When moving at the speed of light time stops

[eyad-996]

If when you're moving at the speed of light time freezes, why then does it take light 8 minutes to reach the Earth from the sun?

 

[ghwellsjr]

If when you're moving at the speed of light time freezes, why then does it take light 8 minutes to reach the Earth from the sun?

Do you think maybe it's because you're not moving at the speed of light?

 

[eyad-996]

What do you mean?

 

[jk22]

time flow is observer dependent in relativity. 8 minutes is measured from an observer on Earth for example.

 

[eyad-996]

Pauli's exclusion principal?

 

[Dale]

Pauli's exclusion principal?

How could that possibly be relevant?

You may want to read the FAQ on the rest frame of a photon:
https://www.physicsforums.com/showthread.php?t=511170

Basically your opening statement "when you're moving at the speed of light time freezes" is fundamentally invalid.

 

[phinds]

If when you're moving at the speed of light time freezes, why then does it take light 8 minutes to reach the Earth from the sun?

As has already been pointed out, you CAN'T move at the speed of light. However, light can, so the second part of your question is meaningful.

Do you understand the concept of distance = rate x time ? Rewritten as time = distance/rate, you could use this to figure out how long it would take you to go 1 mile if you are going 60 miles an hour. How about you apply this to light traveling from the sun to the earth.

EDIT: Do you understand that all I've done here is expand post #2 ?

 

[jk22]

basically Einstein's own question 'what happens if i move at speed of light' is not answered in his theory since nobody can move with that speed (no clock neither)

 

[ThereIam]

Okay, I think there is an interesting question here. I did read the FAQ before posting.

So far we know that because an axiom of the theory of special relativity is that light moves at c, we cannot use that theory to describe time dilation for a photon. One might still ask, DO we have a theory that suggests the meaning of time for a photon? I am still curious.

Or maybe I have misunderstood something?

Edit:

In the FAQ the last bit is "The concept doesn't make sense."

I guess I'm asking if in some other theoretical framework it does make sense?

 

[Dale]

One might still ask, DO we have a theory that suggests the meaning of time for a photon?

Not that I am aware of.

 

[jk22]

in hofstadter's book goedel escher bach it is called the mu-method of answering a question by -deasking- it.

 

[pervect]

One might still ask, DO we have a theory that suggests the meaning of time for a photon? I am still curious.

No. There is a sort of geometry that describes photon's worldlines, and one's ability to make "equally spaced" marks along them, even though one cannot assign a non-zero value to the spacing of the marks.

THis sort of geometry is called an "affine geometry".

It's an interesting topic, but it's a mistake to think of it as having all the properties of "time". That tends to lead only to self contradictions and confusion.

 

[russ_watters]

What do you mean?

Your question started:

If when you're moving at the speed of light...

But you're not moving at the speed of light. You are stationary. The light is moving at the speed of light.

 

[eyad-996]

I'm not talking about me moving at the speed of light, I'm talking about light itself! Light is moving at the speed of light (obviously!) Shouldn't time freeze for light and arrive instantly - since time has stopped for it!?

 

[pervect]

I'm not talking about me moving at the speed of light, I'm talking about light itself! Light is moving at the speed of light (obviously!) Shouldn't time freeze for light and arrive instantly - since time has stopped for it!?

You have some a notion of time, and you assume that light must have some sense of it too. And this idea is wrong.

Time is something that can be measured, and assigned values. This gives geometry a metric structure. We can say "the interval between point A and point B is C seconds".

The geometry of light has an affine nature - it doesn't have measurable "time intervals" at all. We can order A, B, and C, but we can't assign any meaningful numerical intervals to the "distance" between them.

 

[eyad-996]

The geometry of light has an affine nature - it doesn't have measurable "time intervals" at all. We can order A, B, and C, but we can't assign any meaningful numerical intervals to the "distance" between them.

You've been a great help, but from the last paragraph I only understood that time doesn't have measurable time intervals! But why?

 

[pervect]

You've been a great help, but from the last paragraph I only understood that time doesn't have measurable time intervals! But why?

Suppose you have a nice standard plane polarized radio wave.

