The Michelson Myth
The Michelson Myth
"Some of the current applications of optical interferometry are accurate measurements of distances, displacements, and vibrations; tests of optical systems; studies of gas flows and plasmas; studies of surface topography; measurements of temperature, pressure, and electrical and magnetic fields; rotation sensing; high resolution spectroscopy, and laser frequency measurements. Applications being explored include high-speed all-optical logic and the detection of gravitational waves. There is little doubt that, in the near future, many more will be found."
(P. Hariharan "Basics of INTERFEROMETRY", 2007)
You know how a full moon seems to follow you everywhere you go? Well, you can recreate the same eerie experience with a piece of cardboard in which you have made a small hole. Now all you need is a window pane and a light source. I can use the street lamps I can see from my kitchen or from the living room. If I place the cardboard against the glass in such a way that I can see a street lamp through it, then however I shift the cardboard, at least horizontally, I keep seeing the same street lamp!
Figure 3.1 of Hariharan's book is very enlightening, pun intended. It shows one point source, a fatty point on the left, forming the top of a triangle lying on its side, with its two sides crossing a straight line with two slits, and ending at a second vertical line where the screen is supposed to be. The aim of the author is to make us understand the strange behavior of light when it has to go through two slits. The sides represent what light particles are supposed to do, go straight in an oblique line, up, respectively down, to the screen. We would therefore expect bright spots in two places, there where the sides of the triangle meet the base. But then, how to explain the bright spots in the middle, right in front of the part of the wall separating the two slits?
This is where the wave theory was born, and this where it has to be put finally to rest.
For that, we need our stalking moon.
Imagine the cardboard as wide as your window, with small holes cut throughout its width at random, or on the contrary, at very precise intervals. Whatever hole you choose to look through, you see the same moon, or street lamp, staring back at you. What is then happening inside your eye, optically speaking?
Apparently, it looks like that there is one light source for each hole, which then makes it quite natural for light to shine even in the middle section protected by the dividing wall between the two slits.
We have now solved one part of the mystery, why one single light source can create a continuous bright line beyond the two slits. We still have to explain why we see isolated spots instead of a continuous bright line.
For that we first have to remember that a pinhole functions like a magnifier even without a lens, which allows us to say that the spots we see do not represent the light source in its totality, but probably a single ray. The rays meeting at a split separate again on their way to the screen and create the so-called fringes.
Et voilà! All that rests to be done is to prove it empirically, or make it at least as plausible as the wave theory of light.
That shouldn't be too difficult, right?
[see also The Michelson Interferometer]
The Michelson Myth
At the water hole
The idea that you do not need a lens to magnify the image of an object might sound strange, until we remember that what a converging lens does is simply to bring rays together that would otherwise go their own way.
You can use the same idea as with the street lamp, but I find it more clarifying when looking at something more meaningful than a ball of light.
I could tape the cardboard to a window separating the room where I keep my computer from the living room, so that I could look directly upon the screen. I clicked a random text and enlarged the fonts to the maximum making it very easy for me to read them from a distance.
For those who have never processed their own (black and white) negatives and developed their own pictures, you need to know that the distance between the negative and the lens never changes. To make the picture appear larger or smaller you move the whole head in which the lamp, the lens and the negative are housed, up or down. That is what is in fact happening when we move away from, or closer to, the pinhole. The image in one case becomes larger and larger until we are able to see only a small part of a letter because our eye cannot encompass the whole image coming through the hole; or, if we come closer and put our eye against the pinhole, we are able to read whole words.
Since, in both cases, the distance between the lens and the negative, or if you prefer, the object and the pinhole, did not change, the details contained in the image do not change either. One practical problem is that the farther we get from the hole, the less we are able to distinguish any details directly. The only way to be able to do so is have the image projected on a screen or on paper. This way we can approach the image close enough and study it in detail.
Evidently, lighting is crucial, but we must realize that this is a technological problem. Light has no problem crossing billions of kilometers before it reaches our eyes, and should therefore have no trouble crossing the negligible distances we can put between the pinhole and the screen. Our technology is based on our biological makeup and our light detectors function, globally, under the same principles as our visual organs. Theoretically we could use radio "waves" instead of light, and then we would not have to worry anymore about the size of the pinhole, or the intensity of the light reflected by the object. We are, I assume, not so far that we can translate, perfectly, radio signals into shapes and colors, but, again theoretically, there is no reason why it should not be possible to do so sometimes in the future.
Let us look at what is happening at the pinhole more closely.
Imagine the following sentence being enlarged enough that it can be read from a distance through a pinhole.
This is one single sentence.
If you concentrate on the o, and keep your eye against the hole, you will maybe be able to read the whole sentence. But the farther you get the less you will be able to see. It might look like this"
s is one single sent
ne single s
It is very improbable that that your visual acuity will allow you to recognize a single letter after a while. Just like at the optician's. A special screen which would be able to detect radio or whatever electromagnetic "waves" the object would be emitting, and which would translate them into shapes and colors would be able to show you the pixels in the light emitting screen, and more. In fact, the farther you get from the pinhole, the more macroscopic details you will be able to distinguish. Inversely, the smaller the distance between the pinhole and the object, the more (macroscopic) details you can get. In the last case it is because the rays coming from the objects have had no time, in fact no space, to separate, while in the former case the inverse is the case, and the farther you get the more rays come apart and become distinguishable.
The Danger of Laser Light is also theoretical. We tend to forget that it is a technological device that functions quite differently from our eyes or most natural objects. Light is naturally (almost) never monochromatic. Information comes from contrast and colors, something lasers do away with. Because an enlarged ray looks the same as a whole beam we have no way of distinguishing between them, and whatever appears on Ezekiel's screen can be interpreted any way we want. We cannot even exclude the possibility that the concentric fringes are not a technical artifact, just like the image of the filament of a light bulb.
Even the use of a "white" light would not be enough, because it would leave us too much latitude in the interpretation of the results.
No, the only hard proof will come from real images of real objects, with enough colors and contrasts and shape for us to recognize when a part has been enlarged beyond proportion, or spaces between rays are being reproduced.
