What does a photon see as it leaves the sun?

[Camacha]

A while ago, browsing through various clips on Youtube, I came across a video by Scott Manley on SpaceEngine in which he travels from the sun at just over 1c. His comment is "That is what a photon would see as it left the surface of the sun". That got me thinking - is that really what a photon would see? It seemed silly. I found some interesting (though rather concise) material on visible light shifting to x-ray wavelengths in front of the craft, not only causing all sorts of trouble for human passengers but also making background radiation the thing that you would actually see, but what you would see when looking behind is not at all clear. Presumably it would be darkness, but I am not all too sure. Older sources speak of a sort of tunnel vision of normally visible objects, but I think this newer material is a bit more reliable. What is your take on this?

Please note that I am aware that photons do not have experiences and that travelling anywhere near the speed of light is a pipe dream, but that does not mean you cannot have a little fun with the subject.

Around the two minute mark (embedding timestamps unfortunately does not work):

Edited November 4, 2014 by Camacha

[How2FoldSoup]

Technically you don't see anything..

As one approaches the speed of light, length contracts to nothing and time stretches to infinity, so a photon doesn't even know its living in time. It's not really even moving. For example, to move you move 1 meter per second. But at c, there is no time. You don't move how we know it ,you move an infinite amount of meters in an infinite amount of time. The photon just stretches through the entirety of space itself.

To answer: Everything...

Edit: correcting myself

Edited November 4, 2014 by How2FoldSoup

[Camacha]

Technically you don't see anything..

[...]

To answer: Everything...

Everything or nothing? I understand that funky things happen, but both answers are a little too easy Other than that I like your description.

Edited November 5, 2014 by Camacha

[How2FoldSoup]

Okay, well I just replied to this via my phone and it ate the response...I also just failed an exam, so I'm pretty unhappy. A response is coming, I just have to write it up again and cool off. Why is it so damn hard for technology to just do what's programmed to do. an Edit is due later

[Kerbart]

Everything or nothing? I understand that funky things happen, but both answers are a little too easy Other than that I lke your description.

Well keep in mind that measured in our time, it takes a photon approximately a million years to travel from the core of the sun to the surface in the first place. Add relativistic effects and I'm pretty sure the poor photon has given up on looking after that amount of time in the first place.

[MartGonzo]

It depends on your interpretation of quantum experiments.

Everything is a reasonable answer given the standard view of quantum theory but not proven.

The most honest answer you would get from most physicists is "we really don't know"

[*Aqua*]

I think it's pretty close to reality.

[How2FoldSoup]

"we really don't know"

Basically, we can guess though.

Everything or nothing? I understand that funky things happen, but both answers are a little too easy Other than that I lke your description.

That's one of the best answers I can give you. It takes a sort of philosophical understanding to answer, and an opinion.

Say you are Mr. Photon who just got emitted from the surface on the Sun. You are moving at c. According relativity, when you move at C, everything you observe(which will be moving past you at c) will have it's time stretched to infinity, and the space(x, distance, length) contracts to 0. This means that you can see where you, Mr. Photon, will hit and die already. But, because you're not moving because time is infinity so no time is actually passing, you go no where.

For example, Mr Photon starts his journey at t = 0, and ends his journey at t = 0. No time passes, so has he crossed a distance? Lorentz contraction will tell you no. He started his journey at point A, and ended at point B. However, the distance to point A and B is 0, because the space between them has contracted so much.

What does this tell us? It tells us that Mr. Photon simultaneously sees every point on the path along his journey, and is also destroyed in that moment. No time has passed. Nada. t = 0 still. This is why things don't move at the speed of light. If Mr. photon were moving at .99999999999999999999999c you would have almost the same thing happen except that at some point you actually reach point b(and that it's a non zero distance, but VERY small, away) and that t1 does not equal t2 so a minute(again VERY small) amount of time would pass.

So, Mr. Photon traveling at c does see everything whilst simultaneously dying because space and time is not anywhere close to how we think of it in his reference frame.

I hope this is a slightly better explanation, whilst being equally unsatisfying. My response to that is, get used to it. Unfortunately, we just don't know and believe me I want to.

[MartGonzo]

yep, assuming there is a way to connect relativity and quantum mechanics and that both theories being incompatible isn't proof that scientists aren't barking up the wrong tree.

