This is a photograph taken with the bare body of a digital camera on a tripod. A red laser pen is directed into the camera, very close to the center, from a distance of more or less 2 meters. The shutter speed is 1/60s. Notice the strong resemblance with my other pictures taken with a pinhole lens, and examples given by others.



Here is the last of a series of six taken at the fastest shutter speed my camera can manage: 1/4000s.
You will notice that the rings become less and less visible.




It would be difficult to claim that diffraction has anything to do with the way the image is. The opening of a camera body is huge relative to the different wavelengths of light, and so is the sensor area.
This reinforces me in my conviction that what we are looking at is the image of the laser itself, but I am certainly open to suggestions.

This has also been asked by VagabondSpectre. Maybe it seems obvious only to me, but greater distance blur objects, or points together. A simple example are two mountains that appear to be one from a distance, Craters on the moon that are kilometers wide and which are projected in much smaller images with the concomitant loss of details. That means in the case of eclipses or reappearance of moons from behind Jupiter that greater distances would make it more difficult for an observer to pinpoint the moment of disappearance or reappearance. I am sure it represents no problem now, telescopes are powerful enough for us to see the moons peeking from behind Jupiter. After all, if we can see the planets rotating, that should not present any difficulty.

I would be interested to know if Rømer's experiment have been re-done and what the results are. I mean the experiment itself whereby the exact times of eclipse and reappearance are compared, taking into considerations all relevant factors. If is has already happened I would appreciate a link or a reference.

@VagabondSpectre I may expect you to do your homework and referring to where I have handled some other matters is certainly not deceptive.

Also, size does not always matter, and the nice picture you show does not say anything about the quality of the lenses at that time.

I realize I have not answered all objections, but I will try sometimes later.

Thank you for making the effort of stating more clearly your objections.

1. You might be right concerning the fact that with current telescopes we can see planets rotate. I honestly wouldn't know but I am willing to take your word for it.

Please do not forget that we are talking about the 17th century, and I do not think that the telescopes then, which were no better than cheap binoculars, would be capable of such a feast.

2. I will skip this point because I do not see its relevance nor how it could be used against me. I will just wait to hear more from you on this subject.

3. The distinction between parallax and resolution is an artificial one. In fact, parallax makes the lack of resolution evident since we need to move through space, and time, before we can distinguish two objects from each other. Having said that, both are considered as different phenomena, and the fact that I mention them at the same time does not mean I am not conscious of what separates them. I just think it is more a matter of degree and perspective than fundamental differences.

4. Is how you explain things while I am proposing an alternative approach that does justice to some phenomena that established light theories do not explain.
Vision is based on the assumption that we see objects because light reflected off these objects enter our eyes and impinge on our retina , I have given many examples in this thread and in Optics: some problematic concepts, why this view is erroneous, or at least incomplete. I will not repeat myself here neither.

5. It is not entirely clear to me what you mean by dilation effect, and have no idea whether I should agree with it or reject it. I will therefore abstain.

I can see that your argument rests entirely on the assumption that "it takes longer to notice changes in distant objects" despite the obvious fact that bigger telescopes mean more resolution, which can eliminate any setbacks caused by resolution blur. The "no intermediate states" bit is unsubstantiated and must result from a confused understanding of how we carry out astronomical observations... — VagabondSpectre

Concerning the first part of this quote, this is as far as I can see an argument in my favor. We are capable of seeing objects as they really are, therefore with no delay. You reaffirm the idea by stating "bigger telescopes mean more resolution" which seems to indicate that we see distant objects as they are. I am curious as to how you reconcile the idea that telescopes give an accurate image of reality with the principle that it takes time for light to reach us (on that we agree), and that therefore the images we see represent an image of a moment in the past. All I am saying is that we are not looking at the past but at the world as it is now, and that is the puzzle we have to solve.

I do not have all the answers and you will certainly be able to ask questions for which I may have no answer. I do not consider my reflections as a complete and finished theory, but as a work in progress, and I will see where that gets me.

that is exactly what my pictures also show. Regarding my arguments, no I will not repeat them. I will wait for your objections that have to be about what I said, and not about what you think I said. Asking why when you apparently have not even taken the time to read what I wrote is tiring and it is a game I will not play. Quote what you do not agree with and say why you do not agree with it instead of simply asking again and again for clarifications.

I will clarify that nowhere do I claim that the speed of light is infinite. In fact I do not believe that is the case. if you had read what I wrote on the subject you would know that. It is because the speed of light is finite that the theory of light as we know does not make sense. If the speed of light was infinite then we could simply say that we see things where they are when they are there, and we see them immediately because, as Descartes thought, light is infinite.