But then, knowledge is expensive, and I am not sure I can afford all the gadgets necessary to test my views. Thank God for Youtube. Their clips compensate the deafening silence of the academic world.
The Michelson Myth
At the water hole (2)
Look at the image of the moon on your retina while you are moving. Or the image of the street lamp when you are moving the cardboard. The pinhole is situated left or right, up or down, from the lamp. How, then, do you get to see the lamp? It is like the rays first go obliquely in the direction of the hole where they align very nicely in the same original configuration, and from there emit their light through the hole. It is in such situations that the wave theory is the most attractive. Nevertheless, even the wave theory cannot explain how we can have a refraction of the light beams simply by going through a hole. And, if we assume that the light particles are bouncing of the edges of the hole, then we do not need the wave theory.
Of course, we would then have to also assume that the light particles are kept in the same spatial configuration all through their journey. Which means that only a part of the outer periphery of the image will actually come in contact with the edge of the whole, the other particles bouncing of the particles before them and keeping this way the image intact. Because of the recoil, the image at the hole will always be smaller than the hole itself. And what happens then?
If the particles are then deflected through the hole further into the dark chamber, there would be no reason for the particles standing at the same level or on the same line, not to end up all at the same location, in an indistinguishable heap of light.
This is where the concept of wave can turn out to be very useful!
What if, just like by a water wave, the particles are only moving up and down, one after the other? The particles at the hole will make other particles vibrate, and this in all directions.
We are getting closer and closer to Huygens, aren't we?
The only problem with this argumentation is that it is wrong. To see that imagine the image of the street lamp like a light ball flying to the hole in an oblique direction, and stopping just short of the farther edge. It is now blocking the hole, its surface barely (not) touching its outer circle. The fact that nothing but magic would stop some parts of it from hitting the edge and bouncing back does not negate the fact that it will be all the while emitting light into the hole and that light will be going in a straight line. It would be like an electric torch being carried through space in an oblique line while still shining directly forward in the usual way. In fact, there is no reason why we could not replace the street lamp with a flash light, turned on, which we would keep seeing however we move relative to the hole.
Also, Huygens conception assumes that light waves move out of themselves, and have therefore to concentrate their energy on the straight lines and limit the secondary waves at the edges. It is very much a magical process that perpetuates itself against all logic.
I love magic, I just don't think it belongs in science.
That is why I prefer thinking that light rays, just like electric or magnetic forces, have to be renewed constantly. Electromagnetism or gravitomagnetism?
And what does the light do when it goes through the hole? Well, first, some of the outer rays will be blocked by the edges, then, a smaller image will continue its oblique journey, all the while shining forward and left and right. Isn't that neat?
The Michelson Myth
To See the Light
How come we see a light even when there is darkness between us and the light?
Maybe that photography can help us out again. You can take a picture of the end of a tunnel and make sure only a white spot can be seen in a sea of black. What is interesting is that the white will be totally isolated and we have therefore apparently no way of explaining how it could activate the emulsion on one part of the negative without affecting the rest.
If you think in terms of lenses and lines, then the lines which brought the light to the middle of the negative apparently never cut the same plane as the other lines. It is like the negative was laid flat, and the light was dropped from above. But even then, to have such a pristine black surrounding the bright spot is only possible if the light only appeared at the last moment, when it was already at its final destination. For this to be possible can mean only one thing: whatever caused the light to travel to the negative, or to our eyes, was not strong enough to light up the space in between. It seems that light not only disappears in vacuum, but also in the normal atmosphere.
Of course we already knew that. It is the rule of the inverse square law of distance. What nobody, I think, ever realized before, is what it meant exactly. Our eyes, and photographic films, are sensitive enough to react to a stimulus which leaves matter apparently undisturbed.
That raises a very interesting question: is it possible for light, in whatever form, to have an effect on matter without us seeing how it happened, or which path the light took? More to the point at hand, is it possible that a sensitive screen shows fringes while we have no idea how they got there?
I certainly would not advocate such a spooky explanation, but it is no doubt worth investigating.
The Michelson Myth
Additive + Subtractive = Transparent?
I've seen the bright get duller
I'm not going to spend my life being a color
Michael Jackson - Black or White (1991)
[see also Red + Green + Blue = Transparent]
When one looks at the ways colors can be combined (Additive and Subtractive Color) one really wonders how black and white ever came to be considered as non-colors. After all we have no way of knowing what the result of a mix will be unless we project it on a surface which will always have one color or another.
What I find also very interesting is that black is a product of a color mix as well. Who are we then to deny black the status of a color?
In fact, the only reason to stand by such a preposterous claim is to give some justification to the wave theory of light. Which is quite ironic since Newton, the most famous defender of the corpuscular theory of light, was the first one to affirm that white is not a color but the mixture of all colors, which prisms showed separately.
Denying black the status of color is also fundamental, otherwise how could one explain interference? Whether using double slits or Newton rings black is the sole indicator of what is supposed to be the absence of all colors.
As shown in Newton's Rings, the concept of black is very broad, and apparently equivalent to that of dark. In this case, dark orange or dark red. In fact, any shade of dark would do, and if no dark colors are present, white is happy to take the lead.
The very existence of interference phenomena depends therefore on a purely arbitrary classification of light in colors and non-colors.
By the way, the distinction of primary and secondary colors? Also a Newton's idea. He could not separate the prism colors any further. But guess what, you can make any primary color you want by combining two so-called secondary colors, which themselves are made of two so-called primary colors. But which ones were first? And can you speak of first or second at all? Why give such an importance to prisms and rainbows? The latter obviously stand out by their beauty and natural character, and that helps considering prisms also as something special, but those are not scientific arguments, however compelling we may feel they are. The only difference between white and black on one hand, and the other colors on the other hand, is that it takes three colors instead of two to make them. But even that fact is relative, since one can make not only all shades of white and black with three colors, but also all the other colors as well.
So, tell me, why were black and white not colors again? Ah, right, interference phenomena. Okay, that is a good reason. After all, contemporary science seems unthinkable without them, and who wants to be the first to admit that billions were spent on scientific projects built on a misunderstanding?
