Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: CD13 on 21/01/2011 15:43:21
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I'm a biological scientist, so excuse the basic nature of these questions:
As a photon travels at the speed of light in a vacuum, time must be non-existent then, surely? Thus it has no past or future, only the present?
If a photon slows when it goes through a material, where does the lost energy go? And when it speeds up, where does the extra energy come from?
Do tachyons exist? If so, how could they be detected?
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A photon have no other 'speed' than light. That's why I wonder, just like you I guess:) What they really are. And they do exchange 'energy' when getting annihilated, and momentum too. So in a piece of matter they get 'slowed down' due to their 'annihilation' and subsequent 'resurrection' inside the matter. As for where the 'lost energy' goes? Depends on what you think 'energy' consists of.
Myself I do trust in a universe of equilibrium. That means that whatever happens inside it doesn't really take anything 'away'. So in that motto there is no 'energy' lost, only a 'interaction' taking part expressing itself into a transformation, or several rather when discussing that photon 'propagating'.
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From the photon's frame of reference, when it is created at A it instantly appears at B no matter how far away from A. See, http://www.thenakedscientists.com/forum/index.php?topic=34333.0;topicseen
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Hmm, time and photons :)
Should have answered that one too.
Nope, time don't exist for a photon, as far as we know. If it did you could expect them to die of 'exhaustion', well, sort of, getting old and all that. And that's the standard explanation to their timelessness. But there are some non-mainstream ideas in where they do have a 'clock' of some kind.
But as 'time' is a highly subjective matter according to the theory of relativity, changing whenever you look away from your own 'frame of reference' it makes sense. Why not, if time are mutable with speed? Why shouldn't a photon be 'time-less'? After all, nothing goes faster, that we have measured.
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If we would assume a piece of matter near light speed instead it would never become 'time-less'. On the other tentacle it would never reach lights speed in a vacuum either.
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I'm a biological scientist, so excuse the basic nature of these questions:
I'm a non-scientist, so my comments are likely to be even more basic than your questions.
As RH points out, it is only in the F of R of the photon that time does not exist. This seems to apply only to when the photon is travelling in a vacuum, but I find myself wondering if it also applies when it is passing through a medium in which we perceive its speed to be lower. Is it travelling more slowly, only in the observer's F of R?
Tachyons, as far as I am aware, are theoretical particles, so no one knows if they exist. Personally, I think that if they do exist this would imply the presence of a mirror universe. That's probably material for another thread, though. It's also probably rubbish.
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I'm a biological scientist, so excuse the basic nature of these questions:
As RH points out, it is only in the F of R of the photon that time does not exist.
The problem is that in physics, there is no theory that defines the frame of reference of a photon. This mistake is generally made because special relativity tells us that objects with mass have inertial reference frames in which a faster-moving object's clock will run slower than a slower-moving object. If you naively, set the speed of a massive object to the speed of light, you find that it's clock stops.
The problem is that special relativity is derived only for objects with mass, and not for photons. One of the postulates (that the speed of light is constant in all reference frames described by the theory) doesn't hold if you set the speed of the object to the speed of light. Objects with mass can also never move at the speed of light, since that requires infinite energy. So this is never a problem for them.
So in summary, there is no theory for a frame of reference for a photon. Saying they don't experience time is a common mistake made about special relativity.
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I'm a biological scientist, so excuse the basic nature of these questions:
As RH points out, it is only in the F of R of the photon that time does not exist.
The problem is that in physics, there is no theory that defines the frame of reference of a photon. This mistake is generally made because special relativity tells us that objects with mass have inertial reference frames in which a faster-moving object's clock will run slower than a slower-moving object. If you naively, set the speed of a massive object to the speed of light, you find that it's clock stops.
The problem is that special relativity is derived only for objects with mass, and not for photons. One of the postulates (that the speed of light is constant in all reference frames described by the theory) doesn't hold if you set the speed of the object to the speed of light. Objects with mass can also never move at the speed of light, since that requires infinite energy. So this is never a problem for them.
So in summary, there is no theory for a frame of reference for a photon. Saying they don't experience time is a common mistake made about special relativity.
Indeed.
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The problem is that in physics, there is no theory that defines the frame of reference of a photon. This mistake is generally made because special relativity tells us that objects with mass have inertial reference frames in which a faster-moving object's clock will run slower than a slower-moving object. If you naively, set the speed of a massive object to the speed of light, you find that it's clock stops.
The problem is that special relativity is derived only for objects with mass, and not for photons. One of the postulates (that the speed of light is constant in all reference frames described by the theory) doesn't hold if you set the speed of the object to the speed of light. Objects with mass can also never move at the speed of light, since that requires infinite energy. So this is never a problem for them.
So in summary, there is no theory for a frame of reference for a photon. Saying they don't experience time is a common mistake made about special relativity.
But if all matter is made of photons, then all matter can travel at c.
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The problem is that in physics, there is no theory that defines the frame of reference of a photon. This mistake is generally made because special relativity tells us that objects with mass have inertial reference frames in which a faster-moving object's clock will run slower than a slower-moving object. If you naively, set the speed of a massive object to the speed of light, you find that it's clock stops.
The problem is that special relativity is derived only for objects with mass, and not for photons. One of the postulates (that the speed of light is constant in all reference frames described by the theory) doesn't hold if you set the speed of the object to the speed of light. Objects with mass can also never move at the speed of light, since that requires infinite energy. So this is never a problem for them.
So in summary, there is no theory for a frame of reference for a photon. Saying they don't experience time is a common mistake made about special relativity.
But if all matter is made of photons, then all matter can travel at c.
That is absurd. Who said matter would travel at lightspeed?
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Matter is a concentrated energy. If you like, radiation is a free energy - a diffused type of matter. If all matter is made from photon energy, then it contributes to the kinetic energy of the system, and the inertial energy of the system. It does not mean that matter will move at lightspeed. This is in direct contradiction of relativity theory.
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Matter is a concentrated energy. If you like, radiation is a free energy - a diffused type of matter. If all matter is made from photon energy, then it contributes to the kinetic energy of the system, and the inertial energy of the system. It does not mean that matter will move at lightspeed. This is in direct contradiction of relativity theory.
Are you saying that matter and photons are actually two totally different things? I thought you maintained that matter was made from photons, or did I get that wrong?
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I'm a biological scientist, so excuse the basic nature of these questions:
As a photon travels at the speed of light in a vacuum, time must be non-existent then, surely? Thus it has no past or future, only the present?
