Rømer and the speed of light 1676

Hachem

Rømer's argumentation was the reason Descartes' view of instantaneous light propagation was abandoned in favor of the until now accepted view of light traveling at a high but finite speed. His arguments were quite simple, maybe a little too simple, but were universally accepted. By calculating the time it took for the closest moon of Jupiter to reappear from behind the planet, and multiplying the minimal differences between all the observations during a ten year period, Rømer was able to show that the differences when seen from different positions of the earth relative to Jupiter were far from negligible. He was then able to calculate the speed of light reasonably accurately, certainly for his time.

The question is whether the differences in the times of eclipse and reappearance of the moon cannot be interpreted differently, without involving the idea that it takes time for light to travel through space. We all know that when looking through the telescope at a planet like Jupiter, we do not see it rotating about its axis, or orbiting the sun. We get each time a snapshot of a frozen moment in time, and the changes to the images we receive occur in jumps without any intermediate states. This is understood as the effect of parallax, or more simply resolution. Because of the distance two points separated by relatively large distances will appear to our perception as one, and it takes time before we notice the difference between one position and another.

This is exactly the situation which Rømer is analyzing, but instead of understanding it as a case of parallax and resolution, he chooses a very specific approach. He considers the time it takes for astronomers to observe the disappearance or reappearance of Jupiter's moon as a fact that needs no further explanation. If we see the moon appearing at time t that is because the moon appeared at time t. And if we notice that when the earth is at another position, farther from Jupiter, and the moon appears or disappears at time t+x, then x must be caused by the longer distance between the earth and Jupiter.

This is much too easily discounting the fact that we only see immediately the differences between one view and another when we are very close to the object. It is not surprising that Jupiter's moon seems to appear or disappear at a later time than when the earth is closer to Jupiter. The larger the distance between the earth and Jupiter, the more time it will take us to notice a difference between two consecutive moments.

In other words, whatever Rømer and everybody after him might think, he did not prove that it takes time for light to travel through space, and his calculations concerning the speed of light, whatever their merit, are based on invalid arguments.

Hachem

Imagine you point a super Hubble-telescope towards Jupiter to see when IO reappears from behind its planet. Next to you is a colleague with a much less powerful telescope. Would both of you see IO appear at the same moment?

Let's get down to earth in the time of Galileo who is still trying to sell his (stolen) invention to pay his many debts. An admiral of the Venicean navy is using the new revolutionary device, while a lower officer is staring at the horizon hoping to detect an enemy ship before, or at least not too long after his superior. The question is, what would determine the difference between the time the admiral detects the ship, and the time in which the lower officer does the same in turn? It is in fact a very simple operation: if the difference is equal to the time it takes the ship to get in visual range of the naked eye, then we can say that the telescope is showing the location of the ship in real time. If, on the other hand, the difference between the detection times is negligible, then we can say that the telescope allows us to see objects not there where they are, but where they were when their light started its travel towards us.

Now, let me ask you this. What would be the strategic advantage of seeing an enemy ship a few (milli) seconds earlier? Especially in the 17th century. Also, if it is correct, what does it mean that a telescope allows us to see distant objects in real time?

Rich

Now, let me ask you this. What would be the strategic advantage of seeing an enemy ship a few (milli) seconds earlier? Especially in the 17th century.
Also, if it is correct, what does it mean that a telescope allows us to see distant objects in real time? — Hachem

Well there is a lot here, and as I am not sure where you are headed, let's just begin by saying that the advantage of seeing a ship with greater clarity earlier than the Captain of a ship seeing you is the ability to make a decision whether to run or attack.

As for real-time, this leads to a total different discussion about the nature of time. Scientific time has to do with movement in space and the measurement of simultaneity.

But there is also duration (Bergson called real-time), which is the time we are experiencing as life.

Scientific time is homogenous and discontinuous. Duration is heterogeneous and continuous. What we mean by time and distance can get pretty hazy the more we dig into the nature of nature and the nature of perception.

Hachem

@Rich
I saw my second post more as a clarification of the problem posed in the first one. Are we allowed to speak of the speed of light as we do if we are able to perceive distant objects in real time? If looking through a powerful telescope had allowed Rømer to see in real time the reappearance of Jupiter's moon, would he have had any reason to believe that it takes time for the images to reach us? That would in fact mean that the admiral would hardly have any advantage on his officer ( a few milliseconds). Only if the admiral saw the enemy ship there where it was at that time does a telescope have any use for the military. Otherwise it would be just another scientific toy with no strategic significance.

Replace the enemy ship with Jupiter's moon and you would have to admit that Rømer 's calculations are meaningless.

Rich

↪Hachem

Philosophically your question relates to the nature of perception, what we are seeing, and what we are measuring.

