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 Photon path .. ALT Junior Member Posts: 45 Threads: 2 Joined: May 2016 Reputation: 0 06-05-2016, 05:19 AM A very helpful reply, secur. One thing for the minute. You said; The speed of light in vacuum is constant and (a fortiori) not affected by transmitter motion or anything else. Fine. That's pretty clear. And I would say with certainty that the community agrees. Now, one quick question. WHY speed and not velocity? (and yes, I understand the difference between the two). I beg you refrain from 'because SR says so', because it seems that's what we're (or at least I'm) questioning here. secur Member Posts: 165 Threads: 0 Joined: May 2016 Reputation: 0 06-05-2016, 05:56 AM Because "speed" is not controversial but "velocity" is. I don't want to commit to it one way or the other; neither assert, nor deny, that velocity is, or is not, affected by transmitter motion. That's what I intend to nail down ASAP - in days, or months, whatever it takes. ALT Junior Member Posts: 45 Threads: 2 Joined: May 2016 Reputation: 0 06-05-2016, 01:06 PM Hi secur. I was going to write a point for point reply to yours and Schmelzers edifying recent posts, but for brevity I will just say the following, as it seems obvious that our issue distils to this. You confirmed Johnson's comments about reflection occurring with no speed loss, and you added that the physics community also agrees with this. To me, this is HUGELY important, as it goes to the issue of the emission point of the single photon of the laser emitter in my thought experiment, and my contention that such emission occurs in no time. Let me explain my thinking here. If reflection involves NO speed loss, then it can equally be said that it is an instantaneous event, i.e., it occurs in NO time. It is the same as saying .. “look, I just picked point B in that photons path, but in doing so, I didn't slow it down .. therefore, point B is a point of zero dimension” So if reflection of the photon is instantaneous, you can say that emission from a laser is also instantaneous and if you are too stubborn to agree (not you personally) I would then retort .. “well, just make the photon in my thought experiment emit from a reflecting surface. THEN, it's gotta be instantaneous". Put simply, I suspect the emission of a photon is an instantaneous event occurring in no time, and instantly going at full throttle, i.e., c. Therefore, it has NO OPPORTUNITY to be affected by ANY motion of the emitter – transverse or otherwise. And THAT, seems to me, first rate proof of absolute motion / rest. On the issue of speed or velocity concerning the second postulate. OK, I accept that it means to say speed not velocity and that the physics community also means speed. Which is precisely why I've narrowed it down to ONE SINGLE PHOTON. We MUST know that a photon fired from a laser gun is going to have a SPECIFIC direction, therefore .. it is now VELOCITY obeying the c constant. In your most recent, above, in answer to my question “why speed and not velocity” you replied “Because "speed" is not controversial but "velocity" is". Am I to understand from that, that the physics community bases it's theories on levels of controversy ? Rhetorical – the answer is probably, yes. I am agreeing more and more with Calkin's  view that if Einstein had the benefit of a laser, he would have skipped SRT. Your comment that when we really look at light closely, it's a lot more complicated than previously thought – I tend to agree, but add that it might be much LESS complicated if we didn't look at it through our present, tainted glasses. Yes, please look at Cedarholm .. 'nail it down ASAP' as you say .. a worthwhile endeavour. I hope to hear from you soon. Schmelzer Administrator Posts: 215 Threads: 31 Joined: Dec 2015 Reputation: 0 06-05-2016, 01:40 PM Something may happen in a very small domain in very short time, so that in comparison with the size of the whole experiment this looks point-like and instantaneous. It does not follow that this happens instantaneously in a single point. What results - a photon - has some sort of size, the wave length. And even if the wave moves all the time with speed of light, it needs some time for a wave of the size of one wave-length to go through a single point. So you cannot even define an EM wave by fixing, however, the EM field in one point at one moment. But if you cannot even define it, how can you create it? secur Member Posts: 165 Threads: 0 Joined: May 2016 Reputation: 0 06-06-2016, 01:11 AM ALT wrote ----- So if reflection of the photon is instantaneous, you can say that emission from a laser is also instantaneous and if you are too stubborn to agree (not you personally) I would then retort ..