Sunday, November 02, 2008

Does it Matter When a Time Machine is Invented?

On our way to yesterday's soccer game, my daughter brought up the subject of time machines. She thought it would be cool to be the first one to use one. I started thinking about that and I asked her, "What does 'first' mean?" I could see a little crease of concentration on her forehead as she began to contemplate all the wonderful contradictions of time travel. The conversation led to a couple of points.

Does it matter when a time machine is invented? As soon as one has been created, couldn't you just build a second and take it back in time with you? If that doesn't work out, couldn't you just take the blueprints back with you? Wouldn't that be necessary if you wanted to get back to your original time, assuming the machine doesn't move with you?

If the machine moves with you, then there really is no such thing as "first" any more. Here's another brain teaser for you.

Hypothesis: A time machine will never be invented.

Proof: There is no one from the future among us. As soon as a time machine is invented, the chance to go back in time will exist. Since the time machine will exist off into the future from the point it is invented, the chance that someone from the future will visit our time asymptotically approaches 1. Of the set of people who would visit our time, there is a subset that would make themselves known as beings from the future and demand tribute / power / SpeedPasses at Disneyland. As time goes to infinity, the probability that such an event would occur asymptotically approaches 1.

It has not happened, therefore there will be no time machine in the future.

If you see Rod Taylor, run. Not that it will do you any good outside of the cardiovascular exercise you will get, but running always seems to be sound advice when involved in SciFi cataclysms.

Image borrowed from this post over at Riff Trax. The post is worth visiting, the comment thread is pretty funny.


Ohioan@Heart said...

I tend to agree that a time machine, able to go backwards in time, to any arbitrary point in spacetime will never be. (Too many paradoxes exist, although there are some tentative thought experiments that show that quantum mechanics MIGHT actually be sufficiently holistic that any such transists back in time are already coded into the current solutions, so no paradoxes would actually occur.)

There is a small chance that a time machine capable of going backwards in time, can be constructed based on spacetime wormholes, but interestingly, these will only be able to go back as far as the point at which they are contructed. If this kind of time machine exists then the "first" to use it, may still have meaning.

By the way, your Proof assumes that the number of people that can use the/a machine grows faster than the time they'd want to go back and are at least countably infinite. That's two big assumptions.

pilgrimchick said...

Your argument is interesting. The counterpoint to it came to me in the form of an old Star Trek exchange from The Next Generation. A time traveller came aboard the enterprise and spoke with Commander Riker. He explained who he was and where he was from. Riker replied,"We have no record of any of your species visiting our people." The "traveller" laughed and said, "Such ignorant arrogance. The simple answer is that your species has never before interested us."

What if those that invented time machines are not interested in us at this time or prior to now? What if we are too primitive or uninteresting for "time travellers" to visit us now and previously?

Tim Eisele said...

On the concept of not mattering when a time machine is invented, Cheapass Games used to have a game called "US Patent No. 1". The premise was that all the players were time travellers from different eras. You win by assembling a time machine, getting to the day that the US patent office opened, and getting to the head of the line to file for Patent No. 1 on your time machine.

Unfortunately, the game mechanics were not as good as the actual concept (it's a very frustrating game to plan), and it looks like it is currently out of print. It also turns out that there is a bit of a fallacy in the setup: US patents didn't start getting patent numbers until 1836. And Patent No. 1 isn't a time machine, it appears to be a cog-wheel design so that locomotives can climb steep hills.

Ohioan@Heart said...


Two possibilites:

1) Patent #1 isn't a time machine. This implies no one has won the game yet.

2) Patent #1 is a time machine, it just looks like something that helps locomotives climb hills, and some one has not only won the game, they have done so in style.

Anonymous said...

There might be a time machine, but no one has shown themselves in our time to keep it a secret because if we find out there is a time machine, then we won't bother to invent one, therefore they won't have one in their time.

Or, it would destroy the whole space time continuum thing, like in Back to the Future.

Anonymous said...

Marty, you're just not thinking fourth dimensionally!