Photons: The Argument for their Existence?

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Re: Photons: The Argument for their Existence?

Postby BurtJordaan on November 15th, 2019, 1:10 am 

bangstrom » 15 Nov 2019, 05:26 wrote:The question remains of whether Don was measuring the speed of light or measuring the distance between the detectors in units of time.

Don measured the one-way propagation speed of light and that's that. What's more, he confirmed that it is the same for both directions by just taking the laser gun to the other end and fired from there through the two same two detectors.

The rest of the argument is philosophy, not science.
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Re: Text or Context

Postby BurtJordaan on November 15th, 2019, 4:29 am 

bangstrom » 15 Nov 2019, 05:32 wrote:

All light signals we emit are signals into our future and all light signals we receive are signals from our past but I don’t see that represented on your diagram.


I can only see one reasonable interpretation of FD's diagram: all light coming from the past and going into the future are compressed into the yellow dot. So you cannot see light propagating on it. In fact, I see only one use: a simple graphic for what interval means, but IMO it has no other real function. This is why FD has to jump to his radial time diagram, which incidentally is just a space-propertime diagram, whenever he has to show anything else.
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Re: Getting to the Point(s)

Postby Faradave on November 16th, 2019, 2:34 am 

BurtJordaan wrote:FD's diagram: all light coming from the past and going into the future are compressed into the yellow dot. So you cannot see light propagating on it.

Yes. With the caveat that each light quantum transmitted has its own dot. The height of the black & blue arrow is determined by the time and space (in a particular direction) bypassed between emitter and absorber.

BurtJordaan wrote:FD's diagram: … In fact, I see only one use: a simple graphic for what interval means, but IMO it has no other real function.

This thread questions the existence of photons. My diagram, consistent with SR, reveals that light quanta transit pinholes (particle-interaction wormholes) rather than as "massless particles" answers that!

BurtJordaan wrote:FD has to jump to his [curved-space, radial-time] diagram ... whenever he has to show anything else.

That's the "point"! What a light quantum sees as interval contact, real observers (i.e. those with mass) see as a lengthy (& time consuming) paths, varying with inertial frame. (see reflection above) Different internal and external path length defines a wormhole. Zero internal path specifically defines a pinhole.
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Re: Photons: The Argument for their Existence?

Postby BurtJordaan on November 16th, 2019, 5:19 am 

OK, I can see a solution: put your interval-time on two axis, with space-propertime on two axis and marry them into one 3D interval-space-propertime diagram. This means propertime is the common axis and interval and space are orthogonal to each other and to propertime.

Now we can show pinholes and word lines or world tubes to our heart's content. The worldline of light is then simply a horizontal parallel to the space axis at the time of emission and absorption.

I will draw such a combination when I have time and see what it looks like.
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Re: Photons: The Argument for their Existence?

Postby BurtJordaan on November 16th, 2019, 5:12 pm 

BurtJordaan » 16 Nov 2019, 11:19 wrote:OK, I can see a solution: put your interval-time on two axes, with space-propertime on two axes and marry them into one 3D interval-space-propertime diagram.

Here is what I think it may look like (I have ripped the grids of the web). Assuming that one event happens at the origin, with the 2nd events at the tips of the yellow arrows respectively, which are located on a sphere with a radius equal to c in geometric units, i.e. a unity 3D sphere centered on the origin.

Interval-space-propertime diagrams-2.png

The left diagram is for the case where the 2nd event happens at x=z=0.2c, y=0.98c and the right diagram for an event happening at x=0.8c, y=z=0.6c. This means the yellow arrows are unity vectors in interval-space-propertime.

The yellow arrows are also the worldlines of clocks moving at 0.2c and 0.8c respectively, relative to the inertial frame in which the origin is at rest. Remember that clocks measure their own propertime. If v=0 the dotted box collapses to coincide with the green plane (x=0) and if v=c it collapses to coincide with the red plane (y=0). If v=0.707c, the box becomes a 0.707c cube.

Your interval-time diagram corresponds to viewing along the x-axis and my space-propertime diagram corresponds to viewing along the z=axis.

Does this make any sense?

PS: Sorry, I goofed the scale of the left-diagram. The box is shown too fat and wide, but the principle remains the same.
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Re: Photons: The Argument for their Existence?

Postby BurtJordaan on November 17th, 2019, 1:40 am 

I have corrected a little and added a 3rd case for clarity. Unfortunately the resolution went down a bit, but the idea is there.

