Backwards on a train

I had quite an interesting experience on a train today. I almost missed it, so I was kind of out of it when I finally found a seat. I was facing backwards, but I didn’t put much thought into that. As I looked up, I looked outside and it seemed I was going forward. It didn’t take long to figure out that I was looking at a mirror that was showing what was happening behind me, but I found it interesting that my body was convinced I was moving the other direction, at least for a moment. I thought, “what a cool proof of the relativity of motion!” Moving with constant velocity is just like sitting still, and so moving forward or backward feels the same. What was cool is that the little nudges/jolts you feel on a train happened right on cue, and really aided the illusion.

So next I started wondering about what, if anything, would feel wrong. Well, it didn’t take long for the next stop to come up (I could see it out the window coming towards me). I subconsciously prepared for the deceleration (I gather there are lots of people who don’t like that word, but, too bad, I’m on a freebie wifi at the airport so I’ve got to get this down in a hurry ;). However, my body moved the wrong way! Awesome, I thought. That was clear evidence that my visual world was wrong!

Then I noticed a curve coming up. And I wondered if I’d feel it correctly. Any guesses? . . . .

. . . .

Well, it did feel right! Proof that mirrors get front and back wrong but the other two dimensions are preserved. Fun times!

About Andy Rundquist

Professor of physics at Hamline University in St. Paul, MN
This entry was posted in physics, teaching. Bookmark the permalink.

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