If a photon slows when it goes through a material, where does the lost energy go? And when it speeds up, where does the extra energy come from?
Do tachyons exist? If so, how could they be detected?
Sure, by past and present, we mean the past cone and future cone of time. A photon has none of that. It follows a null trajectory. By theory, if it does not travel through time, it surely does not travel through space. Strange how we can measure such a thing, but as soon as we apply theory to the photon, it is not allowed to posses the asbtraction called a frame of reference. Time, space existence if you will, is all contracted out of its reality. Not a single second passes for the photon, nor does it take time to go anywhere.
As for tachyons, we do not believe they exist. Tachyonic Condensation, a mathematical work seems to exclude their existences altogether. However, if they did exist, we would look for Cherenkov Radiation in order to detect them. Such radiation can already be observed.
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Matter is a concentrated energy. If you like, radiation is a free energy - a diffused type of matter. If all matter is made from photon energy, then it contributes to the kinetic energy of the system, and the inertial energy of the system. It does not mean that matter will move at lightspeed. This is in direct contradiction of relativity theory.
Are you saying that matter and photons are actually two totally different things? I thought you maintained that matter was made from photons, or did I get that wrong?
Yes you are wrong, again.
Matter can be made out of photons, it does not necesserily mean that attributes of the photon are carried on. Intrinsic properties in the form of information is almost certainly passed on in order to conserve quantities like charge and spin. It does not mean that the manifestation (matter) obeys the rules which radiation does. Matter and energy are still quite different, even though they are interchangeable via E=Mc2.
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General relativity implies that photons travel in no time in their frame of reference but it seems that people never really took it seriously...
Any particle near a black hole cannot sustain the strong acceleration and will turn into 2 photons (going in opposite direction) that will gain relativistic kinetic energy due to the Doppler effect. But i think half of the photons created as such, will escape the black hole. The black hole will catch E = MC^2/2... For an external fixed referential frame, the photons escaping loose an energy equal to half the gain in kinetic energy of the former particle due to a Doppler red shift in the ascension of the gravitational field...
For an outside observer, the appearing mass M in E=MC^2 at the event horizon is not the relativistic mass, but truly the rest mass. A photon reaching the event horizon will collide with the black hole in a perfect elastic collision. The relativistic kinetic energy momentum gained from the gravitational field before the collision is reciprocal for both, the photon and the black hole... After the collision, the momenta totally cancel each other.
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Matter is a concentrated energy. If you like, radiation is a free energy - a diffused type of matter. If all matter is made from photon energy, then it contributes to the kinetic energy of the system, and the inertial energy of the system. It does not mean that matter will move at lightspeed. This is in direct contradiction of relativity theory.
Are you saying that matter and photons are actually two totally different things? I thought you maintained that matter was made from photons, or did I get that wrong?
Yes you are wrong, again.
Matter can be made out of photons, it does not necesserily mean that attributes of the photon are carried on. Intrinsic properties in the form of information is almost certainly passed on in order to conserve quantities like charge and spin. It does not mean that the manifestation (matter) obeys the rules which radiation does. Matter and energy are still quite different, even though they are interchangeable via E=Mc2.
I thought you said this:
"What terminology do I use which is misleading, if we both agree matter is made from a fundamental energy, most associated to photons..?"
Isn't associating photonic energy with matter about as meaningful as saying that all atoms are really just modified hydrogen atoms?
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I don't know JP, sometimes I feel the best way is to just ignore them.
Holes, I say, holes in our reality :)
But yes, we can't assign a frame to them. Doesn't mean that it is wrong to speak about them as being 'timeless'. From our point of view they definitely have to have an incredibly slow metabolism, or no 'time' at all. And that is a valid point of view.
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But yes, we can't assign a frame to them. Doesn't mean that it is wrong to speak about them as being 'timeless'. From our point of view they definitely have to have an incredibly slow metabolism, or no 'time' at all. And that is a valid point of view.
There are points of view and then there's points of view that are supported by science. Without a scientific model that supports the view that photons experience no "time," it's not valid science to claim so. We don't know how to describe the reference frame of a photon scientifically, so any claims about it not experiencing time in it's own reference frame aren't scientific.
Of course, if you're talking about a photon being "timeless" in other ways, and you define timeless so that it fits scientific models, then you're talking science! For example, photons don't appear to decay, so they might be timeless in that sense. (They can, however, transition briefly into virtual electron/positron pairs.)
However, photons can certainly travel in time. If you shoot a laser at the moon, the photons will arrive at the moon roughly 1 second after they leave your laser. They've traveled 1 second forward in time.
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Well, I talked about their decay, didn't I?
Saying that their metabolism had to be either terribly slow or, as from our viewpoint, non existent. And what that make them, to me that is :) Is 'time less'. If you know a better definition for what they are I'm interested. I don't know any better way to view them :) Well, that should be as 'holes' then but, if so, we will wander of all mainstream definitions.
They are phreaky buggers, ain't they :)
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It is not scientific to dismiss a logical possibility and it is even more so if it answers many unsolved problems in a very simple way... Why to be afraid of simplicity...?
No mathematical expression represent reality in an absolute manner... General solutions hide concepts, specific solutions clarify them. Then you may use your imagination to get new solutions. If i had not found any truth, i would have chosen to write a book about it...
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in physics, there is no theory that defines the frame of reference of a photon
We don't know how to describe the reference frame of a photon scientifically, so any claims about it not experiencing time in it's own reference frame aren't scientific.
Looked at from a slightly different perspective; is there any scientific evidence suggesting that a photon's apparent experience of time exists other than in the F of R of an observer?
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in physics, there is no theory that defines the frame of reference of a photon
We don't know how to describe the reference frame of a photon scientifically, so any claims about it not experiencing time in it's own reference frame aren't scientific.
Looked at from a slightly different perspective; is there any scientific evidence suggesting that a photon's apparent experience of time exists other than in the F of R of an observer?
I'll answer this. The answer is no.
If a photon decayed spontaneously in space, there might be some indication that it experiences a time, but this is not the case. Relative to us however, as JP has noted, photons do experience time.
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Relative to us however, as JP has noted, photons do experience time.
Is that the same as saying that from the F of R of an observer, a photon experiences time?
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Photons interactions appear in time for matter but they have no timerate according to themselves.
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QC, can you clarify this , please?