Poisson's Spot is considered, maybe even more than the double slit experiment, as the ultimate proof that light is (also) a wave. Just like Michelson, Poisson became famous because of a failure. Michelson had failed to prove the existence of the ether, and Poisson, himself a convinced follower of the corpuscular theory, ended up handing up to his rivals the ultimate tool of his defeat. The wave theory of light predicted, according to his own calculations, a bright spot in the middle of the shadow of a circular object. He though that such a ridiculous idea was the final proof that the wave theory of light had to be wrong. But Arago proved that there was indeed a white spot right in the middle of a circular shadow. That was the end of the particle theory of light until 1905 when Einstein dusted it off and gave it its legitimacy back,
Back to Arago's experiment. First, why does it have to be a circular object? The wave theory predicts that all the waves going around the obstacle would interfere destructively with each other because they would all be out of phase... Except for those in the center which would strengthen each other and create a bright spot.
A perfectly logical argumentation.
But why couldn't such a bright spot be created in, say, a rectangular or triangular shadow? Surely some waves could be found that would constructively interfere with each other, even if not at the exact center of the shadow? I wonder what mathematicians have to say about that.
I will not attempt to anticipate their answer and will concentrate on why that cannot be even if the wave theory is wrong, like I hope to ultimately prove.
The idea is very simple and is based on the picture of the end of a tunnel I previously discussed (To See the Light). It has to be the center of the shadow because all the other points do not receive enough light to be visible to the naked eye. Maybe, in the future, when we will be able to measure invisible-visible light (to distinguish it from ultra violet or infrared) we will have a definite proof of what is really happening. Until then, our wits must do the job.
Using the image of the moving electric torch, we can image the rays surrounding the circular obstacle and shining in all directions, their light disappearing very quickly without leaving any trace. Except there where all the rays meet, at the center.
In a way, my analysis indicates that the wave theory of light is right at least on one point: there is definitely constructive "interference" in the center of the shadow!
[I hesitated using this argument because, for a while, it seemed to me that it negated the possibility for light going through a slit to have any effect at all. But then I realized that each ray creating the shadow is unique, while the image of an object consists of many rays that are emitting at the same time. Even a diffraction grating of 1200 lines/mm lets not a single ray through but a whole bundle. If we built a circular slit around the object, I suppose that there would be no shadows left]
The Michelson Myth
The Emperor's Clothes
You know what happens if you shine a laser pen on the wall, and look at the spot through different lenses? Well, it looks, sometimes, suspiciously like the so-called interference patterns through one or more slits. People have been breaking their head for centuries over the meaning of those patterns, and the spaces between them, and here you can see them outside of any slit!
When you think about it, it is not really amazing. Thomas Young, in his "The Bakerian Lecture: Experiments and Calculations Relative to Physical Optics" (1804), or Fresnel in "MÉMOIRE SUR LA DIFFRACTION DE LA LUMIERE", 1818, as well as contemporary teachers like Ezekiel or Wolfson, all make use of lenses (a simple magnifying glass in the case of Fresnel) to examine the spot.
I must admit that I would find it it quite humorous if indeed all the strange effects that have occupied Newton, Huygens, and so many others, would turn out to be effects of the lenses through which those same effects are observed.
Everybody assumes that the use of lenses or prisms is neutral, that we are still looking at light phenomena in their natural state. That strikes me as rather naive.
I am waiting for some equipment and will definitely return to this fascinating issue.
The Michelson Myth
To See the Light (2)
I find this old video clip about diffraction very enlightening in that it shows the different colors live, and not in a computer animation. Look at all the colors displayed and assume that white and black are colors like any other. What would your conclusion be? Would you still think that rays are somehow destructively interfering with each other?
I find that hard to believe.
The Michelson Myth
The Logic of numbers: when goats can fly
The Logic of Numbers
Mister Feynman, lend me your dreams: the False Duality of Light
In the Japanese two-slit experiment interference patterns emerge even though electrons are emitted one at the time. So, as Feynman would say, "how can this be?"
Maybe the way of registering the events is the reason we are facing such a conundrum. If successive single events have the same graphs as that of waves, we should ask ourselves if the graphs depicting wave events are doing justice to the phenomenon. Is the model of crests and troughs really compatible with the facts?.
The intensity of the wave is a numerical value.
What happens if you register the impact of the water at single, well defined moments? A crest and a trough which we consider as simultaneous will be considered as two isolated events, each with an intensity value. The only difference is that instead of putting the result directly in our graph, we put both values separately. The end result will be mathematically the same.
In other words, if you take the wave impacts and register them at intervals comparable to those used for photons and electrons, you will still get the same pattern. Only now the distinction between waves and particles has lost any meaning it ever had!
So, maybe I was right after all. Maybe waves do not exist. Except in our perception and in mathematics.
[I am aware that this analysis still does not explain the existence of the so-called interference patterns. But the discussion is now freed of the dichotomy particle-wave.]
The Michelson Myth
The Logic of numbers: when goats can fly (2)
Where do the interference phenomena come from?
The mathematics developed for wave interference can still be of great help. I refer to the excellent video of Khan's Academy.
There he gives the example of 8 rays and how they behave together.
Here is what he says in short. If the first and the fifth ray interfere destructively, then so will the second and the sixth, the third and the seventh, etc.
But we do not have interference anymore, so how could that help us?
Well, there is interference only if we add them together, which we do not need to. They can be considered as isolated impacts which either hit the screen one after the other, or even simultaneously. Assuming that they would destroy each other is assuming that which the wave theory is supposed to prove. It is quite possible that such a simultaneous impact would be translated into two successive reactions. Also, the shorter the interval the less likely they will arrive simultaneously, and even if they did, they could knock each other off and both recoil.
The question now is, are those empty spots explained by such calculations, because the same logic could be used to explain the bright spots? Well, I think it is the same logic that explains both the empty spaces and the bright spots. It is just a matter of choosing which kind of interactions we are considering. The empty spots will be the places where particles bounce off each other because they arrive simultaneously at the same location, while the bright spots are the places where the particles hit in close succession.
So Khan's explanation remains valid after all, even if there are no interference phenomena and light is not a wave! All we need to do is replace the concepts of crest and through by that of time (and place) of impact.