[How2FoldSoup]

yep, assuming there is a way to connect relativity and quantum mechanics and that both theories being incompatible isn't proof that scientists aren't barking up the wrong tree.

Hey! I like my tree!

I have my doubts on our current system for Quantum Mechanics, but I'll be damned if they haven't stood the test of every experiment we've thrown at it. Yes it's crazy, but the fact remains that it works.

My biggest gripe is that I refuse to believe photons are massless. Something that's massless shouldn't carry momentum T.T Yes, as far as we can tell they are, and no experiments have disproven this, but I still don't like it.

Now, having said that we obviously don't have unified theory, so something is clearly missing and that it doesn't work perfectly. Go bother your local rep and tell them to set aside more funding for science and maybe we'll get there sometime soon. At any rate, we're trying.

[MartGonzo]

Hey! I like my tree!

I have my doubts on our current system for Quantum Mechanics, but I'll be damned if they haven't stood the test of every experiment we've thrown at it. Yes it's crazy, but the fact remains that it works.

My biggest gripe is that I refuse to believe photons are massless. Something that's massless shouldn't carry momentum T.T Yes, as far as we can tell they are, and no experiments have disproven this, but I still don't like it.

Now, having said that we obviously don't have unified theory, so something is clearly missing and that it doesn't work perfectly. Go bother your local rep and tell them to set aside more funding for science and maybe we'll get there sometime soon. At any rate, we're trying.

true, tis a beautiful but slightly baffling tree

[WestAir]

If you broke reality and pushed your camera faster than C, what would things look like as you caught up with photons from behind?*

*You also have a machine that separates space and time so you can modify the space (speed) vector without changing the time vector

[How2FoldSoup]

If you broke reality and pushed your camera faster than C, what would things look like as you caught up with photons from behind?*

*You also have a machine that separates space and time so you can modify the space (speed) vector without changing the time vector

With your machine you're just using a galilean transform instead of the lorentz transformations and relativity doesn't matter whole point of relativity is that as your speed increases towards c, something(that something is time) must compensate, because in our 'verse we physically cannot move faster than 0. It's like saying 2+2=5. It's a logical fallacy.

I'll humor it though because physiks is fun that way. I want to start saying that passing c would act as some sort of threshold where things go from acting normally to bat.... insane. It depends on how you want to follow it I guess. As you pass c, the lorentz contractions would become so intense that you now have negative distance(wrap your head around that!). Nothing happens to time because your machine says so. So the photons would just be appear to be moving towards you at whatever speed above c you are moving. So at c+1 they are moving at you at 1 speed(whatever that unit is).

Something entirely different would probably happen, something that I can't even conceive of because it's impossible in our 'verse. If there's a multiverse with different laws of physiks, go ask one of the other ones. I can't answer that here

[YNM]

There should be nothing that a photon can see, because photons doesn't interact with photons, which describes what is seen.

Matter moving at c can be called as radiation (or inevitably, light, so photons again) and so experience the same thing. Even if you assume that it's still a matter, you'd experience nothing as the value of γ is undefined (γ = (1/√(1-(v^2/c^2)), wrongly mentioned it in other thread)

[How2FoldSoup]

There should be nothing that a photon can see, because photons doesn't interact with photons, which describes what is seen.

Matter moving at c can be called as radiation (or inevitably, light, so photons again) and so experience the same thing. Even if you assume that it's still a matter, you'd experience nothing as the value of γ is undefined (γ = (1/√(1-(v^2/c^2)), wrongly mentioned it in other thread)

Photon's also can't see because they are not alive. That's no fun if you don't play with the idea though. If you aren't diving through the possibilities of physics you aren't having enough fun with your knowledge in my opinion

[N_las]

yep, assuming there is a way to connect relativity and quantum mechanics and that both theories being incompatible isn't proof that scientists aren't barking up the wrong tree.

We only need special relativity to answer the question of this thread. And special relativity is perfectly compatible with quantum mechanics. They are already connected.

My biggest gripe is that I refuse to believe photons are massless. Something that's massless shouldn't carry momentum T.T Yes, as far as we can tell they are, and no experiments have disproven this, but I still don't like it.

