# Thread: What will I see if the mirror will move very fast?

1. Ok so far the scores:
No: 2 (Jilan, KJW)
Yes: 2 ( Boing, X0X)
Any more willing to say one way or another? .....

2. Originally Posted by Jilan
Ok so far the scores:
No: 2 (Jilan, KJW)
Yes: 2 ( Boing, X0X)
Any more willing to say one way or another? .....
Physics is not a sport. Given your basic errors in doing simple physics exercises, your score doesn't count anyways.

3. Originally Posted by write4u
I have and am still waiting for a direct and specific answer to the question of what the observer sees.

a) does observer see him/herself distorted? yes? no? This was the crux of the original question, IMO

The Terrel effect will deform the image because light paths are not equal. I explained this earlier in the thread.

4. Originally Posted by KJW
If the Law of Reflection holds regardless of the motion of the mirror parallel to its plane, then all rays of light will be unaltered by such motion, and images will not be affected.
It was my first intuitive choice, which prompted my question if the observer would even know if the mirror was moving at all. IOW, the obsevers reflection would remain unchanged and remain at a 90 degree angle.

To me this should be a fascinating question for "relativity" enthusiasts.

5. Originally Posted by write4u
It was my first intuitive choice, which prompted my question if the observer would even know if the mirror was moving at all.
Yes, the observer will know when the mirror starts moving. The faster the mirror will move, the more noticeable the Terrell effect.

6. Originally Posted by x0x
Yes, the observer will know when the mirror starts moving. The faster the mirror will move, the more noticeable the Terrell effect.
But a mirror cannot exhibit a terrell effect, there is no observable movement, how would you know which is the condensed mirror and which is the elongated mirror? If you cannot see the beginning and the end of a perfect mirror there is no reference point to gage the length. Come to think of it, perhaps graininess, but
wiki.
Terrell rotation or Terrell effect is the name of a mathematical and physical effect. Specifically, Terrell rotation is the distortion that a passing object would appear to undergo, according to the special theory of relativity if it were travelling a significant fraction of the speed of light. This behaviour was described independently by both James Terrell and Roger Penrose in pieces published in 1959,[1][2] though the general phenomenon was noted already in 1924 by Austrian physicist Anton Lampa.[3]
I don't think this applicable in this case. If it is a perfecrt mirror and you have only a narrow window of observation, nothing changes! All the observer sees is his/her reflection in the mirror and will not know if the mirror is moving or not.

How could we test this? How about firing a photon at the moving mirror and see if it is reflected back to the emitter without deviation.

7. Terrell rotation is the distortion that a passing object would appear to undergo
The reflection image is not a "passing object". It is the mirror that is in motion, not the reflection images

8. Originally Posted by KJW
The reflection image is not a "passing object". It is the mirror that is in motion, not the reflection images
You can view the mirror as stationary and you as being in motion with respect to it. You will not understand this issue until you learn raytracing.

9. Originally Posted by write4u
But a mirror cannot exhibit a terrell effect, there is no observable movement, how would you know which is the condensed mirror and which is the elongated mirror?
Has nothing to do with any "condensed" or "elongated" mirrors.

How could we test this? How about firing a photon at the moving mirror and see if it is reflected back to the emitter without deviation.
You can't really test it but there are many simulations for this effect. I pointed out the links to such simulations several times in this thread.

10. Originally Posted by x0x
You can view the mirror as stationary and you as being in motion with respect to it.
Even in that case, the image of your reflection is still not moving with respect to you.

11. Originally Posted by x0x
You can view the mirror as stationary and you as being in motion with respect to it. You will not understand this issue until you learn raytracing.
You cannot see a difference between an observer (an object) in motion at high speed and a perfectly reflective surface which retains its reflective ability unaffected by the speed at which it passes. It may change, but cannot be noticed by the observer.

12. Originally Posted by KJW
Even in that case, the image of your reflection is still not moving with respect to you.
In raytracing mirrors act as light sources. By virtue of the relative motion between you (the observer) and the mirror you will get a Terrell effect. You will not understand this issue until you change your stance and you learn raytracing. The links I provided, contrary to your claims, are not red herrings, they are very helpful in you understanding the issue.

13. Originally Posted by write4u
You cannot see a difference between an observer (an object) and a perfectly reflective surface which retains its reflective ability unaffected by speed?
I can see it very well. While mirrors retain their capabilities, the also can change frequencies and distort the geometry. So , what is your point?

14. Originally Posted by x0x
I can see it very well. While mirrors retain their capabilities, the also can change frequencies and distort the geometry. So , what is your point?
I am trying to get clarification. ok, so as I understand you, a mirror passing at near "c" would "smear" the reflected image because it does exert a transverse force on the "reflection" of the emitted light (say a photon) by the observer?

15. Originally Posted by x0x
In raytracing mirrors act as light sources.
But a reflection from a moving mirror is not a moving light source.

16. As I understand it the Terrel effect occurs when an observer views a relativistically moving object. Why should it apply to co located observers too?

17. Originally Posted by Jilan
As I understand it the Terrel effect occurs when an observer views a relativistically moving object. Why should it apply to co located observers too?
I think it's reasonable to assume that an image in apparent relativistic motion relative to an observer have the same kinematic relativistic effects as a real object.