The Michelson Myth
From Young to Feynman or from Wave to Quantum
In (1804) Young already showed that the interference patterns disappeared from the shadow of an object when one side of the object was covered. It was just like the famous lecture by Feynman in which he argued that the patterns created by two slits where different from the sum of both slits when water waves, photons or electrons where considered, and not hard particles like bullets.
Feynman celebrated (the anniversary of) the end of logic with a smile: it is not true, he said, that the particle (photon or electron) has to go either through hole #1 or hole #2. Apparently all we could say for sure is how probable it is that it will go though one hole or the other.
I think I have showed that it was Feynman's logic that was faulty, and not Logic itself. Once we reject the wave concepts of crest and trough, and their mathematical translation, there is no reason at all to believe in the (mathematical or scientific) reality of waves. We can affirm with absolute certainty that the particle will necessarily go through either one or the other hole, whether we observe it or not. The fact that observation is equivalent to the blocking of one hole is the reason why the interference patterns disappear. That is therefore what we have to explain.
The whole argumentation by Feynman is based on the putative difference of patterns created by macroscopic elements like bullets, and subatomic particles like photons and electrons. Both in this lecture, and in the third volume of his "Lectures on Physics: Quantum Mechanics", Feynman specifies that the gun shooting the bullets is not really precise, which makes it easier for the bullets to go in the direction of either hole. As I argued, the distinction between a wave and a particle was practically canceled by such an assumption, since a gun shooting straight would most likely hit the panel between the two slits. It is therefore not surprising that in the end the patterns which are wrongly attributed to waves (only) turn out to be applicable to particles (as well).
The problem of the interference patterns turns out therefore to be a false problem. Whether we are dealing with particles or waves, the same patterns are created by two (or more) slits, and those patterns disappear when one slit is covered one way or the other. The fact that interference patterns disappear have therefore nothing to do with the question of waves or particles. In fact, the whole concept of wave becomes suspicious and void of (scientific) meaning. Particles and Waves
I think I have given a plausible explanation of why these patterns appear, and that is at the same time the reason why they also can disappear. Blocking one slit is equivalent, with the caveat of an imprecise gun (and the help of Heisenberg's principle), to letting all bullets go through one slit, with the corresponding distribution and pattern.
And now I am almost afraid to ask: where does that leave Quantum Theory? [see my promise in Bell's Theorem for Dummies or the Collapse of the Wave Function ]
The Michelson Myth
The Logic of numbers: when goats can fly (3)
The presence of empty spaces cannot be explained (solely) by the collision and reciprocal repulsion of particles, since the same spaces are also present when electrons are emitted in successive single shots. Where do these spaces come from?
I think I will have to refer to the fact that we are always dealing with an inaccurate gun, and that locations which receive enough impacts will light up more brightly that those who receive less. The empty spaces look much less empty when the sensitivity of the screen is greatly enhanced. There might be no reason to assume that those empty spaces are totally empty. Except for the fact that light rays might be discontinuous in the width of the beam. Maybe there is an empty space between each two rays, but that is something that will have to wait empirical confirmation.
From Young to Feynman or from Wave to Quantum (2)
The reader might wonder what my final thoughts are concerning interference patterns. Didn't I suggest that they might be artifacts created by lenses, just like refraction phenomena? First, I do not have any final thought yet, and consider my research as a work in progress. Second, both points of view are perfectly compatible. Even if they are artifacts, interference phenomena will not be any less real, and the explanations given last might still be applicable. After all, our eyes are also lenses.
The Michelson Myth
mirror mirror on the wall
Specular and diffuse reflection. It sounds all so plausible. But how are we able to see objects which are not reflected by mirrors? A 3D object will be by definition non-specular and the rays falling on it will be reflected in all directions. Still, vision is usually uneventful. There is only one conclusion possible, we do not see the reflected rays! What do we see then?
Maybe we should make the distinction between how objects reflect rays from the way objects are reflected from them. The way an object reflects rays is the way we see it. But, unlike a mirror, an object does not need to reflect any other object but itself.
Take the surface of the water when it is not reflecting anything but diffuse ambient (day)light. We can clearly see it, but we can also see an object reflected on its surface. Water, just like a mirror, can send us its image as well as that of other objects. But most objects can't. They send only their own image.
We must therefore make the distinction between general reflection of rays which make objects visible, and reflection of rays which makes the image of objects visible.
In fact, this simply says that not every object is a mirror.
Still, the puzzle remains. An object cannot be reflected from a non-mirror, but the non-mirror itself can be reflected and seen. What is then the difference between reflecting and being reflected?
The image of a second object, when falling on a non-mirror, is scattered in the same way as the own rays of the non-mirror. That means that we can see the non-mirror only, even if in somewhat altered colors because of the effect of (the image of) the second object.
The distinction between a non-mirror, as are most objects, and the image of any other object, mirror or non-mirror, is crucial. We see non-mirrors like we see the non-reflecting parts of a mirror. Imagine standing on the side and looking at a mirror. You see its surface like you would see any other object. It is not reflecting anything from its ambient environment to you, only itself. You might as well look at any non-mirror.
The distinction between specular and diffuse reflection therefore only makes sense when we are thinking about how images of objects are reflected from other objects. This distinction does not explain vision. In fact, according to this distinction, we should not be able to see anything unless it is reflected by a mirror!
This confusion is painfully evident in the attempts of Khan to explain vision.
The Uncertainty Principle
The fact that vision does not depend on photons emitted by an object to our eyes makes it in principle possible to observe through which hole an electron has passed without the use of other light than the one created by the passage of the electron or the photon itself. We do not therefore need extraneous light to follow the trajectory of particles. The practical implementation of such a principle is something way beyond my expertise, but I will try to present it as clearly as I can.
Heisenberg's Principle is based on the idea that we need at least one photon to hit a particle and come back to our eye for us to see the particle. If the latter is small enough, the photon will make it deviate from its trajectory, or even annihilate it, irremediably changing the outcome of the observation.
Remember the picture of the tunnel? I apologize for milking the example out, but I don't seem able to think of a better one.