As your example illustrates, one can take various views of this problem all of which result in approximately the same answer. Similarly with quantum mechanics vs. quantum interpretations. Different interpretations, same answers for practical purposes.

This is not to say that having a deeper understanding of the nature of perception, light and space is off no consequence. It probably has lots of consequences, but not related to some practical problems that are currently being solved using Romer's method or otherwise.

Hachem

↪Rich

I honestly have no idea what you mean.

Rich

↪Hachem

I was afraid that would be the case. Suffice to say, the nature of perception is a deep philosophical question as your example suggests - only suggests. I am probably looking at your question in a different way than you intend.

Hachem

Of course perception is involved in every aspect of human life and knowledge. As far as suggesting, it seems to me that it is what you are doing. I would welcome arguments against my analysis.

Hachem

Perception theory, as well as the established theory of light (duality of light) are both based on an assumption that has always been considered inattackable . Even the Ancient Greeks who believed that the light came from our own eyes, just like a flash light in the dark, were, I think, of the same opinion.
This is hardly surprising, after all nothing is visible in the dark: no light, no perception.
This still does not explain the complicated fact of perception. Light as a conditio sine qua non of vision does not mean that light needs to be reflected off objects into our eyes for us to see these objects.
Here is a simple example: a light beam directed away from me will still be visible, as will be the light at the end of a tunnel even if I am standing in complete darkness. It would be difficult to argue that light rays somehow are reaching my eyes when there is no indication of it whatsoever. Furthermore, light intensity diminishes with the square of the distance. After a while, light stops and darkness takes over. That does not mean that somebody who stands way beyond the illuminated area cannot see the light in the distance.
If we link these thoughts to the original discussion then we can wonder whether we are seeing the stars because their light takes time to reach our eyes, or if we see them just like we see a light on earth that does not shine beyond a very limited distance.

Hachem

@Rich

https://philpapers.org/bbs/thread.pl?tId=897#p8097
https://philpapers.org/bbs/thread.pl?tId=1002#p9701
https://philpapers.org/bbs/thread.pl?tId=1006#p9742
https://philpapers.org/bbs/thread.pl?tId=1011#p9778
https://philpapers.org/bbs/thread.pl?tId=1015#p9837
https://philpapers.org/bbs/thread.pl?tId=1021#p9877
https://philpapers.org/bbs/thread.pl?tId=1026#p9932

Concerning Bergson, I think I have read almost all of his books, in French, in high-school. He and Camus were my favorites. But then, I was very young.

Hachem

Is the universe expanding?
Not if Rømer was wrong and we are seeing distant stars the way the admiral was seeing the enemy ship: there where we see them, and not as something shown by light rays traveling trillions of kilometers and taking millions of years to reach us . The question therefore whether Rømer was right in his assumptions has far-reaching consequences that go well beyond some ratiocinations about perception. That is why the discussion of his claims should not be considered as closed once for all. This is an attempt to reopen a discussion that scientists believe has been solved a very long time ago. I claim that they are wrong.

Rich

If we link these thoughts to the original discussion then we can wonder whether we are seeing the stars because their light takes time to reach our eyes, or if we see them just like we see a light on earth that does not shine beyond a very limited distance. — Hachem

This was more or less what I was attempting to suggest. The nature of perception is far from a done deal. If you like Bergson, I think you'll appreciate Stephen Robbins analysis of Bergson on YouTube. Very astute, and like Bergson, way, way ahead of his times.

Hachem

@Rich
Thank you for the link.
Bergson dared put into question the idea that mathematics is the "language of nature" as Galileo announced so proudly. Since then we can say that Galileo has been the unchallenged champion and Bergson, in spite of his Nobel Prize, has been relegated to the "oubliettes". Like Bergson, I do not think that the language of Nature is Mathematics for the simple reason that mathematics is a human language and bears all our strengths and weaknesses. It is an indispensable tool for Science, with the emphasis on "tool".

Rich

↪Hachem

Mathematics it's an interesting "tool", and like philosophical doubletalk and wordiness, is often used by science to obfuscate, intimidate, and bludgeon. Unfortunately, most modern philosophers have become timid in face of the scientific onslaught but maybe they'll find their mojo again. For the most part, other than physics, science really doesn't have much to say about the nature of nature, but it says so much with such self-assurance, it is tough to figure this out.

Hachem

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

Hachem

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.

