Is my line of reasoning flawed?

[SamLuc]

Can someone tell me if I’ve gone wrong somewhere in the following line of reasoning? It’s a line of reasoning which leads me to believe that, when we look at an object underwater, it’s image is actually formed upright (instead of inverted) on our retina.

The reason I assert that the image formed is upright is because the aqueous humour-air interface (which is responsible for the refraction which causes the image to be inverted in most cases) is replaced with an aqueous humour-water interface. Water and the aqueous humour both have a refractive index of approx. 1.34, so little or no refraction will occur when light passes from one to the other. The reason I am paying no attention to the refractive index of the cornea (approx. 1.38) is because the opposite sides of the cornea can be considered as parallel for the purposes of this experiment.
Because the refraction occurring between the two mediums (water and the aqueous humour) in this instance is effectively negligible, rays which are parallel at the cornea can be considered to be still parallel at the lens, as demonstrated in the attached picture. Values I’ve been able to gather for the refractive power of the lens are: 20 diopters when relaxed, and 30-33 during accommodation. Therefore, parallel rays striking the lens will be focused approx. 3-5 cm behind the lens. The distance from the lens to the retina, however, is only 1.4-1.7 cm. The image of the object in the water, therefore, is upright on the retina.

Have I gone wrong somewhere?

P.S. To make the scenario easier to cope with, assume that the object in question is small enough for the light rays reflected off its top and bottom sides into the eye to be parallel.

 

[HallsofIvy]

Surely it has occurred to you that IF your line of reasoning were correct, then objects would not focus on the retina and we could not see underwater. That's not been my experience!

Also, I am puzzled by your statement "The reason I am paying no attention to the refractive index of the cornea (approx. 1.38) is because the opposite sides of the cornea can be considered as parallel for the purposes of this experiment." How did you decide that? It is, after all, the lens (cornea) that is responsible for normal focusing on the retina, not the aqueous humor.

 

[SamLuc]

Surely it has occurred to you that IF your line of reasoning were correct, then objects would not focus on the retina and we could not see underwater. That's not been my experience!

Yes it has occurred to me, but something else also. It seems to me that, according to the prevailing theory of visual awareness, the consequence of an image being formed upright on the retina would be that we would 'actually see' the image upside down (as our brain is supposed to re-invert images formed on the retina - right?). I've tested this a number of times by looking at objects underwater, and I don't see them upside down - I see them upright!

Also, I am puzzled by your statement "The reason I am paying no attention to the refractive index of the cornea (approx. 1.38) is because the opposite sides of the cornea can be considered as parallel for the purposes of this experiment." How did you decide that?

Well, my notion that the opposite sides of the cornea are approximately parallel is based on photographs such as the ones located http://www.cytochemistry.net/microanatomy/Eye/cornea_Iris_and_Lens.htm . And, if they can be considered as being approx. parallel, well then I think I'm correct in saying that light traveling from water-cornea-aqueous humour will behave in the fashion depicted in the attached picture, i.e. it will be refracted through an angle x when it strikes the cornea, but will then be refracted through an angle approx. equal to x but in the opposite direction when it reaches the aqueous humour. So overall, the direction of the light ray after it leaves the cornea would be very close to the direction it was traveling before it reached the cornea.
This is probably the point I'm least sure about; if I'm wrong, please just show me how.

It is, after all, the lens (cornea) that is responsible for normal focusing on the retina, not the aqueous humor.

Ok, but seeing as the refractive index of the mediums on either side of the cornea are equal in this instance, and seeing as I think that is reasonable to treat the opposite sides of the cornea as being parallel, I think (again) that the behaviour of the light rays would be as depicted in the attached picture. So I don't think the refractive index of the cornea is relevant in this instance.

I'm a non-scientist, and you're obviously far more knowledgeable on these topics than myself, so I hope you don't consider my writing arrogant. If my arguments are flawed, please just point out to me where I have gone wrong. And thank you for the reply!

Anyone else, also feel free to let me know if you think my reasoning is flawed.

 

[russ_watters]

The index of refraction issue is why our focus gets screwed up underwater. Other than that, our eyes work the same underwater as in air.

 

[SamLuc]

But do you agree with my conclusion that the image of the object formed on the retina must be upright when viewing underwater (as depicted in the picture attached to my first post, i.e. underwater_vision.gif).
I know I'm possibly beginning to sound like a broken record, but if you don't agree with me, can you just tell me why?

