Well, not exactly. What actually happens is that the image is reversed left to right and rotated 180 degrees. If you hold something with text upside down, it will appear in the spoon right side up but backwards.
And, at least according to Martin Gardner, a standard mirror does *not *reverse left and right - what it does is reverse front and back (assuming you are facing it or facing directly away from it).
Cecil had been told about these “right facing” mirrors, but 17 years on now, has anyone actually seen one? I suppose it would look something like a section of a cylinder as seen from the inside. Would that work? I’ve seen the relection of my reflection, which sort of amounts to a right facing mirror too. The problem was you had to look sort of sideways at it.
The nearly classic “spoon boy” scene in “The Matrix” has commentary on spoon reflections. I have both the DVD, and the 60 dollar “The Art of The Matrix” coffee table book. One or the other, if not both discusses how they (the directors) considered editing the shot, away from the standard reversals, in order to maintain (some) credibility among the main public. They thankfully decided against it, in the final versions.
But “there is no spoon” so what are we talking about anyway?
I have one in my bathroom. It’s a medicine cabinet with a main mirror and two side mirrors on hinges. If you set one of the side mirrors at a right angle to the main mirror and look at the intersection, you will see yourself as the world sees you.
The problem with the two-mirror solution to “right facing” is the line up the middle where the mirrors come together. If you shift the mirrors to slightly less than 90º you can see yourself with your eyes shiftily glancing to the side.
There’s the problem of error as well, on glass bathroom mirrors, as there is a ghost image from the front side of the glass, which is reflected on both the mirror and the other glass front, giving you a reflection that has 3 ghosts.
Even without the glass you have two mirrors. This is unlike the spoon.
It should be possible mathematically to describe a surface more like a spoon, where each ray is reflected once, not twice.
Ususally these puzzles are worked in reverse by computer, calculating one mirror segment at a time. You define the rays you want to arrive at the eye, in terms of 3-D direction, and place the mirror at that point such that you get the reflection you want. There are lots of possible location for that mirror point. Do that for adjacent points, keeping the distances (image size) constant.
Easy to conecive, but perhaps hard to manufacture. For all I know, the result might look like a Fresnel lens, or a quadratic spoon with almost no tolerance for error. And having no particular valuable purpose, it’s not going to get much research money.
Images in the concave side of a spoon aren’t always upside down. If one holds it close enough, the image will be right side up and magnified- just like a woman’s make-up mirror. The convex side will always render a right side up, distorted, smaller image.
A few years ago I found myself wondering why mirrors switch left and right but not top and bottom. After much brain-twisting cogitation I finally figured it out. I was all set to come in here and smugly point out that mirrors reverse front and back, not left and right, and I’ve been beaten to it!
I sometimes feel like I must be the only person in the world who has never thought mirrors “reverse left and right”. How is it confusing? Say you have a mirror on one wall in the house, perpendicular to the window which is to your right. You point towards the window. Which way is your reflection pointing - yes, towards the window. Still to your right. It’s not swapping over
Apparently it uses front-surface mirrors, unlike your bathroom mirrors whose back surfaces are coated for reflection. With front surface mirrors, the line in the middle (where the two mirrors meet) would be much thinner.