If you calculate the invariant time interval, also known as the "proper time" between any two points on the light wave according to relativity, the number you get will be zero.

However, any given observer can mark points along the wave at which the E-field is zero at any given time. And he'll find these points will be evenly spaced. This "even spacing" property happens in spite of the fact that all the proper time intervals are zero.

The distance from A to B, from A to C, and from B to C, measured using the invarinat interval, will all be zero. However, there is a unique point C such that AB and BC are "evenly spaced". This is the affine geometry of the light wave.

The exact spacing depends on the ight wave and the observer. One observer might see an AM radio wave with a 300 meter wavelength - a relativistically traveling observer might see it as much shorter, or longer, due to the doppler effect,

 

[eyad-996]

So light takes time to reach between two points because I (the observer) can feel/ measure time differently from the Light ??

 

[Dale]

That seems like a good way to put it. In your reference frame you are not moving at the speed of light, you experience time, and in your frame light takes time to go from A to B. And light doesn't have a reference frame of its own.

 

[eyad-996]

Thank you all, you have been a great help.
Last post puts it straight and simple.

 

[jk22]

the lorentz transformation is singular for the speed of light i.e. Not defined

 

[Moonraker]

What about this answer:

The time dilation formula is according to http://en.wikipedia.org/wiki/Time_dilation

T‘ = T * sqrt (1-v²/c²).


Set v=c, the proper time of light T’ will always be 0. The lorentz transformation is not defined for the speed of light, but the time dilation formula above is.

However, time is not frozen, the proper life time of a photon is zero.

 

[ghwellsjr]

What about this answer:

The time dilation formula is according to http://en.wikipedia.org/wiki/Time_dilation

T‘ = T * sqrt (1-v²/c²).


Set v=c, the proper time of light T’ will always be 0. The lorentz transformation is not defined for the speed of light, but the time dilation formula above is.

However, time is not frozen, the proper life time of a photon is zero.

Here's a thread you should read:

https://www.physicsforums.com/showthread.php?t=661429

 

[bcrowell]

I don't think any of the previous posts have really addressed the basic misunderstanding invoved in the OP's question. The OP asked:

(1)

If when you're moving at the speed of light time freezes, why then does it take light 8 minutes to reach the Earth from the sun?

The question shows a more basic misunderstanding of frames of reference. Suppose the OP had asked instead:

(2) "If when you're moving close to the speed of light time freezes, why then does it take neutrinos 8 minutes to reach the Earth from the sun?"

The answer is that when we talk about the time taken for something to reach the Earth from the sun, we're implicitly talking about the time as measured in the frame of the earth. But relativistic time dilation would relate the 8 minutes to the much longer time taken in the frame of the neutrino.

A question that didn't involve this misconception would be:

(3) If when you're moving close to the speed of light time freezes, does that mean that only a very short time passes in the frame of a neutrino that, in the Earth's frane, takes 8 minutes to reach the earth?

The answer would be yes.

 

[eyad-996]

Thanks, great answer!

 

[Moonraker]

Here's a thread you should read:

https://www.physicsforums.com/showthread.php?t=661429

Hi ghwellsjr,
which one? are you (mistakenly?) referring to our current thread?
Moonraker

 

[Moonraker]

(3) If when you're moving close to the speed of light time freezes, does that mean that only a very short time passes in the frame of a neutrino that, in the Earth's frane, takes 8 minutes to reach the earth?

The answer would be yes.

I suppose that neutrino's speed in neutrino's frame is not higher than light speed because the distance sun-earth is diminishing in neutrino's frame as well? (according to Lorentz transformation)

 

[ghwellsjr]

Here's a thread you should read:

https://www.physicsforums.com/showthread.php?t=661429

Hi ghwellsjr,
which one? are you (mistakenly?) referring to our current thread?
Moonraker

It was no mistake.

If you had read this thread you would have read this post:

You have some a notion of time, and you assume that light must have some sense of it too. And this idea is wrong.

So then why do you say:

However, time is not frozen, the proper life time of a photon is zero.

This is a wrong statement because time does not apply to a photon. It doesn't have a proper time or a life time or a proper life time or any other time. You shouldn't say that time for a photon is not frozen or frozen. You should say time doesn't apply to a photon which is different than saying that some kind of time of a photon is zero.