 

[selfAdjoint]

Yes it has occurred to me, but something else also. It seems to me that, according to the prevailing theory of visual awareness, the consequence of an image being formed upright on the retina would be that we would 'actually see' the image upside down (as our brain is supposed to re-invert images formed on the retina - right?). I've tested this a number of times by looking at objects underwater, and I don't see them upside down - I see them upright!

And what is wrong with this? You are underwater, and the object you are looking at is underwater, so the simple lens in your eye will put the image of the object upside-down on your retina, and your visual cortex will present it to the rest of your brain as upright. This works the same way underwater as in the air. Why wouldn't it?

 

[Zero]

Here's the question you should ask yourself: does the fact of looking through a window change the way an object is percieved? Looking through water is like looking through air or looking through glass. There is no qualitative difference in the way objects are perceived if they are underwater, or on the other side of a pane of glass.

 

[krab]

SamLuc, I think where you go wrong is in attributing the inversion to the effect of the lens. Think of your iris as a pinhole; no lens at all. The image would still be inverted. All the lens does is focus this inverted image. As you point out, the indices of refraction are so little different in the underwater case, very little focusing happens at all. That's why things are so blurry. I've looked at your illustration. Note that the object you've drawn is about the same size as your iris. Realize that objects this small are simply not visible at all under water.

 

[SamLuc]

selfAdjoint wrote:

so the simple lens in your eye will put the image of the object upside-down on your retina

My first two posts are solely dedicated to demonstrating why the image of the object on our retina is not upside-down in this instance.

selfAdjoint wrote:

This works the same way underwater as in the air. Why wouldn't it?

Again, for the reason outlined in my first two posts.

Zero wrote:

There is no qualitative difference in the way objects are perceived if they are underwater, or on the other side of a pane of glass.

Yes, I have verified this to myself by looking at objects underwater. We see things upright and approx. the same size in both cases. But this presents what seems to me to be a paradox: if the images formed on our retina of objects we view underwater are upright (which, according to my calculations, they are), then, according to the widely-accepted theory that our brain automatically inverts/re-inverts the image before 'presenting it to
the rest of our brain' as selfAdjoint put it, we should actually see things upside-down. But we don't!

krab wrote:

SamLuc, I think where you go wrong is in attributing the inversion to the effect of the lens.

Which lens? The corneal lens or the biconvex lens?

krab wrote:

Think of your iris as a pinhole; no lens at all. The image would still be inverted. All the lens does is focus this inverted image.

Ok. I'm a bit confused. According to my textbooks, there are two main factors which contribute to the refractive power of the eye: (i) the cornea/aqueous humor, and (ii) the (biconvex) lens. They also state that the majority of the eye's refractive power is due
to the cornea/aqueous humor, and that the (biconvex) lens accounts for only a small portion of the eye's refractive power. In my first two posts I have demonstrated why I think that, when viewing an object underwater, the refractive power of the cornea/aqueous humor is effectively obliterated. I also pointed out that (according to my calculations) the refractive power of the biconvex lens by itself isn't enough to invert the image. It is for these reasons that I think the image formed on our retina of an object we view underwater, which is upright to begin with, will also be upright (..and it is the reasoning I used in reaching this conclusion that I think needs to be scrutinized). Are you now telling me that the iris also contributes to the refractive power of the eye? It's the first I've heard of it, and I don't think it's true to be honest.

krab wrote:

Note that the object you've drawn is about the same size as your iris. Realize that objects this small are simply not visible at all under water.

I have been able to identify objects which approximate to this size underwater. But even if one were to look at a larger object underwater, so that the rays from its top and bottom sides were actually beginning to converge when they reach the eye, one should at the very least see the object diminished, if not actually upside-down.

 

[Zero]

This is nonsense. Go read a book on sight and take its word for it.

 

[SamLuc]

Ok, first of all, I have "read a book on sight", but no, I will absolutely not just "take its word for it".

What kind of scientific approach is that? I thought that the most highly regarded method is, when experimental results conflict with theory, one questions/refines the theory. You don't simply discard/pay no attention to the results.

The reason I started this thread is so people could critique my method of interpreting the results I have found. I am more than willing to concede that my method/line of reasoning is wrong if someone can show me how. But, again, I'm certainly not going to just take anyone's "word for it" that a present theory is correct regardless of whether or not experimental evidence is in conflict with it.

You haven't even bothered to ask what my alternative explanation is. But of course your mind is already made up, so no new results would ever change it.

"This is nonsense"

Back up your assertion, or don't bother making it please.

 

[Zero]

The do the experiment. If being underwater changed the way we see something, then a simple experiment would be to take a picture and see what you get.

