Do photons age? Do they remain stationary in x4?

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SUMMARY

The discussion centers on the nature of photons, specifically addressing whether they age or remain stationary in the fourth dimension. Participants assert that photons always travel at the speed of light (c) and cannot be observed from their own reference frame, as doing so would require infinite energy. The conversation highlights the philosophical implications of measuring time and experience for massless particles, concluding that photons do not age because they lack internal structure and cannot experience time in the same way as massive particles.

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  • #31
For something to actually age, it needs to have an internal structure that can change with time.

I disagree...an object without internal structure CAN age...maybe it doesn't change, however...so trying to measure the passage of time utilizing such "something" that does not change would be futile.
 
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  • #32
Naty1 said:
I disagree...an object without internal structure CAN age...maybe it doesn't change, however...so trying to measure the passage of time utilizing such "something" that does not change would be futile.
How do you define "age" when the "older" version of the same thing is indistinguishable from the younger?
 
  • #33
Fredrik said:
I would say that the measured decay rates are the strongest evidence we have for the particles not aging. If the properties of a particle don't change with time, the probability that it will decay during the next second must be independent of how much time has passed since the particle's creation. This implies an exponential decay rate. So the theory that particles don't age (i.e. the theory that particles don't have any properties that can change with time) predicts the correct decay rates.
Very good point. I certainly had not considered it that way. The lifetime of people is not governed by an exponential law precisely because they do age, meaning that the likelihood of decay in the next year changes as a function of the number of years since birth.

So, although you can say that the proper time along a photon's path is 0 you cannot associate that with aging one way or the other.
 
  • #34
So, although you can say that the proper time along a photon's path is 0 you cannot associate that with aging one way or the other.

Brian Greene says you can as I noted in my previous post.
 
  • #35
I found more discussion on Brian Greene's writings here:

http://www.fqxi.org/community/forum/topic/511
MDT & Brian Greene’s Elegant Universe:

In An Elegant Universe, Brian Greene almost characterizes Moving Dimensions Theory’s deeper reality:

“Einstein found that precisely this idea—the sharing of motion between different dimensions—underlies all of the remarkable physics of special relativity, so long as we realize that not only can spatial dimensions share an object’s motion, but the time dimension can share this motion as well. In fact, in the majority of circumstances, most of an object’s motion is through time, not space. Let’s see what this means.” Space, Time, and the Eye of the Beholder, An Elegant Universe, Brian Greene, p. 49

Right here Brian almost grasps MDT. But time is not a dimension. Time is an emergent phenomenon that arises because the fourth dimension is expanding relative to the three spatial dimensions at the rate of c. Let’s rewrite Brian’s paragraph with MDT's insights:

“Einstein found that precisely this idea—the sharing of motion between different dimensions—underlies all of the remarkable physics of special relativity, so long as we realize that not only can the three spatial dimensions share an object’s motion, but the fourth dimension, which is moving relative to the three spatial dimensions, can share this motion as well. In fact, in the majority of circumstances, most of an object’s motion is through the fourth dimension, not the three spatial dimensions. Let’s see what this means.” Space, Time, and the Eye of the Beholder, An Elegant Universe, Brian Greene, p. 49

Most objects are traveling far less than c through the three spatial dimensions. Thus most objects are traveling close to the rate of c through the fourth dimension. To be stationary in the three spatial dimensions implies a velocity of c through the fourth dimension. Ergo the fourth dimension is expanding relative to the three spatial dimensions. To be stationary in the fourth expandning dimension, as is the timeless, ageless, nonlocal photon, implies a velocity of c through the three spatial dimensions. Ergo the fourth dimension is expanding relative to the three spatial dimensions.

dx(4)/dt = ic

Brian Greene continues:

“Motion through space is a concept we learn about early in life. Although we often don’t think of things in such terms, we also learn that we, our friends, our belongings, and so forth all move through time, as well. When we look at a clock or a wristwatch, even while we idly sit and watch TV, the reading on the watch is constantly changing, constantly “moving forward in time.” We and everything around us are aging, inevitably passing from one moment of time to the next. In fact, the mathematician Hermann Minkowski, and ultimately Einstein as well, advocated thinking about time as another dimension of the universe—the fourth dimension—in some ways quite similar to the three spatial dimensions in which we find ourselves immersed.” Space, Time, and the Eye of the Beholder, An Elegant Universe, Brian Greene, p. 49