 

[Moonraker]

This is a wrong statement because time does not apply to a photon. It doesn't have a proper time or a life time or a proper life time or any other time. You shouldn't say that time for a photon is not frozen or frozen. You should say time doesn't apply to a photon which is different than saying that some kind of time of a photon is zero.

I don’t agree. There is no doubt that each photon is sent and absorbed at a precise time.T_emission and T_absorption. Time applies to photons too. This is one of the very few things we know for sure about photons.

 

[Doc Al]

I don’t agree. There is no doubt that each photon is sent and absorbed at a precise time.T_emission and T_absorption. Time applies to photons too.

These are not times measured from the (nonexistent) frame of a photon, they are measured from other quite ordinary frames of reference.

 

[Dale]

I suppose that neutrino's speed in neutrino's frame is not higher than light speed because the distance sun-earth is diminishing in neutrino's frame as well? (according to Lorentz transformation)

The neutrinos speed in the neutrinos frame is 0.

 

[Moonraker]

These are not times measured from the (nonexistent) frame of a photon, they are measured from other quite ordinary frames of reference.

No, the moment of emission is the same for the observer and for the photon.
At the absorption, the clock of the observer shows 8 minutes (Sun-Earth). The “clock” of the photon shows 0 seconds, according to the above-mentioned time dilation formula:
T‘ = T * sqrt (1-v²/c²),
even if the Lorentz transformation does not apply to photons.

 

[Moonraker]

The neutrinos speed in the neutrinos frame is 0.

This would mean that the distance is 0 as well in the neutrino's frame.

 

[Doc Al]

No, the moment of emission is the same for the observer and for the photon.
At the absorption, the clock of the observer shows 8 minutes (Sun-Earth). The “clock” of the photon shows 0 seconds, according to the above-mentioned time dilation formula:
T‘ = T * sqrt (1-v²/c²),
even if the Lorentz transformation does not apply to photons.

You do realize that the time dilation formula is just a special case of the Lorentz transformation, don't you? So if the LT doesn't apply, neither does the time dilation formula.

 

[Dale]

This would mean that the distance is 0 as well in the neutrino's frame.

The distance the neutrino travels is indeed 0 in the Neutrinos frame. Note that that is not the same as the distance between the Earth and the sun.

 

[Nugatory]

even if the Lorentz transformation does not apply to photons.

Be careful here... The Lorentz transforms never apply to things, be they photons moving at the speed of light in all frames, or massive particles and observers moving at less than the speed of light in all frames. They apply to the coordinate systems that we use to assign (x,t) values to events such as "the thing is at point x at time t"

 

[Moonraker]

You do realize that the time dilation formula is just a special case of the Lorentz transformation, don't you? So if the LT doesn't apply, neither does the time dilation formula.

My opinion as well as yours needs to be proved. The fact that one formula is a special case of another does not exclude an extension of its field of application.

The Lorentz transformation does not apply due to a division by 0. The time dilation formula does not share this problem.

In other words: We get no information about proper speed and distances for photons, and there is even no inertial frame of photons, but we get information about the proper time of photons.

There is no reason not to apply the time dilation formula (if there is please let me know), and there are many reasons in favor of application.

 

[Doc Al]

There is no reason not to apply the time dilation formula (if there is please let me know), and there are many reasons in favor of application.

The time dilation formula and the Lorentz transformations depend upon the basic assumptions of relativity, one of which is that the speed of light is invariant and equal to c in all frames. Applied to a frame co-moving with photon, such a statement is gibberish.

 

[ghwellsjr]

My opinion as well as yours needs to be proved. The fact that one formula is a special case of another does not exclude an extension of its field of application.

The Lorentz transformation does not apply due to a division by 0. The time dilation formula does not share this problem.

Yes it does. Time Dilation means a time interval is getting larger for a moving object in a given reference frame. You have to divide by zero to find how long any interval is for a photon.

In other words: We get no information about proper speed and distances for photons, and there is even no inertial frame of photons, but we get information about the proper time of photons.

There is no reason not to apply the time dilation formula (if there is please let me know), and there are many reasons in favor of application.