Photons are only massless if you are one of those purists that only count invariant mass as "real mass". If you use the concept of relativistic mass, then photons have a mass:

The energy of a photon is dependent of its frequency: E = h f

h is the Planck constant.

The mass of a system is fundamentally dependent on its energy content: E = m c²

So the "mass" of a photon kinda is: m = h f / c²

That is consistent with the momentum of a photon.

Momentum is defined as: p = m v

If we insert the "mass" of the photon and its velocity ©, we get p = h f / c

This is exactly the momentum of a photon you can find in every textbook.

So the mass of a photon is much more a semantic question than a physical one.

[YNM]

Photon's also can't see because they are not alive. That's no fun if you don't play with the idea though. If you aren't diving through the possibilities of physics you aren't having enough fun with your knowledge in my opinion

- Camera isn't alive, yet it takes what it's pointed at.

- Microphones is dead yet it records what it says.

- Tools are dead yet they age (or, note down what we did to it).

So watch out...

Back on topic : I don't really know anything else yet... Maybe if I can add photons would feel that it's energy (or mass, relativistic mass) is being lost slightly due to gravitational bending of space, out of the presence of Sun.

[Camacha]

There should be nothing that a photon can see, because photons doesn't interact with photons, which describes what is seen.

I value this more evidence based approach, but I feel this is covered by the disclaimer in the first post. What I ask is, for as far as we know, physically impossible. It is, however, possible to arbitrarily pick a location and/or trajectory and wonder what anything would see from that actual and real place if you were to be there (or if a photon magically sprouted eyes and a way of processing the signals). Just like the center of the Earth or Sun, we will probably never actually see it.

What can be seen ahead of said photon seems to be discussed in some length, but what you see when you look behind is a bit of a mystery to me.

- Microphones is dead yet it records what it says.

- Tools are dead yet they age (or, note down what we did to it).

It might be nitpicking, but for as far as I know and am concerned, anything that has not lived cannot be dead. A rock is not dead, it is inanimate. I will leave the long and arduous discussion on things like limestone to another thread - it is beyond the scope of this one.

Edited November 5, 2014 by Camacha

[How2FoldSoup]

We only need special relativity to answer the question of this thread. And special relativity is perfectly compatible with quantum mechanics. They are already connected.

Photons are only massless if you are one of those purists that only count invariant mass as "real mass". If you use the concept of relativistic mass, then photons have a mass:

The energy of a photon is dependent of its frequency: E = h f

h is the Planck constant.

The mass of a system is fundamentally dependent on its energy content: E = m c²

So the "mass" of a photon kinda is: m = h f / c²

That is consistent with the momentum of a photon.

Momentum is defined as: p = m v

If we insert the "mass" of the photon and its velocity ©, we get p = h f / c

This is exactly the momentum of a photon you can find in every textbook.

So the mass of a photon is much more a semantic question than a physical one.

I'm well aware of this relation. I've derived the very same thing but in terms of wavelength instead of lamda myself. However, as far as science is concerned even with taking relativistic effects into account we cannot find any detectable amount of mass for a photon. This does not mean it's semantics and it's a very real debate. We have had no experimental evidence to prove otherwise. In fact, current calculations of the the total mass of the universe is consistant with this idea. Dark energy and dark matter are different, however there is a part of me that wants to believe that this mass is simply the uncounted mass of photons in the universe.

That being said, this is means that completely illogical things happen if photons have mass. That means when you send out electromagnetic radiation you are also sending out photons and mass with it. Wait, WHAT? Yes. However, we've never noticed any measurable effect of this. Say for example you have a phone and after extensive use you would exchange a lot of photons with satellites and cell towers.. If photons carried mass, you would notice a loss of mass of a phone since it emits radiowaves. That's a bad example because the net change may be very small. What if you had an electrical circuit that ran through an antenna and gave off RF waves, eventually after emitting enough photons the device would lose mass to its ejection of photons. Again, this is clearly not the case.

There is something more to the puzzle that we haven't figured out yet.