What Greene misses is that the time measured on your watch—the ticking seconds—is not the fourth dimension, but it is a phenomenon that emerges because the fourth dimension is expanding relative to the three spatial dimensions. The time measured on a clock or watch relies on the emission and propagation of photons, be it in the context of an unwinding clock spring or an oscillating quartz crystal, or even the beating of a heart. And photons are matter that surf the fourth expanding dimension. As time is so inextricably wed to the emission and propagation of photons, and as photons are matter caught in the fourth expanding dimension, our notion of “time” inherits properties of the fourth expanding dimension. But the fact is that time emerges from a deeper physical reality—a fourth dimension that is expanding relative to the three spatial dimensions.

Brian Green continues on, heading off in the wrong direction that just misses the central postulate of MDT:

“Although it sounds abstract, the notion of time as a dimension is actually concrete.”

But it is not. Can you move to where your watch reads three seconds back in time? Or can you move to where your watch reads an hour back in time? We can walk left or right. We can climb up or down. We can move forwards or backwards. But we can’t move through time like we can through the three spatial dimensions. This is because time, as measured on our watch, is not the fourth dimension, but it is a construct we have devised which is based on the fundamental fact that the fourth dimension is expanding relative to the three spatial dimensions, governing the emission and propagation of photons, by which time is known and measured on our watches.

Brian Green continues on,

“When we want to meet someone, we tell them where “in space” we will expect to see them—for instance, the 9th floor of the building on the corner of 53rd Street and 7th avenue. There are three pieces of information here (9th floor, 53rd Street, 7th avenue) reflecting a particular location in the three spatial dimensions of the universe. Equally important, however, is our expectation of when we expect to meet them—for instance, at 3 PM. This piece of information tells us where “in time” our meeting will take place. Events are therefore specified by four pieces of information: three in space and one in time. Such data, it is said, specifies the location of the event in space and in time, or in spacetime, for short. In this sense, time is another dimension.”

But again, time is different from the three spatial dimensions. Time is inextricably wed to our sense of the past—the order stored in our memory, long with our ability to imagine and dream of future events. The present is where we put our dreams into action. However, the time defined by past, present, and future is not a dimension akin to the three spatial dimensions, but rather it is a phenomenon that emerges because the fourth dimension is expanding relative to the three spatial dimensions, at the rate of c.

You write, "So I don't think Einstein and Minkowski went far enough. They covered measurement, and how events in one reference frame would appear to an observer in another reference frame. That is quite useful in itself, but the real picture seems to be fundamentally much larger than what they covered. We need to go beyond Einstein and include temporal motion, which in turn requires a consideration of non-directional motion, speeds greater than light, non-locality, and so forth. Even better, we need to learn how to think in terms of "motional dimensions" directly, instead of space and time dimensions."

Yes! Feynman sought this mechanism for the ever constant motion of time! He sought source of time's arrows and assymmetries!

And MDT provides this *physical* mechanism for time and all change, and a while host of other physical phenomena.

Indeed, MDT finally provides, in Feyman's words, "the thing that makes the whole phenomena of the world seem to go one way." Time has a definitive arrow because the dx4/dt=ic, or the fourth dimension is expanding relative to the three spatial dimensions at the rate of c. Ergo radiation, which is but matter caught upon the expanding nonlocality of the fourth exapnding dimension, expands outward, but never inward. Ergo time and all its arrows and asymmetries, as well as entropy, as more fully elaborated on in my paper.

Feynman stated, "Now if the world of nature is made of atoms, and we too are made of atoms and obey physical laws, the most obvious interpretation of this evident distinction between past and future, and this irreversibility of all phenomena, would be that some laws, some of the motion laws of the atoms, are going one way – that the atom laws are not such that they can go either way. There should be somewhere in the works some kind of principle that uxles only make wuxles, and never vice versa, and so the world is turning away from uxley character to wuxley character all the time – and this one-way business of the interactions of things should be the thing that makes the whole phenomena of the world seem to go one way. But we have not found this yet. That is, in all the laws of physics that we have found so far there does not seem to be any distinction between the past and the future. The moving picture should work the same going both ways, and the physicist who looks at it should not laugh."--(The Distinction of Past and Future, from The Character of Physical Law, Richard Feynman, 1965)

MDT has finally found "the thing that makes the whole phenomena of the world seem to go one way."