Honestly, though, there is no reasoning going on here at all, in the slightest.

 

[Zero]

The point is, I guess, it is your brain that flips the image when it travels from the eye through the optic nerve. If the image hit the retina rightside-up, the brain would show everything in water upside-down. Get it?

 

[SamLuc]

Then do the experiment. If being underwater changed the way we see something, then a simple experiment would be to take a picture and see what you get

Oh my God! I have done the experiment. Me looking at an object underwater and verifying that I see it upright constitutes actually carrying out the experiment. Perhaps one of the simplest experiments ever conceived, but an experiment nonetheless.

There is absolutely no point whatsoever in taking a picture. Firstly, the apparatus inside the camera will behave differently to the apparatus inside my eye. Secondly, consciousness is a completely personal experience. You completely miss the point!

Honestly, though, there is no reasoning going on here at all, in the slightest.

I don't know what you're trying to do here - bolster your reputation as a forum moderator by pasting the young heretic perhaps? - but you are the one who is being unreasonable! To recap on my line of reasoning:
(i) Water and aqueous humour have approx. the same refractive index. Therefore, when viewing an object underwater, rays which are parallel before reaching the cornea are approx. parallel when they leave the cornea. (I clearly explain my reason for believing that the cornea doesn't significantly alter the overall direction of the light in my second post - don't be afraid to look at it now, don't just dismiss my belief as unfounded!)
(ii) Once the refractive power of the cornea/aqueous humour has been effectively obliterated, the refractive power of the lens (which is at most 20 diopters) isn't enough by itself to invert the image (see my first post for elaboration).

As I have already said, I am willing to accept that my line of reasoning might be flawed. In fact that's the reason I presented it here, so people could analyse and criticize it - point out any possible errors. But to assert that "there is no reasoning going on here at all" is to practice bigotry, and is absolutely unfair. You have twice knocked what I've said, and haven't once even attempted to point out where I've gone wrong.

 

[Zero]

Here, let me repost this part, the relevant part, ok?


The point is, I guess, it is your brain that flips the image when it travels from the eye through the optic nerve. If the image hit the retina rightside-up, the brain would show everything in water upside-down. Get it?

 

[Zero]

Originally posted by SamLuc
Secondly, consciousness is a completely personal experience. You completely miss the point!

This has nothing to do with consciousness, and everything to do with physics and neurology. Your brain flips EVERYTHING that hits the back of your eye. If something hits your retina "right-side up", it will always appear upside-down. Period. That's the way your brain and eye are wired together, there's nothing to debate here.


Interesting thinking, but no dice...I'm sure you bug the pure heck out of your teachers, don't you?

 

[SamLuc]

If the image hit the retina rightside-up, the brain would show everything in water upside-down. Get it?

Yes, I do get the fact that according to the now most widely-accepted theory, this is what should happen. My acknowledgment of this fact has been a subtext of what I've said almost from the beginning. Geez!

Another subtext of what I've been saying is that if my line of reasoning is correct, there exists evidence (which almost everyone has themselves witnessed - as almost everyone has looked at objects underwater I would imagine) that contradicts this theory. Get it?

 

[Zero]

Originally posted by SamLuc
Yes, I do get the fact that according to the now most widely-accepted theory, this is what should happen. My acknowledgment of this fact has been a subtext of what I've said almost from the beginning. Geez!

Another subtext of what I've been saying is that if my line of reasoning is correct, there exists evidence (which almost everyone has themselves witnessed - as almost everyone has looked at objects underwater I would imagine) that contradicts this theory. Get it?

No, I really don't. Since taking a picture with any camera doesn't show an inverted image, that shows pretty authoritatively that the image does exactly the same thing as it would if it were on land. I don't understand why you would think that two different things were happening, when we see the exact same thing on land or underwater. Since our optic nerve doesn't change when we go underwater(see, it is inside your head, and doesn't get wet...) the image must be hitting the inside of your eye the same underwater as it is on land.

 

[SamLuc]

I'm sure you bug the pure heck out of your teachers, don't you?

I don't have any teachers. I'm sorry if I seem like an arrogant little s**** by the way. But I've put a lot of thought into this, and I'm not going to just accept people telling me that I'm wrong unless they show me how I'm wrong.

I've got to call it a day for now, but I might post my alternative explanation tomorrow, if yourself or anyone else is interested! Heck, I might even post if no one is interested. I promise - it can explain the paradox I think my line of reasoning exposes (although it does raise other questions).

Thanks for putting up with me! And I think I might even have enjoyed the discussion.