18. Originally Posted by write4u
You cannot see a difference between an observer (an object) in motion at high speed and a perfectly reflective surface which retains its reflective ability unaffected by the speed at which it passes. It may change, but cannot be noticed by the observer.
.
Some more perspectives.

You cannot see a mirror. And that's the point. He does not emit light.

But if you admit that he his reflecting light, knowing were they come from and where they go is crucial. Feynman explanation is the best. I don't see how this kind of added path won't be skewed. Even in the up-down axis (path are longer)

KJM introduce other situations, and each time I also get the conviction that frequencies would also changes, but then it is me who is wrong ;-)

Also looking at a mirror implies movement. When you look at you left ear and when you look at your right, the line of sight changes. (like if your image rotates a little)
You are not looking at your picture glued on a 2D mirror. You'll notice instantly the difference.

19. Originally Posted by KJW
But a reflection from a moving mirror is not a moving light source.
This is a non-sequitur, I disproved your DIFFERENT claim, that "a mirror is not a moving light source". Why are you moving the goalposts of the debate?
Until you make a shift in your paradigms and start learning (relativistic) raytracing, you will not gain full understanding of the issue.
Let's try an easier way: the approaching train will appear rotated away from the viewer (see the many links I pointed out) due to the Terrell effect. The mirror stuck to the side of the train and the images on it will be twisted just the same.

I think it's reasonable to assume that an image in apparent relativistic motion relative to an observer have the same kinematic relativistic effects as a real object.
Agreed 100%.

20. Ok, so the image has this distortion in the mirror frame, but when it gets back the observer again isn't it negated?

21. Originally Posted by Jilan
As I understand it the Terrel effect occurs when an observer views a relativistically moving object. Why should it apply to co located observers too?
1. Co-located observers with "what"?
2. Where did you get multiple observers?

22. Originally Posted by x0x
1. Co-located observers with "what"?
2. Where did you get multiple observers?
I meant observers co located with the source. Or, in this example, the source.

23. Originally Posted by Jilan
I meant observers co located with the source. Or, in this example, the source.
Try to phrase the question properly.

24. Originally Posted by x0x
Try to phrase the question properly.
Sorry, I thought it was obvious given the context (a mirror).

25. Originally Posted by Jilan
Sorry, I thought it was obvious given the context (a mirror).
Yes, the question was obvious. An obvious word salad.

26. Originally Posted by x0x
Yes, the question was obvious. An obvious word salad.
X0x, are you feeling OK? You seem a bit angry today?

27. Originally Posted by Jilan
X0x, are you feeling OK? You seem a bit angry today?
No, just amused by your crankish posts.

28. Originally Posted by Jilan
Originally Posted by x0x
Yes, the question was obvious. An obvious word salad.
X0x, are you feeling OK? You seem a bit angry today?
Get a room. Will ya ?

29. Originally Posted by Boing3000
.
Some more perspectives.

You cannot see a mirror. And that's the point. He does not emit light.
Actually, this is not correct. We see mirrors all the time. They do act as light sources. Actually, all objects in a scene (even the non-shinny ones) act as light sources. There is a field of physics (raytracing) that deals with these effects.

30. I meant mirror do not shine. OK, apple do not shine either, that's what I keep repeating to Steve before a sack me.

I suppose that's what you meant, the light reflected became mirror's light.

I stand corrected.

31. Originally Posted by x0x
Actually, this is not correct. We see mirrors all the time. They do act as light sources. Actually, all objects in a scene (even the non-shinny ones) act as light sources. There is a field of physics (raytracing) that deals with these effects.
SpeedFreak's comments recently suggested to me that it was time to take everyone off my ignore list. It's good for me because I absolutely detest arguing and name calling and
I hate holding grudges even more. So I've decided to start from scratch.

What do you mean when you use the term "source" of light?

32. If you shoot light at a mirror that is moving towards you, does that light reflect back to you with a blueshift?

If you shoot light at a mirror that is moving away from you, does that light reflect back to you with a redshift?

If the answer to the above questions is yes, then the motion of the mirror affects the light.

If the answer to the questions is no, then the motion of the mirror does not affect the light.

Correct?

33. @x0x,

question: at what point does an image become a fixed image in a moving mirror? The mirror does not retain any physical properties of the light it reflects, it just reflects what it sees @ "c", correct?

If it sees the same stationary image it will always reflect the stationary image. Note that earlier I asked if the reflected image becomes "smeared" because the reflected image is subject to transverse motion.

I am not sure if that question has been answered yet. At what point does any relativistic effect become apparent? On the mirror itself or "on the way back " to the observer?

I read the wiki article on ray tracing and to me did not address the question as posed. It seems to be connected with virtual reality more than our RW xample. However I did run across this, Specular Rreflection
Specular reflection is the mirror-like reflection of light (or of other kinds of wave) from a surface, in which light from a single incoming direction (a ray) is reflected into a single outgoing direction. Such behavior is described by the law of reflection, which states that the direction of incoming light (the incident ray), and the direction of outgoing light reflected (the reflected ray) make the same angle with respect to the surface normal Specular reflection - Wikipedia, the free encyclopedia
question: if the "surface normal" is a moving perfect mirror located @ 90% right angle to the observer, does the speed of the surface normal affect and alter the specular reflection of a stationary object?