You say: of the photon "if it does not travel through time, it surely does not travel through space", and: "Not a single second passes for the photon, nor does it take time to go anywhere."
Taken together, these two statements seem to say that a photon does not travel through space.
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Relative to us however, as JP has noted, photons do experience time.
Is that the same as saying that from the F of R of an observer, a photon experiences time?
The word "experience" brings with it a lot of connotations that muddies the picture a bit, as photons, not being conscious, don't experience anything as we humans do (or aliens in Geezer's case). Could you define more rigorously what you mean by "experiencing time"?
Alternatively, I can ask you a simple question:
A photon is emitted by the sun at time t=0 and is absorbed by your eye at time t=8 minutes. Is this "experiencing time"?
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it is 8 minutes for matter at no relative speed from the earth and the sun, certainly not for the photons...
I think what QC meant is that you cannot separate time and space. But it is theoretical.
According to Kaluza-Klein Theory, the charge is a fifth dimension. If the photons are made of charges (but having a total of zero), time and gravity could be an effect of the charges going at a slower speed than the speed of light... And it would generate relativity... Because all particles have charges, even the neutron. So all particles would have its own referential clock associated to its charge.
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Well, during my extensive intergalactic travels, I've yet to see a photon transmogrify itself into something else. They don't seem to decay or nuthin, whereas, AFAIK, everything else does.
Ergo (that's Alienspeak for therefore) photons (if they exist at all) seem to be exempt from the ravages of time.
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True, Geezer. Not decaying is a specific requirement as opposed to "not experiencing" time. Photons clearly still move through time in all Einsteinian reference frames.
By the way, the usual argument goes that photons are massless, so they move at the speed of light, and therefore they don't experience time. To complicate matters, gluons are theoretically massless, but they lack the stability of photons: they hate existing in isolation. Does this mean they don't experience time?
I think this is another case, as happens so often in science, where precise language is important, as is being very precise about what claims science can make about photons and what claims are philosophy. (Thinking about the way a photon sees the universe from it's point of view is an exercise in imagination, not science!)
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It's probably more philosophical that anything else, but I think energy does seem to "leak out" of everything over time, so one way to explain why that does not seem to happen in the case of photons is to exempt them from time.
Surely it's only important in the photon's frame of reference? How we perceive that "time" is not relevant.
We know that time "slows down" for things that travel fast. Why is it unreasonable to think that, at the extreme limit of speed, time essentially stops, or does not even exist.
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JP the Guardian of the Standard Model, you are very hard to convince but i must say you are often my first source of motivation to work and think harder about all this...
There is absolutely no proof that photons experience the passage of time. In fact, the mathematical equations of the Standard Model imply that photons have no timerate. In the contrary, Relativity as a whole would be crushed... I understand it is quite difficult to manage but it has to be this way if you look at the photons behaviour.
Geezer's arguments seem right to me.
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General Relativity equations are not valid for sizes smaller than the Planck Length and it doesn't explain what happen to the electromagnetic and nuclear forces beyond that in a black hole... It just supposed to vanish... Because it is not tied up with Quantum Theory...
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In fact, the mathematical equations of the Standard Model imply that photons have no timerate.
Really? Can you give me an equation?
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It's probably more philosophical that anything else, but I think energy does seem to "leak out" of everything over time, so one way to explain why that does not seem to happen in the case of photons is to exempt them from time.
But clearly that can't be true. The fact that photons are absorbed and emitted shows that they aren't exempt from time. They have to move through it!
I do get the point about a photon's non-decay possibly being related to it's internal clock, but without a scientific model to describe that internal clock (and relativity ain't the way to do it!), is this a scientific question? Would it be better to say "It doesn't decay" and be done with it?
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It's probably more philosophical that anything else, but I think energy does seem to "leak out" of everything over time, so one way to explain why that does not seem to happen in the case of photons is to exempt them from time.
But clearly that can't be true. The fact that photons are absorbed and emitted shows that they aren't exempt from time. They have to move through it!
I do get the point about a photon's non-decay possibly being related to it's internal clock, but without a scientific model to describe that internal clock (and relativity ain't the way to do it!), is this a scientific question? Would it be better to say "It doesn't decay" and be done with it?
Yes. The process of creating and destroying them does involve time. I just think it's a reasonable extrapolation from the observed fact that they don't decay, and the fact that they travel at c to assume that time is meaningless in their frame.
I certainly can't prove it, but I don't think you can prove my hypothesis is invalid either [;D]
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Hi I have no qualification in science, so please correct me. Also this is my first post here on this forum.
I have been taught in school about an equation for calculating time dilation.
T= factor by which the moving object has it's time shortened
t= time experienced by some stationary object
v= velocity of moving object
c= speed of light
T = t/sqrt(1-v^2/c^2)
The important part here is the bit in the square root, which if equal to zero makes the whole thing undefined.
For a photon, v = c
So sqrt(1-c^2/c^2) is the denominator
This simplifies to sqrt(1-1) = sqrt(0) = 0, which means the amount of time experienced is undefined, because t/0 is undefined.
Long story short, the amount of time experienced by a photon during one second of real time is 1/0, undefined (according to my understanding of this equation).
Below is a graph showing how time dilation varies over speed, units on the x axis are c.(source: Wikipedia)
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2F4%2F4f%2FTime_dilation.svg&hash=89e4d0126ad66a71642112461383c1b3)
The value on the y axis becomes infinitely large as it approaches 1, but it never reaches 1 (similar to the way y=1/x approaches, but never touches the y or x axis).
I am concerned, as there may be some other equation or consideration I am not aware of that can work around the "undefined" result to the equation above. I am also concerned I have made an error, as I thought someone else would have pulled the numbers out earlier, perhaps they are irrelevant to the question somehow?
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Photon has a limited energy,therefore can not touch "1" too. [;)]
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Light is not matter, it has no mass. Special Relativity is a special solution and therefore, you cannot conclude anything beyond its limits with it. Alone it is paradoxical...
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T = t/sqrt(1-v^2/c^2)
That is indeed the equation for time dilation, but it only applies for objects with mass, whereas photons are massless. You can't just use it for photons, even though it makes it look like you'll divide by zero getting "undefined" time. The derivation of that equation requires assuming that you're not dealing with massless photons in the first place.
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Light is not matter, it has no mass. Special Relativity is a special solution and therefore, you cannot conclude anything beyond its limits with it.