To be stationary in a lab means to move at c through the fourth dimension. So it is that absolute rest may be defined as maximal aging, but this can never be ascertained in an inertial frame cutoff from the surrounding environment, as time is measured relative to the velocity of light and distance, which are ultimately measured relative to time. This tautological definition of time and the velocity of light and the velocity of light and time is something Einstein noted.



Dr. E (The Real McCoy)


http://www.fqxi.org/community/forum/topic/511
 
  • #36
`Biological age' should be distinguished from `chronological age'. The former tracks the wear and tear of an organism over time, the latter the amount of time that has passed for an organism. While 'biological age' clearly refers to organisms, its use could be extended to other systems, to track their changes too.

Biological age clearly must involve change. A forty year old man in a sixteen year old's body implies that certain changes have gone slowly for him and also is illegal in some countries. Chronological age does not so obviously require change (though if time necessarily requires some kind of change, it may) and it's theoretically possible for periodic system to `experience' time, in that it goes through a sequence of changes, yet returning to exactly the same qualitative state.

(Perhaps, then, here I disagree with Fredrik's last post :cry:)

It seems to me that the argument that the decay rate of fundamental particles shows that their `biological' age does not change - they are intrinsically the same for the whole of their lifetime. But the notion of time passed, and in particular, relativistic time dilation, also makes sense for muons - they do have a half life, which is a function of the proper time, and fast traveling muons live longer.

By contrast, traveling on light-cones, not even this much can be said for photons.
 
  • #37
As Brian Greene points out in the Appendix to Chapter 2 of The Elegant
Universe, we note that from the space-time position 4-vector
x=(ct,x1,x2,x3), we can create the velocity 4-vector u=dx/d(tau),
where tau is the proper time defined by
d(tau)^2=dt^2-c^-2(dx1^2+dx2^2+dx3^2). Then the "speed through
space-time" is the magnitude of the 4-vector u,
((c^2dt^2-dx^2)/(dt^2-c^-2dx^2))^(1/2), which is identically the speed
of light c. Now, we can rearrange the equation
c^2(dt/d(tau))^2-(dx/d(tau))^2=c^2 to be c^2(d(tau)/dt))^2
+(dx/d(tau))^2=c^2. This shows that an increase of an object's speed
through space, (dx/d(tau))^2)^(1/2)= dx/d(tau) must be accompanied by
a decrease in d(tau)/dt which is the object's speed through time,
which also may be considered the rate at which time elapses on it's
own clock d(tau) or the proper time, as compared with that on our
stationary clock dt.

So it seems that as an object propagates at c through the three spatial dimensions, it must propagate at 0 through the fourth dimension.

Hence it would seem that photons remain stationary in the fourth dimension. For if they moved at all in the fourth dimension, their velocity would be greater than c, which is impossible.
 
  • #38
brunoeinstein said:
So it seems that as an object propagates at c through the three spatial dimensions, it must propagate at 0 through the fourth dimension.

Hence it would seem that photons remain stationary in the fourth dimension.
This is certainly not correct. The fact that the proper time along a lightlike worldline is 0 does not imply that the worldline does not go through coordinate time.

Btw, although the four velocity of any timelike particle has a magnitude of c, the four velocity of a lightlike particle is undefined.
 
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  • #39
yossell said:
`Biological age' should be distinguished from `chronological age'.
I guess I would use "age" to refer to the former and "proper time" to refer to the latter.
 