In Special Relativity, Einstein defines time as that which a clock measures. A clock cannot be made out of just photons, it requires massive particles. Massive particles cannot travel at the speed of light. Therefore a clock cannot travel at the speed of light and there is no definition for time at the speed of light. It's a meaningless concept.

 

[TomTelford]

If I may...

It might be semantics but it could be more appropriate to say that time comes into existence when "things" move slower than the speed of light rather than saying time "freezes" at c. That time itself is related to this slowness and things that move sub-c.

While the math may go all screwy when t'=0, the concept that light comes into existence, is absorbed/transformed and passes through the points in between on "it's" straight line all simultaneously is hugely interesting. There are implications on a photon's behaviour since it is limited to experiencing it's entire existence with no time even though we observe it to have traveled for potentially billions of years. That the conditions that allow a photon to be created and absorbed in it's frame must be correlated to those in ours in order for us to experience light(radio, gamma, etc) at all.

I know I'm wandering into philosophy but a simple div/0 error should not stand in our way to understanding all of this.

 

[ghwellsjr]

If I may...

It might be semantics but it could be more appropriate to say that time comes into existence when "things" move slower than the speed of light rather than saying time "freezes" at c. That time itself is related to this slowness and things that move sub-c.

While the math may go all screwy when t'=0, the concept that light comes into existence, is absorbed/transformed and passes through the points in between on "it's" straight line all simultaneously is hugely interesting. There are implications on a photon's behaviour since it is limited to experiencing it's entire existence with no time even though we observe it to have traveled for potentially billions of years. That the conditions that allow a photon to be created and absorbed in it's frame must be correlated to those in ours in order for us to experience light(radio, gamma, etc) at all.

I know I'm wandering into philosophy but a simple div/0 error should not stand in our way to understanding all of this.

It's not just an issue of dividing by zero. Did you read my previous post or the rest of this thread? There is no meaningful definition for time applied to a photon. A photon has no experience of any kind. A photon has no frame. You need to read before you write.

 

[nitsuj]

... a simple div/0 error should not stand in our way to understanding all of this.

It doesn't

Read what that simple math is saying. In fact take it a step further, and consider what the measured phenomena is.

geometrically the div/0 error makes sense...and...yup...we're still discussing geometry, not trying to identify what nothing is.

 

[Moonraker]

The time dilation formula and the Lorentz transformations depend upon the basic assumptions of relativity, one of which is that the speed of light is invariant and equal to c in all frames. Applied to a frame co-moving with photon, such a statement is gibberish.

That is not precise:

1. Lorentz transformation depends upon the basic assumptions of relativity, one of which is that the speed of light is invariant and equal to c in all inertial frames. However, a photon may be considered as a frame but not as an inertial frame.
2. Time dilation (and also Lorentz contraction) should not be confused with Lorentz transformation.
3. Do not confuse the case v>c with v=c. v>c is ruled by a general principle, v=c is "only" ruled by the problem of division by 0.
4. Applying time dilation and Lorentz contraction to photons is not gibberish but leading to clear positive results.

 

[WannabeNewton]

2. Time dilation (and also Lorentz contraction) should not be confused with Lorentz transformation.
4. Applying time dilation and Lorentz contraction to photons is not gibberish but leading to clear positive results.

Time dilations and length contractions are special cases of a general lorentz transformation. I'm not sure how to respond to #4 because I don't see what your argument is in support of the (meaningless) concept of applying time dilation or length contraction "to photons". You just keep repeating that statement over and over without any physical justification.

 

[Moonraker]

Yes it does. Time Dilation means a time interval is getting larger for a moving object in a given reference frame. You have to divide by zero to find how long any interval is for a photon.

The so-called time dilation formula compares proper time of two frames. The photon has a proper time, the observer has a proper time, they are comparable, and no time is divided by 0 (see above-mentioned formula). Sure, please do not climb onto the photon for measuring the time of the observer! This will not work (division by 0). The photon is not an inertial frame.

It's a meaningless concept.

For photons, their life time is an instant of 0 seconds, and in their frame space is contracted to zero. This is fitting harmoniously with the rest of the special relativity.