I do not think that. Therefore, I say that the theory of light cannot explain vision and certainly cannot explain the fact that when we look through a telescope the object is there where we see it, when we see it. The same way we look at somebody coming down the road, still a few hundred meters away from us, and we know it will take some time for him to reach us. Light theory as it is can easily explain this last example, but it breaks down when it comes to distant objects and great distances.

The setting is exactly as I described it. A camera body to which were attached extension rings, empty tubes, usually to allow getting closer to the object. Here they lengthen the focal length and makes the image much darker, needing longer pressure times. The pinhole lens , known as a Holga pinhole lens. with a pinhole diameter of .25 mm, is attached to the tubes. There is no other lens involved. The light goes therefore through an empty hole. I could have used a self-made pinhole camera made out of a shoe box as it were.

As far as Romer is concerned, I am sorry but I do not feel like repeating myself. I will of course answer to any argument you might have that goes beyond simple appeal to authority.

1. The pinhole lens has a Nikon fitting but is not made by Nikon.

2. Your assumption of diffraction is not reasonable, Why should a collimated beam diffract when going through an empty opening?

3. Even assuming diffraction, the question still remains of why there should be such differences between the different images on the basis of shutter speed alone. I would very much like to see some calculations that take the speed of light into consideration, and explain to me the differences.

4. You are defending the theory or theories of light as they are taught. I have no problem with that. But referring to them is not enough. I will be very happy and obliged if you could show me where I went wrong, but appealing to authority is not enough.

You seem to agree with me, so I am not sure what I should say. maybe you are right and what the admiral sees is such a tiny speck on his officer's retina that the latter is not conscious of it. I will remind you that beyond a certain distance even that speck will not be captured by the retina.

The point is: when the admiral sees the enemy ship,and maybe we should transpose this in a Star Wars decor, a ship some millions of light years ago. The question is, where is that ship when the admiral sees it in his telescope? Assuming some Star trek kind of warp drive, you still can divide the distance by its speed and predict how long it will take the ship to get within range. And that is only possible if you are seeing the ship there where it is, at the moment it is there.

First, diffraction should not be a problem since we are talking about a 0.25mm aperture, with no lens. The different wavelengths are measured in nanometers.
Concerning your objection about my Rømer analysis you are assuming that which I think he had no right to do. If you assume that you are seeing the moment when a moon appears from behind Jupiter you have already decided that the difference between the times of observations can only come because of the distance and the speed of light. I do not know how to make it any clearer, but this obviously, as least to me, the case of a circular argument. Your theory has to be right for it to be right.

This is a sliver taken out of the first picture. Personally, it reminds of the images made of light going through gratings with hundreds of slits or more, and where the different bright and dark spots are explained by constructive and destructive interference. Here, we are dealing with collimated light that goes unimpeded through a hole and shows the same characteristics.
I think that people forget that laser lights are made of diodes, therefore of discrete objects that, however close to each other, keep a certain distance from each other. I find this a much simpler explanation than what the wave theory has to offer.

This post belongs in my other discussion Rømer and the speed of light 1676

It should be possible, with better equipment, to shine a laser light exactly through the center of a pinhole, something I failed at miserably.
Theoretically, this laser light should cross the threshold unimpeded and hit the screen or sensor. But then, the same could be said of the part of any scene that happens to face the hole directly. We would get something like the infamous Spot of Poisson: every image should show in its center a bright spot that receives light unimpeded, even if the conditions, like shutter speed, make it difficult for the other rays to reach the sensor.
But then, that is not what is happening, is it? If anything we are confronted with the Anti Spot of Poisson. Even the light that should go unimpeded through the center of the hole, seems somehow to be diminished or even extinguished by a shorter shutter speed.

Where is Poisson when you need him?

Light is supposed to travel at 300.000 km/s. How could there be a difference of less than 1 second between a picture where the laser spot is visible, and another one where it is not, and that over a distance of 2 meters?
Even taking into account the imprecision of cameras and laser pens, all images should be as bright as they can be for the camera. Even the fastest time a modern camera can have, around 1/4000s, should make it possible for the laser light to travel 75 km, that is more than 35000 times the distance it has to travel from the pen to the camera. If we take a shutter speed of 1/400s light would be able to travel 750 kilometers, but it would still be unable to form an image on the sensor of the camera?
I am no mathematician, and I get my figures very easily wrong, so maybe that is one of those cases where a genius with numbers will shame me by pointing at simple but oh so fundamental mistakes. I will be waiting and ready to learn.