The light coming from the entrance impinges on our retina as well as the negative in our camera, but does not leave any trace in its wake until it has reached them. Instead of a tunnel, imagine looking at the two slits and observing the path taken by each photon or electron. Theoretically, we should be able to observe what is happening without changing anything to the outcome. After all, we do not need to add any detector or project any light in their path.
This does not mean that vision somehow happens in a magical way, that the light at the end of a tunnel impinges on our retina by jumping over the distance separating us and leaving no trace behind it. It just means that there is something missing in our knowledge of light and vision.
As importantly, it means that Heisenberg's Principle is not necessarily true.
The Michelson Myth
mirror mirror on the wall (2)
George: what is an incident ray?
You: easy, it is the way a ray falls on a surface, and it is equal to the ray of reflection?
George: you sure?
You: You sure.
George: What happens if you move?
You: the ray moves with me?
George: which one?
You: is that a trick question? You want me to say something stupid, is that it?
George: you don't need my help for that, kid.
You: well, if you're so smart, why don't you tell us?
George: okay. You decide, by your position, which ray will be the incident ray. In other words, first you choose the reflecting ray, and then you see the incident ray.
You: so there are no rays, really.
George: I didn't say that, did I?
You: it is implied in what you did say.
You: if, wherever you stand, you get an incident and a reflecting ray, that means that you are in fact creating them. So, there are no rays.
me (chuckling): he got you there, Georgie.
George: don't call me that!
You: why not? Georgie?
George: I'm not the little kid in "IT"! Okay, brat, tell us why there are no rays.
You: when you shine a lamp in one direction, you are creating a beam. Everybody can see that. But, turn yourself into the Ant Man, and go stand in the beam. Can you still distinguish rays in there? Will you be able to see your shadow and decide in which direction the rays are going?
George: I see what you mean. It would be like being in a room intensely lit through half opaque walls, floor and ceiling. Or a cloudy day. There would be no shadow and light would seem like coming from everywhere. Still, that does not mean that there are never rays.
You: okay, imagine yourself at the theater. The lights are all out, except for one spotlight directed at the artist on stage. Nothing stops you from walking around in the dark, and looking at the artist from different perspectives, each time picking up new incident rays. Right?
You: which incident rays are you looking at? After all, you are still standing in the dark, and the spotlight is still directed at the artist.
George: Me? Some help here?
me: nope. I like it when you get spanked by the kid.
George: okay, You. Hit me!
You: There is something reaching your eyes, and it is all around the spot of light. In fact, if you replace the spot of light with a star, we could say that millions of years away from the star, in all directions, you will still be able to see it. If you turn the spotlight or the star off, then there is nothing more to see. You turn it back on, and it is again detectable from far away. Since we know that it takes time for light to reach us, we have to admit that what we are seeing is not the spotlight or the planet itself.
George: so? Nothing new here.
You: except for the fact that it does not matter whether your are looking at an artist in a darkened theater or a far away star? Solve one problem, and you will probably solve the other one also.
George: okay. How do we solve it?
You: I have no idea. That's what we have Me for.
me: I am afraid nobody is going to like what I have to say.
George: try me.
You: and me.
me: I don't think we have any idea what light is made of.
George: what about Maxwell's equations?
me: They all have to do with electricity and magnetism. The question is, is light an electromagnetic wave like Faraday, and Maxwell, thought it was?
You: what about radio waves? You can't say they don't exist, can you? I mean, we wouldn't even have cable if not for radio waves!
me: I will not get into whether radio waves are indeed waves or something else. I will limit myself to light, that is complicated enough.
You: but television is light!
me (sigh): yes it is.
me: the end product is light. But we have no idea how it comes about. At least, I don't think we do.
You: I don't understand it. Why complicate things? If you can make radio waves, and light, with electricity and magnetism, then why think those waves could be something else?
me: it's like Laurel's magic lighter really. He flips his thumb and makes light, and Hardy has no idea how he does it.
George: we know a bulb emits light because the filament gets red hot.
me: and led lamps don't get (as) hot, not to mention organisms which can emit light even if their core temperature is very low.
You: yeah, about that. I have always wanted to know how they do it.
me: I have no idea, kid. Look it up.
You: oh well, it's not that important.
me: the point is, light can be made in very different ways, and maybe they all come down to the same principle, electromagnetic waves, and I just don't understand it.
George: yeah, probably. But you are not going to give up, are you?
me: I can't. I have to understand it. And I think that vision is the key.
You: so you agree with me, then. The artist under a spotlight in a dark theater or a far away star, both are the same problem!
You: so, it does not really matter whether space is empty or filled with air. What about the ether?
me: it is still in the running, even if I don't really believe in it. After all, it is not any worse than dark matter.
You: about that...
George and me: look it up!
You: okay, okay, no need to shout!
George: still, obviously light makes it possible for us to see. If it is completely dark we see nothing.
me: yes. But as I said, we see light in the dark, and nothing to explain how it reached our eyes.
You: hidden variables!
me: come again?
George: he means just like with Einstein. You know, how particles seem to communicate faster than light? [Bell's Theorem for Dummies or the Collapse of the Wave Function]
me: that's what I thought too, but what do you mean, You?
You: well, that we think that light can cross millions of light years, while it is in fact a local phenomenon. It is something else that is doing the traveling.
George: yes, electromagnetic waves!
me: that is the whole point. What Faraday and Maxwell called electromagnetic waves are in fact local phenomena. Now we need to find out what happens between the source and its destination.
George: I don't understand what you mean.
You: he means, the fact the artist is visible is a local phenomenon. What we have to explain is how we can see him.
George: you mean how human vision works.
me: that too, but mostly the conditions under which human vision can work. It is in fact one and the same question, except that it goes beyond the physiological or psychological makeup of humans. There is the material aspect, and then there is the physiological adaptation to this aspect. You need the first one to understand the second, but at the same time you need the second to understand the first. It would be easier if we were Aliens, then we would be able to concentrate on the first, first, and analyze the second later. But as humans we have to analyze them both at the same time, and that is quite tricky.
George: von Neurath's boat.