 

[TomTelford]

It's not just an issue of dividing by zero. Did you read my previous post or the rest of this thread? There is no meaningful definition for time applied to a photon. A photon has no experience of any kind. A photon has no frame. You need to read before you write.

If not, then elaborate, but that seemed to be the point upon which this thread was piling up on.

Yes and yes, and many others on this topic.

I disagree. We may not have a transformation function that produces a singular result but that is not necessarily a restriction on the term "meaningful definition". What I am proposing is that if the Lorentz transform cannot "define" time "meaningfully" then other methods should be developed. These terms have a natural ambiguity so ask if I am using them a certain way before telling me I'm wrong, thank you.

We must allow a photon to have an "experience" as there are defined changes in its existence which can be correlated to observed changes. The whole point is to attempt to rationalize change without time.

It most definitely has a "frame" of some kind even if it is difficult to define mathematically.

I have read a great deal, thank you, on a great many subjects. You need to know when to make suggestive commentary and when not.

Now, to reiterate: I was suggesting that instead of assuming a frame that includes time as the "normal" case and attempting to understand the "timeless" state of a photon we could attempt the exercise from the opposite direction. It could be that time itself is somehow anomalistic.

If I was not clear, I apologize.

 

[Nugatory]

While the math may go all screwy when t'=0, the concept that light comes into existence, is absorbed/transformed and passes through the points in between on "its" straight line all simultaneously is hugely interesting.
...
I know I'm wandering into philosophy but a simple div/0 error should not stand in our way to understanding all of this.

When the math goes all screwy, that's the math trying to tell us that we're misusing it; and the way to advance our understanding is to stop torturing the math in an effort to force a confession out of it.

We got here in two steps. First, a previous poster has tried plugging the value v=c into the time dilation formula, without recognizing that the time dilation formula is derived from the relationship between the x and t coordinates in one frame to the x' and t' coordinates in another frame moving at a speed of less than c relative to the first frame. The result is seductive but altogether meaningless nonsense.

The second wrong step (easy to take, because the nonsense of the first step is indeed very seductive) came when you allowed the s-word, in boldface above, to lead you further astray. We all agree (I hope) that "simultaneous" means "at the same time"; but what exactly does THAT mean? Here's a slightly oversimplified definition:

If two events have the same Minkowski t coordinate in some reference frame, then we say that they are simultaneous in that frame.

(footnote 1: I specified "Minkowski" because I don't want to go anywhere near the rathole of GR and simultaneity conventions and coordinate time. Please, please, please don't send this thread down that rathole? Please?

footnote 2: This definition works just fine for classical Newtonian physics as well; I'm not making up some weird non-intuitive definition of simulataneity here)

But note that according to this more precise definition of "at the same time time", the emission, passage, and absorption of a light signal is NEVER simultaneous.

 

[ghwellsjr]

Yes it does. Time Dilation means a time interval is getting larger for a moving object in a given reference frame. You have to divide by zero to find how long any interval is for a photon.

The so-called time dilation formula compares proper time of two frames. The photon has a proper time, the observer has a proper time, they are comparable, and no time is divided by 0 (see above-mentioned formula). Sure, please do not climb onto the photon for measuring the time of the observer! This will not work (division by 0). The photon is not an inertial frame.

Frames don't have Proper Time, they have Coordinate Time. The Time Dilation formula compares the Proper Time of a material object to the Coordinate Time of an Inertial Reference Frame in which the object is moving at some speed. If you transform the coordinates of events from one IRF to another one moving with respect to the first one, you can get a different Time Dilation for the same object. Events associated with a photon will always transform between frames such that the photon continues to have a speed of c in all IRF's. Material objects can have different speeds in different IRF's and therefore different Time Dilations. The concept of Time Dilation is meaningless for photons. I can point you to numerous examples of how this works in other threads.

If you don't agree with this, then please show me an example of what you mean when you say "The so-called time dilation formula compares proper time of two frames."

It's a meaningless concept.

For photons, their life time is an instant of 0 seconds, and in their frame space is contracted to zero. This is fitting harmoniously with the rest of the special relativity.