34. Originally Posted by Physicist
.

First off I have a question about what you said above, i.e. you said that a mirror acts like a light source.
Yes, this is a well known fact in raytracing.

Do you hold that objects that don't generate light such as a light bulb etc are light sources merely because they emit light?
There is no answer to this question because it doesn't make sense.

If so then what do you mean when you use the term "source" of light?
Anything that either generates or reflects light. There are some excellent raytracing links that I suggested eralier in the thread, you might want to have a look at them.

35. Originally Posted by write4u

I am not sure if that question has been answered yet. At what point does any relativistic effect become apparent? On the mirror itself or "on the way back " to the observer?
On the way back to the observer. Did you see the links I recommended earlier in the thread?

question: if the "surface normal" is a moving perfect mirror located @ 90% right angle to the observer, does the speed of the surface normal affect and alter the specular reflection of a stationary object?
In general, mirrors increase or decrease the frequency of the light incoming from other light sources, depending on the relative motion between mirror , light source and observer. I addressed this issue mathematically earlier in the thread. It is not along thread, so it should be easy to find the post.

36. Originally Posted by SpeedFreek
If you shoot light at a mirror that is moving towards you, does that light reflect back to you with a blueshift?

If you shoot light at a mirror that is moving away from you, does that light reflect back to you with a redshift?

If the answer to the above questions is yes, then the motion of the mirror affects the light.

If the answer to the questions is no, then the motion of the mirror does not affect the light.

Correct?
The short answer is that the motion mirror-source-observer affects the frequency of the observed light. The way frequency is affected is explained in post 36.

37. Originally Posted by x0x
On the way back to the observer. Did you see the links I recommended earlier in the thread?
OK, that i can understand and accept that time of travel of the image to and back from a fast moving mirror may cause a delay in the ability of the observer to receive the reflected light, but then my next question was, in which way would this relativistic effect become apparent if the image is constantly reflected by the passing flawless mirror. Would the result be an accurate reflection, but in in a shifted position?
If so, which way will it shift, to the left of to the right of the observer due to the reversal of the reflected observer? Or would the reflected image become elongated ?

In general, mirrors increase or decrease the frequency of the light incoming from other light sources, depending on the relative motion between mirror , light source and observer. I addressed this issue mathematically earlier in the thread. It is not along thread, so it should be easy to find the post.
You are correct that "in general" there will be a natural aberration, but in this case we are speaking of a hypothetical "perfectly flawless mirror" which causes no aberration of any kind. It reflects the observer exactly as it receives the image, but it reflects the image in reverse. In the reflected left is right and right is left, which really confuses me trying to visualize any relativistic aberration.

38. Originally Posted by x0x
The short answer is that the motion mirror-source-observer affects the frequency of the observed light. The way frequency is affected is explained in post 36.
IMO, post 36 assumes a different scenario from the one in front of us. It is not relevant in this context of the OP. But I admit all thse equations are meaningless to me in context of visualizing the results.

39. Originally Posted by x0x
Yes, this is a well known fact in raytracing.
Please show me at least one textbook where this "well known fact" is found. If you can't find one then don't bother. To me this is mere semantics and I have no interest in it.

40. Originally Posted by SpeedFreek
If you shoot light at a mirror that is moving towards you, does that light reflect back to you with a blueshift?
Yes. To see this one merely transforms to the rest frame of the mirror. In this frame the mirror to be at rest. When a photon with frequency f strikes it then it bounces off with the same frequency f. When you use these facts in applying the Lorentz transformation you'll get a blue shift. Same argument applies with a red shift.

Originally Posted by SpeedFreek
If the answer to the above questions is yes, then the motion of the mirror affects the light.

If the answer to the questions is no, then the motion of the mirror does not affect the light.

Correct?
Correct.

41. Originally Posted by x0x
There is no answer to this question because it doesn't make sense.
Forget it. I wrote it down wrong and I can't recall what I was asking.

Originally Posted by x0x
Anything that either generates or reflects light.
Where did you get this definition from?

Originally Posted by x0x
There are some excellent raytracing links that I suggested eralier in the thread, you might want to have a look at them.
There are 139 posts here. How am I supposed to find it in that many posts?

42. Originally Posted by Physicist
Forget it. I wrote it down wrong and I can't recall what I was asking.

Where did you get this definition from?
Raytracing books and papers.

There are 139 posts here. How am I supposed to find it in that many posts?
Go to the beginning of the thread. Start with post 6.

43. Originally Posted by SpeedFreek
If you shoot light at a mirror that is moving towards you, does that light reflect back to you with a blueshift?

If you shoot light at a mirror that is moving away from you, does that light reflect back to you with a redshift?

If the answer to the above questions is yes, then the motion of the mirror affects the light.

If the answer to the questions is no, then the motion of the mirror does not affect the light.

Correct?
Correct. But that does not give any answers relevant to the scenario as posited. Observer is always at the same distance from the mirror, it just passes the observer unnoticed to the observer. The only way is to see if the reflected light in the passing mirror is in any way affected by the speed at which the mirror passes the observer, but always presents a flawless reflective surface perpendicular to the observer.

The mirror does not move away or toward the observer. The mirror is passing the observer at right angles so the distance between observer and mirror is always the same. Moreover the observer has a narrow field of view which cannot observe anything but his own image as reflected in the passing mirror.

