(You could then split accelerations in two, one being a local (constant) uniform acceleration, the one equal to Earths gravity according to the equivalence priciple, the other being non uniform accelerations, which Earth does not show.)
« Last Edit: 11/03/2013 16:38:26 by yor_on »
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Re: what is the nature of a photon ?
« Reply #25 on: 11/03/2013 16:50:14 »
I don't expect it to shift energy myself?
But if you instead went out to measure a same sun, shining on all those planets, being of a same distance to them. Would you now expect the energy to be different between planets?

And remember that this is quite lose definitions from me, they are not very strict, because with different mass you also should be able to expect different definitions of 'clocks' and 'rulers' when comparing between any and each of them. Meaning that I avoid those strict definitions :) Yes, I'm a coward..
==

Another way of looking at it might be that, if uniform motion equalize any other uniform motion, no matter what mass you're in, while measuring that light bulb inside that black box. Then I don't see how it can matter? Because if mass mattered for this experiment we would only have a equivalence between the same amount of mass in a uniform motion, as it seems to me.
==

Then again, this one is really interesting simplified. If I was to define it from some smallest point instead, I'm not sure what position I would take? The one I'm presenting is how I got it, but?
« Last Edit: 11/03/2013 17:24:47 by yor_on »
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Offline simplified

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Re: what is the nature of a photon ?
« Reply #26 on: 11/03/2013 17:54:20 »
Probably Einstein had Great gravitational field,which was fastly moving the Earth to him...

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Re: what is the nature of a photon ?
« Reply #27 on: 11/03/2013 18:05:29 »
From my side it's about what a 'frame of reference' should mean, from scaling. If we were to use some small definition I would use Plank scale, but that one is not really measurable, so we need to go up in scale. We can measure on electrons and atoms though. And then you have HUP there too. But we have a definition of being 'at rest' with something as defining when you are in a same 'frame of reference'. So, am I, or am I not at rest with that light bulb, on Earth, measuring a energy from it? To you I'm not, right? But according to how I get it, I am, macroscopically defined. Maybe Pete can clear this one out?
=

And yes, it has to do with the gravity locally measured. Do that introduce different 'frames of reference' relative being 'at rest' with different mass. If it does you should be correct and we should be able to measure different energies, being inside that 'black box'. If it doesn't then my assumption should be correct. And as it all goes back to a light quanta, propagating in a gravitational field, we will have to introduce some sort of interaction with gravity's 'energy' as I think, ignoring the geodesic, using your definition. And as that means a intrinsic clock to me?
« Last Edit: 11/03/2013 18:30:42 by yor_on »
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Re: what is the nature of a photon ?
« Reply #28 on: 11/03/2013 18:18:20 »
I don't know what is space-time.Can it define what is at rest?

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Re: what is the nature of a photon ?
« Reply #29 on: 11/03/2013 18:35:14 »
The one you don't think exist heh :)
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Re: what is the nature of a photon ?
« Reply #30 on: 11/03/2013 18:43:45 »
SpaceTime, to me, is about clocks and rulers. Those get their definition from 'c' as a constant speed of light in a flat space (a vacuum containing no resistance, no gravity, and SR), relative mass, 'relative motion', and accelerations (becoming GR). And I think that should be it? Or is there something I'm missing?

Gravity being a preferred direction to me.
==

Well, actually there is. Shows you that you better think, before you act (never been that good at that:)

Light is only defined as being 'c', relative a inertial observer, finding no inertia acting on him (no acceleration). If light speed instead was based on pure emissions, no matter where they took place, GR wouldn't be here. Because then it wouldn't matter if there was a acceleration or not, light would still be 'c' as measured from any observer.

A modern redefinition of this is to take into consideration the way uniform accelerations and gravity is equivalent, and so define it as 'c' relative gravity, acting on the geodesic (path) of the light. This one may be of interest Einsteinís Investigations of Galilean Covariant Electrodynamics prior to 1905. 
==

The thing is that I keep forgetting stating the differences between SR and GR. To those of you old enough to have read it from Einsteins direct thoughts, or having a good physics background, that is important, and it should be to me too, but I forget :) Senility ahoy.