Edit: Grammar

[N_las]

That being said, this is means that completely illogical things happen if photons have mass. That means when you send out electromagnetic radiation you are also sending out photons and mass with it. Wait, WHAT? Yes. However, we've never noticed any measurable effect of this. Say for example you have a phone and after extensive use you would exchange a lot of photons with satellites and cell towers.. If photons carried mass, you would notice a loss of mass of a phone since it emits radiowaves. That's a bad example because the net change may be very small. What if you had an electrical circuit that ran through an antenna and gave off RF waves, eventually after emitting enough photons the device would lose mass to its ejection of photons. Again, this is clearly not the case.

There is something more to the puzzle that we haven't figured out yet.

What are you talking about? It is EXACTLY so that electromagnetic radiation carries mass away from objects.

I hope you are aware that the sun loses mass by fusion. This mass doesn't vanish, but is carried away by the sunlight.

If you have a cellphone with a 12.16 Wh battery, and you use it until the battery is empty, it will be a bit lighter:

E = mc²

12.16 Wh/c² = 4.87 × 10^-13 kg

It is just a miniscule amount, but this mass doesn't vanish into nothingness, but is carried away by electromagnetic radiation (mostly by infrared photons because of the cellphones warmth)

An molecule (A) in an excited state is a tiny bit heavier than the same molecule in ground state. If the molecule drops from the excited state into the ground state, it loses that bit of mass. The mass is carried away by the photon. If this photon then hits another molecule (, it may put it into the excited state. Now the second molecule ( is a bit heavier.

Molecule A lost mass, and molecule B gained it. The photon transfered the mass between those molecules. If you consider that experiment as a closed system, and you would somehow measure the mass of the system, you wouldn't see a decrease in mass while the photon is between A and B. The System would always have the same mass:

- First is molecule A "heavy" and molecule B "light".

- Second is molecule A "light", there is a photon with a certain mass, and molecule B is "light"

- Third is molecule A "light" and molecule B "heavy"

I worked for a while at an antimatter-source at a research reactor. The source produces positrons and electrons out of gamma radiation. positrons and electrons clearly have mass, but were did it come from? It didn't come from nowhere: The gamma photon (just electromagnetic radiation) had this mass before it was turned into the matter-antimatter pair.

There are many unknown things in physics, but your claim "There is something more to the puzzle that we haven't figured out yet" is just wrong in relation to the mass of photons. There isn't anything left in that puzzle. It is just that many prefere to not use the label "relativistic mass". From that "purist" perspective photons don't carry mass, because only invariant mass counts. It is really just a semantic and didactic question. The science behind it is clear and without any questions left.

Edited November 6, 2014 by N_las

[How2FoldSoup]

What are you talking about? It is EXACTLY so that electromagnetic radiation carries mass away from objects.

I hope you are aware that the sun loses mass by fusion. This mass doesn't vanish, but is carried away by the sunlight.

If you have a cellphone with a 12.16 Wh battery, and you use it until the battery is empty, it will be a bit lighter:

E = mc²

12.16 Wh/c² = 4.87 × 10^-13 kg

It is just a miniscule amount, but this mass doesn't vanish into nothingness, but is carried away by electromagnetic radiation (mostly by infrared photons because of the cellphones warmth)

An molecule (A) in an excited state is a tiny bit heavier than the same molecule in ground state. If the molecule drops from the excited state into the ground state, it loses that bit of mass. The mass is carried away by the photon. If this photon then hits another molecule (, it may put it into the excited state. Now the second molecule ( is a bit heavier.

Molecule A lost mass, and molecule B gained it. The photon transfered the mass between those molecules. If you consider that experiment as a closed system, and you would somehow measure the mass of the system, you wouldn't see a decrease in mass while the photon is between A and B. The System would always have the same mass:

- First is molecule A "heavy" and molecule B "light".

- Second is molecule A "light", there is a photon with a certain mass, and molecule B is "light"

- Third is molecule A "light" and molecule B "heavy"

I worked for a while at an antimatter-source at a research reactor. The source produces positrons and electrons out of gamma radiation. positrons and electrons clearly have mass, but were did it come from? It didn't come from nowhere: The gamma photon (just electromagnetic radiation) had this mass before it was turned into the matter-antimatter pair.

My disclaimer to this is that I am tired, and I will double check in the morning but I'll answer before I go to sleep.