 

[Zero]

Originally posted by SamLuc
I don't have any teachers. I'm sorry if I seem like an arrogant little s**** by the way. But I've put a lot of thought into this, and I'm not going to just accept people telling me that I'm wrong unless they show me how I'm wrong.

I've got to call it a day for now, but I might post my alternative explanation tomorrow, if yourself or anyone else is interested! Heck, I might even post if no one is interested. I promise - it can explain the paradox I think my line of reasoning exposes (although it does raise other questions).

Thanks for putting up with me! And I think I might even have enjoyed the discussion.

Well, don't strain yourself TOO much...your grasp of refraction and all that seems fairly solid, but the biology contradicts you.

 

[pallidin]

Certainly this theory was well laid-out, perhaps more so than some I have seen for a "non-scientist".
Without a doubt a great deal of thought has been given towards this, and I must venture to say that SamLuc has much to offer in the future.
But for now his theory appears to be flawed for reasons well pointed-out by others.
SamLuc, it is often the case that brilliant minds will ocassionally focus incorrectly on aspects of knowledge not well understood by themselves. That's OK. The intensity of the endeavor is certainly noteworthy.
Let us relax a moment and consider your theory irrespective of the knowledge you have/do not have regarding it. What does one do in this case, for themselves?
One thing which can be done is to try and design a simple, practicle experiment to investigate the claim. Such endeavors help to unlock the "block" we often place before ourselves in higher thought.
Trust me, SamLuc, I have "tunnel visioned" more than once while working on projects, just speaking for myself.
OK, back to the problem.
Let's design your experiment, and let's keep it as simple as possible.
Obtain a wash basin sufficient in size so as to allow it to be filled with water and allows one to submerged at least the part of ones head which would include the eyes.
Obtain a fork, spoon, or other similar non-symetric object.
Place it beside the basin, on the outside of it, and note its orientation.
Carefully lift it up and place it in the basin, in as best an accurate same-orientation as before.
Not being funny, submerge your head enough to where your eyes are completely enveloped in the basins water.
Looking now through AND A PART OF the water interface, observe if the orientation of the object has changed.
Fair enough?
Also, bear in mind that the eye does not exactly work in the way you illustrated. In fact, your illustration is only accurate if the object source was a point source directly in-line to the CENTER of the cornea and NOT as large as shown in perspective illustration.
So it would be a point source, devoid of orientation(no top, no bottom)
In any event I look forward to your comments.

 

[russ_watters]

Originally posted by SamLuc
Oh my God! I have done the experiment. Me looking at an object underwater and verifying that I see it upright constitutes actually carrying out the experiment. Perhaps one of the simplest experiments ever conceived, but an experiment nonetheless.

Certainly, but what you are suggesting is contrary to your experimental result!

There is absolutely no point whatsoever in taking a picture. Firstly, the apparatus inside the camera will behave differently to the apparatus inside my eye. Secondly, consciousness is a completely personal experience. You completely miss the point!

Ok, now I see the point: you're arguing consciousness, not science. Scientifically your reasoning is flawed and that's all we're prepared to discuss here.

But a few more experiments: next time you are underwater, orient yourself upside down and see what happens. Then face straight down and rotate horizontally. What should you see according to your hypothesis (what exactly is your hypothesis, btw? - that when you feel water against your eyeball your brain decides not to nvert the image?)?

Also, try redoing your first drawing with an object that is substantially larger - say, if the eyeball is 1" in diameter, make the object 12" in diameter and 12" from the eye. See if you can make the lines not cross...

 

[SamLuc]

pallidin, thank you very much for your polite, well-considered and encouraging response. I appreciate it. And I agree with you that one should be wary of tunnel visioning - I certainly hope that's not what I'm doing. I have carried out the experiment you outlined, and - I'm not sure what results you expected but - the orientation of the object does not change. I carried out the experiment just as you suggested (I used a fork, spoon, and even a screwdriver), but noticed no perceivable change in the orientation/size of the object. This is actually the same experiment I've carried out myself, although it is a far easier means of carrying it out, so thank you for drawing my attention to it (up until now I've been running baths and making trips to the nearest swimming cove; the thought of using a basin never even occurred to me - silly me!). Anyway, the result I got when I carried out your version of
the experiment is the same as the ones I got in earlier experiments, and seems to me to re-highlight the paradox I mentioned already.

pallidin wrote:

Also, bear in mind that the eye does not exactly work in the way you illustrated. In fact, your illustration is only accurate if the object source was a point source directly in-line to the CENTER of the cornea and NOT as large as shown in perspective
illustration.
So it would be a point source, devoid of orientation(no top, no bottom)

Ah, I didn't understand why you were saying this at first, but I think I do now. Do you not think what I'm saying has a lot of validity anyway however? I really think it does to be honest.

russ_watters wrote:

what exactly is your hypothesis, btw? - that when you feel water against your eyeball your brain decides not to nvert the image?