« Last Edit: 11/03/2013 21:29:37 by yor_on »
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Re: what is the nature of a photon ?
« Reply #31 on: 11/03/2013 19:07:57 »
From that a ideal definition of being 'at rest' should be co-moving in a flat SpaceTime, shouldn't it? Or in a 'same gravitational potential'. And that's a question of what scales would mean for it, to me? And I'm still wondering about that one.
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Re: what is the nature of a photon ?
« Reply #32 on: 11/03/2013 20:42:34 »
Hmm :)

. If you fall with the gravity, the gravity disappear for you.
No,that doesn't.Gravity increases my energy.
He's correct. If you're in a uniform gravitational field and you're in free fall then you're frame of reference is for all practical purposes an inertial frame of reference with no field present. That's exactly why Einstein said that you can transform away a gravitational field.

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Re: what is the nature of a photon ?
« Reply #33 on: 11/03/2013 22:42:05 »
Quote from: lightarrow
Why a photon can't be deflected?
First off Iím restraining my discussion to special relativity (SR). In SR there is nothing that interacts with a photon that can deflect it. As I recall it, and I may e wrong, I donít consider Compton scattering to be deflecting the photon since a photon is destroyed when it hits the electron and a new one produced. Otherwise the photon canít be deflected as an electron is i.e. via the electric field. No such field for deflecting photons exit that Iím aware of,
Ok. If a photon cannot be deflected, which is the utility of talking about the "relativistic mass of the photon"? It corresponds to its energy (via multiplicative constant) and there isn't any other context in which you use it.
Quote

Quote from: lightarrow
Let's say that you are right about relativistic mass of a photon: the formula E = mc2, with m as the relativistic mass, is correct for photons only, not for tardyons.
That is incorrect. Some people even define relativistic mass as m = E/c2.

It can be shown that if p = mv where m = relativistic mass then it can be shown that E = mc[sup[2[/sup]. Iíve derived that relationship here - http://xxx.lanl.gov/abs/physics/0308039

Of course, but if you remembere we were talking of the fact longitudinal and transverse relativistic masses are different so the equation E = mc2 is however wrong for non stationary bodies, because you can't use it for both cases at once.

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Offline simplified

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Re: what is the nature of a photon ?
« Reply #34 on: 12/03/2013 16:57:28 »
Hmm :)

. If you fall with the gravity, the gravity disappear for you.
No,that doesn't.Gravity increases my energy.
He's correct. If you're in a uniform gravitational field and you're in free fall then you're frame of reference is for all practical purposes an inertial frame of reference with no field present. That's exactly why Einstein said that you can transform away a gravitational field.
My free fall slows down my time.Einstein was wrong.What is uniform gravitational field at free fall?
« Last Edit: 12/03/2013 17:11:03 by simplified »

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Re: what is the nature of a photon ?
« Reply #35 on: 12/03/2013 17:53:18 »
Are you thinking that if you're in a free fall under gravity, you're still in a gravitational field?
Then you have another definition of it than Einstein had Simplified, and you will need to make it a proposition that covers most any situation relativity takes up. And the point there is that it need to fit relativity, at least those parts we have measured directly, or indirectly, as muons. So you need your idea to cover, for example, why muons can go further than their allowed 'time' if measured at rest. And as they are particles of mass we find them to exist measurably. Read that paper I linked and use it to test your ideas.
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Re: what is the nature of a photon ?
« Reply #36 on: 12/03/2013 18:32:50 »
Are you thinking that if you're in a free fall under gravity, you're still in a gravitational field?
Then you have another definition of it than Einstein had Simplified, and you will need to make it a proposition that covers most any situation relativity takes up. And the point there is that it need to fit relativity, at least those parts we have measured directly, or indirectly, as muons. So you need your idea to cover, for example, why muons can go further than their allowed 'time' if measured at rest. And as they are particles of mass we find them to exist measurably. Read that paper I linked and use it to test your ideas.
Who did make experiment "muon at free fall"?I thought I said that my free fall slows down my time.

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Re: what is the nature of a photon ?
« Reply #37 on: 12/03/2013 20:06:57 »
So you define it such as a free fall, following a geodesic slows down time locally? Ok, then do you define it such as with different uniform motions you get different 'time'? And do you define it relative the gravity?

