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Author Topic: If a photon is travelling at the speed of light, does time not exist for it?  (Read 23700 times)

Offline CD13

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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?


 

Offline yor_on

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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'.
« Last Edit: 21/01/2011 16:31:09 by yor_on »
 

Offline Ron Hughes

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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
 

Offline yor_on

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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.
==

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.
« Last Edit: 21/01/2011 20:08:53 by yor_on »
 

Offline Bill S

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Quote from: CD13
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.
 

Offline JP

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Quote from: CD13
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.
 

Offline QuantumClue

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Quote from: CD13
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.
 

Offline Geezer

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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.
 

Offline QuantumClue

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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?
 

Offline QuantumClue

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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.
 

Offline Geezer

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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?
 

Offline QuantumClue

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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.
 

Offline QuantumClue

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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.
 

Offline CPT ArkAngel

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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.
« Last Edit: 07/02/2011 04:27:22 by CPT ArkAngel »
 

Offline Geezer

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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?
 

Offline yor_on

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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.
 

Offline JP

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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.
 

Offline yor_on

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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 :)
 

Offline CPT ArkAngel

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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...
« Last Edit: 25/01/2011 23:02:44 by CPT ArkAngel »
 

Offline Bill S

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Quote from: JP
in physics, there is no theory that defines the frame of reference of a photon

Quote from: JP
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?
 

Offline QuantumClue

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Quote from: JP
in physics, there is no theory that defines the frame of reference of a photon

Quote from: JP
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.
 

Offline Bill S

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Quote from: QC
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?
 

Offline CPT ArkAngel

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Photons interactions appear in time for matter but they have no timerate according to themselves.
 

Offline Bill S

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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.
 

Offline JP

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Quote from: QC
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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