The question is if a perfectly flawless moving mirror will reflect the image straight back to the observer who is stationary and perpendicular to the mirror or if the observer will see the reflection having been altered in any way when it arives back at the observer.

44. Originally Posted by x0x
Raytracing books and papers.
First off, the only ray tracing books that I can see in Amazon don't appear to be very scientific. They appear technical in nature, i.e. base on applications rather than physics. Most aren't even in English either. I asked where "you" read it. What textbook did you read it from or see it in? I can pretty much tell you where I learned nearly every physics term that I know. Do you?

Here's a website where you can download just about every textbook that there is - Electronic library. Download books free. Finding books
Please search for such a raytracing book and tell me the page number of where it's found.

Here's a website where you can download many papers in science and technology- Electronic library. Download articles free. Finding articles
Please search for such a raytracing paper and tell me the page number of where it's found.

Originally Posted by x0x
Go to the beginning of the thread. Start with post 6.
And do what?

45. Originally Posted by Physicist
First off, the only ray tracing books that I can see in Amazon don't appear to be very scientific.

I don't see anything in your background that qualifies your opinion to be valid. You are simply criticizing a subject that you know nothing about. Most authors are PhD's, some are full professors with double degrees (CS/math and physics).

They appear technical in nature, i.e. base on applications rather than physics.
This is , of course, false. The people writing these books and papers are , in many instances, professional physicists, with advanced degrees. You only have a BA.

Most aren't even in English either.
Your list of objections gets more ridiculous by the whine.

I asked where "you" read it. What textbook did you read it from or see it in? I can pretty much tell you where I learned nearly every physics term that I know. Do you?
I listed quite a few links. I can list more. I also published on the subject in peer reviewed journals.

Please search for such a raytracing book and tell me the page number of where it's found.
You can do it yourself, you might learn something in the process. You are questioning fundamentals, like the fact that mirror-like object act as light sources, you should find this FACT in EVERY book on the subject. Search for "Global Illumination Model".

And do what?
Click on the link. Can you do that by yourself or you want me to do it for you, like the other basic stuff you asked for me to do for you?

46. Originally Posted by write4u
Observer is always at the same distance from the mirror,
No, he's not, the train ends at some point and the mirror INCREASES its distance from the viewer as the train keeps receding.
Not only that, the train suffers from the Terrell effect, its image is getting twisted away from the viewer.

it just passes the observer unnoticed to the observer.
This part makes no sense, what are you trying to say?

The only way is to see if the reflected light in the passing mirror is in any way affected by the speed at which the mirror passes the observer,
As explained multiple times in this thread, the image is affected.

The mirror does not move away or toward the observer.
This is incorrect, see above.

The mirror is passing the observer at right angles so the distance between observer and mirror is always the same.
This is false, see above.

Moreover the observer has a narrow field of view which cannot observe anything but his own image as reflected in the passing mirror.
You are now making up stuff, nowhere is this condition present.

The question is if a perfectly flawless moving mirror will reflect the image straight back to the observer who is stationary and perpendicular to the mirror
The observer is NOT "stationary to the mirror".

47. Originally Posted by x0x
I don't see anything in your background that qualifies your opinion to be valid.
You know nothing about my background and I see nothing in your background to even suggest that you've ever even opened an optics text.

On the other hand I've studied optics as a physics major and the electrodynamics coursework that is required to understand the physics of light. I've studied classical electrodynamics all the way through in graduate school as well. I've also studied relativistic optics.

Originally Posted by x0x
You are simply criticizing a subject that you know nothing about.
You're ignorance is horribly large in this case. You're unable to grasp the fact that I'm not criticizing anything. You made a claim and I want to see justification for that claim. You're notorious for making claims, which are deeply rooted in ignorance, and then absolutely refuse to back them up. That's business as usual for you. In this case you are trying to give everyone the impression that you're some sort of expert in ray tracing. So I asked you for a specific reference so I could verify it for myself and what did you do? You do what you've done since the late 90's, you start insulting me. I've reported this post and you'll probably be suspended for it now.

Originally Posted by x0x
I listed quite a few links. I can list more.
And yet you want me to search the entire thread and try to determine which one is what you're talking about.

Originally Posted by x0x
I also published on the subject in peer reviewed journals.
Liar. If that's true then prove it. We can't believe anything you say. Your reputation is too stained for that.

Originally Posted by x0x
You are questioning fundamentals, like the fact that mirror-like object act as light sources, ...
This is where you're poor understanding of what you read causes you problems. I know that a mirror acts like a light source. That's a fact of nature. The question I asked was
What do you mean when you use the term "source" of light?
I never questioned that it *acts* like a source. That's a fact. I asked whether you were claiming that it ***IS*** a source. However you were too ignorant to understand that simple fact and so it led you into a wild rampage which might just lead you to being suspended.