The propagation speed of light (or photons) is fundamental (it's the second postulate) to Special Relativity. But, as I said before, a precise definition of time and space are also fundamental and your ideas of time and space applied to photons are not defined and do not fit harmoniously with the rest of SR nor is there any need for them. It's not like there is a hole in SR that needs to be filled in. The track you are going down will lead you astray to understanding SR. Furthermore, it is speculation that is not permitted on this forum and if you continue, you will likely get banned.

 

[TomTelford]

>nitsuj - Exactly. Which is what I have been pondering for quite some time. I have been looking at this time/no time dilemma from the perspective of an (infinitely) many to one relationship that occurs in data analysis from time to time. There are methods of reconciliation and I'm trying to apply them in this instance although my knowledge level in physics and related maths is not yet strong enough... getting there. It does indeed make sense at least as far as I have been able to poke at it. But there are implications of "no time"; it isn't simply a dead end.

>Nugatory - Agreed, that math seemed not to be applicable.

... the "S" word huh? Okay. I didn't know how else to express what I was thinking. However even if "simultaneous" means as much to a photon as time itself, it does permit a certain view of our frame from the photon's perspective which does involve simultaneity. Time may not be defined for the photon but location is not defined for us from it's perspective. Things are and are not at locations (or locations are or are not... very confusing). I'm not sure if this relates to the idea of d=0 which I am very skeptical of. Any readings in this direction would be appreciated.

 

[ghwellsjr]

It's not just an issue of dividing by zero. Did you read my previous post or the rest of this thread? There is no meaningful definition for time applied to a photon. A photon has no experience of any kind. A photon has no frame. You need to read before you write.

If not, then elaborate, but that seemed to be the point upon which this thread was piling up on.

I did elaborate in my previous post. Here, read this:

In Special Relativity, Einstein defines time as that which a clock measures. A clock cannot be made out of just photons, it requires massive particles. Massive particles cannot travel at the speed of light. Therefore a clock cannot travel at the speed of light and there is no definition for time at the speed of light. It's a meaningless concept.

Yes and yes, and many others on this topic.

I disagree. We may not have a transformation function that produces a singular result but that is not necessarily a restriction on the term "meaningful definition". What I am proposing is that if the Lorentz transform cannot "define" time "meaningfully" then other methods should be developed. These terms have a natural ambiguity so ask if I am using them a certain way before telling me I'm wrong, thank you.

The Lorentz transform does not define time at all. It was defined by Einstein in a two-step process. First, as I said before, it's what a clock measures at a particular location. Then to define time at a remote location a second clock is placed and the two clocks are synchronized using the definition of light propagating at c. This process, along with rigid (material) rulers define the concept of an Inertial Reference Frame. None of this can apply to a photon. And there is no need for it to. You are creating a problem where none exists. Furthermore, your proposal is against the rules that you agreed to when you signed on to this forum and I don't want to be part of this kind of activity. This forum is to learn relativity, not to add to it with your own personal concepts. I'm warning you to stop or you will likely get banned.

We must allow a photon to have an "experience" as there are defined changes in its existence which can be correlated to observed changes. The whole point is to attempt to rationalize change without time.

It is not possible to observe a traveling photon or the propagation of any light, let alone, observe any changes. Where did you get the idea that there are "defined changes in its existence"? What do you mean by "The whole point is to attempt to rationalize change without time"? I doubt that you will get up to ten posts before you get banned.

It most definitely has a "frame" of some kind even if it is difficult to define mathematically.

Unless you can do it, how can you say that it can definitely be done? (I see a ban coming on.)

I have read a great deal, thank you, on a great many subjects. You need to know when to make suggestive commentary and when not.

I'm making a strong warning: stop this nonsense or you will get banned.

Now, to reiterate: I was suggesting that instead of assuming a frame that includes time as the "normal" case and attempting to understand the "timeless" state of a photon we could attempt the exercise from the opposite direction. It could be that time itself is somehow anomalistic.

If I was not clear, I apologize.

Instead of apologizing, I suggest you delete all your posts quickly before you get banned so that you can continue to learn what relativity is all about. If you do it quickly enough, I will delete mine and hopefully others will too. Maybe you can still survive.