No, this is not my hypothesis. Please read my posts in the links provided below. They explain it very clearly. I hope I don't seem rude, but I wouldn't be doing it justice by trying to summarise it in a few lines.

russ_watters wrote:

Also, try redoing your first drawing with an object that is substantially larger - say, if the eyeball is 1" in diameter, make the object 12" in diameter and 12" from the eye. See if you can make the lines not cross...

Good point, but the reason I chose an object so small that the rays reflected off its top and bottom sides into the eye were parallel was for the fact that this makes the entire experiment far simpler. And I actually have used an object which approximates to this size when carrying out the experiment myself, so I see no need to carry it out using a larger object, and thereby complicating matters. The object I used BTW was two flat
pieces of lego of contrasting color (yes, I'm being serious) - one on top of the other. Their total height is 6 mm, which is close to the diameter of the pupil (can range from 2-8 mm), so considering the rays of light to behave as depicted in my first picture is a
reasonable position in my opinion.

Anyway, I explain my hypothesis in threads located
http://www.scienceforums.net/forums/showthread.php?threadid=2700 BTW - a nice site, but my ideas weren't getting the thorough scrutinizing they're getting here, and which I wanted them to receive. Please read what I've written and think about it before dismissing what I'm saying (if that's what you decide to do, although I hope it isn't).
Also, I have thought of some ideas which I think could possibly resolve the new problems which (after resolving the one for which it was initially constructed) my hypothesis presents. They're only ideas, but if anyone wants to discuss them, or any other aspect of
my hypothesis, then please feel free to do so. Thanks!

 

[russ_watters]

Originally posted by SamLuc
No, this is not my hypothesis. Please read my posts in the links provided below. They explain it very clearly. I hope I don't seem rude, but I wouldn't be doing it justice by trying to summarise it in a few lines.

To reinforce what every english, history, and science teacher I have ever had taught me: you must be able to state your thesis in two, preferably one sentence. Otherwise, you lose clarity, you don't gain it.

Good point, but the reason I chose an object so small that the rays reflected off its top and bottom sides into the eye were parallel was for the fact that this makes the entire experiment far simpler. And I actually have used an object which approximates to this size when carrying out the experiment myself, so I see no need to carry it out using a larger object, and thereby complicating matters.

So you see no reason to pursue a line of investigation that appears to directly contradict your thesis? Hmm - that seems like it would be the first thing you would want to do.

In any case, as the critic (this is how an editor of a technical paper would put it): if you see no need to investigate a possible flaw, I see no reason to give you any more of my time or publish your paper.

Stepping back into my role as a mentor/moderator, if you did investigate the suggested similar case, you would realize the flaw in your argument (and its already been pointed out): the particular object you selected is too small to accurately/adequately examine how our eyes actually work.

Their total height is 6 mm, which is close to the diameter of the pupil (can range from 2-8 mm), so considering the rays of light to behave as depicted in my first picture is a reasonable position in my opinion.

Interesting point: going from your first sketch, how exactly would a changing pupil diameter change the way your eyes focus? It appears from your picture that pupil diameter matters for focusing. Clearly, this is not the case. That is another flaw (actually, its the same flaw, just another manifestation) as I pointed out above.

I skimmed through the sci-forums threads. All I can say is that asserting that "seeing" takes place in any other manner besides the conventional explanation requires some hard evidence of which your thought experiment does not provide. Light enters your eye, is focused and projected onto your retina, the information is captured by your rods and cones, and the information is sent to your brain where it is interpreted (formed into a full, upright image).

 

[SamLuc]

russ_watters wrote:

To reinforce what every english, history, and science teacher I have ever had taught me: you must be able to state your thesis in two, preferably one sentence. Otherwise, you lose clarity, you don't gain it.

Ok. Here's my hypothesis/theory/thesis (whatever you want to call it) - basically paraphrased from my threads in scienceforums (the ones linked to above - note to other readers: please read them to fully understand my argument):

(i) The act of seeing in normal circumstances (with, it seems, the exclusion of phenomena such as dreaming) does not take place in the brain; it takes place at some stage before light from an image reaches the retina.
(ii) The phenomenon of ‘seeing’ occurs when the superposition of states of the quantum entities being observed - in this case photons - collapses; the cause of this collapse being the measurement/registration of the visual information in V1 (striate cortex) and beyond (i.e. V2, V3, V4 etc.).