Hachem

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?

fishfry

what would determine the difference between the time the admiral detects the ship, and the time in which the lower officer does the same in turn? It is in fact a very simple operation: if the difference is equal to the time it takes the ship to get in visual range of the naked eye, then we can say that the telescope is showing the location of the ship in real time. If, on the other hand, the difference between the detection times is negligible, then we can say that the telescope allows us to see objects not there where they are, but where they were when their light started its travel towards us. — Hachem

I can not believe that this is the correct explanation. If a photon is capable of reaching the outer lens of a telescope; it is certainly capable of going a few more inches or feet and reaching a retina.

In fact the admiral with the telescope and the underling with his naked eyes must necessarily see exactly the same set of objects. The telescope simply magnifies an image so that it can be processed in detail by the eye/brain system; whereas the naked eye image can't be resolved in sufficient detail.

In other words the underling is looking for a tiny little spec that takes up only a tiny little spec's worth of retinal cells. The telescope makes it so that tiny little spec's worth of photons is spread out over a larger area of the retina.

It can't have anything to do with the fact that the telescope is a couple of feet long hence getting the photons first, if that's what you're saying.

A similar thing happens with photography. If I stand in one spot and take a picture with a wide-angle lens then a telephoto lens, the telephoto is simply cropping the field of view. If you had enough resolution you could shoot exactly the same shot with a wide angle lens and then crop it in the computer.

I'm no expert on telescopes or optics so if I'm missing something let me know. As I understand it, it's just about making a given set of photons take up a larger portion of the retina via telescopic magnification.

VagabondSpectre

↪Hachem

What you've produced is called an Airy Disk, which results from the light which diffracts when traveling through a very small aperture (comparable to it's wavelength) and is then redirected by your camera lens.

Regarding Romer, as far as I understand it, since he knew when the distance between Jupiter and the Earth was growing or shrinking (and by approximately how much), he was able to correlate changes in eclipse duration with distance gained or lost between the Earth and Jupiter during the actual eclipses.

Matters of resolution aren't problematic for his observations because the emergence of light after the eclipse was not dependent on having a detailed image, but merely the presence of light.

I'm not exactly sure what your main criticism of Romers analysis is. You suggest that there are these periods of no intermediate "updates" between the images we collect of distant moons, but in reality different photons are continuously and somewhat unpredictably (at very small time scales) striking our photo-receptors. Our ability to get continuous updates is limited only by our willingness to gather the photons with sufficient speed and at sufficient scales.

The way telescopes defeat the resolution problem is simply by gathering more photons and refocusing them into a size our own eyes can interpret. (bigger telescopes see farther because they gather more light from far away points which are slowly diffusing, thus increasing resolution).

Could you clarify exactly why it is that low resolution observations in Romers experiment makes an alternate model viable?

Hachem

↪VagabondSpectre

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.

Hachem

↪fishfry

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.

VagabondSpectre

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. — Hachem

Light diffracts as it travels as it travels around the edge of an object, in this case, the inside edges of your pinhole. How far away from the pinhole is the camera again? Two meters?

Since when does Nikon make a lens-less camera?

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. — Hachem

The hypothesis is that the time difference is caused by a finite speed of light. The experiments and calculations based on that assumption lead to the creation of a model with repeatable predictive power. The fact that we can use the underlying assumptions to make reliable predictions is what lends credulity to this particular model.

If you have some other proposed mechanism for the deviations in eclipse duration I would love to hear it, but parallax can be accounted for and issues of resolution are not relevant.

Your theory has to be right for it to be right. — Hachem

The theory needs to retain it's predictive power and to not be contradicted by some competing or better theory. If you're really looking to upset our physical and scientific understanding of light as non-instantaneous you might as well start with the best modern measurements and experimental evidence rather than digging up poor poor Romer...

Hachem

↪VagabondSpectre

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.

VagabondSpectre

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

Can you explain your setup in more detail? A laser pointer is shining at a mounted pinhole lens that is attached to a camera (a camera with a separate internal lens?). Or do you have a barrier of foil somewhere in-between the two meter gap between the camera and the laser pointer? (if so, where?).

If the diffraction pattern is caused by the pinhole, you should be able to see it projected onto the back wall (you might need to find the right distance to see the pattern clearly) without any need for a camera. If the diffraction pattern is caused by the glass lens of the camera, then using the pinhole as a pinhole projector will not reveal the diffraction pattern. You should be able to test this yourself!.

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

When a photon passes close to the edge of something it can become diffracted (it's direction changed). The closer to the edge of the pinhole that a given photon is, the greater the angle of diffraction.

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. — Hachem

The longer the shutter is open, the more photons the camera collects over a period of time, and so we see a cumulative sample of exactly where photons are striking the photo-receptors over that given period of time.

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. — Hachem

I think the burden is on you to show where Romer went wrong, and I don't think you've sufficiently done that. You haven't addressed the main evidence for Romer's hypothesis (that the speed of light is finite) which is the reliability with which that model allows to make highly accurate predictions.