Those are two pictures taken with a pinhole lens, attached to 3 sets of extension rings, and the whole attached to a Nikon body.
The red light you see is a laser pen directed towards the lens, as close to the center as I could position it. The second picture, where the spot is hardly visible, was taken with a shutter speed of 1/60s. The first one with 30 seconds.
There were more, showing the laser spot in different shape depending on the shutter time.
Here is another one (about 5 seconds exposure time).
The following shows that the shorter the exposure time, the less rings are visible, until they disappear all together. Here is one with 1s.


I have the following remarks that I hope will show that we should not take the established theories of light for granted.
1) Can the speed of light play a role in the differences we observe between one picture and the other?
2) Should we consider the dark bands as destructive interference patterns? Or are they simply the image of the laser lamp and its wiring?

The shots were taken at around 2 meters.
The pinhole diameter 0.25mm

Where is my image now (3)
Instead of a monochromatic ray box, try using, as I did, two red and one green laser pens. You will notice that the green beam does not coincide with the intersection point of the red mean. That is no surprise, Newton called it different refrangibility, and it was a central aspect of his analysis.

But, let us again attempt not to be blinded by the beams, and try and understand how an image of different colors is formed.

We have now three beams, two red one green, coming from laser beams which have been set along each other, facing a convex lens.

Optics has concentrated on the paths these light beams took and, I think, somehow ignored what happened to the image of the three little pigs.
Suppose now that we want the lens to show us, inverted or not, the image of those three pens. What should we do?

Well, if you asked a photographer he would tell you that you have to measure the light reflected off the pens themselves, and not their reflected beams. Again, just like taking a picture of the sun. You will have somehow to neutralize the strength of the solar rays before you can take a snapshot of the fiery planet. Accordingly, your exposure time will be much longer than it would be on the basis of the beams reaching the camera.

What is an essential question is whether it will be possible to take a picture in which all three laser pens, and the color coming out of them, would be as sharp. In other words, will we be able to take a sharp picture of the green pen, and, at the same time, in the same picture, show the red beams as sharply as their Martian brother?

That sounds like a stupid question, after all we constantly take pictures of multicolored objects, and we never have problems with that. All colors are depicted as sharply.

This brings us to a very familiar issue in Optics:

Chromatic aberration
One can find many examples of so-called CA on Youtube, but you will have to be very critical since not everything that is presented under this title truly deserves it. Still, it gives a realistic indication of the problems people get confronted with in their everyday use of cameras.

Let us analyze a picture of our three little pens and ask ourselves if we can make sense of the concept of CA.

The green beam is obviously a game breaker. It would be much easier if it just did what the two do, and met with them at the same intersection point.

The problem of course is whether that behavior could honestly be called an aberration. Mister Green is doing what it always has done, and what its nature compels it to do. And that is, when in the company of other colors, to refract according to its own nature.

Still, pictures which show such an effect are considered somehow as faulty and in need of amelioration. It is the most obvious at the edges and that is, when you come to think of it, not really surprising.

Remember that we have no problem taking pictures of multicolored objects or scene, and the accepted explanation is that CA is not perceptible when not at the edges.

My own humble opinion is that there is, in general, no CA at the center of a picture because having a sharp image of multicolored objects is never a problem.

The problem is when we are taking a picture where the beams themselves and their behavior is registered by the camera.

Let us go back to our simple example and I will try to explain it as clearly as I can.

There is a difference between a picture of the pens, and the color they propagate from their mouth, and a picture of the beams that come out of those mouths. The deviating behavior of the green beam is only present in the second case. We have no trouble depicting green and red objects with the same degree of sharpness if they are at the same distance from the lens.

In other words, when light is projected on a surface, there is no CA present, but when beams are registered we can be witness of the different degrees at which different colors are refracted.

One again, we have to make the distinction between images, and the path of light beams.

edit: I put a gray filter, a so-called ND-filter, between the beams refracted through the lens, and a white sheet of paper. I had not trouble getting a sharp image of two red and one green spots. Better lighting on the pens, and a more powerful filter, would have given a clear image of all three pens and the color coming out of them. Every pen and colored mouth as sharp as the other.

This clearly shows that the different refraction angle of each color does not play any role in the formation of the image. Only when it is registered as such, as a beam.