Exactly my point. Special relativity doesn't apply to describe the point of view of photons, and therefore using it to conclude how they "experience" time (or anything else) is flawed.
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A photon drags potential mass.Momentum has not Lorentz's factor for speed of photon.And energy has not Lorentz's factor for speed of photon.Without Lorentz's factor:
Kinetic Energy = mv²
Momentum = mv
Momentum and energy of objects have Lorent's factors for speed.
With Lorentz's factor:
Speed of recoil of objects for momentum = L*v
Speed of recoil of objects for energy = L*v/√(L+1)
Then : Kinetic Energy = mv²L²/(L+1)
Momentum = mvL
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The word "experience" brings with it a lot of connotations that muddies the picture a bit,
Bad choice of word. [:I] How better to express it? What about: Is it only in the F of R of an observer that a photon appears to travel through time?
A photon is emitted by the sun at time t=0 and is absorbed by your eye at time t=8 minutes. Is this "experiencing time"?
As you rightly point out, this would be experiencing time only if the photon were able to experience anything.
Another requirement would be that what the photon was experiencing was 8 minutes travel.
Would this not be faster than light travel? [;D]
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The process of creating and destroying them does involve time.
Does a photon exist before it is created? - No.
Does a photon exist after it is destroyed? - No.
When is a photon created? - In the present.
When is a photon destroyed? - In the present.
Can we establish that any time is involved between creation and destruction, other than that which is perceived by an observer? - So far I see no evidence of this, so are we just airing our personal beliefs?
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Hi, JPC, welcome. Good to see someone who posts some maths I can understand. [:)] That's rare. Keep it up.
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The word "experience" brings with it a lot of connotations that muddies the picture a bit,
Bad choice of word. [:I] How better to express it? What about: Is it only in the F of R of an observer that a photon appears to travel through time?
That's true, but it also describes all cases. Since there is no F of R of a photon, all frames from which it is observed belong to non-photon observers, and all observers observe the photon moving forward in time.
Can we establish that any time is involved between creation and destruction, other than that which is perceived by an observer? - So far I see no evidence of this, so are we just airing our personal beliefs?
Exactly my point! All observers known to science (the observers of SR and GR who can't be moving at the speed of light) see the photon moving through time. There are no other scientifically viable observers in our current models, so talking about time passing or not passing for them (i.e. from a photon's perspective) is opinion without basis in science. I think it's proper to say that time from a photon's point of view isn't well-defined, so that the question of time passing for them from their point of view isn't well-posed within our current models.
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The process of creating and destroying them does involve time.
Does a photon exist before it is created? - No.
Does a photon exist after it is destroyed? - No.
When is a photon created? - In the present.
When is a photon destroyed? - In the present.
Can we establish that any time is involved between creation and destruction, other than that which is perceived by an observer? - So far I see no evidence of this, so are we just airing our personal beliefs?
How do you explain the observation that photons do not decay over time when everything else does? Seems like pretty good evidence to me [:D]
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in physics, there is no theory that defines the frame of reference of a photon
We don't know how to describe the reference frame of a photon scientifically, so any claims about it not experiencing time in it's own reference frame aren't scientific.
Looked at from a slightly different perspective; is there any scientific evidence suggesting that a photon's apparent experience of time exists other than in the F of R of an observer?
I'll answer this. The answer is no.
If a photon decayed spontaneously in space, there might be some indication that it experiences a time, but this is not the case. Relative to us however, as JP has noted, photons do experience time.
QC, it's the other way around as I see it. It's to our frame of reference the photons take time, to their 'own', if that one exist, time can't exist. At least not as we experience it, if it did we should observe a 'decay', just as JP describes it.
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Saying that because they are 'massless' they do not apply to our 'reality'?
Is that science?
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Maybe we should start up a thread about what makes particles decay. I've been thinking about it, and it seems like a pretty deep topic.
Let's say for the sake of argument that we take relativity and tack on an additional set of reference frames for objects moving at the speed of light. We define time as not existing in these reference frames which means that particles moving at the speed of light don't decay. The problem is that gluons, which are massless, would be in these reference frames too. But gluons do decay! Therefore, these reference frames can't be purely a function of velocity, which would be odd... Then you'd have one type of reference frame for photons moving at light speed in which time didn't pass and a completely different type for gluons moving at light speed in which time passed.
The other issue is this: aren't electrons also stable? They can certainly annihilate in collisions, but I don't think that one left alone would spontaneously decay into photons... I'm not a particle physicist, so I could be wrong on this.
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Nope JP, 'time' is a macroscopic property as I see it. You're lifting up indirect evidence for something not measurable in themselves and theoretically described as 'decaying' as a macroscopic 'truth'. That's not correct.
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On the other tentacle, that's just what I do when I discuss photons as 'time less' :)
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So yes JP, in a way you're perfectly correct.
But there is a difference, we don't see gluons.
But we do see photons.
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The other issue is this: aren't electrons also stable? They can certainly annihilate in collisions, but I don't think that one left alone would spontaneously decay into photons... I'm not a particle physicist, so I could be wrong on this.
When an atom does emit an electron (beta decay), I don't think it travels quite at c, but I don't know if it decays or not.
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Photons do, and can decay. They just don't decay spontaneously in space. There is a big difference there.
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in physics, there is no theory that defines the frame of reference of a photon
We don't know how to describe the reference frame of a photon scientifically, so any claims about it not experiencing time in it's own reference frame aren't scientific.
Looked at from a slightly different perspective; is there any scientific evidence suggesting that a photon's apparent experience of time exists other than in the F of R of an observer?
I'll answer this. The answer is no.
If a photon decayed spontaneously in space, there might be some indication that it experiences a time, but this is not the case. Relative to us however, as JP has noted, photons do experience time.
QC, it's the other way around as I see it. It's to our frame of reference the photons take time, to their 'own', if that one exist, time can't exist. At least not as we experience it, if it did we should observe a 'decay', just as JP describes it.
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Saying that because they are 'massless' they do not apply to our 'reality'?
Is that science?
When I say relative to us, I mean it requires observers like us to attribute a time pass. JP and myself are talking about the same thing.
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The other issue is this: aren't electrons also stable? They can certainly annihilate in collisions, but I don't think that one left alone would spontaneously decay into photons... I'm not a particle physicist, so I could be wrong on this.
When an atom does emit an electron (beta decay), I don't think it travels quite at c, but I don't know if it decays or not.