  • #40
DaleSpam said:
This is certainly not correct. The fact that the proper time along a lightlike worldline is 0 does not imply that the worldline does not go through coordinate time.

yes dale,

indeed our watches would continue ticking as photons zoom on by.

i assume that you are picturing a space-time diagram and a light cone. the time on that space-time diagram is in our frame.

what brian greene is saying is that the photon is moving along with the fourth dimension, as it is staying stationary in x4. as the velocity of all objects through space-time is c, and as all of a photon's velocity is directed through space (x1, x2, x3), it must thus be stationary in the fourth dimension (x4).

that is what the math is saying.

best. :)
 
  • #41
brunoeinstein said:
what brian greene is saying is that the photon is moving along with the fourth dimension, as it is staying stationary in x4. as the velocity of all objects through space-time is c, and as all of a photon's velocity is directed through space (x1, x2, x3), it must thus be stationary in the fourth dimension (x4).

that is what the math is saying.
No, from your comments about the fourth dimension you are clearly referring to coordinate time and a photon clearly is not stationary in coordinate time.

Also, your references to the four-velocity apply only for timelike particles, not lightlike particles. The four-velocity is not defined for a photon's worldline (division by 0). That is why you have to use an affine parameter instead of proper time for a photon.
 
  • #42
DaleSpam said:
No, from your comments about the fourth dimension you are clearly referring to coordinate time and a photon clearly is not stationary in coordinate time.

Also, your references to the four-velocity apply only for timelike particles, not lightlike particles. The four-velocity is not defined for a photon's worldline (division by 0). That is why you have to use an affine parameter instead of proper time for a photon.

Indeed a photon is not stationary in time as we measure it on our watches.

But too, a photon does not age.

Or are you saying that Brian Greene is wrong? "Brian Greene writes in the Elegant Universe:

pg 49

...in the majority of circumstances (slow speeds) most of an objects motion is thru time, not space...the maximum speed through space occurs if all of an objects motion through time is diverted to motion through space...thus light does not get old; a photon that emerged from the big bangis the same age today as it was then.

"

Greene states "thus light does not get old; a photon that emerged from the big bang is the same age today as it was then."

This is true.
 
  • #43


Do photons age?
Time has no meaning in photon rest frame, nor for any zero mass particle moving at c. Time is "experienced" only by mass particles. Therefore, only interaction of photon and a mass particle yields information about time.
 
  • #44


Kitesurfer said:
Do photons age?
Time has no meaning in photon rest frame, nor for any zero mass particle moving at c. Time is "experienced" only by mass particles. Therefore, only interaction of photon and a mass particle yields information about time.

so you agree with brian greene i take it?

Greene states "thus light does not get old; a photon that emerged from the big bang is the same age today as it was then."

This is true.
 
  • #45


brunoeinstein said:
so you agree with brian greene i take it?

Greene states "thus light does not get old; a photon that emerged from the big bang is the same age today as it was then."

This is true.

Yes.
A photon that was emitted 13 plus billions years ago, right after the initial condensation of electrons / protons that made the universe transparent to photons and enabled its propagation without scattering on mass particles (circa 300 thousands years after the big bang), is received by our detector via its interaction with a mass particle in the detector. Only then a time is recorded, i.e. it has a meaning.
 
  • #46


Kitesurfer said:
Yes.
A photon that was emitted 13 plus billions years ago, right after the initial condensation of electrons / protons that made the universe transparent to photons and enabled its propagation without scattering on mass particles (circa 300 thousands years after the big bang), is received by our detector via its interaction with a mass particle in the detector. Only then a time is recorded, i.e. it has a meaning.

More from Brian Greene & Einstein,

"Einstein proclaimed that all objects in the universe are always traveling at one fixed speed--that of light. . . We now see that time slows down when an object moves relative to us because this diverts some of its motion through time into motion through space. The speed of an object through space is thus merely a reflection of how much of its motion through time is diverted." -- p. 50, THE ELEGANT UNIVERSE (read it for yourself if you log in @ https://www.amazon.com/dp/0375708111/?tag=pfamazon01-20)

1. "Einstein proclaimed that all objects in the universe are always traveling at one fixed speed--that of light." --Brian Greene

2. Fact: A photon travels at c through the three spatial dimensions.

3. "The speed of an object through space is thus merely a reflection of how much of its motion through time is diverted." --Brian Greene

4. Because a photon moves at c through the three spatial dimensions, a photon's "motion through time must be entirely diverted."

5. Ergo, a photon has no velocity component in the fourth dimension.

6. Ergo a photon stays at the same place in the fourth dimension, as it has no motion in the fourth dimension, all its "motion through time being diverted," as Brian Greene and Einstein state.
B.E.
 