Originally Posted by x0x
This is , of course, false. The people writing these books and papers are , in many instances, professional physicists, with advanced degrees. You only have a BA.
You're ignorance is causing you problems again. I have an MS in physics, not a BA. I'm merely 8 credits short of an MS (two classes) which basically means, with my experience, that I have an MS. And that's confirmed by all the physicists I know at MIT who know me very well. Too bad you're unable to e-mail then to verify it but we know that the though scares you. Or is it that you assume that answer you're looking to ask so you think you don't need to ask it? ROTFL

I know physics ten times better than you could ever hope to from what I've seen of your posts. The fact that you were totally unable to follow the derivation which showed that a uniform gravitational field is the result of hollowing out a cavity as discussed months ago. That's a very simple problem to solve and understand and yet it through you for a loop.

Give it up. We all know who you are. We know the sock puppet that you are and we know that you're now lying about your knowledge and education. Give up

It was clearly a mistake to give you another chance but every time I've given you a chance since the late 90's you've messed it up. Back into the ignore list for your inability to cease insults.

48. Originally Posted by x0x
This is , of course, false. The people writing these books and papers are , in many instances, professional physicists, with advanced degrees. You only have a BA.
You're ignorance is causing you problems again. I have an MS in physics, not a BA. I'm merely 8 credits short of an MS (two classes) which basically means, with my experience, that I have an MS. And that's confirmed by all the physicists I know at MIT who know me very well. You could check it since I have many job references from many physicists. A few of them at MIT and others in other states and countries. All of which give me wonderful glowing recommendations. As I said, you could check them but since all of the responses would make you look absolutely foolish you wouldn't dare.

The problem with x0x's claim is that he used the wrong term. The proper way to say what he was trying to was that a mirror acts like a source of images. Nobody correctly states that a mirror is a proper source of light. It's not wrong, per se. It's merely a poor way to phrase it. Sources of light are things that tend to use energy to generate and emit light. A light bulb is a source of light as is an LED and the Sun. Things that we're willing to call a source of light which don't produce energy are things like the sun bouncing off the moon to give us moonlight.

49. Originally Posted by Physicist
You're ignorance is causing you problems again. I have an MS in physics, not a BA. I'm merely 8 credits short of an MS (two classes) which basically means, with my experience, that I have an MS. And that's confirmed by all the physicists I know at MIT who know me very well. You could check it since I have many job references from many physicists. A few of them at MIT and others in other states and countries. All of which give me wonderful glowing recommendations. As I said, you could check them but since all of the responses would make you look absolutely foolish you wouldn't dare.

The problem with x0x's claim is that he used the wrong term. The proper way to say what he was trying to was that a mirror acts like a source of images. Nobody correctly states that a mirror is a proper source of light. It's not wrong, per se. It's merely a poor way to phrase it. Sources of light are things that tend to use energy to generate and emit light. A light bulb is a source of light as is an LED and the Sun. Things that we're willing to call a source of light which don't produce energy are things like the sun bouncing off the moon to give us moonlight.
I am sorry that I offended you but the fact of the matter is that the books on the subject are written by people with PhD's, many of them are full professors that have double degrees (physics and CS, like I do) who have spent a lot of time and work publishing the papers and the books, so it is not right for you to rubbish their work. Also, the fact is that you do have a BA, not an advanced degree, not an MS.

The proper way to say what he was trying to was that a mirror acts like a source of images.
No, I wasn't. Mirrors and mirror-like objects act as light sources. I provided you with a link, you should read it.

Nobody correctly states that a mirror is a proper source of light.
Actually this is a basic fact in raytracing. If you tried opening the books that you rubbished in your prior post, you would have learned that.

50. And x0x is back talking to himself yet again.

51. Originally Posted by x0x
No, he's not, the train ends at some point and the mirror INCREASES its distance from the viewer.
No, the scenarion includes an endless flawless mirror in motion and a stationary observer who can only observe his/her image reflected by the mirror. There are no other points of reference.
This part makes no sense, what are you trying to say?
The mirror is flawlessly perfect and to the observer always presents the same appearance, thus the observer does not know if the mirror has moved or not. The mirror always looks like same mirror to the observer.
As explained multiple times in this thread, the image is affected.
But no one has explained the why and how, other than the reflected image must travel a short distance back to the observer. If the reflected light has transverse motion then the observer will see himself shift as a complete object.
a)This is incorrect, see above.
b)This is false, see above.
Both have been answered, see above.

You are now making up stuff, nowhere is this condition present.
It is implied in the question. There is only a stationary observer looking at his own reflection in a moving (unbeknown to the observer) mirror.
The observer is NOT "stationary to the mirror".
You and I know that, but the observer does not, because the image he sees will alwyas be the same in the endless perfect mirror passing him. The observer only sees himself reflected in the (to him) unchanging mirror.

Set aside any and all "other scenarios", just for the moment.

I am in agreement on the effect of the return time of the reflection as it must travel a short distance back and that takes a small amount of time, which could affect the trajectory. Does this passge of time shift the entire image of the observer or should we expect the observer to see an altered image of him/herself? And again, why and how could this alteration of the observers reflected image be made observable?

I am also in agreement that the mirror is moving relative to the observer but it does not have any properties that can be observed as moving relative to the observer. To the observer the mirror appears to be stationary, and according to relativity, in that case, the observer would appear to be stationary relative to the mirror. No?

52. Originally Posted by write4u
No, the scenarion includes an endless mirror.
No, it doesn't. It includes a "very long mirror", not an endless one. Read here.