You're right. An electron can never travel at c since it has mass. I didn't mean to imply that it did. Because it has mass and can't move at c, it has a reference frame within relativity, unlike a photon, and so it experiences time in it's reference frame. But I think it's also stable.
I was making two points. One of them is that stability of a particle isn't necessarily a good definition of the lack of passage of time. If electrons are stable, they have a reference frame in special relativity in which time passes. I'd be interested to know if they're stable or not and what characteristics of particles influences their stability, but that's probably a topic for another thread and we'd need some particle physicists!
The second point I was making is that if you insist on adding a reference frame for a photon, and you believe that SR is basically correct, that reference frame should depend only on the photon's speed. (I've argued strongly against this, since there's no good science behind it!) Therefore anything of zero mass, moving at the speed of light should have the same "timelessness" property as a photon. If you're assuming that instability of a particle is a sign that it experiences time passing in it's own reference frame, then gluons experience time they aren't stable! But gluons are massless and move at c, so they should be in the same kind of "timeless" reference frame as a photon!
I think there's two conclusions you can draw from this:
1) There's something fundamentally wrong with just tacking on a reference frame for things moving at light speed and calling it "timeless" (by basically setting v=c in the equations of SR). You can (and I have) argued this from the derivation of SR, in which setting v=c is wrong because the equations of SR are invalid in that case.
2) It's probably wrong to define "timeless" reference frames as those held by particles which are stable. That concept of time doesn't agree with the concept of time in special relativity, at any rate, so even if you did define it this way, I'm not sure how much use it would be. You'd basically just be using the word "timeless" to replace "stable," and it wouldn't have any real relation to measurements time as used in other areas of physics.
But let's take a step back. We need to agree on terms, since the definitions of time and "timeless" I'm arguing from are very precise.
Proponents of a "timeless" photon, what does "timelessness" mean in precise technical terms?
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Ok JP - super speculative question.
i. In a superconductor the condensate of cooper pairs can act through the higgs mechanism to give a mass to the photon.
ii. If a photon has a mass - can it still be travelling at maximal velocity within that material? i.e. this is not just a photon travelling slowly because of a refractive index greater than 1 - it's a Marks and Spencer's photon(sorry scrub that) - it's a photon travelling at less than the speed of light.
iii. Would this change the decay characteristics? Could this provide a difference between the timeless epithet and travelling at lightspeed?
I agree with you, I think, that the example of the gluon already knocks that into the long grass; but perhaps evidence from the photon would be more conclusive.
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Photons do, and can decay. They just don't decay spontaneously in space. There is a big difference there.
You got more details on that - I would be interested
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As a non-scientist it would be presumptuous of me to describe myself as a proponent of a "timeless" photon, and I think we might need to be sure of some consensus on a definition of time before tackling timelessness.
I am probably agreeing with JP when I say I think terminology is an important factor. I know I have another question, I know what it is, but it will take a little thought to frame it in words that will ensure that everyone else knows what it is, or is that just wishful thinking? [:-\]
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Yep Imatfaal, I'm curious to that statement too. QC, you have a link to that?
And JP. The frame existing for a photon is the one where we observe it.
The frame existent for a gluon is theory, no direct observations possible as far as I understands?
That we from indirect observations define something we call a gluon is true, as you pointed out before, but there's no direct observations possible. And as far as I understands it does not exist inside a observable time frame, which to my eyes place it outside Plank time. If you know different JP, link me up :) That's one of the really weird ones to me. That something outside Planck-time actually 'interacts' inside it.
As for if a photon have an 'internal frame'? I don't think so myself which in a way makes the discussion meaningless as it works from another principle, as I guess, than our arrow of time. But it does not makes it meaningless to call it 'time less' from our perspective, as we only have that proposition to work from. That is three dimensions (possibly more:) and 'time'.
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Matthew, I'm not entirely sure what happens to a photon in matter. Is the slow down in a superconductor sufficiently different to, say, glass? The way I usually understand a photon moving in matter is that it is propagating at the speed of light in between the bits of matter, but interactions with the matter essentially cause it to take longer to get through. I don't think this should change its decay properties, or the fact that it moves at the speed of light in between those interactions.
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"When the temperature was lower than the Planck scale, the universe was an expanding gas of relativistic particles. These particles include quarks and leptons, the gauge bosons such as photons, gluons, and W and Z bosons, and perhaps more exotic particles like the supersymmetric partners of the standard model particles, heavy right-handed neutrinos, gauge bosons related to grand unification theories, etc. As the temperature cooled below the masses of certain particles (such as the W and Z bosons) they “freeze out” and decay, i.e., they are not longer created by inverse reactions of their decay products due to the lower temperature. Some of these particles with a short life time had disappeared long ago, and some with a long life time may still be with us today in the form of dark matter." From Quark-Gluon Plasma and the Early Universe
This description seems to agree with my assumption JP?
That Gluon's are under Planck scale. And if they are then you might want to question the idea of them being 'particles' too. Any particle making 'sense' to us will show a gravitational 'potential'. Do virtual particles do that? If they do, then one might consider finding the 'missing mass' in their 'interactions' with all 'thingies' over Planck scale
But if they don't they are something outside of 'SpaceTime' to my eyes.
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The more I try to think, the more questions I seem to find, so here goes with some thoughts and a question arising out of them.
If we assume that frame of reference = inertial frame = rest frame, then it makes perfect sense to argue that a photon cannot be assigned a frame of reference because in the rest frame of any object, the velocity of that object itself is zero.
Relativity says that photons always move at the speed of light, so we might reason that, according to relativity, a photon would have to travel at the speed of light in its own frame of reference, which doesn’t seem to make a lot of sense.
However, relativity does not define a frame of reference for a photon; all it does is state that a photon must travel at c in the frame of reference of everyone and everything else.
Bearing in mind that in relativity all motion, or lack of it, is relative, are we saying that a photon has no frame of reference in which it is stationary relative to itself?
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Matthew, I'm not entirely sure what happens to a photon in matter. Is the slow down in a superconductor sufficiently different to, say, glass? The way I usually understand a photon moving in matter is that it is propagating at the speed of light in between the bits of matter, but interactions with the matter essentially cause it to take longer to get through. I don't think this should change its decay properties, or the fact that it moves at the speed of light in between those interactions.