I am much more interested in life than in gadgets. I have discovered that there is much, much more good health and joy in dance, singing, and the arts than can be found in gadgets. Quality trumps quantity, and life trumps science. — Rich

nothing wrong with that.

The Daoists, who were great observers, developed a tremendous understanding of the nature of life. What they couldn't do is kill millions of people with a single gadget. That took a better understanding of chemistry (which begins with direct observation and intuition, e.g. alchemy). Unfortunately, much ancient knowledge which is quite superior is being lost. The good news is that it can be recovered by direct observation and creative intuition. — Rich

I am afraid I do not share such a romantic view of ancient knowledge.

I think you should remember that we are talking about science, and not experience. The discussion which of the two is closer to reality sounds like a metaphysical conundrum. Don't make it a competition between knowledge and intuition like Bergson much too easily did. As far as I am concerned, they feed on each other. Knowledge is as primitive as intuition, and to be able to gauge distances is a condition for survival.

I am a great believer in Science, and at the same time the most skeptic of all.

https://philpapers.org/post/17142

edit: maybe more to the point, I found those two posts that more directly relate to the phase of the discussion. But let me state that I have no opinion on whether the universe is a hologram or not. I am afraid it is way above my pay grade!

https://philpapers.org/post/17290
https://philpapers.org/post/17298

Why does ray tracing work (even if it is wrong?)

Imagine a super ray box, one, just as big, with not 5 but 500, or even 5000 beams? How would all those beams behave?
There is no reason why they should behave any differently than the main 5 we can see on the video clip.
By the way, if you need a reliable image of the ray box and of the beams coming out of it, you will have to go further than the first point at which all 5 become distinguishable. You will have to wait until the spatial relationship of the elements of the image is proportional to that of the same elements in the object. In other words, just like in the object, the image will have to show 5 beams equally spaced from each other.
I wonder, and I must precise that I have not made the experiment yet, whether that image. with the beams equally spaced, will be there where ray tracing says it should be.

Let me know if you have the opportunity to do such an experiment.

Concerning the question in the title, I also have to admit that I am not really sure I've got the answer.
Consider the following as a first attempt.

Ray tracing is based on a fundamental assumption, that each point on the object reflects (or propagates) light in all directions, a physical impossibility which is then covered up by the even more slippery concept of wave.
As we can see each time we shine a light beam through a lens, this assumption is blatantly false.
We do not need to use laser beams, normal light going through splits would give the same results.

Back to our puzzle: how could ray tracing be so accurate if it is wrong?

My first reaction would be to say that it is geometrically accurate, even if empirically wrong. When tracing the ray from each point of the object -and let's take the perennial arrow as our model- each point of the arrow will be represented (ideally) by one point of the image, and all those points will be easily linked by a single line equivalent to that of the arrow.
What ray tracing does is, I think, start from this empirical situation and try and find a logical, geometrical explanation as to how all these points appear to be connected. And the assumption of each point reflecting multiple rays appears to be the perfect solution.

I would like to coin the expression "ad hoc rationality" to express a natural thinking process which consists in finding, or inventing, reasons that explain for us the behavior of not only objects and processes, but also of people.
The danger of such a procedure is that we can easily be tempted to stop looking at the empirical facts and only see what the theory tells us to see.
Such a danger is inevitable and should not be exaggerated, since there is no alternative for such a way of thinking.
Furthermore, mere rational and logical explanations meet sooner or later empirical obstacles they cannot explain away anymore.

I think such a simple video clip as the one presented above, can be such a wall.

Thank you. But I was just about done. This was a side-street I was walking, with no real definite end to it.

I have, in another forum, spent as much time and energy that I could, based on my non-physicist background. And metaphysical debates have the annoying property of having no end. There are no knock out arguments for me to hit you with, and I do not think you have any in your possession either.

But it's all right, such an open ending is exactly what makes science interesting as far as I am concerned. What worries me is the theological devotion of people who call themselves scientists or materialists. BTW, I am old-fashioned, and for me materialism has more of a socio-political connotation than a metaphysical one. I have always felt closer to Marx than to Engels.

I find metaphysical materialism as is known in, among other places, American universities, as simplistic as Engels' attempts at philosophy.

Please read the previous posts. You barge in and expect us to start all over again. That is not reasonable.

[Scratches arse and reaches for tin foil hat....] — apokrisis

I personally have no problem with the idea of a universe expanding. After all, it is as reassuring or scary as the idea of a finite world. A little like being afraid to reach the end of the earth and then fall off in the emptiness.