“well, just make the photon in my thought experiment emit from a reflecting surface. THEN, it's gotta be instantaneous". ----- Sorry that doesn't work, because SR (and Lorentz, and established physics) says photon reflection angle is NOT affected by the motion of the reflecting surface! Only when the photon is emitted does the motion matter - in my view, anyway. ALT wrote ----- In your most recent, above, in answer to my question “why speed and not velocity” you replied  “Because "speed" is not controversial but "velocity" is". Am I to understand from that, that the physics community bases it's theories on levels of controversy ? Rhetorical – the answer is probably, yes. ----- No, it's only me trying to avoid controversy with that phrasing. Indeed I'd tend to say establishment physics takes the opposite approach. They seem to want to deliberately provoke controversy. ALT wrote ----- I hope to hear from you soon. ----- Don't hold your breath! ALT, I intend to get to the bottom of this. I don't know how long that will take. ALT Junior Member Posts: 45 Threads: 2 Joined: May 2016 Reputation: 0 06-06-2016, 12:01 PM (This post was last modified: 06-06-2016, 12:33 PM by ALT. Edit Reason: correction ) Schmelzer wrote; Something may happen in a very small domain in very short time, so that in comparison with the size of the whole experiment this looks point-like and instantaneous.  It does not follow that this happens instantaneously in a single point.  What results - a photon - has some sort of size, the wave length.   And even if the wave moves all the time with speed of light, it needs some time for a wave of the size of one wave-length to go through a single point.  So you cannot even define an EM wave by fixing, however, the EM field in one point at one moment.  But if you cannot even define it, how can you create it? ------------------------------------------------------------------------------------------- Exactly what does one mean by 'a single point' ? What else than zero ? Take a time line of two seconds, and mark off a mid point - a single point (your words). What is that time value of that single mid point ? Zero. The first second is complete in itself, as is the second. Get as infinitesimal as you like - it is still zero. Therefore, no ADDITIONAL time is involved in that mid point. It is zero. Convert those two seconds to light seconds. Same thing applies, if you say that no speed is lost and that c is maintained. The crossing of that point (of zero temporal value) is instantaneous. perhaps a startling thing to consider, but .. where is my logic failing ? Interestingly, I searched for a precise definition of 'point' from a physics perspective, and it was difficult to find. But I found this fascinating thing; https://en.wikipedia.org/wiki/Point_particle For example, for the electron, experimental evidence shows that the size of an electron is less than 10 (to the minus) 18 m.[6] This is consistent with the expected value of exactly zero. Exactly zero - now there's a surprise. And it's specifically about an electron. PS - the separation marks between posts seem to have disappeared, so I've added the dotted line to differentiate between your post and mine. Hi secur. Firstly, please understand, I am not pressing you to continue with this. I am merely replying. ALT wrote ----- So if reflection of the photon is instantaneous, you can say that emission from a laser is also instantaneous and if you are too stubborn to agree (not you personally) I would then retort ..“well, just make the photon in my thought experiment emit from a reflecting surface. THEN, it's gotta be instantaneous". ----- Sorry that doesn't work, because SR (and Lorentz, and established physics) says .. That 'because' may be circular if it is SR that I  am questioning. .. photon reflection angle is NOT affected by the motion of the reflecting surface! Only when the photon is emitted does the motion matter - in my view, anyway. Please see my comment to Schmelzer above. No speed loss .. point of reflection .. instantaneous! ALT wrote ----- In your most recent, above, in answer to my question “why speed and not velocity” you replied  “Because "speed" is not controversial but "velocity" is". Am I to understand from that, that the physics community bases it's theories on levels of controversy ? Rhetorical – the answer is probably, yes. ----- No, it's only me trying to avoid controversy with that phrasing. Indeed I'd tend to say establishment physics takes the opposite approach. They seem to want to deliberately provoke controversy. OK, noted. Controversies aside, we agree the physics community uses the word speed in the second postulate. But I legitimately converted that speed to velocity in my thought experiment. I said earlier; Which is precisely why I've narrowed it down to ONE SINGLE PHOTON. We MUST know that a photon fired from a laser gun is going to have a SPECIFIC direction, therefore .. it is now VELOCITY obeying the c constant. You didn't comment on that. ALT wrote ----- I hope to hear from you soon. ----- Don't hold your breath! ALT, I intend to get to the bottom of this. I don't know how long that will take. Secur, I am not rushing you or trying to continue this conversation, which is getting somewhat repetitive, in any case. I hope you do get to the bottom of it - at some .. point :-) Schmelzer Administrator Posts: 215 Threads: 31 Joined: Dec 2015 Reputation: 0 06-06-2016, 02:53 PM What one means by 'a single point' ?  In fact, I couldn't care less.  It's not me who claims that something really happens only in a single point.  More seriously, points are only an idealization.  What is idealized is a small region, small in comparison with the other distances which play a role in the particular question.  