53. Originally Posted by x0x
No, it doesn't. It includes a "very long mirror", not an endless one. Read here.
Se, you are avoiding the question by insisting that somehow the observer knows that the mirror is in motion, because it has a beginning and an end.

Ok, if the event occurs before the nose or the rear of the mirror can be observed, what then?
How big do you visualize this mirror? I vizualized it as big enough and long enough to remove any point of reference for the observer for as long as it takes for the observer to see his own image reflected back to him.

Indulge me and look at it from the perspective I have described. I have only simplified the OP question to its basics. Forget the train, the platform, the background, just for a moment. There is only an observer who is unaware that the mirror is moving perpendicular to his/her stationary position, because there are no other points of reference during that event.

54. Originally Posted by write4u
Se, you are avoiding the question by insisting that somehow the observer knows that the mirror is in motion, because it has a beginning and an end.
I am not avoiding anything, I am pointing out that you are not considering the whole setup of the problem. You are missing components and you are making up stuff that isn't there.

Ok, if the event occurs before the nose or the rear of the mirror can be observed, what then?
What "event" are you talking about? This problem is about images forming in a moving mirror.

How big do you visualize this mirror?
As long as a train. The OP tells you that.

I vizualized it as big enough and long enough to remove any point of reference for the observer for as long as it takes for the observer to see his own image reflected back to him.
This is a word salad that cannot be parsed. The train is parked, accelerates away, recedes into the distance, like any normal train.

I have only simplified the OP question to its basics.
No, you haven't, you are making up your own scenario. Why don't you try to work out the OP scenario before making up your own?

Forget the train, the platform, the background, just for a moment. There is only an observer which is unaware that the mirror is moving perpendicular to his/her stationary position, because there are no other points of reference during that event.

If pigs had wings, they would fly helicopter-style. <shrug>

55. Originally Posted by x0x
Originally Posted by KJW
But a reflection from a moving mirror is not a moving light source.
This is a non-sequitur, I disproved your DIFFERENT claim, that "a mirror is not a moving light source". Why are you moving the goalposts of the debate?
Where did I make the claim that "a mirror is not a moving light source"? Anyway, it is a moot point because I have already proven that a mirror moving parallel to its plane obeys the Law of Reflection.

Originally Posted by x0x
Until you make a shift in your paradigms and start learning (relativistic) raytracing, you will not gain full understanding of the issue.
Instead of presuming that I do not know ray-tracing, maybe you should take a closer look at the implications of what I said in post#100:

Originally Posted by KJW
Consider a person standing in front of a stationary mirror. Suppose an observer moves past this person at relativistic speed in a direction parallel to the mirror surface. In the frame of reference of this observer, light is emitted by the person and is reflected by the moving mirror back to the person. From the Law of Reflection in the person's frame of reference, we deduce that the Law of Reflection also holds for a moving mirror in the observer's frame of reference. If the Law of Reflection holds regardless of the motion of the mirror parallel to its plane, then all rays of light will be unaltered by such motion, and images will not be affected.

56. Originally Posted by write4u
Moreover the observer has a narrow field of view which cannot observe anything but his own image as reflected in the passing mirror.
This is unnecessary. If we consider the mirror to be an infinite plane in relativistic motion parallel to the plane, then the entire image, not just the image of ourselves near the normal to the mirror, is unaltered by the motion of the mirror. The crucial issue is the invariance of the mirror plane with respect to its motion, not the motion of the points of the mirror with respect to the observer.

57. Originally Posted by x0x
I am not avoiding anything, I am pointing out that you are not considering the whole setup of the problem. You are missing components and you are making up stuff that isn't there.
No, I have removed stuff which is not pertinent to the question. This also removes all the references and links about trains approaching and receding, which is not pertinent to the question.
What "event" are you talking about? This problem is about images forming in a moving mirror.
And that is not an event? Give me a break please.
As long as a train. The OP tells you that.
We got off the train a long time ago as it clutters the fundamental question of the relationship between the observer and the mirror.
This is a word salad that cannot be parsed. The train is parked, accelerates away, recedes into the distance, like any normal train.[
Show me where the OP describes that scenario. Are you per chance making up stuff that isn't there?
No, you haven't, you are making up your own scenario. Why don't you try to work out the OP scenario before making up your own?
We are working on the scenario as I understand the OP intention. The OP only mentions a train because all relativistic questions use the train scenario. It is merely a prop and cannot be used in the fundamental question of what happens to the reflected image in a moving mirror with no other frames of reference.
If pigs had wings, they would fly helicopter-style. <shrug>
No, that is not correct, even when trying to be sarcastic you are wrong. Sorry, but so far I have seen just one post from you which I agree with. The rest is just "your" interpretation of the OP question, with stationary trains starting to move and disappearing into the distance, which completely misses the point. <shrug>

58. Originally Posted by KJW
This is unnecessary. If we consider the mirror to be an infinite plane in relativistic motion parallel to the plane, then the entire image, not just the image of ourselves near the normal to the mirror, is unaltered by the motion of the mirror. The crucial issue is the invariance of the mirror plane with respect to its motion, not the motion of the points of the mirror with respect to the observer.
I am glad you agree that the introduction of the train is irrelevant and your rephrasing of my "endless mirror" to an "infinite plane" puts the OP question in proper perspective, IMO. Mine was an attempt to narrow the field of observation, to remove other points of reference, but you have expanded the field of observation so large that it also removes all other points of reference. I can accept that as a still more fundamental contextual scenario.

