The baffling mirror puzzle

Before I start the puzzle, a little bit about myself as it pertains to this article. I am a physician and I write articles on all kinds of fields except medicine, which I know very well. I like to study other disciplines and share my research with young people in Manipur. I am not a politician but sometimes I write about politics in Manipur when I am asked to.

Being a doctor does not bar me from writing about anthropology or linguistics. They are not rocket science. I also try to be a creative writer and as such I formulate hypotheses about certain topics. After all, they are theories just like the Big Bang or the Black Hole. If someone does not agree with them one should give reasonable arguments with common sense.

About the puzzle, many people think it is odd biologically that we cannot see our own faces without mirrors. This age-old puzzle of the mirrors never ceases to puzzle scientists, philosophers, psychologists, mathematicians, physicists and common men.

I am still baffled. Some of you might know the right answer. However, it will pique interest and curiosity of many others. Most people go through their lives without ever considering it, and once considered it can remain a puzzle for life.

The simple puzzle that I am going to present to you is why the word AMBULACE is printed or stencilled reversed in front of ambulance cars in the UK, as - - - A-U-MA

The answer is when you see an ambulance coming behind with its siren blazing and you look in the rear view mirror of your car, you will see it as AMBULANCE ie reversed and you give way.

The puzzle is also why any writing eg AMBULANCE appears as horizontally reversed though not upside down.

Here is the clue. When you stand and look in a (vertical) standing mirror, your reflection, the ‘mirror image’ is reversed ie left to right reversed. Hold a cup in your right hand and look in the mirror. The cup is in his left hand and not in the right. Now hold the cup in your left hand and the cup is in the right hand of your image.

The mirror image is a reflected image of an object that appears identical but reversed as a reflection of substances such as a mirror or water.

But when the plane of the mirror is (horizontal) lying on the floor, the mirror does reverse up and down, which you might have noticed - an upside down landscape while looking in the surface of a pond or a lake.

Before I go further, I may remind you that there are normal people who cannot distinguish between left and right hand. I have a very smart female friend Elizabeth, who has this problem. The only way for her to distinguish from left to write is by wearing a watch on her left hand. The hand with the watch is her left hand.

‘Right’ and ‘left’ are relative depending on our deciding which direction is ‘up’ and ‘front’ first. We have invented the words ‘right’ and ‘left’ because we need them often to distinguish between the two orientations, not only just referring to the two sides of our body, but also all kinds of other things with two sides.

‘Up’ is a straight forward direction to define, such as away from the centre of the earth. But comparing ‘right’ or ‘left’ with ‘up’ is not a fair comparison. There are millions of beings floating within the waters of the ocean. They are symmetrical around two axes, but they have no natural ‘right’ or ‘left’ direction, nor any natural ‘up’ and ‘down’ direction.

We learnt in school that objects we see fall on our retina upside down and reversed, but our brain is adapted to see them as we see them upright. It’s the same on the old camera film and the display screen of modern digital cameras.

Prof Richard Gregory at Bristol University, UK - an engineer, philosopher, psychologist and historian all combined in one, seems to have solved the problem in his book, Mirror in Mind (1996).

Here is an expert’s explanation. Look in the mirror as you would normally do. Wave your right hand. The image in the mirror will wave on the right side of the mirror. It will be the same with your left hand. Now on a thin exercise-book size (A5) paper draw with a thick felt pen the letter “R”, and on another, “L”. Hold the R in your right hand as you normally look at it. Do the same with L in your left hand.

The R will still be on the right hand side of the mirror and L on the left hand side of the mirror, but they will be reversed in the mirror. The R in the mirror looks exactly the same as the one you are holding but reversed. It goes the same for the L. But the image in the mirror is holding the R in his left hand, not his right, and L in his right hand.

The reason according to this expert: he is not a real person; to say that he is holding R in his left hand means that you have mentally placed yourself in his position. Mirrors do reverse in an out. They reverse the direction perpendicular to the plane of the mirror.

Another more scientific explanation goes like this. In geometry, the mirror image of an object or two-dimensional figure is the virtual image formed by reflection in a plane mirror (must be optically symmetrical). It is of the same size as the original object, yet different.

Two-dimensional mirror images can be seen in the reflections of mirrors or other reflecting surfaces, or on a printed surface seen inside out.

In three-dimensions, the concept of mirror images includes the inside parts, even if they are not transparent.

As an example, if we look at a picture or object in our hand and then turn it towards a mirror, the picture and thus its mirror reflection have made left-to-right ‘flip over’ of 180 degrees. It is thus not the mirror itself, but our own relative position and viewing point that has caused the apparent left-to-right reversal. I am still no wiser.

The best explanation I can understand is a résumé of Gregory’s book, ‘Mirrors in mind’ by Richard Dawkins, who explains science in a prose that is easily understandable by the laymen. The following essay is from his book, The Oxford Book of Modern Science Writing.

How can a mirror distinguish right-left from up-down, even though many people don’t know their right from the left? Many people will think there is no problem – because your top is reflected from the top of the mirror, the bottom from bottom of the mirror, the left from the left and the right from the right, But this is where the puzzle starts; the mirror is optically symmetrical – up-down and right-left – yet the reflected image is only reversed one way: right-left.

Now the question is do plane mirrors always switch right and left? He asks you to try an experiment with a match and its box. Hold a match horizontal and parallel to a vertical mirror. What happens? When the head of the match is to the right, its image is also to the right. It is not right-left reversed. Now take the match-box and view it in the mirror. Its writing is right to left reversed. So the match and its box behave differently. Why is the match not reversed though the match-box writing is reversed?

He gives another related puzzle: hold a mug with writing on it to a mirror. What do you see in the mirror? The reflection of the handle is unchanged – but the writing is right-left reversed.

He gives further examples. (1)Writing on a transparent sheet, such as an overhead transparency, does not show reversal when held before a mirror. (2) When writing on a transparent sheet is turned around, so that its front and back surfaces are switched over, the image is reversed. (3) An opaque sheet of writing or a book must be turned around to face the mirror – then the image is reversed. (4) When the transparent sheet is rotated around its horizontal axis, it is vertically and not horizontally reversed.

The reason is - a mirror allows us to see the back of an opaque object though we are in front of it. But to see its front, in a mirror behind it, the object must be rotated. When, say, a book is rotated around its vertical axis to face the mirror, its left and right switch over. It is that produces mirror reversal. It is really object reversal.

I hope many of you have already understood it, but I still have some difficulty.

The writer is based in the UK

Email: imsingh@onetel.com

Website: www.drimsingh.co.uk

21-Oct-2012 / 12:35 AM / Dr Irengbam Mohendra Singh / 0 Comments