Where did Romer go wrong? Why is this interference pattern even pertinent to his observations?

Hachem

↪VagabondSpectre

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.

Hachem

↪VagabondSpectre

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.

VagabondSpectre

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 when it comes to distant objects and great distances. — Hachem

Why does the contemporary assessment of the speed of light break down when it comes to distant objects and great distances?

When the captain looks through a telescope, he is seeing the light entering the telescope, which is more or less the same as the light that is entering the eyes of the sailor below. The captain can actually recognize the distant ship because the telescope gathers much more light from a wider area than a normal human eyeball does and so gains additional resolution. There is no contradiction of any kind. We don't see objects as they are even when using big telescopes, we see them as they were when those photons were originally emitted, and over long distances there are no issues. As long as we get a steady stream of photons to record even a single point of light is sufficient to measure the emergence of Jupiter's moon after an eclipse; resolution issues would not cause it to blip in and out of existence (and even if it did we simply get a bigger telescope and problem solved).

Where is the break down? Don't repeat yourself though, please try and make your argument clear this time...

VagabondSpectre

The question of your refraction pattern has no apparent connection with your hypothesis(?) that telescopes have access to light that might be millions of miles away as opposed to physically passing through them.

Regarding your experiment: It's what happens when you shine a laser through a small aperture.

Hachem

↪VagabondSpectre

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.

VagabondSpectre

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. — Hachem

OK, I will highlight the crucial points of error numbered, in bold and underlined and explain why they are errors down below

The question is whether the differences in the times of eclipse and reappearance of the moon cannot be interpreted differently, without involving the idea that it takes time for light to travel through space. (1) We all know that when looking through the telescope at a planet like Jupiter, we do not see it rotating about its axis, or orbiting the sun. (2)We get each time a snapshot of a frozen moment in time, and the changes to the images we receive occur in jumps without any intermediate states. (3) This is understood as the effect of parallax, or more simply resolution. Because of the distance two points separated by relatively large distances will appear to our perception as one, and it takes time before we notice the difference between one position and another.

This is exactly the situation which Rømer is analyzing, but instead of understanding it as a case of parallax and resolution, he chooses a very specific approach. He considers the time it takes for astronomers to observe the disappearance or reappearance of Jupiter's moon as a fact that needs no further explanation. If we see the moon appearing at time t that is because the moon appeared at time t. And if we notice that when the earth is at another position, farther from Jupiter, and the moon appears or disappears at time t+x, then x must be caused by the longer distance between the earth and Jupiter. (4)This is much too easily discounting the fact that we only see immediately the differences between one view and another when we are very close to the object. (5)It is not surprising that Jupiter's moon seems to appear or disappear at a later time than when the earth is closer to Jupiter. The larger the distance between the earth and Jupiter, the more time it will take us to notice a difference between two consecutive moments. — Hachem

1: We do see rotation of planets, especially when we have powerful telescopes. Planets and moons are so large and rotate relatively slowly though, so it's very hard to notice with the naked eye in real time (like trying to notice the movement of shadows due to the rotation of the earth). We definitely observe rotation and we definitely observe orbits.

2: Yes, there are "intermediate states". Photons tend to come very tightly packed one after the other, and so unless you want to get down to the time interval between photon strikes (which decreases as the light gathering aperture gets smaller) there is a practical continuous stream of photons to measure.

3: Parallax and resolution are not the same thing, and parallax has little or nothing to do with this experiment. Parallax is the apparent motion of objects due to changing perspectives of observation, which unless you can correct me has nothing to do with visible light after the emergence of Jupiter's moon following an eclipse. Resolution is not an issue either, as we do not need to see Jupiter's moon with any high degree of detail whatsoever, we just need to see when the light from it becomes visible after it's emergence from behind Jupiter.

4: We see differences in distant objects as light reflecting those differences reaches us. This has long been proven since the invention of more powerful optics and more sensitive measuring equipment. Low resolution and distant objects can sometimes be hard to analyze, but luckily, in this case, being obscured and then unobscured by a planet creates a strong flashing signal for us to look for and to measure.

5: In order for what you say here to be true, some sort of time dilation effect would need to be acting on the light coming from more distant places, effectively slowing it down and making it appear to move more and more slowly. This does happen to occur over unfathomably long enough distances, but luckily, again, we can see the emergence of Jupiter clear as day. No resolution issues, no parallax complications, and correcting for special/general relativity is of almost marginal consequence.

Now that I've laid out my objections more clearly, 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...

Hachem

↪VagabondSpectre

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.

Rømer and the speed of light 1676

Welcome to The Philosophy Forum!

Categories

More Discussions