I am in total agreement with that interpretation of the OP question, which allows us to concentrate on the dynamics between a stationary observer and his/her reflection in a moving "uniform reflective infinite plane".

59. Originally Posted by Physicist
Boeing3000 - Consensus means general agreement, not total agreement. I know how much you have a fondness for x0x even though it's misled. But then again what you're fond of is something I'm not interested in.
You know nothing about my fondness of anything (John Snow). To be clear you and x0x scores the same lame high score on my prick'O meter. The reason is clear, you are in competition in that dimension, and all your (and his) post shows the competition is still running.
Note that in the dimension "I am going to throw my degree at your face", you scores way higher then him.

And I don't even know what it this "something" you are interested about. Please continue to make subtle allusion of what it could be (surely not vanity)

Personally, I am interested to understand the problem at hand. And x0x and KJM scores a better score then you on the "Explain the situation please"'O meter. If you don't like my opinion, just don't ask it, or put me on ignore. Refuting arguments is way easier when you don't listen to them.

I am the one with a BA in computing here. And ray-tracing is a passing hobby. If I where to include the effect of various time travel of light between moving object in a scene, I could kiss such simplicity goodbye.
I am also not conflating that kind of toy computing ray-tracing with a physics approach of reality.

Also, be so king to learn to click on Ctrl-F (or Cmd-F if you have a Mac) before trying to explain to me what a consensus is.
So look at how a conversation is supposed to be done, I am going to walk you through the process. Because Jilan, Write4u, chaimc and me are interested to learn something.

Originally Posted by write4U
No, the scenarion includes an endless flawless mirror in motion and a stationary observer who can only observe his/her image reflected by the mirror. There are no other points of reference.
Originally Posted by KJW
This is unnecessary. If we consider the mirror to be an infinite plane in relativistic motion parallel to the plane, then the entire image, not just the image of ourselves near the normal to the mirror, is unaltered by the motion of the mirror. The crucial issue is the invariance of the mirror plane with respect to its motion, not the motion of the points of the mirror with respect to the observer.
I also think that aspect has not been explained successfully be x0x. But KJM arguments are enlightening.

I cannot see any invariant here. Even an infinite mirror with no-reference point, does not change the setup. In this infinite frame, there is an variant, the momentum of the scene, which nobody sees. If the mirror is indeed fix on a train, you would see the wheels.
And the wheels would be distorted (only because they would rotate ? No they would be length contracted). So the mirror also is. As far as I can understand.

Another way I have put this is that even if the mirror is moving parallel to it surface, there is only ONE line of sight with minimal(or no?) aberration. The perpendicular one. If you look at you entire reflection(from left to right, up or down) you are rotating the mirror.

Another way to discard the in variance of the reflection is to imagine a grid of horizontal laser beams oriented at 45° to the mirror surface. They are in the radio frequencies so the mirror is transparent for them (but not our eyes, we have special glasses on). Both mirror and us at rest.
In this setup, if I start moving, laser beams will start shifting in frequencies and geometry, but what about MY light (I hold the torch) ? When I get to the speed where beams coming "toward" me are so blue shifted they are in the visible range, shouldn't they start bouncing of the mirror ? Isn't the the mirror properties changing ?
In the same setup, if the mirror start moving I think relativity tells us the same events should happens, even if the geometry and frequencies observed differs. Being length contracted the mirrors atoms would be closer, and more then likely influence the reflection properties of the mirror ?

60. Boeing3000 - I noticed that you put a "Like" on that post where I emptied my ignore list to forget old grudges, forgive and forget type of thing. Then nearly in the same breath you post an extremely rude insult about a prickometer and you're once again back in the ignore list where it's obvious even more now that you never should have come out. You're an arrogant person and you have no place posting here with all the other decent people. Be gone with flamers like yourself.

61. As you quoted me, I should like to respond to some of your observations.
Originally Posted by Boing3000
You know nothing about my fondness of anything (John Snow). To be clear you and x0x scores the same lame high score on my prick'O meter. The reason is clear, you are in competition in that dimension, and all your (and his) post shows the competition is still running.
Note that in the dimension "I am going to throw my degree at your face", you scores way higher then him.

And I don't even know what it this "something" you are interested about. Please continue to make subtle allusion of what it could be (surely not vanity)

Personally, I am interested to understand the problem at hand. And x0x and KJM scores a better score then you on the "Explain the situation please"'O meter. If you don't like my opinion, just don't ask it, or put me on ignore. Refuting arguments is way easier when you don't listen to them.

I am the one with a BA in computing here. And ray-tracing is a passing hobby. If I where to include the effect of various time travel of light between moving object in a scene, I could kiss such simplicity goodbye.
I am also not conflating that kind of toy computing ray-tracing with a physics approach of reality.

Also, be so king to learn to click on Ctrl-F (or Cmd-F if you have a Mac) before trying to explain to me what a consensus is.
So look at how a conversation is supposed to be done, I am going to walk you through the process. Because Jilan, Write4u, chaimc and me are interested to learn something.

I also think that aspect has not been explained successfully be x0x. But KJM arguments are enlightening.