The reason I didn't want to simply state it like this is because this will seem largely implausible to anyone who hasn't read the rest of my posts, and who is unaware of the reasoning which has led me to these conclusions.
Of paramount importance in understanding my theory is the distinction between: 1. Where the act of seeing occurs, and 2. What is necessary for the act of seeing to occur.


russ_watters wrote:

So you see no reason to pursue a line of investigation that appears to directly contradict your thesis? Hmm - that seems like it would be the first thing you would want
to do.

I didn't realize it at first, but, I've actually done the experiment with a "substantially larger" object, according to your suggestion. And I clearly stated in my 4th post (page 1 of this thread):

But even if one were to look at a larger object underwater, so that the rays from its top and bottom sides were actually beginning to converge when they reach the eye, one
should at the very least see the object diminished, if not actually upside-down.

I have verified to myself on a number of occasions (including this morning, using pallidin's version of the experiment) that when I view large objects underwater, I don't see them upside-down or diminished. I see them the same size and upright.

russ_watters wrote:

Stepping back into my role as a mentor/moderator, if you did investigate the suggested similar case, you would realize the flaw in your argument (and its already been pointed out): the particular object you selected is too small to accurately/adequately examine how our eyes actually work.

I also stated (in the same post, in reply to krabs assertion that "objects this small are simply not visible at all under water") that:

I have been able to identify objects which approximate to this size underwater.

I wasn't lying when I said this, and I verified this fact to myself again this morning using pallidin's version of the experiment. Not everyone's eyesight might be sharp enough to do this, but mine is. Maybe you don't believe me, but that's not my fault.

russ_watters wrote:

In any case, as the critic (this is how an editor of a technical paper would put it): if you see no need to investigate a possible flaw, I see no reason to give you any more of my time or publish your paper.

Getting my theory published isn't of concern to me (at least at the present time).

russ_watters wrote:

Interesting point: going from your first sketch, how exactly would a changing pupil diameter change the way your eyes focus? It appears from your picture that pupil diameter matters for focusing. Clearly, this is not the case. That is another flaw (actually, its the same flaw, just another manifestation) as I pointed out above.

I honestly don't understand your argument here.

russ_watters wrote:

All I can say is that asserting that "seeing" takes place in any other manner besides the conventional explanation requires some hard evidence of which your thought experiment does not provide.

Firstly, I have actually based my theory on two experiments: (i) viewing an object underwater, and (ii) the 'inverting goggles' experiment which I refer to in the second of my scienceforum threads. Secondly, they are not 'thought' experiments. They are
experiments which myself and others have actually carried out, the results of which do constitute "hard evidence" for what I am saying.

P.S. I notice that I'm getting worked up again. I don't want to seem ungrateful for your taking the time to analyse my theory. I do appreciate it, and thank you!

 

[russ_watters]

Originally posted by SamLuc
I didn't realize it at first, but, I've actually done the experiment with a "substantially larger" object, according to your suggestion. And I clearly stated in my 4th post (page 1 of this thread)...

I have verified to myself on a number of occasions (including this morning, using pallidin's version of the experiment) that when I view large objects underwater, I don't see them upside-down or diminished. I see them the same size and upright.

So there's an apparent contradiction there: large objects most certainly do appear upright underwater, but you say (I have not verified it) that small objects appear upside-down. That contradiction requires further investigation: not just looking at an object underwater, but also re-doing the diagram to explain it.

I honestly don't understand your argument here (re:pupil size).

You said yourself you selected the object size in order to make the rays parallel. If the pupil diameter changes, the rays are no longer parallel and the flaw I described before is again exposed. Again, this is why you need to re-do the diagram for a more general case.

Getting my theory published isn't of concern to me (at least at the present time).

You were asking for a critique. Now you're saying you don't want one? Why exactly are you here then?

Firstly, I have actually based my theory on two experiments: (i) viewing an object underwater, and (ii) the 'inverting goggles' experiment which I refer to in the second of my scienceforum threads. Secondly, they are not 'thought' experiments. They are
experiments which myself and others have actually carried out, the results of which do constitute "hard evidence" for what I am saying.

Actually, no: since an accepted explanation already exists, you need to do significantly more than simply assert another explanation. You need to prove it mathematically - with the diagram. You made one attempt, we pointed out a limitation, and the limitation needs to be addressed, otherwise you haven't really given us anything.

