You might want to check out the June 19th issue of The New Yorker, then: it’s mostly about a woman who grew up with strabismus and then, as an adult, suddenly gained stereoscopic vision. It’s also got a lot of neat stuff about visual perception in general.
Er, the article by Oliver Sachs is mostly about the woman. Not the whole magazine.
I met a guy this week, an engineer, so presumably well educated, who was expounding Velikovsky’s Worlds in Collision and telling me that it has now been “scientifically proven” that Venus is indeed a captured comet. I was working for this guy, so I just said that really, that was amazing, I had no idea. I still have no idea.
I think this is a symptom of too much specialized knowledge and overblown self-esteem. I’m an engineer, and presumably well educated, but my knowlege of the sciences has a pretty narrow focus. I know quite a lot about orbital mechanics, for example, but exactly jack shit about astronomy. If somebody told me that Venus was a captured comet I’d know that it was BS, but I wouldn’t be able to competently refute it from “owned” knowledge. I’m not qualified. I stayed out of the discussion about 3D images in mirrors because my understanding of parralax and such is just dimly remembered mental detrius from an optics class I was forced to take as a degree requirement twenty years ago.
I work with a few people who have very little science background, and to some of them all “science” is a single body of knowledge that they never learned. Because I’m a “scientist” (again, I’m an engineer, but the distinction is lost on some people) they expect me to be able to intelligently comment on everything from General Relativity to organic chemistry. I can’t.
The problem is that some people don’t know what they don’t know, and assume they’re competent in areas where they’re ridiculously underqualified. The guy you met was probably overconfident because of the fact that he’s quite knowlegdable in his particular field, and just arrogantly assumes that that competence carries over to other areas of “science”.
It’s an easy trap for the self-impressed to fall into, especially when everybody else they deal with on a daily basis doesn’t have any scientific training at all.
I was at about the same age when I had another demonstration of the speed of sound. We lived a few blocks away from a cricket ground, and if you listened to the cricket on the radio, the cheers from the crowd came from the radio a second or two before they came from the real crowd. (Even though the radio signals had probably travelled at least 400 miles, going to a central studio, then back to the local radio station).
I first noticed it from seeing kids bouncing a basketball from some distance away.
That’s called parallax and works with monoscopic or stereoscopic vision because everything is moving past your field of vision, which it would do if you had one eye or two. Stereoscopic vision is what would allow you to determine approximately how far away each of these things scrolling past are from your vantage. The further away something is the harder it becomes to gauge its distance because the differences in what one eye sees compared to the other becomes ever more subtle. This can be made even harder when there is no suitable frame of reference against which the distant object can be measured (such as the moon.)
With stereoscopic vision, your brain basically takes the two points of reference given it by your eyes and translates that into the third dimension (triangulation) giving you the perception of depth.
The problem is the same with economics. It’s frustrating.
People seem to assume that because they handle money, they’re qualified economists and can speak authoritatively on the subject. New Urbanists, for example, prosletyze so-called public spaces without understanding the Tragedy of the Commons. If such issues were so simply solved, it wouldn’t have taken so long for the problem to be defined & studied. Same with their notion that more-eyes = more-safety, completely ignoring the Kitty Genovese murder and the avalanche of social psychology work that event precipitated.
Cool!
I actually wrote that without the benefit of having read the original thread, thus thinking I made me a (lame) funny by likening the theory of time travel to Superman’s highly fictitious exploits in his debut movie.
I had no idea anyone would have actually turned that into some kind of bizarre theory. Not the idea that travelling faster than light would send one back in time (which is a valid theoretical hypothesis and the one the movie was trying to convey) but that the idea of making the earth go in reverse would turn back the clock. Because that’s just silly. Monty Python silly.
Having read that thread however, I now see that it is possible that someone can indeed mistake Monty Python’s Flying Circus for a documentary…
I still can’t quite work out what the deal was with that guy; all the evidence suggested he was just playing us along, but after he was pitted, he did actually go out and buy a science book recommended by Scotth, something which I wouldn’t have expected a troll to do. I don’t get it.
This discussion about the mirror is fascinating me. One thing I never could wrap my mind around was the 3-D ness of the mirror. When I looked in the mirror without my glasses on, things that were far away from the mirror were blurry, just like they’d be if I was looking at them regularly from that distance. But the mirror was right there inches from my face. Why couldn’t I see fairly clearly?
It’s one of those things where I know I’m missing some easy explaination, but I just couldn’t get it to make sense.
Maybe he just had a really cruel father who delighted in continually filling his kid’s head with utter BS, not realizing that he was far more deeply impressionable than most kids and would take all that crap straight into adult(teen?)hood.
