Is time travel Possible? If so should we do it?

[Gav]

Theoretically possible...

Let's not forget that Hawking has recently stated that black hole theory is probably wrong (and forfeited a set of Encylopedia's as a result).

[neevel]

Keep in mind that most such speculations take the form of physicists (engaging in a bit of not-overly-serious play) putting together a long string of "semi-plausible" assumptions. By semi-palusible, I mean something along the lines of: "we have no particular reason to think this is so, but there's also nothing that definitively says it can't be". After layering several of these assumptions on top of one another, the likelihood of the final result actually being accurate is pretty small. Like I said, the people engaging in such speculation generally don't pretend for a moment that it's serious science. But then someone from Discover magazine (which is sort of the New York Post of science) catches wind of it, knows that a cover story titled "Time Travel Revealed" will sell a lot of copies, and a few months later it's all over newstands.

So, when talking about stuff like this, remember that you need to take it in the right spirit: fun speculation, perhaps with a slightly better rational basis than most Star Trek sci-tech-babble, but nothing that's likely start making it into refereed journals on a routine basis.


-Dave

[MikeHarm]

The interesting thing to me about time travel is, suppose you are sending things back in time, so they arrive before you sent them. If you had enough of an interval what if after whatever you were going to send arrived you decided to smash the machine or such so that it couldn't of made the trip.

Perhaps its playing with fire but it would I think be a great way of testing wether the universe agrees that we have free will or not.

[Rogue]

Ok, let's assume time travel is possible like in Terminator II.
The microchip, from the Terminator arm in T1, was the key to Cyberdyne's AI program and ultimately, the end of the human race. Once that chip was destroyed shouldn't the Terminator cease to exist at that moment?
This ponder has no scientific ramifications but I'm open to other theories.

[mrbiggs]

Here's a paradox, using only the basics of time travel:

Let's say I invent a time machine, so I go back 50 years and kill Hitler. Immediately, the world switches to a new timeline. In this NEW timeline, I'm born, and stuff, but of course I never go back into time; Hitler is already dead. So who killed Hitler?

If you don't get that one, then:

I go back in time and kill my grandfather.


Isaac Asimov wrote a short story whose basic plotline was some guy discovering that all the Ancient Greeks got their information from a book that was sent from the future. And they go through and discuss it, but at the very end of the story, one of them says, "but where did the information come from?" (Or words to that effect). So...time travel presents too many paradoxes. Can't exist.

BTW, does anyone have a link to an article about those photons? That sounds interesting.

[DHCJr]

Heinlein had a very good short story called "By His Bootstraps". The basic story is about this college student cramming for finals. He is confronted by this guy who he doesn't recognize who wants to recruit him and then a second guy comes in to argue against him going. There is a fight and he is knocked through a whole. He ends up in a place with an old guy there, who ask him to do him a favor by picking up some things through a time portal and to recruit a guy that they need. He goes back and finds out the person he is recruiting is him and the second person is also him.

It has many of the arguments here and is a good story.

[Gav]

Here's a paradox, using only the basics of time travel:

Let's say I invent a time machine, so I go back 50 years and kill Hitler. Immediately, the world switches to a new timeline. In this NEW timeline, I'm born, and stuff, but of course I never go back into time; Hitler is already dead. So who killed Hitler?

If you don't get that one, then:

I go back in time and kill my grandfather.


Isaac Asimov wrote a short story whose basic plotline was some guy discovering that all the Ancient Greeks got their information from a book that was sent from the future. And they go through and discuss it, but at the very end of the story, one of them says, "but where did the information come from?" (Or words to that effect). So...time travel presents too many paradoxes. Can't exist.

BTW, does anyone have a link to an article about those photons? That sounds interesting.

Those are classic Time paradoxes. According to the theory yes you can build a time machine but you can only go back to when the Time machine was built. So no going back to kill Hitler or your grandfather.

[ReverseLunge]

Those are classic Time paradoxes. According to the theory yes you can build a time machine but you can only go back to when the Time machine was built. So no going back to kill Hitler or your grandfather.

What if you used the time machine that your grandfather built before he got your grandmother pregnant?

[Rogue]

What if you used the time machine that your grandfather built before he got your grandmother pregnant?

He's gotcha there.

[mrbiggs]

I recently finished a book (The Fabric of the Cosmos , by Brian Greene-copyright 2004), that went into time travel to some extent. He didn't mention any successes, which would have been relevant to the book.

He did mention "teleportation" of a photon that was successfully completed a few years ago, but this teleportation was slower than light speed. It did involve argon gas, so maybe that's what you all are thinking of.