I have another experiment you can try: I just so happen to have a simple converging lens (magnifying glass) and a means for testing what a projected image looks like (a high intensity, clear light bulb). Using a piece of paper as a screen (your retina), the image produced always appears inverted, regardless of the focus (position of the screen wrt the focal point). If what you are saying were correct, the [out of focus] image would at some point shrink to zero size and then flip as it gets more and more out of focus. It does not. I left my digital camera at work, so I can't post any pics tonight: perhaps tomorrow, unless you care to try this experiment for yourself.

I also think you may need a refresher on diagramimming optics (I know I did). http://dept.physics.upenn.edu/courses/gladney/phys151/lectures/lecture_apr_14_2003.shtml is a good one.

Now I'm going to throw a bit of a monkey wrench into the works. Using the magnifying glass to magnify an object (object is closer to the lens than your eye) does produce an upright image while using the magnifying lens to make the image smaller (object is further from the lens than your eye) produces an inverted one. So can you do it with just your eye? No: since the virtual image is on the same side of the lens as the real one you can't see it (fig 13.13). But others (doctor, retinal scanner id machine) can use this principle to image your retina.

 

[SamLuc]

I'm in a rush so I don't have time to respond to everything you've written straight away, but there's one very important I need to clear up.

russ_watters wrote:

So there's an apparent contradiction there: large objects most certainly do appear upright underwater, but you say (I have not verified it) that small objects appear upside-down. That contradiction requires further investigation: not just looking at an
object underwater, but also re-doing the diagram to explain it.

No! I have been saying that small objects also appear upright. That's what my argument hinges one.

I wrote in my second post (1st page):

I've tested this a number of times by looking at objects underwater, and I don't see them upside down - I see them upright!

I hope this is the source of the lack of accord between us, as if it is, well, it's all just a misunderstanding. To be absolutely clear on what I'm saying: I see all objects upright and the same size when I look at them underwater.

I'll try to respond to the rest of what you've said later. I just wanted to clear up that very important point first. But thanks again for your time anyway.

 

[russ_watters]

Originally posted by SamLuc
I'm in a rush so I don't have time to respond to everything you've written straight away, but there's one very important I need to clear up.

No! I have been saying that small objects also appear upright. That's what my argument hinges one.

I hope this is the source of the lack of accord between us, as if it is, well, it's all just a misunderstanding. To be absolutely clear on what I'm saying: I see all objects upright and the same size when I look at them underwater.

Ok, yeah, I misunderstood. I thought you were saying that small objects appear upright and larger ones upside-down. Fair enough.

The problem now is that all you have here is two cases and no real difference between them to support your conclusion.

Case 1: in air, objects appear upright and in focus.
Case 2: in water, objects appear upright and out of focus.

So all that has changed is that the objects are not in focus. Do you see why we have such a hard time accepting that not seeing a difference in orientation means there is a difference in orientation?

So the key to understanding this issue then (clearly) is in understanding your diagram.

You forced me to get a refresher on optics (not a bad thing: I'm here to learn too) and to go back and reread some of the thread and I found one I missed. Krab's post is absolutely correct (sorry, krab)and I needed to take that refresher in optics to realize its importance.

ANY image created by passing light through an aperature, lens or no lens, gets inverted.

SamLuc, I think where you go wrong is in attributing the inversion to the effect of the lens. Think of your iris as a pinhole; no lens at all. The image would still be inverted. All the lens does is focus this inverted image. As you point out, the indices of refraction are so little different in the underwater case, very little focusing happens at all. That's why things are so blurry.

HERE is a description of how a pinhole lens works. Since the aperature is so small, the only rays that pass through it are the ones that result in the image always being in focus (or nearly so). As you make the aperature larger, the image gets more and more out of focus (look at the two diagrams on the page I linked). Now clearly, a hole with no lens has no refracting capability whatsoever, yet it always produces an inverted image. This is where you went wrong:

By selecting a case where the object and iris were the same size, you inadvertently made it possible for an erroneous diagram to be drawn without clearly (to me anyway) revealing the flaw. If you try again with a much larger object, you'll see the clear flaw: with no refraction capability at all, the light rays must cross (on average) at the center of the aperature (space where the lens should be). In the page I linked, check out fig 13.12. That's what your diagram should look like. Note the line going through the center of the lens. Since at the center of the lens, the two sides are parallel, that's the point on the lens where there is no refraction, so the light passes straight through.

Part of the problem may be in that there are two different ways to show the diagram. http://wshs.wtvl.k12.me.us/~physics361/optics/theeye.html one, while useful for showing focal point, doesn't accurately represent what happens in your eye. The image is projected onto your retina, not focused to a point on your retina.

