No Up-Down Inversion in Mirror Images

 No Up-Down Inversion in Mirror Images

In the Question Corner of The Hindu of July 20, 2025, the reason for left to right inversion is very well explained. In engineering, we call this rotational symmetry. Such inversion is acknowledged to make manufacturing (drawings for manufacturing) less burdensome. If one carefully notices the doors on either side of a metro or even an Indian Railway coach, one would notice right-left inversion (the handle on IR coaches will be on the right on one side of the coach and on the left on the other side).

However, the ending of the explanation is wrong in one respect: “... mirrors don’t prefer...up-down.” But, one never sees the up-down inversion in mirrors; only left-right inversion is seen. One’s head is never seen “below” his/her feet in the mirror image. The reason is gravity acts in one definite direction, always head-to-toe!

I need to add a truly personal note here. I, on my own, realized that such left-right inversion happens in mirrors not only when you face the mirror−which is what almost anyone who had given this matter a thought would have considered−but also when you stand (or sit) side-ways to the mirror. I realized this when travelling by the college bus merely about eight or nine years ago (when I was superannuated from my job at the age of 60) sitting in a row of seats behind a student who was busy typing out an SMS on her mobile. I saw her doing that with her fingers of her left hand. Curiosity got the better of me and I kind of craned my neck to see fingers of which hand she was using. It was not a big surprise but a mini-Eureka moment: She was typing out with the fingers of her right hand whereas the glass pane on the window indicated those of the left hand!

The lesson? If you get curious about anything, take every opportunity to see how else, besides listening to those in the know, you can learn stuff.

Raghuram Ekambaram