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  • #47
brunoeinstein said:
I found more discussion on Brian Greene's writings here:
This was only your third post in this forum, and you're already quoting a crackpot who keeps creating new accounts here just to be able to post his "moving dimensions" nonsense. (No, not Greene). It's not hard to guess who you are. And linking to crackpot stuff is against the forum rules, no matter who you are.

brunoeinstein said:
More from Brian Greene & Einstein,
I think Greene's explanation of SR is really bad, so I wouldn't recommend anyone to try to learn SR from his writings.
 
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  • #48
Fredrik said:
This was only your third post in this forum, and you're already quoting a crackpot who keeps creating new accounts here just to be able to post his "moving dimensions" nonsense. (No, not Greene).

sorry about that!

i was searching for greene's passage on photons not aging nor traveling through x4, and came across the passage.

perhaps we should stick to greene's text which i found at amazon.com: https://www.amazon.com/dp/0375708111/?tag=pfamazon01-20

if you log in, it will let you read it directly as they have made that page available. or, perhaps you have the book.

More from Brian Greene & Einstein,

"Einstein proclaimed that all objects in the universe are always traveling at one fixed speed--that of light. . . We now see that time slows down when an object moves relative to us because this diverts some of its motion through time into motion through space. The speed of an object through space is thus merely a reflection of how much of its motion through time is diverted." -- p. 50, THE ELEGANT UNIVERSE (read it for yourself if you log in @ https://www.amazon.com/dp/0375708111/?tag=pfamazon01-20)

1. "Einstein proclaimed that all objects in the universe are always traveling at one fixed speed--that of light." --Brian Greene

2. Fact: A photon travels at c through the three spatial dimensions.

3. "The speed of an object through space is thus merely a reflection of how much of its motion through time is diverted." --Brian Greene

4. Because a photon moves at c through the three spatial dimensions, a photon's "motion through time must be entirely diverted."

5. Ergo, a photon has no velocity component in the fourth dimension.

6. Ergo a photon stays at the same place in the fourth dimension, as it has no motion in the fourth dimension, all its "motion through time being diverted," as Brian Greene and Einstein state.



B.E.
 
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  • #49
Fredrik said:
I think Greene's explanation of SR is really bad, so I wouldn't recommend anyone to try to learn SR from his writings.

What, specifically, do you find "really bad" about Greene's explanations of SR?

Are you saying that he is wrong? If so, how so, specifically?

It is not enough in life nor education to criticize others in an ad hominem manner, but one must always a) qualify one's statements, and b) suggest the better path for everyone's elucidation.

Who do you suggest we learn SR from?

Thanks in advance!

:) BR
 
  • #50
brunoeinstein said:
but one must always a) qualify one's statements,

Practice what you preach much?
 
  • #51
yossell said:
Practice what you preach much?

I hope so! Where do you think I am falling short?

I will make amends to correct any shortcomings.

Thanks! :)
 
  • #52
Fredrik said:
I think Greene's explanation of SR is really bad, so I wouldn't recommend anyone to try to learn SR from his writings.

Hello Fredrick,

I did some research on Brian Greene. He is one of the most famous physicists of our era, and too, he is one of the most famous teachers of physics.

http://en.wikipedia.org/wiki/Brian_Greene
http://www.columbia.edu/cu/physics/fac-bios/Greene/faculty.html

Please elaborate on why you say that, "Greene's explanation of SR is really bad, so I wouldn't recommend anyone to try to learn SR from his writings."

Greene is a world-renown scientist with degrees from Oxford in theoretical physics.

Why do you think that he is not good?

The New York Times Book Review wrote:

The New York Times Book Review - George Johnson
Greene...explor[es] the ideas and recent developments with a depth and clarity I wouldn't have thought possible. He has a rare ability to explain even the most evanescent ideas in a way that gives at least the illusion of understnding.He developes one fresh new insight after another...In the great tradition of physicists writing for the masses, The Elegant Universe sets a standard that will be hard to beat.
--http://search.barnesandnoble.com/The-Elegant-Universe/Brian-Greene/e/9780375708114#TABS

Scientific American - Chris Quigg

Beautifully told...The Elegant Universe presents the ideas and aspirations — and some of the characters — of string theory with clarity and charm...a thoughtful and important book.

