Photon in a Box

[Hadron]

Einstein's "Photon in a Box " is fatally flawed. There can be no recoil by the box when a photon is emitted. The emitting electron simply drops to a lower energy level to lose (-e = -h) where (h) is Planck's Constant. The photon has an energy (e = h) and so energy is conserved at the atomic level with none left over for box momemtum change.

 

Then when the photon collides with the box'es wall, only one of two things can happen:

 

First, it's reflected but there is no energy left for transfer to the box because this would require the reflected photon to have an energy less than (h), the indivisible minimum Planck value.

 

Second, if the photon is absorbed, the absorbing electron gains energy (h) and the photon is annihilated for an energy loss of (-h). Thus all energy is conserved with, again, none left for transfer to the box.

 

Therefore, the box could never move.

 

Not only the above, but the entire experiment is pure sophistry and quite unnecessary to its supposed purpose. From it, we wind up only with the posit of photon mass (m = e/c2 = h/c2) and (e = h) for photon energy.

 

Obviously, (e = h) is not a general expression of (e = mc2).

[Klaynos]

Einstein's "Photon in a Box " is fatally flawed. There can be no recoil by the box when a photon is emitted. The emitting electron simply drops to a lower energy level to lose (-e = -h) where (h) is Planck's Constant. The photon has an energy (e = h) and so energy is conserved at the atomic level with none left over for box momemtum change.

 

Then when the photon collides with the box'es wall, only one of two things can happen:

 

First, it's reflected but there is no energy left for transfer to the box because this would require the reflected photon to have an energy less than (h), the indivisible minimum Planck value.

 

Second, if the photon is absorbed, the absorbing electron gains energy (h) and the photon is annihilated for an energy loss of (-h). Thus all energy is conserved with, again, none left for transfer to the box.

 

Therefore, the box could never move.

 

Not only the above, but the entire experiment is pure sophistry and quite unnecessary to its supposed purpose. From it, we wind up only with the posit of photon mass (m = e/c2 = h/c2) and (e = h) for photon energy.

 

Obviously, (e = h) is not a general expression of (e = mc2).

 

But E=hf, no e=h. So you can just get altered frequencies to provided any required energy.

 

Also E=mc² is not valid for photons, it's a simplification for stationary objects, which photons never are.

 

You want E² = (mc²)² + p²c²

[Cap'n Refsmmat]

[Thread split from previous location because it was off-topic.]

[swansont]

Moved to physics (yes, it's possible to get stuff out of pseudoscience & speculations)

[Mr Skeptic]

Don't forget that photons have momentum p = hf/c, and can have any energy E = hf. Both momentum and energy must be conserved. Photons can also lose energy if they are red-shifted... how might this play out with the box?

[Hadron]

I agree that the box experiment is not valid in determining mass-energy equivalence. That was my whole point. Einstein erred in his "thought experiment".

 

However, my argument stands regardless of how many photons are emitted per second. There can be no frequency shift since the emitting device moves with the box and relative velocity is zero.

 

So, only the fates I described can befall any photon regardless of frequency of repetition. In the special case of Einstein's experiment, (f = 1).

[Graviphoton]

The photo in a box is certainly not wrong.

 

First, lets get a few concepts out the way.

 

Does the photon have mass? The short answer is no.

 

Some people find it difficult to comprehend a photon as being massless because it can be deflected by the gravity of, let us say a star. One way to explain this is by saying light couples to gravity, because light also generates curvature and curvature is the equivalence of gravity. However, there is too little amount of light to have any major gravitational effects in our universe, except for perhaps 32 years after big bang, when the universe was flooded in light particles. For those who like math, here are some more reasons why the photon does not have mass.

 

Some people like to say that the photon has mass because the photon has energy E=hf, where (h) is 'Planck’s constant' and (f) is the frequency of the photon. Thus, they tend to assume that because it has energy (E) it must have mass (M) because of Einstien’s mass-energy equivalence equation E=Mc^2...

 

They also say that the photon has momentum, and momentum is related to mass p = Mv where (v) is velocity and (p) is for momentum. Yet, you cannot justify it having mass using this argument. This is actually 'relativistic mass' - which is nothing but the measure of energy which will change with velocity. It isn't actually mass, even though mass and energy are related. In physics jargon, the mass of an object is called its 'invariant mass,' and the photon has no invariant mass. Now, a massless particle can have energy and it can have momentum, simply because mass is related to these through the equation E^2 = M^2c^4 + p^2c^2, which is subsequently zero-mass for a photon because E = pc for massless radiation (remember, c means the speed of light). So yes, the photon has momenta and energy, and can deliver a punch out of it when it hits a surface, but it doesn't have mass.