EM radiation carries energy, not mass. There are similarities but they are fundamentally different things. As you have stated E=mc^2, so we know that Energy is interchangable with in effect. However, this does not mean that photons carrying energy suddenly become massive.

I appreciate your questioning of my knowledge of fusion, yes I know very well what it is. You are correct, some energy from the sun is lost in the form of photons. However, the majority of the mass lost by the Sun is alpha and beta radiation. The Sun emits billions of particles every second and not all of them are photons. The point that all mass that leaves the Sun through photons is completely incorrect. Some of it is carried away as particles, and the rest is converted to energy in the form of photons.

As I've stated above, what energy is lost is carried away as energy, not as mass. I appreciate your use of Einsten's equation. Go find a phone with a 12.16 Wh battery and find the mass to within 16 sigfigs to see if there is a difference between fully charged and empty. I would love to be proven wrong.

Again, this is the amount of energy contained within a mass. Now that you are using a molecule and not a phone that is presumably at rest, I can quote you the entire equation:

E = (M^2c^2 + p^2c^4)^(1/2)

You will note that because there is a p, we cannot have particles in motion in this equation and that term would go to 0, giving us Einsten's famous E=mc^2.

However, because there is momentum in particles moving between energy states we have to take into account the total energy of the system. Most of the places where you say mass should be replaced with energy. Photons carry energy and momentum. This is fact, we have proven it. Does a laser feel any heavier when you shoot it at your hand? There should be at least 10^20 photons hitting your hand every second but this doesn't mean your hand gets more massive.

About gamma rays - they carry a lot of energy and momentum. p = h/lamda, their wavelength is on the order of 10^-15. Thats a damn small wavelength and a pretty large momentum for a single photon to carry. This allows the gamma ray to smack into other particles and allow them to emit an electron, and an oppositely charged electron, a positron. The gamma ray merely transfers its energy to these new particles, not its mass. That's like saying if were to punch my big brother that I would lose part of my fist inside of him. I know real world analogies don't work for quantum mechanics but it's the same principle. Instead, I would punch him so hard he explodes into 2 different pieces flying in opposite directions and that I screwed up the spin on one of his pieces.

Goodnight!

Edit: I need to add, we do not know where electrons get their mass from. EM radiation and particles are still a damned mystery to physics. If you claim to know otherwise, publish it with tested experiments and please let the rest of the physics community know. This bothers the hell out of me while learning it and I would like a better explanation. You'll have to be convincing though. I have looked not just at the theory but also at the math that proves that this is how the universe works.

Edited November 6, 2014 by How2FoldSoup

[N_las]

EM radiation carries energy, not mass. There are similarities but they are fundamentally different things. As you have stated E=mc^2, so we know that Energy is interchangable with in effect. However, this does not mean that photons carrying energy suddenly become massive.

You suffer from a misunderstanding of "E=mc^2". It doesn't mean that you can interchange a certain amount of energy for a certain amount of mass, losing energy and gaining mass in the process. It DOES mean that Energy and mass is the same thing, mass is the measurment of the energy content of a system. Every system with the energy-content E has automatically the mass m, and every system with the mass m must contain the corresponding energy E.

I appreciate your questioning of my knowledge of fusion, yes I know very well what it is. You are correct, some energy from the sun is lost in the form of photons. However, the majority of the mass lost by the Sun is alpha and beta radiation. The Sun emits billions of particles every second and not all of them are photons. The point that all mass that leaves the Sun through photons is completely incorrect. Some of it is carried away as particles, and the rest is converted to energy in the form of photons.

My point wasn't that ALL the mass the sun loses is photons. But those photons the sun is sending out got their mass from the fusion process.

As I've stated above, what energy is lost is carried away as energy, not as mass. I appreciate your use of Einsten's equation. Go find a phone with a 12.16 Wh battery and find the mass to within 16 sigfigs to see if there is a difference between fully charged and empty. I would love to be proven wrong.

As long as you use the concept of relativistic mass, the energy that was carried away was automatically mass. I will provide a thought experiment at the end of this reply.

Again, this is the amount of energy contained within a mass. Now that you are using a molecule and not a phone that is presumably at rest, I can quote you the entire equation:

E = (M^2c^2 + p^2c^4)^(1/2)

You will note that because there is a p, we cannot have particles in motion in this equation and that term would go to 0, giving us Einsten's famous E=mc^2.