The London Review of Books - Ellis

...I can only say that Greene's book is an explanatory tour-de-force...It would be hard to imagine anyone producing a clearer account than this of the difficult ideas involved, and Greene even brings out something of the actual excitement of scientific discovery...

Are you saying, Fredrick, that Greene as these sources are not to be trusted? What are your credentials, if we may ask? Perhaps that will help us to put your opinion in proper perspective? Thanks!

Given the unanimous praise for Brian Greene & his book, as well as for Einstein, coming from everywhere, I am going to have to keep with this explanation & interpretation:

More from Brian Greene & Einstein,

"Einstein proclaimed that all objects in the universe are always traveling at one fixed speed--that of light. . . We now see that time slows down when an object moves relative to us because this diverts some of its motion through time into motion through space. The speed of an object through space is thus merely a reflection of how much of its motion through time is diverted." -- p. 50, THE ELEGANT UNIVERSE (read it for yourself if you log in @ https://www.amazon.com/Elegant-Univer...der_0375708111&tag=pfamazon01-20)

1. "Einstein proclaimed that all objects in the universe are always traveling at one fixed speed--that of light." --Brian Greene

2. Fact: A photon travels at c through the three spatial dimensions.

3. "The speed of an object through space is thus merely a reflection of how much of its motion through time is diverted." --Brian Greene

4. Because a photon moves at c through the three spatial dimensions, a photon's "motion through time must be entirely diverted."

5. Ergo, a photon has no velocity component in the fourth dimension.

6. Ergo a photon stays at the same place in the fourth dimension, as it has no motion in the fourth dimension, all its "motion through time being diverted," as Brian Greene and Einstein state.



B.E.
 
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  • #53
Bruno...

The time measured on a clock or watch relies on the emission and propagation of photons, be it in the context of an unwinding clock spring or an oscillating quartz crystal, or even the beating of a heart. And photons are matter that surf the fourth expanding dimension.

really humorous...nice try! but insofar as current science has determined, purely speculative...

Einstein proclaimed that all objects in the universe are always traveling at one fixed speed--that of light
..

that's not quite the quote... ...you mean "...traveling through spacetime.." at one fixed speed...so it's the spacetime interval that IS invarient...

I do agree with the rest of your post immediately above including " Please elaborate on why you say that, "Greene's explanation of SR is really bad, so I wouldn't recommend anyone to try to learn SR from his writings."...for a largely non mathematical discussion of relativity Greene does a good job..and is consistent from what I have seen with several other prominent physicsts.
 
  • #54
Naty1 said:
Bruno...



really humorous...nice try! but insofar as current science has determined, purely speculative...

..

that's not quite the quote... ...you mean "...traveling through spacetime.." at one fixed speed...so it's the spacetime interval that IS invarient...

I do agree with the rest of your post immediately above including " Please elaborate on why you say that, "Greene's explanation of SR is really bad, so I wouldn't recommend anyone to try to learn SR from his writings."...for a largely non mathematical discussion of relativity Greene does a good job..and is consistent from what I have seen with several other prominent physicsts.

Yes, I agree. Above I quoted: "1. "Einstein proclaimed that all objects in the universe are always traveling at one fixed speed--that of light." --Brian Greene



BE :)
 
  • #55
thanks all! well, seems like we're making some progress on a consensus!

at this point, is there anyone who does not agree with this, or finds fault with the following:

More from Brian Greene & Einstein,

"Einstein proclaimed that all objects in the universe are always traveling at one fixed speed--that of light. . . We now see that time slows down when an object moves relative to us because this diverts some of its motion through time into motion through space. The speed of an object through space is thus merely a reflection of how much of its motion through time is diverted." -- p. 50, THE ELEGANT UNIVERSE (read it for yourself if you log in @ https://www.amazon.com/Elegant-Univer...der_0375708111&tag=pfamazon01-20)

1. "Einstein proclaimed that all objects in the universe are always traveling at one fixed speed--that of light." --Brian Greene

2. Fact: A photon travels at c through the three spatial dimensions.

3. "The speed of an object through space is thus merely a reflection of how much of its motion through time is diverted." --Brian Greene

4. Because a photon moves at c through the three spatial dimensions, a photon's "motion through time must be entirely diverted."