It’s just a damn good thing he didn’t watch Brazil…
Because you’re not looking at the mirror itself, but rather the image that is being reflected in the mirror. This works on any reflective surface.
Consider this: Everything we see is the result of light bouncing off of it. No light, no vision. When you look at something, you are seeing the light rays that have bounced off of it and into your eyes. Stereoscopic vision and your brain’s triangulation allow you to gauge the approximate distance of the object you’re looking at (see above). When you look at a photograph, the light is boucing off of the sheet of photo paper the image is on, thus the image appears two-dimensional. When you look at a mirror however, the light is being reflected to your eyes from the objects and light sources behind you, not from the mirror itself, thus the image still has depth.
Ouch. So close, and yet so, so wrong. In very low light situations we do see in monochrome, where raising the light some will make it possible for us to see colors again. The reason for this is not some special “moon-white light” bleaching the color out of everything. It is because we have two different types of light receptors, cones and rods. Cones, which perceive in color stop working in low light levels, whereas the rods which only see black and white become more sensitive because bright light tends to overwhelm them. One of the reasons that red light is used in areas like astronomy and photo developing is because red doesn’t overwhelm the rods as much as other colors do.
So your friend is right in that you don’t perceive color in very low light situations, but completely off his rocker when it comes to why. When light strikes the eye receptors, those cones and rods don’t care where the light is from, just how bright it is.
I’ve had a similarly interesting demonstration. My Mom lives about ten minutes away from us. We’ve been talking on the phone during thunderstorms where I head thunder through the phone before hearing it from outside. That was cool.
I’ve done some time on Yahoo!Answers giving smart and often smart-alecked answers. I’ve answered the whale question before, maybe I should go back for some more punishment.
About the mirror image dispute:
Many times when people disagree, they are not disputing facts, they are disagreeing about the meaning of words. I call it a squirrel argument after the anecdote repeated here.
The correct answer to the question “is a mirror image two dimensional or three dimensional?” is “it depends what you mean by dimension.”
To me, a mirror image is flat. It has length and breadth, but no depth. you can’t reach into the mirror, nor does the image stick out of the mirror. To me, then, the image is two dimensional. Other people may talk about things such as parallax in a mirror image, and claim that the image is three dimensional. The dispute is really about the use of language
One of the newspapers I read has a daily feature called “Burning Questions”, where readers submit their [del]burning[/del] stupid questions like “Is the acid in acid rain the same as the kind made in laboratories?” and other readers supply their answers. I suspect whatever fact-checking goes on consist of the editor deciding whether things “sound right” because one day one guy asked why water drains in different directions in the north and south hemisphere and another guy told him it was because if you picture the earth as a flat circle, a swirl in one direction on one side will appear to go in the other direction on the other.
I can’t really see where the language used is an issue here. The question is: Is the image in a mirror three-dimensional? The language here is pretty clear because we know that the three dimensions in question here are length, width and depth (X, Y and Z). The question is really, “Can one perceive depth in a mirror’s reflection?” The answer, unequivocally, is “yes.” Stereoscopy still works in a mirror’s image; your brain can still triangulate distance because your eyes are still feeding it two different angles of incidence, because the mirror still reflects angles of incidence. Such information does not exist in a two-dimensional image – by definition.
Right. If you do the geometric construction of the mirror images of two points at different locations it’s obvious that the light from the two points arrives at the eye at different angles.
Stand in front of a mirror. With the left eye closed turn your head slightly to the right so that the tip of the right ear is just barely visible. Then close the right eye and open the left. You can no longer see the ear just as is the case with an actual three dimensional head.
No, that’s YOUR personal interpretation of the question.
A carving is a three dimensional object. You can close your eyes and feel the shape of the carving through touch. Try doing that with a mirror image. It’s flat. it has no depth. It’s two dimensional.
THAT’s where the language matters. We aren’t disputing facts here, we just use “three dimensional” to mean two different things.
The fact that you needed to restate the question to make it clear is prima facie argument that definitions are, indeed, part of the problem. Our stereoscopic vision calculates and shows depth because each eye receives a slightly different image from the other. When we look at a painting of the view out my window, each eye gets the same picture, which is different from the actual view where my eyes each see a slightly different picture through the pane of glass.
The point is not to argue whether one can perceive depth in a mirror, or whether the definition of image is this or that. The point is that when one is asked whether an image is two dimensional, it doesn’t seem unreasonable to answer affirmative. If each eye receiving a slightly different image is what provides depth perception, and if each eye received the same image one would have no depth perception, then it seems reasonable to conclude that a particular image has no depth in and of itself.