 

Now... a strange situation can arise if light is trapped inside a container. If light is trapped inside of a box with mirrors inside of it, so that it cannot escape, (now the mirrors would need to be cold enough so that the mirrors do not absorb the light-energy), the total momentum is said to be zero, but the energy is not - thus, the light can contribute a very small amount of mass to the box! Now, one can say that the light in the box must have mass to even add any mass to begin with - but actually, it is more accurate to say it contributes to the mass - but do not use this as some kind of justification that light indeed has mass. That is simply not true. A photon can decrease the invariant mass value of E/c^2 each time a system emits a photon... likewise, a system can increase its invariant mass by a value of E/c^2, if it absorbs a photon particle.

 

Now, relativity can't be complete, also it is a classical system, so it doesn't take into account the uncertainty principle. But apart from that, relativity has worked quite well experiementally, even increasing the lifespan of little particles. Its best not to wave your hands in protest until you actually learn about the theory itself, which is a task in itself.

[Zephir]

..Does the photon have mass? The short answer is no....

The slightly more comprehensive answer should sound, photon has a well pronounced relativistic (i.e. dynamic) mass, while its rest mass is bellow 10E-50 kg limit, which should correspond the deBroglie mass of photon of deBroglie wavelength comparable with the observable Universe diameter). Which is well bellow experimental limit so far, I admit - but some serious experiments trying to detect rest mass of photon are in development. Another evidence of nonzero photon rest mass follows from experiments with photon-photon scattering, for example.

 

And no, the photon hasn't "just the momentum". If we trap some photon into resonator, it should exhibit a real measurable weight difference due the mass energy equivalence principle (E=mc^2=hf) - not just momentum.

 

 

The physics is no good place for short minded people with schematic thinking.

[Klaynos]

Mass energy equivalence does NOT mean the photon has mass. The concept of relativistic mass isn't really used any more as it is missleading, it is generally considered that there is ONLY rest mass which is called mass (normally) and is a Lorentz invariant.

 

This has been discussed indepth in another thread including references....

[swansont]

Setting up an experiment to measure the photon's rest mass does not necessarily imply that it has one. Measuring zero is usually a very tough experiment, and getting a smaller upper bound is worthy of publication.

[Zephir]

..mass energy equivalence does NOT mean the photon has mass...

Why not? Is the m=E/c^2 equation violated at the case of photon?

[timo]

Not exactly violated but the concept of relativistic mass isn't really used any more as it is misleading. It is generally considered that there is ONLY rest mass which is called mass (normally) and is a Lorentz invariant.

 

This has been discussed indepth in another thread including references and also mentioned in this very thread.

[swansont]

Why not? Is the m=E/c^2 equation violated at the case of photon?

 

Wrong equation.

 

[math]E^2 = p^2c^2 + m^2c^4[/math]

[Zephir]

Wrong equation.

Why wrong?

 

Whether the photon doesn't increase the mass of resonator, into which is being trapped? Which equation would describe this phenomena, after then?

[insane_alien]

its wrong because E=mc^2 only applies when an object is at rest. a photon at c is quite obviously not at rest.

 

E=mc^2 is a special case of the equation swansont posted, it is only valid when momentum is zero, photons have momentum. to get the right numbers, the mass term has to be zero.

[Zephir]

...it is only valid when momentum is zero, photons have momentum....

OK, I've no problem with this - but which equation describes the increasing of resonator mass after trapping of photon into resonator, after then?

 

A) None, no mass increasing should be observed. Here's no way, how to detect, the photon is inside from outside.

 

B) None, it's completelly new phenomena, worth honoring by Nobel price.

[Klaynos]

I think we're going to have option:

 

C) [math]E^2 = p^2c^2 + m^2c^4[/math] can be applied when the photon is absorbed.... Some energy may be converted into mass.

[swansont]

OK, I've no problem with this - but which equation describes the increasing of resonator mass after trapping of photon into resonator, after then?

 

A) None, no mass increasing should be observed. Here's no way, how to detect, the photon is inside from outside.

 

B) None, it's completelly new phenomena, worth honoring by Nobel price.

 

Option C. The resonator remains at rest, so the resonator's mass in indeed larger. You would see this if you had a standing wave inside the resonator.