5. Ergo, a photon has no velocity component in the fourth dimension.

6. Ergo a photon stays at the same place in the fourth dimension, as it has no motion in the fourth dimension, all its "motion through time being diverted," as Brian Greene and Einstein state.



B.E.

if there is anyone who does not agree with the above, please share your opinion and characterize why you do not agree with the above. thanks all!
 
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  • #56
brunoeinstein said:
But too, a photon does not age.
I agree, but that has nothing whatsoever to do with its passage through coordinate time (your x4).

Regarding Brian Greene, he is a good physicist, but you are quoting a pop-sci book of his. Like all pop-sci books it is necessarily very sloppy. It is not a useful reference, nor is it intended to be.
 
  • #57


brunoeinstein said:
1. "Einstein proclaimed that all objects in the universe are always traveling at one fixed speed--that of light." --Brian Greene
This is sloppy useage. He is referring to the norm of the four-velocity, which is only defined for massive particles. Not photons. You cannot extend conclusions or reasoning based on this to photons or other massless particles.


brunoeinstein said:
4. Because a photon moves at c through the three spatial dimensions, a photon's "motion through time must be entirely diverted."
Meaning that its proper time is 0.


brunoeinstein said:
5. Ergo, a photon has no velocity component in the fourth dimension.
Incorrect. You are confusing coordinate time (the fourth dimension) with proper time (the spacetime interval along a worldline).
 
  • #58


DaleSpam said:
"1. "Einstein proclaimed that all objects in the universe are always traveling at one fixed speed--that of light." --Brian Greene"
^^^^
This is sloppy useage. He is referring to the norm of the four-velocity, which is only defined for massive particles. Not photons. You cannot extend conclusions or reasoning based on this to photons or other massless particles.

So are you saying that Einstein's statement, "Einstein proclaimed that all objects in the universe are always traveling at one fixed speed--that of light." does not apply to photons?

Are you saying that light (photons) doth not travel at the speed of light?

You do realize, that that is entirely ridiculous. Right?

It doth appear that you are the one who is being sloppy, sir.
BE :)
 
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  • #59


brunoeinstein said:
Are you saying that light (photons) doth not travel at the speed of light?
Read what I said:
DaleSpam said:
This is sloppy useage. He is referring to the norm of the four-velocity, which is only defined for massive particles. Not photons. You cannot extend conclusions or reasoning based on this to photons or other massless particles.

Green's quote (misattributed to Einstein) can either refer to the norm of the four-velocity or the norm of the three-velocity. If it refers to the norm of the three-velocity then it is simply not true, and if it refers to the norm of the four-velocity then it does not apply to photons since the four-velocity is undefined for them.

You seem to be confusing three-velocity and four-velocity as well as confusing proper time and coordinate time. Your confusion is not surprising if your sole source of information on relativity is a pop-sci book.
 
  • #60


DaleSpam said:
Read what I said:

Green's quote (misattributed to Einstein) can either refer to the norm of the four-velocity or the norm of the three-velocity. If it refers to the norm of the three-velocity then it is simply not true, and if it refers to the norm of the four-velocity then it does not apply to photons since the four-velocity is undefined for them.

I read EXACTLY what you said and I responded to it.

Everyone can see that I am responding to EXACTLY what you said, as I quote EXACTLY what you said.

DaleSpam said:
"1. "Einstein proclaimed that all objects in the universe are always traveling at one fixed speed--that of light." --Brian Greene"
^^^^
This is sloppy useage. He is referring to the norm of the four-velocity, which is only defined for massive particles. Not photons. You cannot extend conclusions or reasoning based on this to photons or other massless particles.

So are you saying that Einstein's statement, "Einstein proclaimed that all objects in the universe are always traveling at one fixed speed--that of light." does not apply to photons?

Are you saying that light (photons) doth not travel at the speed of light?

You do realize, that that is entirely ridiculous. Right?

It doth appear that you are the one who is being sloppy, sir.
BE :)
 

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