I am trying to split two phenomena - you rightly describe how a photon moves through material via interactions; this is the case within glass. The photon moves at light speed between interactions but overall at a slower speed- I think that's the best explanation I have read, not sure if it isnt a bit hand-wavy though.
But within a superconductor, electron pairs (cooper pairs) form a condensate. It is thought that this condensate can act like a bosonic field and emulate the higg's field. But in a superconductor (as opposed to everywhere else) this higgs-like field will provide mass (very very small) for the photon. I would imagine a photon with mass would be forced to travel slower than a photon without mass. A subluminal photon (and I still don't think it really works) would be free from any argument that time is meaningless for it as it is moving in a normal frame of reference.
I will dig out references for the cooper pair condensate field - I hope.
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Does the mass of the photon in this scenario exist other than in the F of R of an observer?
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That one doesn't make sense imatfaal?
If you consider the 'Higgs field' it exists everywhere according to the idea?
And then the difference would be that space isn't superconducting?
And that a photon acquire a mass inside a condensate?
Sounds very much like a theory without any foundation in experiments to me?
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This description seems to agree with my assumption JP?
That Gluon's are under Planck scale. And if they are then you might want to question the idea of them being 'particles' too. Any particle making 'sense' to us will show a gravitational 'potential'. Do virtual particles do that? If they do, then one might consider finding the 'missing mass' in their 'interactions' with all 'thingies' over Planck scale
But if they don't they are something outside of 'SpaceTime' to my eyes.
I don't think that gluons are under the planck scale any more than photons are. Every fundamental particle in the standard model is a point particle, but their wave functions are smeared out over larger areas. I assume gluons do cause gravity, but just like a photon causing gravity, you can't really measure it since they're so tiny.
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Bearing in mind that in relativity all motion, or lack of it, is relative, are we saying that a photon has no frame of reference in which it is stationary relative to itself?
Exactly what I'm saying. Until we can experimentally access that reference frame to make tests on it, it's not a scientific theory. That's why all the discussion on such a frame is basically philosophy or personal opinion, not science.
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Matthew, I'm not entirely sure what happens to a photon in matter. Is the slow down in a superconductor sufficiently different to, say, glass? The way I usually understand a photon moving in matter is that it is propagating at the speed of light in between the bits of matter, but interactions with the matter essentially cause it to take longer to get through. I don't think this should change its decay properties, or the fact that it moves at the speed of light in between those interactions.
I am trying to split two phenomena - you rightly describe how a photon moves through material via interactions; this is the case within glass. The photon moves at light speed between interactions but overall at a slower speed- I think that's the best explanation I have read, not sure if it isnt a bit hand-wavy though.
But within a superconductor, electron pairs (cooper pairs) form a condensate. It is thought that this condensate can act like a bosonic field and emulate the higg's field. But in a superconductor (as opposed to everywhere else) this higgs-like field will provide mass (very very small) for the photon. I would imagine a photon with mass would be forced to travel slower than a photon without mass. A subluminal photon (and I still don't think it really works) would be free from any argument that time is meaningless for it as it is moving in a normal frame of reference.
I will dig out references for the cooper pair condensate field - I hope.
Interesting. It sounds like what's going on is that the superconductor is behaving mathematically similar to the Higgs field, but physically it isn't. In that case, the photon won't physically have mass, but will slow down like it has gained mass via the Higgs mechanism. I don't think it would decay... that would be very odd. It would be interesting to see the paper, though!
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are we saying that a photon has no frame of reference in which it is stationary relative to itself?
Exactly what I'm saying
OK, but how can a photon be in motion relative to itself? [???]
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Just because it has no frame in which it's stationary does not mean that is has a frame in which it's in motion with respect to itself.
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At the risk of over simplifying things (a common failure among aliens) I would speculate that the only way to avoid becoming a decadent imperialist lackey is to zip along at c. Now, photons of one sort or another do seem to be able to do that, presumably because they have no rest mass. (Because they are not resting like a bunch of decadent imp......)
So, if particles that have a rest mass (and therefore are not able to zip along at c) don't seem to decay, or lose energy, or alter in some way or another over time, my "theory" kind of falls apart.
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Heh, JP that one was lovely :)
"Just because it has no frame in which it's stationary does not mean that is has a frame in which it's in motion with respect to itself." I'm sure the way you thought of it will make a ultimate sense but reading it is soo sweet :) You will have to explain your thinking there.
And yes, assuming that gluons are 'inside Planck size', also assuming that there goes the border between what is 'reasonable' from the physics we know? you will have a point. But to me all of those emergences are exactly 'emergences' getting new properties as they scales up. That means that to me a gluon is an expression of interactions observed inside our macroscopic 'reality' leading us to define them as existing. But on their own 'scale', as I see it outside Plank size, they are nothing like it, just as I expect 'times arrow' to be an emergence needed for our macroscopic universe.
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Heh, JP that one was lovely :)
"Just because it has no frame in which it's stationary does not mean that is has a frame in which it's in motion with respect to itself." I'm sure the way you thought of it will make a ultimate sense but reading it is soo sweet :) You will have to explain your thinking there.
It seemed like Bill was assuming that you only have two options:
1) the photon has a reference frame in which it's at rest with respect to itself,
2) the photon has a reference frame in which it's moving with respect to itself,
and obviously (2) is a bit nonsensical. There is a third option. The photon has no reference frame (at least not one we know how to describe in terms of it's motion). That's the one that's true since the above options are not allowed in relativity.
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So, if particles that have a rest mass (and therefore are not able to zip along at c) don't seem to decay, or lose energy, or alter in some way or another over time, my "theory" kind of falls apart.
That was my point with the electrons. Also, gluons do zip along at c and do spontaneously decay.
Maybe we can save a lot of this for another thread, but I believe the reason why things that move at c tend to be stable is that being massless is a requirement for forces to act over long range (which is probably the same as saying that being massless is a requirement for force-carrying bosons to be stable). However, gluons have an additional property that determines how they behave: color charge. The color charge changes how they interact with the force and makes them short-lived.
So I guess the conclusion is that masslessness is a necessary requirement for force-carrying Bosons to be stable, but it isn't sufficient.
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What makes it so remarkable is how few types of interactions there are needed for creating a SpaceTime, as the color-force tells us. One might expect it to be more complex. And yeah, I knew it would make sense :)
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Let's look on some sense of photon travel [:D]
The water pillar is history of events. The water level constantly increases. Movement of a wave on a surface is movement of a photon. Event of movement of a photon does not plunge in the past. [:)]
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Movement of a wave on a surface is movement of a photon.