Interval-space-propertime diagrams-4.png
Interval-space-propertime diagrams


I'm still pondering about the possible use of such a diagram. Perhaps just for pedagogy?

It will be nice if animated...
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Re: 3 Way Tie

Postby Faradave on November 17th, 2019, 3:46 am 

I have to think about it more but "Interval-Space-Propertime" seems a splendid idea at first glance! Since space-propertime has such a Euclidean look and feel, I was never convinced it could sustain intervals directly. Conventional (pseudo-Euclidean) spacetime attempts this but only with great distortion. Your solution gives intervals a chance to be visualized without imposing equivalence to space. Very interesting as an aid to understanding without implying an actual underlying structure.

I don't want to disturb you're train of thought but it's interesting to recall that the equation for timelike intervals differs from the one for spacelike intervals (to avoid Minkowski's √(-1) ):

Spacelike interval (applies when ∆x > ∆t):
d²= ∆x² - ∆t², which rearranges to ∆x² = ∆d + ∆t²

Lightlike interval (applies when ∆x = ∆t): ∆d = 0

Timelike interval (applies when ∆t > ∆x):
d²= ∆t² - ∆x², which rearranges to ∆t² = ∆d² + ∆x²
The latter suggests that time (as opposed to propertime) is represented in the red plane (with interval-space coordinates?

Light Agreement.png
Left: Euclidean interval-time coordinates reveal light transmission as interval contact (i.e. "pinhole") in the limit as spatial separation equates to temporal separation. This spacelike approach (from ∆x > ∆t) finds speed limit c while slowing down from imaginary superluminal speeds. Right: Euclidean interval-space coordinates find the same interval contact in the limit as temporal separation equates to space. This time like approach (from ∆t > ∆x) sees real speeds increasing to limit c.
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Re: 3 Way Tie

Postby BurtJordaan on November 17th, 2019, 7:44 am 

Faradave » 17 Nov 2019, 09:46 wrote:Timelike interval (applies when ∆t > ∆x):
d²= ∆t² - ∆x², which rearranges to ∆t² = ∆d² + ∆x²
The latter suggests that time (as opposed to propertime) is represented in the red plane (with interval-space coordinates?

Yes, I suppose one can say that, but it will always (by definition) just give the coordinate time (which is obviously also its propertime) of the reference inertial clock. In the particular case diagrammed, it is just c, with c=1 if you like.

Spacelike intervals are ignored in space-propertime, because the purpose is normally to picture real worldlines. I suppose one can concoct a way to represent "tachyons", i.e. by just rotating the wordline by more that 90 degrees, but I think it would quickly become rather meaningless.

Your "pinhole contact" is fine, because it is just the null worldline (of light) viewed along the x-axis of the diagram, i.e. viewing a zero-dimensional mathematical point.
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Re: Photons: The Argument for their Existence?

Postby hyksos on November 17th, 2019, 5:08 pm 

dandelion » November 3rd, 2019, 9:34 pm wrote:Here is more about that-
“Heisenberg gives a telling story about how he got the idea. He was walking in a park in Copenhagen at night. All was dark except for a few island of light under street lamps. He saw a man waking under one of those, then disappearing in the dark. Then appearing again under the next lamp. Of course, he thought, man is big and heavy and does not “really” disappear: we can reconstruct his path through the dark. But what about a small particle? Maybe what quantum theory is telling us is precisely that we cannot use the same intuitions for small particles. There is no classical path between their appearance here and their appearance there. Particles are objects that manifest themselves only when there is an interaction, and we are not allowed to fill up the gap in between. The ontology that Heisenberg proposes does not increase on the ontology of classical mechanics: it reduces it. It is less, not more. Heisenberg removes excess baggage from classical ontology and is left with a minimum necessary to describe the world”. https://arxiv.org/pdf/1508.05543.pdf

There is a social problem manifesting. If I begin to respond to direct quotes from arxiv articles, I am no longer even interacting with the people on this forum. If I spilt several paragraphs of ink responding to the above quote, I would be "conversing" with a person who is not even present here.

Your intention that the above quote somehow verifies or corroborates some regularly spewed claim on this forum that "photons don't exist". I will point out why the above quote says the exact opposite of that. Here :

Particles are objects that manifest themselves only when there is an interaction, and we are not allowed to fill up the gap in between.

The problem is that they do manifest themselves. This quote literally says that they manifest. This is precisely what is observed in nature -- particles manifest.

I will also point out that this quote says particles not just photons. It is not merely photons that act like this. By some accident of the history of modern physics, we have lengthy stories of photons being "corpuscles of energy transmitted".