So to recap:
-Any aperature inverts an image.
-A lens takes the inverted image and brings it into focus.
-A "pinhole lens" does not require an actual glass lens because due to its small size, the only path light can take through it will end up creating an (inverted) image that's in focus.

 

[SamLuc]

Hi russ.
That link on diagramming optics was helpful thanks. I carried out that experiment you mentioned, but got different results - you can find them http://www.samluc.com/science/vision/converging_lens.html .

I also didn't understand what the "monkey wrench" you were referring to was. And one last thing, before I get round to responding to your most recent post: I hadn't originally planned on divulging my entire theory here (although I'm grateful for people's taking the time to look at it now that I actually have). I only wanted to see if anyone could find something wrong with the line of reasoning I outlined in my first post. People on these forums quickly realized that my reasoning led to a paradox however (which I hadn't expected them to), and began telling me my line of reasoning must be incorrect because of this paradox. I then pointed out that, in my opinion, my line of reasoning wasn't necessarily incorrect as I think I have an explanation which could resolve that paradox; and it is that explanation that constitutes my theory. Next thing I knew, my thread was moved to the 'Theory Development' forum.

But anyway, in relation to your most previous post. I have to say, I didn't understand krab's argument about the iris acting as a pinhole. I'm going to have go read the link you provided and think about this one, as to be honest I can't get my head around it straight away. Thanks again, and I'll get back as soon as I can.

P.S. For newcomers to this thread, it started off as a discussion of the reasoning I outlined in the first post, but evolved into a discussion of my theory outlined http://www.scienceforums.net/forums/showthread.php?threadid=3076 ).

 

[SamLuc]

Treating the iris as a pinhole

Ok, I think I've grasped the concept of the iris as a 'pinhole'. And if this is the way the iris & pupil really work, the reasoning I outlined in my initial post certainly does seem to be flawed. I confess that I didn't understand this argument when krab first raised it, although it was a very good point. I thought his statement 'The image would still be inverted' was based on some further refraction which he considered an effect of the iris, which didn't make any sense to me at all. This of course was not what his statement was based on, and I confess that my failure to understand was largely due to my ignorance of how pinhole cameras actually work (a state of affairs which russ_watters has helped me to remedy by providing an informative link on the topic). Thank you for your very valid point krab.

Anyway, even if this really is how the iris & pupil work (which I don't necessarily accept as fact, although I think its quite likely and it does make sense to me, even if all the diagrams in all my textbooks seem to depict a different scenario), we still have a paradox. Even if the images formed on the retina aren't upright, they should still be significantly diminished. What we 'actually see' therefore should be accordingly diminished in size also. As I pointed out earlier however, this is not the case. As far as I've been able to discern myself through my own experiments, we see everything underwater the same size.

Treating the iris as a pinhole, and ignoring the effect of the biconvex lens, I have tried to demonstrate why the size of the images formed on the retina will still significantly differ when viewing an object underwater and viewing it in normal circumstances in a diagram located http://www.samluc.com/science/vision/iris_as_pinhole.html . I think this diagram demonstrates how the eye should work for a more 'general' case russ_watters. But again, if you see any flaws, don't hesitate to let me know. As a result of the image formed on the retina being diminished when underwater, the prevailing theory of visual awareness would suggest that what we see should also be diminished, akin to what we see when we look through a diverging lens. However, as I pointed out already, as far I have
been able to discern, it isn't.

russ_watters wrote:

So all that has changed is that the objects are not in focus. Do you see why we have such a hard time accepting that not seeing a difference in orientation means there is a difference in orientation?

Yes, I do. But I have been thinking about this for approximately a year now, and, the more I do, the more I become convinced that there is a difference in orientation. And I believe the reason we don't see this difference in orientation is because the 'act of seeing' takes place before it arises (i.e. at some stage before light from an image actually reaches the retina). Again, to those who consider this hypothesis highly implausible, let me distinguish between what is necessary for seeing to take place and where it actually takes place. What is necessary for it to take place - registration in striate cortex and beyond of the visual information collected at the retina - causes (I suggest) the collapse of the superposition of states of what we are actually observing, i.e. photons - which is a well-accepted phenomenon. So, in my opinion, my explanation isn't actually that implausible at all, as it calls on a mechanism which is widely-acknowledged to exist.


EDIT (May 7th 2004): I have finally discovered that the line of reasoning I outlined in the first post was indeed wrong. See THIS thread to see where I went wrong.