No it isn't. The idea that a photon is a wave in matter was discredited with the aether theory.
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There is a third option. The photon has no reference frame (at least not one we know how to describe in terms of it's motion). That's the one that's true since the above options are not allowed in relativity.
What about the possibility that the photon has a frame of reference in which it is stationary relative to itself and time?
Is that more of an assumption than saying that because we cannot describe the F of R of a photon, it cannot have one?
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There is a third option. The photon has no reference frame (at least not one we know how to describe in terms of it's motion). That's the one that's true since the above options are not allowed in relativity.
What about the possibility that the photon has a frame of reference in which it is stationary relative to itself and time?
Is that more of an assumption than saying that because we cannot describe the F of R of a photon, it cannot have one?
If you can't scientifically describe the F of R of a photon, does it matter if it has one? It's just a matter of opinion unless there's an actual model for it.
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I
Matthew, I'm not entirely sure what happens to a photon in matter. Is the slow down in a superconductor sufficiently different to, say, glass? The way I usually understand a photon moving in matter is that it is propagating at the speed of light in between the bits of matter, but interactions with the matter essentially cause it to take longer to get through. I don't think this should change its decay properties, or the fact that it moves at the speed of light in between those interactions.
I am trying to split two phenomena - you rightly describe how a photon moves through material via interactions; this is the case within glass. The photon moves at light speed between interactions but overall at a slower speed- I think that's the best explanation I have read, not sure if it isnt a bit hand-wavy though.
But within a superconductor, electron pairs (cooper pairs) form a condensate. It is thought that this condensate can act like a bosonic field and emulate the higg's field. But in a superconductor (as opposed to everywhere else) this higgs-like field will provide mass (very very small) for the photon. I would imagine a photon with mass would be forced to travel slower than a photon without mass. A subluminal photon (and I still don't think it really works) would be free from any argument that time is meaningless for it as it is moving in a normal frame of reference.
I will dig out references for the cooper pair condensate field - I hope.
What would happen to its spin if it gained a mass? It's spin 1 normally having two degrees of freedom instead of three due to its 'masslessness' But gaining a mass should change that, shouldn't it?
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To be honest Yoron - I am struggling to find a good write-up on it. Lots of papers mention it in passing, and several refer to a section in Ryder but no decent explanation. Not sure what exactly you mean by tying up the degrees of freedom and masslessness
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The spin of a photon is defined as having two degrees of freedom, that in its turn is a headache. "Let us go back to the photon statistics formula derived by Bose. There is a factor "2" sitting on the numerator of this formula. The usual explanation is that it is because photons are massless particles. Then why not 1 or 3 ? Bose argued that the photon can have two degenerate states. This eventually led to the concept of photon spin parallel or anti-parallel to the momentum.
The question of why the photon spin should be only along the direction of momentum has a stormy history. Eugene Wigner (1939) showed that the internal space-time symmetry of massless particles is isomorphic to the symmetry of two-dimensional Euclidean space consisting of one rotation and two translational degrees of freedom. It is not difficult to associate the rotational degree with the photon spin either parallel or anti-parallel to the momentum, but what physics is associated with the translational degrees of freedom. These translational degrees were later identified as gauge transformations. This does not solve the whole problem because there is one gauge degree of freedom while there are two translational degrees of freedom. How do they collapse into the one gauge degree of freedom? This problem was not completely solved until 1990."
"If electrons had total spin s=1 then there would be three possible spin projections sz={−1, 0, or +1} ... and you would find orbitals with three electrons in them. You can’t occupy a given orbital more times than are allowed by the spin multiplicity because of the (Pauli) exclusion principle."
So a photon that actually is of spin 1 still doesn't have three degrees of freedom. But if we give it a mass?
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Spin is weird. (http://www.thenakedscientists.com/forum/index.php?topic=36548.msg342325#msg342325)
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If you can't scientifically describe the F of R of a photon, does it matter if it has one? It's just a matter of opinion unless there's an actual model for it.
I'm not really nit-picking here, honest, [:)] just trying to get things straight in my own mind.
Given that you can't scientifically describe the F of R of a photon, would it also be true to say that you cannot scientifically establish that it does not have one? I accept that even if this is the case, the whole thing comes down to a matter of opinion, and that some opinions have more weight behind them than others. In the midst of a sea of strongly held views, though, I often find myself wondering what is established fact and what is opinion.
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It depends on your definitions, Bill. Frame of reference in physics tends to refer to Einstein's inertial frames of special relativity. In that case, you can say conclusively that the photon has no frame of reference. (The same is true for local coordinate frames in general relativity.)
If you want to use a different definition of frame of reference in order to allow the photon to have one, you'll have to define it first, and justify it's usefulness as a physical model.
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JP,
What happens in the case of matter? I realize that matter can't travel at the speed of light, but is it possible to extrapolate the effects on time as it approaches c to arrive at a conclusion about what might happen at c, or does the math simply go haywire long before you get there?
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The math goes haywire. The problem is that simply taking the limit as v->c doesn't account for the fact that the mass goes to zero. If you do the appropriate limit taking, you get something like 0/0, I recall...
That, and all of special relativity deals with observers who always observe light as moving at c. The math just doesn't hold if you throw out that assumption.
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The math goes haywire. The problem is that simply taking the limit as v->c doesn't account for the fact that the mass goes to zero. If you do the appropriate limit taking, you get something like 0/0, I recall...
That, and all of special relativity deals with observers who always observe light as moving at c. The math just doesn't hold if you throw out that assumption.
I had a nasty feeling that might be the case [;D] Thanks!
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Thanks, JP, but I'm still struggling a bit here.
We seem to have moved from saying that we can't scientifically describe the F of R of a photon, to saying conclusively that the photon has no frame of reference.
let's stick with "inertial frame", so you know I'm not trying to come up with my own definition of F of R. [:)]
The reasoning seems to go something like this: A photon must always be observed as travelling at c, so it cannot share an inertial frame with anything else.
Arguing that photon must be stationary relative to itself is meaningless; therefore it is meaningless to suggest that a photon occupies an inertial frame.
Am I getting closer?
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I think you're understanding me, Bill. The reason I was saying things like "science can't describe the F of R of a photon" rather than categorically ruling them all out is just because some of the suggestions here have been to introduce new models specifically to define a F of R of a photon.