The notion that the "long" formula containg the momentum p is the fundamental formula, and Einsteins original equations is just a special case for "p = 0" is wrong.

The more fundamental formel IS "E=mc^2", and it holds perfectly true, as long as "m" is regarded as the relativistic mass.

But purists (who don't like the concept of "relativistic mass") want a formula where the "m" stants for the invariant mass. This formula is the one you provide. But in any actual calculation, you can come to the same result, by regarding "m" as relativistic mass and using the simple formula "E=mc²"

However, because there is momentum in particles moving between energy states we have to take into account the total energy of the system. Most of the places where you say mass should be replaced with energy. Photons carry energy and momentum. This is fact, we have proven it. Does a laser feel any heavier when you shoot it at your hand? There should be at least 10^20 photons hitting your hand every second but this doesn't mean your hand gets more massive.

As the temperatur in my hand is rising, so does its energy content and its mass. Your artifical distinction between mass and energy is a thought barrier you have installed because you only regard invariant mass. See my thought experiment at the end of this reply.

About gamma rays - they carry a lot of energy and momentum. p = h/lamda, their wavelength is on the order of 10^-15. Thats a damn small wavelength and a pretty large momentum for a single photon to carry. This allows the gamma ray to smack into other particles and allow them to emit an electron, and an oppositely charged electron, a positron. The gamma ray merely transfers its energy to these new particles, not its mass. That's like saying if were to punch my big brother that I would lose part of my fist inside of him. I know real world analogies don't work for quantum mechanics but it's the same principle. Instead, I would punch him so hard he explodes into 2 different pieces flying in opposite directions and that I screwed up the spin on one of his pieces.

By transfering its Energy, the gamma photon automatically transferd the corresponding amount of mass. Your analogies are really bad. The gamma ray didn't smack the electon out of the "other particle". The electron and the positron were pair-created out of the photon. The photon lost its energy (and mass) in the process, while the positron and electron gained that energy (and mass).

Consider the mass defect in nuclear fission. Your original atom has a certain nuclear binding energy. This nuclear binding energy is automatically a part of the mass of the original nucleus. If you split the nucleus, you release a bit of the binding energy. The fission products (including any stray neutrons, electrons or alpha particles) have LESS binding energy and automatically they have LESS mass. How do you explain that. If "E=mc²" does mean that you could interchange a certain amout of energy for a certain amount of mass and reverse, by REDUCING its binding energy, it should have PRODUCED Mass.

In reality, "E=mc²" isn't an "exchange rate", but it means that the Energy "E" IS automatically the mass "m". The fission products have LESS binding energy, and hence LESS mass. The Energy that was binding energy is converted to kinetic energy of the fission products, and gamma photons. If you calculate the relativistic mass of the fission products and of the photons, no mass is lost. The whole process conserved energy AND mass, because both are one and the same.

Let me give you a thought experiment, that is hopfully convincing:

I claim that the "relativistic mass" is real. The concept of "invariant mass" may make certain calculatons easier, but it isn't more fundamental, because sometimes there is no clear distinction.

Furthermore, mass and energy aren't two different things that can be exchanged, increasing one quantity while decreasing the other. This is a rampant misunderstanding. Mass and Energy are the same thing, and every amount of energy is automatically a certain amount of mass. By decreasing the energy of a system, its mass will decrease. The lost energy had to go somewhere, and the lost mass went the same way.

Consider a positron-electron plasma. If the observing time is small enough, this plasma is stable (they will annihilate eventually, but only after a small amount of time). We have 1 kg of plasma. We contain it into a 0.1 kg box. From the outside, we don't know what is inside. What will we get, if we measure the invariant mass of the box? If we are at rest with the box, and we put a force of 1.1 N on the box, it will accelerate with 1 m/s². So the invariant mass seems to be about 1.1 kg (the mass of the empty box plus the mass of the plasma)

If the positrons and electrons in the box annihilate over time, they "become" gamma photons. Assume the walls of the box are perfect mirrors for gamma photons, so after some time, there are only photons left in the box. But from the outside, we can't know what is happening inside the box. We only see a box. What will we get, if we measure the invariant mass of the box after the whole plasma is annihilated? The same as before! The box still seems to have the invariant mass of 1.1 kg.