You: what you said about reflection. That we see objects the way they are reflected, or the way they reflect light, even though their rays are not what make us see them.
me: yes. Unless it is a mirror, with specular reflection, all other objects would be, if we believe geometric optics, either invisible to us, or look completely different in a mirror than they would look in direct perception. In fact we probably would not recognize them as being the same objects, except by memorizing both their appearances, in and outside of the mirror.
George: what about physical optics?
me: if there are no interference phenomena, and light is not a wave, then physical optics ceases to exist.
George: not many people will follow you there. But back to geometric optics. How do we see objects then?
me: it is I think easiest to imagine objects as having their own illumination, as if everything was fluorescent. Once you do that, it does not matter how you conceive the way their image reaches our eye. You might as well go back to the ancient theory of light coming out of our eyes like a torch, and shining on the objects. Or you can assume the existence of some kind of radiations emitted by the objects and activating our optic neurons.
George: those are two quite different points of view.
me: both rests on the assumption that something is traveling between the eyes and the object.
You: is there another way, then?
me: I don't think so. And that's the problem. We need something to do the traveling, and it's got to take time. It can't be instantaneous.
George: so, back to electromagnetic waves.
me: or some form of it. The way it is now, electromagnetic waves cannot explain vision, only visibility. It is different with sound. There the same principles can be used to explain how sound is created, and how it reaches our ears.
George: why not the same with light? The way it is created is the way it makes us see objects.
me: that would be the most reasonable assumption, but it appears that we do not know how we can see objects, even if we accept the electromagnetic waves idea.
You: why not? A wave comes from space, hits an object, and reverberates all around, making us see the object.
me: except for the wave part, I think that what you say is very plausible. Still, that means a lot of changes to the theory as it is.
George: such as?
me: First there is the matter of the duality of light. It is a very opportunistic position because there is no rule as to when light behaves like a particle, or when it is a wave. The only guiding principle is how convenient it is for the scientist to consider light as a wave or as a particle.
George: okay. What else?
me: then we have the mystery of the photon. Does it really exist? How can a few photons illuminate an object so that this object is seen by hundreds if not thousands of people? Where do the photons that make the people see the object come from?
You: so, the photon has to go?
George: yes, but what do you put in its place?
You: the electromagnetic wave? But then, your version of it? The school of fish?
me: you mean particles whose effects look like that of waves?
You: yes, exactly.
me: that view is not without its problems.
George: such as?
me: well, first it is not obvious how an image can be propagated through space. My metaphor of an infinite number of copies of all sizes is just that. A metaphor. We still have to explain how that works in practice.
me: We are dealing with at least four groups of phenomena:
0) what is the nature of these waves?
1) how do these waves travel?
2) how do they affect objects?
3) how do they affect our perception organ?
Concerning this last point, I think I have shown that we in fact have no idea how it is possible to see colors, since there are no colors registered in the brain. The Brain: some problematic concepts
If we make abstraction of this difficulty, we can maybe deal with the second question by assuming that those electromagnetic waves somehow make objects shine, just like cathode rays make gases shine, and make therefore objects visible. We still have to explain how this light travels to our eyes.
George: again, why complicate things? Geometrical optics may not explain vision, but it gives a very rational explanation of how rays can reflect off objects. Maybe you can use the same rules for whatever is impacting on the objects and on our retina.
me: I don't see any problem with that. Instead of a wave-particle duality, we would then have a visible-invisible duality, different from the visible-invisible distinction of wave theory, even though not necessarily incompatible.
You: isn't that enough then?
me: not really. How come we see the ambient light, and not only isolated objects in a sea of darkness, but not see how rays off an object are reflected to our eyes? How can matter react to light in one case, and not in the other?
You: back in the tunnel.
me: I'm afraid we always end up in there. See, that means that, even in daylight, the objects we see might as well be isolated from each other, instead of being linked to each other and to our eyes by ambient light. It would be like living on a very dark planet where light comes from objects alone. Each time we have to move from one object to the other, we have to do it in total darkness. The ground and every plant, animal or building on it would be visible, as would be birds and planes in the sky, but instead of ambient light, we would have ambient darkness.
George: so, what is your solution?
There is of course a very simple solution to the tunnel problem.That the darkness surrounding the light spot in the theater or in the tunnel (or on the dark planet), is itself a color.
I will have to get back to you on that.
The Michelson Myth
mirror mirror on the wall (3)
I have argued that the distinction between specular and diffuse reflection only makes sense within the framework of the distinction between mirrors and non-mirrors. We can see objects which present a diffuse reflection even tough it should be theoretically impossible. Diffuse reflection determines the possibility of an object to become itself a mirror, but it does not play any role in our ability to see it or to be reflected by other mirrors.
How then do we see objects?
Imagine an object with an irregular surface reflecting rays in all directions. Obviously, it is also reflecting something to our eyes, otherwise we would not be able to see it. What is it then reflecting, and how?
Well, simply put, it is reflecting all the light that is falling on it, from all directions. That is why we can see it from any perspective.
At the same time, it is also reflecting rays the way geometric optics tells us it is, and one can assume that unless they somehow fall in our direction, that these rays will not play any role in our perception.
The problem with geometrical optics is that it is limited to single rays, while objects are, in general, illuminated by ambient light. Even lasers, not to mention spotlights, create beams that are too broad to be confined by geometrical optics. And for that, you don't even need to shrink your size like Ant Man.
The example of the artist under a spotlight confronts us with the question how light can reach our eyes without leaving any trace on the way. The obvious solution, that our eyes, or our cameras, are more sensitive than matter is difficult to entertain since nothing in our experience would justify such an explanation. A solution which is incompatible with both the Newtonian view and wave theory, is that black, or more precisely here, darkness, should be considered as a color, at least in a practical sense. Understood this way it becomes completely understandable that a bright spot can be seen surrounded by darkness. It would be exactly like watching a white spot on a red screen, except that the red has been replaced by a shade of black, or darkness.
Seeing Darkness (2)
This cannot be obviously the last word on darkness. The least of the implications is that such a view gives quite a twist to the idea of dark matter, or cosmic background radiation. But then, anything I could say on these subjects would be gratuitous speculation of a layman.