 

The interesting case is, as you mention, of small numbers of photons, or a single photon, where you might actually observe the recoil of the resonator as the photon reflects. In that case, the resonator has momentum, but this reverses itself at the opposite reflection. In the center-of-momentum frame, you should still observe an increase in mass; the object has more energy and no translational kinetic energy (the average of p goes to zero for times long compared to 2d/c).

 

A resonator is too massive to actually do this and observe the difference, but something that you can do is mass spectrometry on atoms, and if a nucleus is in an excited state, it will have a different mass. And scientists have observed this. I'll try and find a link.

 

edit: found one, blogged about it "Discovery of a Nuclear Isomer in [sup65[/sup]Fe with Penning Trap Mass Spectrometry,” by Block, et. al.

[Zephir]

... can be applied when the photon is absorbed....

Where? Absorbed by pair of electron orbitals, which are serving as a resonator as well? Such absorption replaces one resonator just by another smaller one...

Option C. The resonator remains at rest, so the resonator's mass in indeed larger..

But the photon doesn't. In fact, its energy is moving all the time inside of resonator - no matter, whether it's absorbed by resonator cavity itself, or by some smaller cavity between orbitals or atoms.

 

The case of nucleus in spectrometer is nice, but it doesn't detect photon mass, but the excited nucleus mass.

[Graviphoton]

Zeph

 

You are fudging the truth. Relativistic mass is a measure of energy. The word mass is misunderstood in this context, as i have already explained.

[Zephir]

.. as i have already explained...

Where, please?

 

It isn't actually mass, even though mass and energy are related. - the claim, no reasoning here.

 

In physics jargon, the mass of an object is called its 'invariant mass,' and the photon has no invariant mass. - the claim, no reasoning here.

 

Now, a massless particle can have energy and it can have momentum, simply because mass is related to these through the equation E^2 = M^2c^4 + p^2c^2 - the claim, simply based on circular reasoning...

 

one can say that the light in the box must have mass to even add any mass to begin with - but actually, it is more accurate to say it contributes to the mass - but do not use this as some kind of justification that light indeed has mass. That is simply not true.

 

But actually, it is more accurate to say, this is simply no relevant reasoning again... ;-))) Do not use this as some kind of justification of anything.

 

You guys are believing in your textbooks so much, you're not even able to distinguish between claim (tautology) and reasoning (induction). You're just a new sort of believers of modern era, who only have switched the Bibles. And this is just bad and sad.

 

One can prove/explain whatever by such approach, don't you think? This is not, what the science is supposed to be.

[Graviphoton]

You will see i posted here already, showing the math, and misunderstanding of it. If you continue to misunderstand,then nothing i will say will help you develop.

[Zephir]

..you will see i posted here already, showing the math, and misunderstanding of it.....

You cannot prove some claim by math, which claims exactly the same... These Jehovah's Witnesses are quite naive in their arguments at times...

 

But we should understand, why even photon has its mass. It's not just because some equation will become simpler (i.e. by Occam razor criterion). This is mainly because the photon is localised particle. For example, we can follow the path of gamma ray photons inside of spark chamber or Spinthariscope with high precision.

 

 

What does it mean? If something contains an distinct energy in restricted space, it deflects a spacetime at the same time by GR due the equivalency of energy density gradient and space-time curvature (Ricci tensor). And such deflection is caused by inertial mass by GR.

[iNow]

You cannot prove some claim by math, which claims exactly the same...

Good point. We should stick to .jpg and .gif images alone.

[Zephir]

Good point. We should stick to .jpg and .gif images alone.

In general, the consecutive logic of math language isn't a tool of imagination, but description. In fact, the rigor of math isn't supposed to allow multiple intepretations - on the contrary, it was designed to be an WYSIWYG tool ("what you see is what you get"), i.e. as exact and specific, as possible.

 

The paralellism of perception mediated by array of pixels can serve as an opposite, therefore the pixel pictures are good, if you wanna to explain some concept by illustrative way, but not to describe it or to replicate (i.e. to publish), because the single picture can be understood/interpeted by many ways by different people.

 

Another example, where the photons are manifesting their mass is so called materialization of radiation. During this the pair of photons interacts mutually under formation of new massive particles. We can interpret such process easily as a result non-ellastic Compton collision of photon pair, during which their mass remains at place.

 

 

By my opinion, the pair production violates even the zero rest mass of photon assumption, as the particles without rest mass (i.e. those fulfilling the Bose-Einstein statistics) can never interract mutually. The incorporation of this process into QFT formalism will therefore make a quantum field theories operating in 3D+T spacetime non-renormalizable, because in this moment the same place will switch its formal model suddenly.