What we are talking about is the ontological value of cosmology. You are convinced of the veracity of the whole story, while others in this discussion are not. Again, I could buy into the idea of an expanding universe. What I do not buy in are the current cosmological theories.

assume further my dear sir.

Time, even as objective phenomenon, is never neutral. When you make biological processes run at two times their normal speed, you are not effectuating an algebraic process, like multiply both the nominator and the denominator by the same number, and the original number will not change.
Biological, and certainly psychological processes are what they are because of their rhythm, change the rhythm, and you will make organs work two times harder, age two times faster, and emotions completely change from quite to frantic.

edit: the difference between I did it my way by Sinatra and the other guy, the dj?

I already know the argument, and it is the most ridiculous thing I have ever heard. Ask biologists.

This is indeed different than the experience of time which philosophy talks about. Why do you conflate the two? — Agustino

I don't, Einstein does, and before him his teacher that invented it.

Because Time is not an objective phenomenon? In this I completely agree with Bergson.

I won't speak for Rich, but I find the concept of space-time a metaphysical monstrosity.

Then you are expressing one of the contradictions Rich was warning about.

is that a yes?

It depends which equations you elevate to ontology. — Agustino

How about space-time? Should it be elevated to an ontology?

The assumptions you are worrying about are neither true nor false, but useful. That's why they are assumptions and postulates, and not truths. — Agustino

I wouldn't have any problems with that. Only, as Rich indicated, RT and QM come with ontological claims and so does contemporary science. This thread is a clear example of these ontological claims. Is the universe expanding? That is neither merely an assumption, nor an approximation but a hard claim that the universe as we know it is expanding.

That is what I meant with cosmology is metaphysics with mathematical formulas, and that is what I think Rich means when he says we should beware giving ontological value to RT and QM

To sum up the whole discussion. We have no idea whether the universe is expanding or not. Some say it does, some say it does not.

I can confirm this attitude in Physics forums. They are very good at regurgitating textbook knowledge and abhor critical questions. I have even been banned just for daring claim that Optics is not necessarily correct. My confidence in critical thinking among scientists, whether forum users or academics, is very low.

@MikeL
anyone. I am interested, in this case at least, in direct feedback on the argumentation, and much less on a general discussion, which I also consider as important, of RT and QM. In other words, are the arguments I am using solid or fallacious?

Okay. Any feedback on the validity of my argumentation concerning muons?

I would like to present something that I wrote some time ago, when I was researching Relativity and Quantum Theory. I would be interested in your reactions on this single issue of the decay rate of muons and how RT and QM very often are self fulfilling prophecies. But especially the first point, the second being too wide and too deep for fast solutions.

https://philpapers.org/post/18962

edit: even though it is not exactly about the expansion of the universe, it concerns light and how it is conceived. That's when my interest started in the subject of light.

The Aperture Problem (2)

The video clip mentioned earlier is a perfect illustration of the AP. Imagine putting a diaphragm right after the convex lens, and slowly closing it. It is immediately obvious that rays will be cut off and less than 5 beams will be projected on the screen.

Such a mutilation of the original scene would of course be very noticeable, and the fact that it does not happen with cameras teaches us something that hardly gets any attention in textbooks: the aperture has to be placed at or very close to the focal point. That is the only way a closed diaphragm cannot have any influence on the field of view.

My question therefore remains: how can a smaller aperture have any influence on the depth of field?

The accepted explanation is that superfluous rays are weeded out by the diaphragm, enhancing hereby the sharpness of the image.

I also found a preposterous explanation based of the degree in which rays diverge from each other around the focal point. https://www.youtube.com/watch?v=6XMk9jFcnlA

These explanations all sound logical when one accepts the rules of ray tracing. But only then.

I think you certainly should keep digging in this direction. My inclinations are different if certainly not opposed to yours.
Right now I am still wondering how distant stars can be reflected on our retina and how the moon can be reflected on a lake.
I am completely unsatisfied with the theory of the duality of light and will continue my reflexions and modest experiments with photographic gear (professional lab gear to study light is simply out of my reach), and see where that gets me.

You have taken a very bad example for predictions. There are no predictions in this case, only conjectures. Cosmology is metaphysics with mathematical formulas. It is good of you to have confidence in Science. So do I. But I refuse to accept blindly what scientists tell me. Once again, even when all scientists agree on something it is still no guarantee that it is true. It is certainly an indication to take it seriously as long as there is no better alternative. But it should not be a reason to close our minds to other possibilities, how crazy they may sound at first.