I am perfectly fine with the Unitary Wave Evolution picture of the universe. That is how the matter and energy behave when not being observed. That has been experimentally verified so many different times in so many different ways, I don't even know where to begin. But at the act of measurement, the universe is univocal, and snaps the quantum waves into a particle. That is what is observed and it always does this "snapping" thing. (What the internet community dubs the "collapse of the wave function" ). That is what the above quote is principally claiming.

we are not allowed to fill up the gap in between.

This is just a re-hashing the Copenhagen Interpretation. We already know that Werner Heisenberg was an advocate of that interpretation. And I'm not spilling any more ink on this because I'm not going to talk to disembodied articles.
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Re: Photons: The Argument for their Existence?

Postby TheVat on November 17th, 2019, 9:37 pm 

"regularly spewed"

Friendly chat is the objective here.
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Re: Worldly Wisdom

Postby Faradave on November 17th, 2019, 11:57 pm 

hyksos wrote:claim on this forum that "photons don't exist". I will point out why the above quote says the exact opposite of that. … -- particles manifest.

Which is not to deny that phenomena other than "particles" (e.g. waves, quantum states) may also have manifestations.

But consider two massive particles manifesting themselves by classical collision. Each particle has a worldline. Their single point of contact is not a worldline.

No worldline, no particle, even if the point of contact is a lightlike zero interval. It so happens, that close up all "contact" resolves as 4D interval contact. A squiggly line in a Feynman diagram indicates but doesn't change that.
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Re: Worldly Wisdom

Postby hyksos on November 18th, 2019, 3:51 pm 

Faradave » November 18th, 2019, 7:57 am wrote:
hyksos wrote:claim on this forum that "photons don't exist". I will point out why the above quote says the exact opposite of that. … -- particles manifest.

Which is not to deny that phenomena other than "particles" (e.g. waves, quantum states) may also have manifestations.

But consider two massive particles manifesting themselves by classical collision. Each particle has a worldline. Their single point of contact is not a worldline.

No worldline, no particle, even if the point of contact is a lightlike zero interval. It so happens, that close up all "contact" resolves as 4D interval contact. A squiggly line in a Feynman diagram indicates but doesn't change that.


No worldline, no particle, even if the point of contact is a lightlike zero interval.

I'm going to have to apologize to several people on this forum.

In many years passed, I have been ignoring Cramer's Transactional Interpretation of QM. My reason for avoiding it was that I did not understand it. In recent weeks I have doused my self up the neck in CTI, and I am gaining a much clearer understanding.. and a newfound admiration for it.

At this juncture, I could either write about CTI in a lengthy reply post appearing here in this thread -- or my other option -- create an entirely new thread on it. Due to my lack of confidence in communicating the topic I have just learned, I am going to opt with the former.

A squiggly line in a Feynman diagram indicates but doesn't change that.

I think this pretty much characterized my thinking about the topic of a photon's existence and trajectories. I was taking the squiggles very seriously as ontological baggage. I think Feynman himself would have warned me to be more careful with the squiggles. My thinking (in my head) was something along "But! But! Field Theory has the trajectories in the diagrams! "

The Feynman diagrams are used on every particle, and that was my jumping-off point about photons being "first class". In any case, I can set off in a completely different direction now...
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Re: Photons: The Argument for their Existence?

Postby hyksos on November 18th, 2019, 5:16 pm 

CTI
Cramer's Transactional Interpretation. Okay. Lets do this.

I had two choices for how to write about this topic. Either I could go with a Mach–Zehnder , or use the Princeton professor's office. The Mach-Zehnder is way easier for people who think diagrammatically, while the Princeton office window example is more 'narrative' in tone. I'm going with the office window example ( sorry to those who think best in diagrams ).

Is CTI the same thing as Wheeler-Feynman Absorber Theory? I don't know. But who cares, lets press on.

At Princeton, a physics professor sits at his desk in his office. There is a window in the office that leads out to a parking lot outside with a few shiny cars. A photon approaching the office window will either reflect from the window and go back outside, or pass through the window and come into the office to land on a bright patch on the ceiling. At a particle shallow angle, the probability of reflect-back-out versus transmit-into-office is 50/50. A flip of a coin.

In all of nature, what decides or determines what choice the photon makes? The professor can justifiably tell a visitor that the photon of sunlight that just came into his office acted that way indeterminately. The photon's choice to reflect or transmit is perfectly random, and determined by nothing in the past or anywhere else in the universe. That's a sound, pragmatic answer. Pragmatic in the sense that we haven't fallen off into the deep ends of interpretations of quantum mechanics.