I cannot see any invariant here. Even an infinite mirror with no-reference point, does not change the setup. In this infinite frame, there is an variant, the momentum of the scene, which nobody sees. If the mirror is indeed fix on a train, you would see the wheels.
And the wheels would be distorted (only because they would rotate ? No they would be length contracted). So the mirror also is. As far as I can understand.
This is the reason why I (and possibly KJM) wanted to remove such frames of reference so that we have defined the fundamental question to its bare bones.

Earlier in this thread I mentioned that the mirror would contract or expand, depending on its motion, however I tried to overcome that variable with the example of a perfectly uniform mirror. Even if this mirror contracted or expanded and its atoms would be packed denser or more dispersed, the image would not be affected, with the exception of greater or lesser definition. Which also prompted the question if at near "c" the reflection would become smeared. I have not seen anyone address that yet.

Another way I have put this is that even if the mirror is moving parallel to it surface, there is only ONE line of sight with minimal(or no?) aberration. The perpendicular one. If you look at you entire reflection(from left to right, up or down) you are rotating the mirror.
Which prompted me to suggest a narrowly focused observation instrument so that the observer is forced to remain focused on a small area (only the observers reflection), which would minimize the mirror rotation effect

Another way to discard the in variance of the reflection is to imagine a grid of horizontal laser beams oriented at 45° to the mirror surface. They are in the radio frequencies so the mirror is transparent for them (but not our eyes, we have special glasses on). Both mirror and us at rest.
In this setup, if I start moving, laser beams will start shifting in frequencies and geometry, but what about MY light (I hold the torch) ? When I get to the speed where beams coming "toward" me are so blue shifted they are in the visible range, shouldn't they start bouncing of the mirror ? Isn't the the mirror properties changing ?
In the same setup, if the mirror start moving I think relativity tells us the same events should happens, even if the geometry and frequencies observed differs. Being length contracted the mirrors atoms would be closer, and more then likely influence the reflection properties of the mirror ?
The last paragraph is out of my league, so I'll leave that to more learned minds.
In any case thanks for recognizing my genuine interest in the subject along with other posters. It is a fascinating problem.

62. Originally Posted by Physicist
You're an arrogant person
That's true. I am. A lot of people tell me that. It is an fact in my universe.
And you are too. I won't put you on ignore, because your arrogant post are still interesting, physics wise.

Originally Posted by Physicts
and you have no place posting here with all the other decent people.
I don't think so. But then I can agree to disagree... I hope that you'll realize that splitting people between decent and not, sounds a little childish.

63. {...didnt notice that there is "page 2" and I lost contact two days ago(?) with page and wandered where you have all gone. Silly me.

You all are throwing degree MA and MS's and PhD's in the air and I have hardly finished 12 yrs highschool and I must admit that I feel honored that I have managed to create such an intrigging conversation..I LOVE IT!
}

I read every post in this chain, some I understood and some I didnt (yet...?) BUT i can tell that I hit right on target into a very uncertanity area of science.

I have a reason for this question and maybe I would share it with you one day.

In the mean time, as I found that this "experiment" will not lead to me to my direct "goal" , I have deviced a different setting. I dont know if you all saw it but I would love to have your elighting opinions there too .

[url]http://www.thephysicsforum.com/general-discussions/6385-next-through-key-hole.html[/ur

Thanks!

64. Originally Posted by write4u
Earlier in this thread I mentioned that the mirror would contract or expand, depending on its motion, however I tried to overcome that variable with the example of a perfectly uniform mirror. Even if this mirror contracted or expanded and its atoms would be packed denser or more dispersed, the image would not be affected, with the exception of greater or lesser definition. Which also prompted the question if at near "c" the reflection would become smeared. I have not seen anyone address that yet.
Indeed, sticking to the OP question is necessary. But removing "visual" reference is not changing anything. What do little mark on the mirror spaced by 1 meter would change to the reflection ?
The definition (the frequencies) may be disturbed. But what I understand from the answers is that it would not. I still cannot understand how.
The geometry will be, and an image is a composite of an infinite lines of sights. Only one is perfectly perpendicular.

Originally Posted by wrtie4u
Which prompted me to suggest a narrowly focused observation instrument so that the observer is forced to remain focused on a small area (only the observers reflection), which would minimize the mirror rotation effect
I am confident that its not a valid approach. A forced observer would see nothing but whats in front of him. But the eyes HAVE of focal angle anyway. Light is coming from all the fov (field of view). And we have two eyes... which allow to detect aberrations/3D only by moving them and comparing the "differences". But let not escape the OP. The comparison is done between a "at rest straight on staring" reflection and a near C reflection.

Originally Posted by write4u
The last paragraph is out of my league, so I'll leave that to more learned minds
I was just trying to add a literal neutral "grid" to the OP experiment, to help visualize things

65. ADMIN ACTION : I need everyone here to read the "Warning" notice in the Announcements section ! I am temporarily closing this thread for a period of two days to cool down the rising tensions.

66. Originally Posted by Boing3000
To be clear you and x0x scores the same lame high score on my prick'O meter.
Three day suspension. Next time it will be seven days. Do it again and it will be permanent.

67. Originally Posted by x0x
Your list of objections gets more ridiculous by the whine.
You can't stop yourself, can you. Three day suspension.

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