From the inside, we can explain that by the photon pressure on the walls. By accelerating the box, a red- and blushift of the photons will produce a different photon pressure at the opposing walls of the box, so they produce a resistance against the acceleration.

But from the outside, we don't see and know that, and we don't care. From the outside, the box seems to have always just an invariant mass of 1.1 kg, it doesn't matter what happens inside. So the invariant mass of an object can be just the "relativistic mass" of the photons in disguise.

You may say: The plasma lost mass, it was converted to energy, and now the photons have this energy. But what does that even mean, if the whole system behaves just as if it still had the original mass. Heck, even the gravity from the box doesn't change!

And this is the case for every system. It doesn't matter how energy is converted, it always carriers its equvialent in mass. By adding 16 Wh chemical energy to my battery, it will get heavier. (The energy source, maybe a burning piece of coal, will get lighter). By compressing a mechanical spring, it gets heavier. By inducing a current into a superconducter, it gets heavier.

This isn't any new physics, or just something a guy tells you on the internet. It is the fundamental meaning of the formula E=mc²

http://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence

Quote:

"Whenever any type of energy is removed from a system, the mass associated with the energy is also removed, and the system therefore loses mass. This mass defect in the system may be simply calculated as ÃŽâ€m = ÃŽâ€E/c2, and this was the form of the equation historically first presented by Einstein in 1905. However, use of this formula in such circumstances has led to the false idea that mass has been "converted" to energy. This may be particularly the case when the energy (and mass) removed from the system is associated with the binding energy of the system. In such cases, the binding energy is observed as a "mass defect" or deficit in the new system."

The whole idea that mass and energy can be coverted into each other is just a missunderstandig, rampant because some people are to fanatic with there "invariant-mass-purism", bad high-school teachers and bad didactic choices by college professors.

The question if a photon has a mass or not IS just a semantic one. Even if you claim that a photon doesn't have mass, because you are only regarding "invariant mass" as real: By putting a perfectly massless box around the photon, with perfect mirrors on the inside, the box suddently has "invariant mass"... exactly in the quantity one could have calculated as relativistic mass of the photon.

Edited November 6, 2014 by N_las

[rkman]

SpaceEngine... - is that really what a photon would see?

No. SpaceEngine does not take relativity into account.

[Camacha]

SpaceEngine... - is that really what a photon would see?

No. SpaceEngine does not take relativity into account.

Obviously. Missed the rest of the post?

[How2FoldSoup]

Stuff

Look, as you said we are arguing over a semantic debate. Essentially we are saying the very same thing but a different in word choice. We can nitpick back and forth its mostly irrelevant.

At any rate, I quoted the initial formula wrong from memory. It is E=(m^2c^4 + p^2c^2)^(1/2). This is not wrong. This is how E=mc^2 is derived. I don't know how you can say that E=mc^2 is just some stand alone equation that Einstein just came up with. This equation is how he did it. E=mc^2 does not work for massless particles, such as photons, and that terms to 0. This gives you E= pc which you have already stated what this means. This is where it comes from. I'm not sure how you can work through so much else and assume that the base equation is wrong.

I can use wikipedia too. Just 2 sections above yours, from I can quote.

"Here the (pc)^2 term represents the square of the Euclidean norm (total vector length) of the various momentum vectors in the system, which reduces to the square of the simple momentum magnitude, if only a single particle is considered. This equation reduces to E = mc^2 when the momentum term is zero. For photons where m0 = 0, the equation reduces to Er = pc."

E=mc^2 means that any energy contributes to the mass of a system. That being said, since photons are massless E=mc^2 does not apply to them. They have zero restmass.

I appreciate your thought experiment and I will put more than the 5 minutes of thought between reading it and writing this response before I reply to it. That being said, I'm not an expert in plasmas and I don't have a lot of experience with them.

As you say your conclusion, we are arguing semantics and that to me is a pointless waste of time. We will keep reiterating the same points, I've read too many internet arguments to expect it to end any differently. While I disagree with what you say, I've left a lot of points unaddressed and I intend to do so.

This was simply a thread on what would you see if you were traveling with a photon and it can get back to that now.