So it's a mystery to science why the photon did what it did. Even the distinguished professor doesn't know how that happened -- well -- unless that professor is John Cramer.

To Cramer there are certain things in the universe that determined the photon's choice. I will list them,

absorber : where the photon ended up inside the office. The 'sink' if you want.

emitter : where the photon began in the parking lot. aka 'source'

Retarded Wave : our familiar wave function, Schroedinger wave, or whatever you wanna call it. "Retarded" because it started along in spacetime before and advanced wave.

Advanced Wave : some mysterious Cramer-only object. It acts just like a the usual work-a-day wave function, but moves backwards in time. "Advanced" because it started along in spacetime after the Retarded Wave.

(using R-wave and A-wave to avoid having to type a lot.)

Even though R-wave and A-wave are called "waves" , the correct way to visualize them is spheres centered around a source point in spacetime. When these "waves" propagate it is exactly like a sphere expanding from that point.

The R-wave moves forwards in time. This is the familiar wave function we all know and love from 1st semester quantum. It begins its journey on a car parked at Princeton and expands outwards as time progresses through the campus air and collides with various objects on the way, trees, sidewalk, buildings and their windows -- sort of like a shockwave from an explosion. One piece of the R-wave encounters the window to the aforementioned office.

The A-wave though. This is tricky. It propagates backwards in time. In formal terms, the A-wave "begins" inside the office somewhere on the ceiling and expands outwards from that point... but does this "expansion" backwards in time. In particular, this A-wave "begins" on the ceiling's spacetime point in the future. This is why it is given the name "Advanced".

(Although these next visuals should not be taken seriously) they will help the reader to visualize the A-wave in more human terms. What would a backwards-in-time propagating wave look like to a human standing nearby? Visualize a video of an explosion with a shockwave. Now play the video in reverse. The shockwave is spread all over the landscape at the end of the video ... then it coalesces into a point at the beginning of the video. (We are watching from end-to-beginning. Reversed) You might even say the coalescing into a point is in the 'proper future' of the observer who presses 'reverse' button on the video player.

Hence the quote-un-quote "emission" of the A-wave is in the future of a forward-time moving observer. And a the forward-time observer "experiences" A-wave as a spherical wave coalescing into a point in space.

Now that the groundwork is down, lets translate this craziness into the Princeton photon.

Let time t=0 correspond in regularly experienced time (forwards), such that it is the moment where we would say the sunlight photon was reflected from the shiny parked car. At this spacetime location the R-wave is squeezed to a point on the surface of the car's paint. On the other hand, the A-wave is still spread out all over the campus. It will only be quote-un-quote "emitted" from the office ceiling in the future, which to our wristwatch is watch is something like t=2 microseconds. The R-wave spreads. But the A-wave coalesces, joining up from many pieces of the environment and shrinking back into the office window, finally all meeting up at the spacetime point at the ceiling.

In more formal terms, the choice to reflect means the photon would have been absorbed by some tree, or likely some brick on some nearby building on campus. Whereas the choice to enter the office window by refraction entails the photon would be absorbed by an electron in the ceiling.

Cramer asserts that the choice to reflect or transmit into office is determined at the moment of the photon's emission from the car surface. In particular, the ontological commitment here is that it is determined at this place in spacetime. The helpful visualization is to remember that the photon has a 50/50 chance to take either path. The two ends of the either path will contain two absorbers. Namely

1. the brick absorber for reflected path.

2. the office ceiling absorber for the transmitted path.

Both brick and ceiling emitted an A-wave in the future, which propagated into their proper past. So the car photon is acted upon as a competition between brick-absorber-A-wave and ceiling-absorber-A-wave. The deterministic mechanism is : whichever of those A-waves was on top of the surface point of the car at the time of the emission of the photon.

The car-emitter-R-wave expands from there, and "follows" the ceiling-absorber-A-wave as it coalesces back into the window and into the office, will all the requisite changing of direction inherent in refraction through glass. The R-wave moves in lockstep, as it were, with the A-wave.

{insert animated GIF of expanding circle moving along with a shrinking one.}

In publications, acolytes of CTI go on to explain how a purely waves-only picture is sufficient to account for what is observed. They stop referring to photons a few pages in, and start saying that these emitters and absorbers perform a "transaction" -- hence the Transactional Interpretation. Many of them openly write :

"There are no photons".
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