Friday, January 25, 2013

Iteration of the Grandfather Paradox

A student wanted to ask me a hypothetical question. Well, I'm game.

"Assume that someone invented a time machine. Then I go back in time and kill him before he has a chance to invent the time machine. Did I go back in time?"

I'm well-versed in science fiction tropes. So, I went with the parallel universes response--the universe created by killing the time machine inventor would be different than the one the student originated from.

This was not the response the student wanted. Apparently, she'd been asking various friends this, convinced that the only solution was that then she never would have gone back in time. The friends found my answer amusing, saying that I'd "schooled" her.

I hadn't intended to shame her or "school" her. She asked a question that I had an answer to.

So, I introduced her to the grandfather paradox. It was pretty much what she had come up with, just in a slightly different form. And that one blew her mind as well.

Deep thoughts are good things. (Even if it was a history class, and this was not history.) I posed some other questions that were just as mind twisting, and we got into an interesting discussion about physics and science and science fiction and...


We both jumped when the student's shoe hit the ceiling. What he was doing that made it fly off his foot...

So, back to work. I glared at that boy. Asked him what the blank? (I was good. I didn't swear.) He was more chagrined than anything. He didn't expect the shoe to do that. (Although what he was doing that made this possible didn't seem to be an issue to him.)


The class got back to the study guide that they were working on. And another student asked me if I watch Doctor Who. Well, as a matter of fact...


  1. Your kids sound like a lot of fun. And their little distractions if it weren't for the atmosphere of schooling might even be considered kinda cute. But, since it is a school, discipline discipline discipline.

    I enjoyed this grandfather paradox discussion.

  2. Love the time travel question. I'd immediately show them Back to the Future...

    I had a student who turned a disposable camera into a taser and zapped a classmate with it. The kid jumped straight out of his seat. I'm not sure why student #1 thought I wouldn't notice.

  3. The thing about being a teenager is that you're absolutely sure about everything you say and you can't imagine that there are any other answers ever.

    Sounds like a fun class.

  4. Given that there is only one universe and one time-line what would be your answer to the student's question? Just curious.

    1. I'm not sure. Either the traveler would not have gone back, waking as if from a dream. Or, the traveler must then go back again.

      There's a reason I went for the parallel universe reply.


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