This small region may, anyway, contain information about directions, or, similarly, the "moment of time" or so can contain information about velocities. ALT Junior Member Posts: 45 Threads: 2 Joined: May 2016 Reputation: 0 06-07-2016, 06:30 AM (This post was last modified: 06-07-2016, 06:52 AM by ALT.) Secur, just reading through our prior comments, there is something I want to clarify; Don Johnson (from his paper) A similar confirmation of Lodge's insight can be found in the assumption (not exclusive to SRT) that light bouncing back and forth between front-surfaced mirrors loses no time during the reflection process (i.e., absorption and re-emission process). ALT (to secur) Firstly, what is the current view of the physics community on this ? And secondly, what is your view ? Secur; Physics community agrees with that. Of course reflection involves a phase change, and momentum loss, but no speed loss. ALT; So if reflection of the photon is instantaneous, you can say that emission from a laser is also instantaneous and if you are too stubborn to agree (not you personally) I would then retort .. “well, just make the photon in my thought experiment emit from a reflecting surface. THEN, it's gotta be instantaneous". Secur; Sorry that doesn't work, because SR (and Lorentz, and established physics) says photon reflection angle is NOT affected by the motion of the reflecting surface! Only when the photon is emitted does the motion matter - in my view, anyway. Now, Johnson's comments are clear, as above. He made no mention of 'only angles' not been affected – he mentioned the whole reflection process – absorption, re-emission, etc. Not been aware of the physics communities prevailing view on this, I asked you what it was, and you said they agree. But in your final quote above, unless I am mistaken, you say something quite different. Can you please clarify, and also, distinguish more clearly between the communities view and your view. (06-06-2016, 02:53 PM)Schmelzer Wrote: Hi Schmelzer; What one means by 'a single point' ? Either something or nothing .. apparently ... In fact, I couldn't care less.   Lot's of wiggle room there .. It's not me who claims that something really happens only in a single point.  By proxy, it seems the scientific community is saying this if they agree that the reflection process happens instantaneously, as seems to be the case. More seriously, points are only an idealization.  What is idealized is a small region, small in comparison with the other distances which play a role in the particular question.  This small region may, anyway, contain information about directions, or, similarly, the "moment of time" or so can contain information about velocities. I don't necessarily disagree, in fact, I'm a great fan of Ouspensky who (together with Kant, I believe) says much the same. But that tends now to philosophy .. even mysticism. From a current physics point of view, however, can you really have a few bob .. sorry, bucks for you Americans .. each way ? The CRUX; A single photon fired from a laser emitter has velocity, and, consistent with the second postulate, is independent of emitter motion. Absolute motion / rest ! QED ! Schmelzer Administrator Posts: 215 Threads: 31 Joined: Dec 2015 Reputation: 0 06-07-2016, 07:00 AM Some may say "instantaneously", but this is sloppy speech, nothing serious. "Too short to be relevant for the actual problem" would be more appropriate. I do not see any mysticism in the idea that we cannot decide by any observation if something really happens in a single point or only in a small region, too small to be seen in details. Of course, our theories can describe something down to arbitrary small distances. But in most cases, these theories disqualify themselves, because for arbitrary small distances they give some singularities. Like the Newtonian $$\frac{1}{r}$$ potential. I'm not an American, not a native English speaker, and do not understand your last point. ALT Junior Member Posts: 45 Threads: 2 Joined: May 2016 Reputation: 0 06-07-2016, 11:22 AM (06-07-2016, 07:00 AM)Schmelzer Wrote: Some may say "instantaneously", but this is sloppy speech, nothing serious.  "Too short to be relevant for the actual problem" would be more appropriate.  I do not see any mysticism in the idea that we cannot decide by any observation if something really happens in a single point or only in a small region, too small to be seen in details.  Of course, our theories can describe something down to arbitrary small distances.  But in most cases, these theories disqualify themselves, because for arbitrary small distances they give some singularities.  Like the Newtonian $$\frac{1}{r}$$ potential.   I'm not an American, not a native English speaker, and do not understand your last point. My last point. I meant a 'bet each way'. A 'bob' is a term for an English shilling. Thus, a bob / buck (dollar) each way. Just my quirky (although my wife would say 'stupid') sense of humour. No offence was intended. Yes, sloppy speech. I would suppose that in the world of particle physics, at that fundamental level of reality, instantaneous or not makes a world of difference. I can't see how it could not. But it seems you are saying  that 'in no time/space' is approximately the same as 'in some time/space' ? I have difficulty in accepting that. Anyway, the issue of whether reflection is instantaneous or not was somewhat an aside. Getting right back on track, I rest my case on; A single photon fired from a laser emitter has velocity, and, consistent with the second postulate, is independent of emitter motion. Thus, absolute motion / rest can be proven. « Next Oldest | Next Newest »