If you do, then inside a 'black box', deep space with no tidal forces, can you prove that gravitational field? By some local experiment inside that black box. And how will you prove a motion? No windows, no outside peeking. Inside, by a experiment.
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Re: what is the nature of a photon ?
« Reply #38 on: 12/03/2013 20:22:30 »
And do you expect different uniform motions to change your experiments inside that black box. Uniformly moving following a 'geodesic' in a gravitational field (free fall)
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Re: what is the nature of a photon ?
« Reply #39 on: 12/03/2013 23:38:09 »
Sorry lightarrow but I've discussed relativistic mass until I was blue in the face. I won't discuss it again. I've already said everything that can be said in that article that I wrote on the subject. I wrote it so I wouldn't have to keep repeating the same old explanation over and over and over again. If you disagree with it then so be it. If it isn't in there then I have nothing to say about it. Every question that could be asked on the subject is addressed in that paper. There's no reason for me to ay anything else on the subject. If nobody wants to read it then they really don't want to know what I have to say about it. Plain and simple. :)
« Last Edit: 12/03/2013 23:53:18 by Pmb »

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Re: what is the nature of a photon ?
« Reply #40 on: 13/03/2013 02:07:02 »
Although I'm loathe to get into one of those infernal discussions about the definition of mass I will say this. One has to be careful about when the relationship P = mU where m = proper mass, P = 4-momentum and U = 4-velocity. Suppose you have an ion in an electric field. This relationship doesn't hold because it doesn't take into account the inertia of the stress imposed in the ion due to the electric field.

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Re: what is the nature of a photon ?
« Reply #41 on: 13/03/2013 12:15:28 »
So you define it such as a free fall, following a geodesic slows down time locally? Ok, then do you define it such as with different uniform motions you get different 'time'? And do you define it relative the gravity?

If you do, then inside a 'black box', deep space with no tidal forces, can you prove that gravitational field? By some local experiment inside that black box. And how will you prove a motion? No windows, no outside peeking. Inside, by a experiment.
Gravitational mass is energy which creates gravitational field.Gravitational interaction exists  even in the black box.I can measure all gravitational mass in the black box.I can create motionless clock and moving clock inside the box.Using exact measurements ,smart scientists can calculate changing external factor of my slowing of time inside the black box. :P
« Last Edit: 13/03/2013 12:26:36 by simplified »

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Re: what is the nature of a photon ?
« Reply #42 on: 13/03/2013 14:23:51 »
Yes, I think you can, using light as your clock, maybe splitting it relative a rotating mirror, and using a interferometer. What will that tell you inside your black box about motion? When it comes detecting that gravitational field, you either have to assume that this will create a detectable motion inside your box, or? That you're not 'moving' at all.

In relativity that uniform motion or geodesic only are described as detectable relative another frame of reference though. A acceleration is something else, detectable locally as a blue or/and red shift, depending on which way you measure in relation to the light source, and your accelerations direction. Well, as I think of it.
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Re: what is the nature of a photon ?
« Reply #43 on: 13/03/2013 15:48:56 »
Yes, I think you can, using light as your clock, maybe splitting it relative a rotating mirror, and using a interferometer. What will that tell you inside your black box about motion? When it comes detecting that gravitational field, you either have to assume that this will create a detectable motion inside your box, or? That you're not 'moving' at all.

In relativity that uniform motion or geodesic only are described as detectable relative another frame of reference though. A acceleration is something else, detectable locally as a blue or/and red shift, depending on which way you measure in relation to the light source, and your accelerations direction. Well, as I think of it.
There experimental measurements with atomic clocks do not coincide with usual  calculatings.
From your own source the photons ,which have passed through a mirror labyrinth, have blue shift. :)
« Last Edit: 13/03/2013 16:31:13 by simplified »

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Re: what is the nature of a photon ?
« Reply #44 on: 13/03/2013 20:09:28 »
Do you mean the Michelson-Morley experiment? That was about finding a aether. The assumption was that as the light went different ways, the original light split into two parts, when it joined after going around, it would show to become out of phase. Out of phase with each other would mean that the light had found some 'resistance' due to a aether. But it didn't matter, that light was still in phase, same as when it was sent out. But it should work, as I think, to find a 'preferred motion' inside that box too. The other way is to measure some light source(s) set up inside that box, why not the middle of it, and then try to find blue and red shifts relative your position, measuring the light.