The Michelson Myth
The Principle of Cathode Rays is incompatible with both the Newtonian and the wave theory of light. In fact, it is incompatible with the quantum electromagnetic view also. All three conceptions are namely based on the same rule: the nature of the source determines the reaction of the object. Light of a certain wave length, color signature, or energy level impacts on an object which then reacts by absorbing or transmitting the light back in eventually a changed form. What is absorbed, as well as what is reflected, both belong to the source.
Cathode rays are supposed to be produced by an electrical current that emits identical electrons which in turn elicit specific reactions in the residual gases left in the tube in the form of colored spots on a screen. The colors come from the gases, not from the identical electrons.
Also, it is very important that the number of gas molecules be drastically reduced by vacuum pumping, thereby creating an almost-vacuum. But light as we know it is in fact invisible in a vacuum, so that we expect cathode rays to be more visible the more gas molecules are present in the tube. Which is exactly the opposite of what happens in experiments.
If we applied the CRT principle to light in general then we would have to say that stars and planets emit the same stream of electrons, and that the colors we see are produced locally. The same would hold for our sun, and the way objects appear to us on earth. Also, light rays should be visible everywhere in space, and we should see a constant show of colors, instead of a black firmament.
Such a view does not sound really plausible. We have therefore to make a distinction between light phenomena created by electromagnetic means like in a Cathode Ray Tube, and the light we get from the sun and distant planets. The question then is whether Maxwell's equations can indiscriminately be considered as valid in all circumstances.
Don't expect any answer from me on such a technical matter.
The Michelson Myth
Reflections on Reflection : Feynman revisited
Feynman deals with the puzzle of reflection already in the introduction of QED. How can a photon know when to reflect and when to go through? That is the mystery that Feynman ultimately accepts as insoluble: "I am not going to explain how the photons actually "decide" whether to bounce back or go through; that is not known. (Probably the question has no meaning.) I will only show you how to calculate the correct probability that light will be reflected from glass of a given thickness, because that's the only thing physicists know how to do!" (p.24)
Is there a way to solve this puzzle in a classical way?
Let us recall the analysis of mirrors and non-mirrors, and the matter of specular vs diffuse reflection. We are dealing with glass and matter, surfaces that reflect less perfectly than mirrors or smooth metallic surfaces. Also, remember that incident and reflection rays are somewhat in the eyes of the beholder, even if it is an inanimate photo-multiplier!
Also, the correlation with thickness reminds me of the two-slit experiment. Just like in the latter, the graph drawn on the basis of data of reflection by two or more surfaces definitely shows a wave pattern. But at the same time, the photo-multipliers undeniably react to single impacts. Like Feynman said in his video lecture, "photons (and electrons) come in lumps".
Doesn't that sound suspiciously familiar, patterns that are supposed to indicate the presence of waves (because their graphs look like waves?) but end up being attributable to particles?
Allow me a quick confession: I have no idea what the thickness of the glass has to do with anything, and even if I try to give an explanation it will be more to show that a classical analysis is possible, than to claim any empirical validity.
Replace the glass plates and the photo-multipliers with the lone artist under a spotlight in an otherwise dark theater. Wherever you choose to stand, you will be able to see the artist, and therefore will rightly think that some rays are being reflected into your eyes.
You now may give yourself leave and be replaced by a photo-multiplier. Just like you, this photo-multiplier can be placed anywhere one wishes, as long as there is a direct line of sight to the artist, or to the glass plates.
You will understand that I refuse to let my analysis be determined by the numerical figures (0 to 16% of the light reflected, with an average of 8, in a sinusoidal pattern) that Feynman takes as irrefutable starting point. Still, even a wrong point of view if consequently applied has to be taken seriously. What is important here is that the majority of photons, or whatever they are, are transmitted, and a small number is reflected.
If we assume that the surface of glass plates will not be completely smooth, otherwise they would simply be mirrors and reflect almost all the rays instead of letting most of them pass through, then we can imagine that, just like any non-mirror, they will reflect only a small percentage of the incident light. Since that will be the case from any perspective one looks at the object, I dare conjecture that the quantity of reflected light will depend on the number of photo-multipliers or observers present, even if the percentage may turn out to be only 4% as measured from the first surface.
The behavior of photons falling on glass plates does not look particularly out of the ordinary, it is what happens with all non-mirrors under the light.
About the thickness. As I said, I have no idea why it should play such a central role. What is obvious to me is that there is no reason to attribute a mysterious behavior to the light, and even less to consider Nature as "absurd". Once we have accepted the possibility that reflection and transmission are determined by the irregularities of the glass, then there is no reason not to look for "rational" reasons why thickness is so important.
Let me clarify a possible misunderstanding. Feynman rejects the possibility that there are as he says "spots and holes" which would respectively block some rays and let others pass. He quotes Newton saying "because I polish glass", for knowing as a fact that "the finest scratches and therefore equally small spots do not affect the light." (p.18)
I find this a very weak argument since it assumes a perfectly smooth surface of the glass plates which is also (one of) the aim(s) of the optic industry, to optimize light absorption of lenses and minimize reflection. Such a perfection can certainly not be demanded of glass plates, and certainly not in Newton's time.
The reverse of a good lens is a good mirror, and that demands not only a smooth surface, but also a dark background, in the case glass is used, or dense material as when metals are used, to counter absorption.
In other words, the most natural situation is one where absorption (transmission) or reflection are both simultaneously present, and special efforts must be made to create artificial objects where one or the other is minimized.
The idea defended by Feynman that "spots and holes" cannot be accepted as a reason for the existence of both reflection and transmission has therefore to be taken with a grain of salt. Especially when we think that according to the last atomic model matter consists for a greater part out of empty space!
I must say that reading, and even more looking at listening to Feynman explain his little arrows, I cannot shake the impression of a con artist trying to convince his audience that the aces he pulled out of his sleeve really appeared magically. Maybe it is his, probably purposefully prominent [wow, is that an alliteration or what!], New York accent that makes him sound like a "wise guy" in a movie.
Anyway, the absurdity of Nature sounds more and more like the absurdity of QED.