But if you stick, like you say, to inertial frames defined by relativity, then there is none for the photon, simply because they don't exist within special relativity. You correctly point out that it would be wrong to simply add on an inertial frame in which the photon is at rest. (I'd add on to your description that a photon can't be at rest with respect to itself because the frames described by special relativity all require that light moves at light speed in those frames.)
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Matter is a concentrated energy. If you like, radiation is a free energy - a diffused type of matter. If all matter is made from photon energy, then it contributes to the kinetic energy of the system, and the inertial energy of the system. It does not mean that matter will move at lightspeed. This is in direct contradiction of relativity theory.
Are you saying that matter and photons are actually two totally different things? I thought you maintained that matter was made from photons, or did I get that wrong?
Yes you are wrong, again.
Matter can be made out of photons, it does not necesserily mean that attributes of the photon are carried on. Intrinsic properties in the form of information is almost certainly passed on in order to conserve quantities like charge and spin. It does not mean that the manifestation (matter) obeys the rules which radiation does. Matter and energy are still quite different, even though they are interchangeable via E=Mc2.
If matter is made out of photons and matter has mass, that would give photons mass as well...
And photons, by my understanding, don't have mass.
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If matter is made out of photons and matter has mass, that would give photons mass as well...
And photons, by my understanding, don't have mass.
It's a disputed point Locke - but the answer some might give is: that mass and energy are equivalent (everyone should agree that E=mc^2) and thus the energy of a photon pair can become the mass of a particular (pair of) particles (this is also agreeable); others go on to say that ALL matter can be considered to be made of photons (this is where the argument lies).
Bear in mind you need really energetic photons - the lightest particles you are gonna create will prob be a positron electron pair and even these will require light well into the gamma rays
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Some questions and thoughts :)
First of all. Isn't 'c' a valid frame for photons in any frame seen? Accelerating or inertial (uniformly moving)? And if I argue that light is 'timeless'? Well, that depends on what you define 'time' as, I would say. Is it 'time' it takes for light to wander 13.7 billion light-years from the 'visible' edge of our universe? If you to that add what 'expansion' did to the space it 'wandered' in it has been awfully stretched (like 47 Billion light years one-way), as a wave that is, as a photon it can't be stretched at all, as far as I know?
As a 'light-quanta' it shouldn't be able to lose any energy without a 'interaction' either, as far I know? As such all energy it has should be the same from 'source' to 'sink'. And all of those descriptions are valid as I understand it. 'scientifically so.' But the 'trick' is to choose your definition to what the radiation does, isn't it? Why I differ a light quanta and a photon is in the indeterminacy of a photon seen as a wave-packet, where it start and ends as I understands it. But as a light quanta, again as I understands it, we expect it to be of the same defined 'energy' from source to sink. And what we call a photons red or blue shift will then only be a relation to the 'frame of reference' observing it.
Now, this is a questionable approach, but never the less the one taken as I understands it, and from 'Science' no less. A better approach is to admit that if you observe a photon, or light-quanta you will annihilate it. To observe or interact with a wave is not the same though :) as we can see when looking in a mirror, although there you can actually use both descriptions, photons or waves, to describe it. As with waves, the red and blue-shift makes more sense in form of frequency and energy getting 'stretched out'.
When it comes to a expansion though, stretching a 'light-quanta' or photon? Even when it comes to wave packet this sounds very far fetched, how exactly can a mere 'distance' down-shift a photon? It won't stretch at all as far as I can see, it's with gravity and speed we use red or blue shift and then as only relative the observer, if we we define them of invariant light quanta. To make a light-quanta 'stretch' you better start with giving it a 'size', otherwise it's a exercise in futility. and if you don't define it a 'size' then you have distance doing what we only attributed to gravity and speed before, 'down-shifting' light-quanta.
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The real problem here is when someone suggests that photons just are like bullets coming from our universal machine guns (Suns). Then a red-shift should be fewer 'bullets' per 'time unit' and a blue-shift more bullets per 'time unit'. That one seems to work until we consider one light-quanta/photon moving. Because if we do so, it is my understanding that this light quanta will express the same red and blue shift, and just as easy as any amount of photons then would do by being 'together'. Now, if my understanding of this is wrong :) Then I'll go with the 'machine gun description'. But if I'm right a photon somehow manage to express its red and blue shift some other way. And if it does I suggest it to be a relation, that is, two different 'frames of reference' interacting.
(The Pound–Rebka experiment (http://en.wikipedia.org/wiki/Pound%E2%80%93Rebka_experiment) did just that, if I understood it right, testing one photon 'jumping' between atoms.)
" When an atom transits from an excited state to a base state, it emits a photon with a specific frequency and energy. When the same atom in its base state encounters a photon with that same frequency and energy, it will absorb that photon and transit to the excited state. If the photon's frequency and energy is different by even a little, the atom cannot absorb it (this is the basis of quantum theory).
When the photon travels through a gravitational field, its frequency and therefore its energy will change due to the gravitational redshift. As a result the receiving atom can no longer absorb it. But if the emitting atom moves with just the right speed relative to the receiving atom the resulting doppler shift will cancel out the gravitational shift and the receiving atom will be able to absorb the photon. The "right" relative speed of the atoms is therefore a measure of the gravitational shift. The frequency of the photon "falling" towards the bottom of the tower is blueshifted. Pound and Rebka countered the gravitational blueshift by moving the emittor away from the receiver, thus generating a relativistic Doppler redshift"
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Anyway, now I will use my own trick. If we keep on persisting that photons 'propagates' then we know that they don't 'die', by that alone. And then I will use that for defining them as 'timeless', that is as observing them from my frame of reference, or you from yours JP :) Or anyones 'frame', willing to dispute it. And to dispute, you will need to prove that a photon 'decay', if you now missed that. My definition is valid for all frames I know of too, as long as you don't let a light-quanta/photon 'interact'.
And you can start with defining if it interacts in a redshift/Hubble/expansion. Then you need to define that from two scientifically equally valid truths at least the light-quanta/photon and the wave. And as far as I know they all two/three are experimentally proven.
(Then we come to what I find the nicest solution, that light don't 'move' at all :)
That takes care of it. Now we only have the photons/waves relations defining how it will behave, and even though 'c' will be as valid a concept as ever it now becomes a axiom, or a constant if you like, just as the Feigenbaum constant.)
Heh.
So, yes JP, I will call them 'timeless' :)