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Re: what is the nature of a photon ?
« Reply #45 on: 13/03/2013 20:39:32 »
The point is that the Pound and Rebka gravitational red and blue shifts measured in a stairwell at Harvard in 1959 is about the observer measuring between frames of reference, just as Nist found clocks to tick differently at different height. But you moving in a uniform motion, without resistance, in space, becomes moving 'with the gravity's preferred direction'. you don't have any 'frames of reference' inside to measure against. You are 'at rest' with gravity, as well as 'at rest' with the box, and the light source, no matter from where you measure it, inside that box.  That is a classical 'black box experiment'/ thought experiment.
==

Or put this way, as long as your feet are firmly placed on the ground, you're not 'at rest' (relative gravity). Then you will find frames of reference. In a free fall (read geodesic) it becomes different. There is no 'gravity' inside that black box, and without that?
=

And it's not really fruitful to think of geodesics as being some sort of equivalence to magnetic field lines. We can assume the lightbulb, placed in the middle of that black box, to send out 'photons' in a sphere formed direction from it.

And all of those 'paths' must be geodesics in a uniform motion, per definition.
« Last Edit: 13/03/2013 21:31:28 by yor_on »
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Re: what is the nature of a photon ?
« Reply #46 on: 13/03/2013 21:27:25 »
Wanna make it real weird :)

Imagine a really big black box, uniformly moving in a gravitational field. So inside it we have no gravity, then imagine yourself accelerating a smaller black box, containing a happy race of dwarfs, measuring a light bulb inside that.

Now we have one big black box, containing no gravity, which inside it have a smaller black box, uniformly constantly accelerating, finding a gravity.

So what is gravity?
=

Now add another smaller box (steered by the proud race of hitchhiker mice) relative the 'small box'. It accelerates inside it, but in the opposite direction, taking out the acceleration the 'small box' use, relative the big one.

So, can we define that as being 'still', relative what? And, if we do, can we define it as being 'at rest' with big box?
And, if we do, are then both of those boxes, the smallest and biggest, now equivalent?

Uniform motion :)
Accelerations

and relative motion.

heh.
« Last Edit: 13/03/2013 22:58:06 by yor_on »
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Re: what is the nature of a photon ?
« Reply #47 on: 13/03/2013 22:15:13 »
Let's do it the other way.

Assume that you can measure different uniform motions (locally measured).
Will 'c' survive that?

'c' is defined relative a inertial observer uniformly moving in a geodesic.
A geodesic is a definition of a 'path of no resistance/gravity' locally, relative both the space and the gravity.
So wherever there is a geodesic there must be 'gravity'.

Space can't be flat, it can possibly be unmeasurable, but gravity has a infinite reach.
That means that you can't state. 'Well, gravity ends here.'

So if you want 'absolute motion' instead of 'relative motion', which means that you must be able to differ 'uniform motions' inside black box measurements, you destroy the definition of 'c' too. Because with absolute motion you must introduce a very strange idea of emissions of light always being at 'c', no matter how we find that uniform motion (inertial observers) to differ from another, measuring in that black box.

Can you see how I think there? Just as with the box in the box above, we now can assume that two boxes, one inside another and with both being in different 'uniform motion', must be related to some absolute frame of reference, defining a 'real' uniform velocity/geodesic/speed.

And that one would be even weirder than the one we have, as it seems to me. As both boxes must find 'c' in a two way experiment. So what would 'c' be a constant relative if so?
=

and remember that we define space as homogeneous and isotropic. Meaning that space should look much the same, viewed from any position, looking at mass distributions relative space. When using uniform motions as 'relative' and 'equivalent' you can define them 'at rest'. All uniform motions becoming the exact same relative 'c'. Using 'absolute motions' that statement must be wrong.

And? what the he* is 'c' then a constant relative? Because we can measure it to exist in any uniform motion, in a two way experiment? It's not theoretical.
« Last Edit: 13/03/2013 23:05:39 by yor_on »
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Re: what is the nature of a photon ?
« Reply #48 on: 14/03/2013 00:34:36 »
Travel of the photons in the labyrinth takes some time.The same time makes you and your black box approach to the big mass.In closer space to gravitational object photons have more energy. :P
« Last Edit: 14/03/2013 09:04:01 by simplified »

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Re: what is the nature of a photon ?
« Reply #49 on: 14/03/2013 01:35:28 »
:)

Ahem, think it's your turn to present arguments Simplified.
Just use your logic to show me how you think it is done.
And try to be as clear as you can so we get how you think there.
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