The Michelson Myth
["Harry Potter, The Chamber of Secrets"]
Feynman describes in his third lecture in QED, a variation of the two-slit experiment. One light source S, two slits A and B, and one detector D. A photon has 1% chance of passing through each of the slits alone, either A or B. That is also what is measured when a detector is put at each slit, giving a total of 2%. The problem is that when both slits are open, we measure a 4% chance of a hit at detector D. Feynman's explanation is of course interference and the absurdity of Nature.
Let us see if we can find a rational explanation for this new version of the two-slit experiment.
When one slit is closed 100 slits will get you one hit, which means that 99 attempts will be in vain. But then, when a second slit is open, the 99 photons have still a chance that one of them may pass through the second slit.
Even if we are allowed only 100 photons in total, a photon that then goes through slit number two does not eliminate the chance for the remaining photons to pass through slit number one.
In short, opening an extra slit is doubling the chances of each slit of letting a photon pass, which would explain perfectly how we get the 4% at D when both slits are open!
What are we then measuring at the slits A and B?
Personally, I think that, because we are dealing with a thought experiment, the idea of two extra detectors in such a small space, is not really realistic, while a detector D certainly is. I am therefore assuming that D is used for counting the number of hits for each slit alone, and also for both open.
Of course, I may be wrong, because if it is possible to put detectors at A and B and measure the photons passing through, then their added results should be equal to that of D, and not even interference would allow another conclusion. The question whether the detectors are reliable or not shouldn't even be posed. If they are not reliable, then anything is possible and the experiment should be discarded. We have therefore to assume that they are reliable, and then there can be no difference between their common result and that of D.By the way, I will come back to the question of the reliability of Feynman's thought experiments, I have the impression that he uses them as a way of getting accepted what couldn't otherwise be proved by arguments or real experiments. But then, that is something that Einstein was also very good at.
The Michelson Myth
Magical Me (2)
[I am afraid you will probably need Feynman's book, QED, to follow my argumentation. I will limit myself to fig.68 (p.104 in the Princeton University Press, ed. 2006).]
Feynman claims to have an explanation for the reflection of photons by glass. He had first assumed, as a simplification, that it all happened at the surfaces of the glass. Now he wants to show that in fact it happens inside the glass, even though the detailed calculations ultimately turn out to be equivalent to those made under the assumption that only the surfaces are involved.
Whatever the case, his little arrows are supposed to give the solution and his drawings to illustrate each step.
We are dealing with a beam of light entering a piece of glass which he has divided into 6 layers to make it easier for the reader/listener (it was first a lecture) to follow his reasoning. The first drawing (a) simply shows the source, the almost perpendicular path through the six horizontal layers, and a line going back up towards the detector A, and symbolizing the reflected light. The following drawing (b) is the one in which Feynman, unknowingly, shows the implicit assumptions in his thinking. Making use of a space-time graph, he draws vertical lines for time, the monochromatic source S, the detector A, and a line for each of the 6 layers.
We notice immediately that S is emitting photons successively in time, as may be expected, but then we see that each photon goes nicely to one particular layer, one higher than the preceding photon.
This is of course quite miraculous. How did each photon know where to stop and be annihilated by an electron, which then creates a new photon and sends it in the direction of the detector?
Obviously Feynman had already solved the problem in his head, and the drawing was the result of his unspoken thoughts. After that his elaboration on how all the little arrows magically seem to explain everything sounds very artificial, since all it does is confirm his implicit conclusions.
Conclusions which he never explicitly presents. But then, maybe his conviction that Nature cannot be understood rationally, or with common sense, was explanation enough. After all, as he so often claims, he does not explain Nature, because he does not understand it, nobody understands it. All he can do is show how it is, "and if you don't like it, go somewhere else!". So, what is one miracle more or less?
The Michelson Myth
Magical Me (3)
Back to the second lecture. The issue is the paths photons take when hitting a plane surface. Classical theory advertises the equality of the angle of incidence with the angle of reflection, while QED affirms that a photon can take any path from the source S to a detector D, even if it means going to the extreme ends of the surface and then to the detector, that is following the longest path. But experience tells us that light goes in a straight line, that incidence equals reflection, so , how can we reconcile both these views? The solution is that most paths cancel themselves out, leaving only the paths of least time which are very close to the classical model.
Feynman considers this as a triumph for QED because it arrives at known and accepted conclusions on the basis of the calculations of probabilities, his famous arrows.
The cancellation of the unwanted paths is of course interference in sheep's clothes, even if Feynman consequently speaks of photons and not of waves. But then, as he will argue in his following lectures, in QED electrons can destroy photons which can create electrons (and positrons) which can create photons. So, it is all for the best really.
Gratings are according to him a proof that photons do not only follow the incidence and reflection rule, but can indeed travel all possible paths on their way to the detector. The trick is to cancel cancellation and keep only the photons that bounce off to the right (or all those that bounce off to the left), and that is exactly what a grating does.
Since Feynman, as I already mentioned earlier in another post, jumps indiscriminately from individual photons to light in general, we will have to keep in mind what I will call the Hitachi principle: successive individual impacts by photons, or electrons, have ultimately the same effects as that of a beam (or wave) of light emitting millions of photons, or electrons, at the same time.
Once we do that we start to wonder why there should be any cancellation. When we look at a light beam hitting a surface we can certainly distinguish a path which is more illuminated than others, and which undeniably follows the classical lines. But, at the same time, there are regions surrounding this path which even if less bright, are certainly receiving parts of the beam, until darkness takes over. So, what seems wondrous when considering isolated photons becomes much less strange when the whole scene is taken into account.
Feynman is certainly right to attend his audience to the limitations of the classical view of incidence and reflection. But then he overshoots and makes it seem like the way light behaves cannot be understood by any rational means, only probabilistic calculations.
Real life teaches us that light, even if it goes in straight lines, does not go straight forward only, it spreads in all directions, or at least a cone . This is an empirical fact and is not any stranger than the fact that some rays do move straight forward. The Law of Reflection offers indeed a very limited view which is contradicted by our own perception and experience. We do not need to stand in the same angle as the incident ray to be able to see it. And apparently, neither does a photomultiplier.
On the other hand, Feynman's probabilistic view, whatever its practical merits, is not necessary to give an account of the phenomena of light. We can reject the simplicity of the law of reflection without embracing the irrationality of quantum theory.