Time Travel

[Chandrasekhar]

This thread is dedicated to speculation of what the phrase "time travel" could mean in a realistic context, depictions of time travel in popular media, theories (I use the term loosely) for how time travel might work, and whatever discussions crop up around these three things.

As there's no concrete facts to really back up the concept of time travel, rampant speculation and conjecture are welcome here. Whatever ideas you (or someone else) have had about time travel, feel free to express them here.

I'll start off the discussion by mentioning a book I read a while back. It's Pastwatch by Orson Scott Card. I won't give away any plot spoilers here, but the book puts forward a set of rules for time travel. In this book, sending "something" back in time invalidates all the events between the point to which that "something" was sent and the point from which it was sent. If the change is significant enough, it's quite possible that nothing resembling the event where this "something" was sent back in time will occur. Thus, this theory throws aside causality, and that "something" can be said to have appeared from thin air. As a side note, it is impossible for you to return to "your" time, because the events that led to your time period have been invalidated.

This is in sharp contrast to a certain Michael Crichton book (I believe it was Timeline). Using this book's system, you might decide to send someone back in time for five hours. In this case, you'll press the button, wait five hours, and then bring them back. The person you send back in time will also experience five hours of time before they are returned to the present. It is assumed to be impossible to change the events of the past enough that the present is altered to the point where you were never sent back.

Another popular system used in many books and games is the "time travelers' immunity" system. In this one, you might watch a History channel documentary about an ancient city being razed to the ground by an invading army. Not liking this story much, you hop in your time machine and convince the general of the invading army to spare the city. When you return to your time, you may find that the world has changed so much that you were never born, but your time traveler's immunity means that you're still around.

I prefer the first system, myself. It doesn't open up as many possibilities as some of the others, but it seems to be mostly free of those paradoxes that bug me when I read a story that violates them. So, feel free to comment on these, contribute your own archtypes, or otherwise chat about time travel!

 

[Masquerouge]

I agree that the first statement is more likely. What I hate is that it sort of validate Doc's theory in Back to the future 2, the silly drawing with parallel lines, but hey... can't have it all.
So yes, going back in time actually puts you on a different space-time than where you started from, meaning your impacts can not affect your original timeline - and also you can not go back to that original timeline.

 

[Turner]

Chronosphere by Allen Steele is a pretty good look at going into the past and changing it. L.E. Modesitt Jr also had a duology about people who can timetravel. Timediver's Dawn and The Timegod. Interesting reads there.

Timetravel's fun to play with. Little changes can make a big difference years down the road.

 

[warpus]

Pastwatch is an excellent book and is almost better (if not better) than Ender's game.

 

[capslock]

I like Slaughterhouse 5. It gives a different view of time and time travel that I think makes a little more sense.

Basically everything has already happened, from the begining of time to the end. It all happened in one instant. Its just our perception that makes it seem linear. Time travel is merely jumping between experinces, not physically traveling.

Its a pretty cool book.

 

[Irish Caesar]

I agree that the first statement is more likely. What I hate is that it sort of validate Doc's theory in Back to the future 2, the silly drawing with parallel lines, but hey... can't have it all.

This makes the most sense to me. I think it's interesting how much the creators drew this one out...

Spoiler if you honestly haven't seen Back to the Future, see it! :

When old Biff returns to 2015 after giving young Biff the almanac, he disappears. Somehow by making himself rich, he ends up dying at a younger age and not living to 2015. The DVD notes postulate that Lorraine would have shot him by the 1990's...

What doesn't make sense about this, though, is that nothing else changes at this point. Biff disappears, but the rest of Hill Valley is the normal one, it's not instantaneously changed. Unless it cleaned up real good between 1985 and 2015, which seems unlikely to me.

 

[Turner]

This makes the most sense to me. I think it's interesting how much the creators drew this one out...

Spoiler if you honestly haven't seen Back to the Future, see it! :

When old Biff returns to 2015 after giving young Biff the almanac, he disappears. Somehow by making himself rich, he ends up dying at a younger age and not living to 2015. The DVD notes postulate that Lorraine would have shot him by the 1990's...

What doesn't make sense about this, though, is that nothing else changes at this point. Biff disappears, but the rest of Hill Valley is the normal one, it's not instantaneously changed. Unless it cleaned up real good between 1985 and 2015, which seems unlikely to me.

I always wrote the spoiler off to the fact that it was a branch of the timeline, not the 'main' line itself.

Spoiler But if you recall... :

When he returned the time machine to Doc/Marty, he looked like he was having problems breathing, and that could have been before the changes moved down the time line. I don't know how to describe this, other than how Modesitt does it in the TimeGod world...the 'Winds of Change' move down the timelines, and Old Biff simply beat the changewinds to Doc/Marty's time. Keep in mind, Marty didn't instantly disappear when he got his mom attracted to him, instead of his dad doing it to her.

 

[Tenochtitlan]

Impossible. Time doesn't really exist. Think about it. It's just a comparative rate of atomic or molecular movement. It's a measure of movement.

Can you take something and make it look like it did in the past? Yes. You have to reverse every single process it went through from the present to the point in it's past in which you want to take it to. You won't take it to the past though. You will just make it have the same properties and dimensions it had in the past. We will all be still in the year 2006. The object may think it's in another time but in reality it is still in the present, with us.

Can you take something and send it to the past? No. To do that, you would have to reverse every single process that happened in the universe until that point in the past is reached. That, in itself, is impossible.

There is no past. There is no future. There is just now.

 

[Mott1]

This is in sharp contrast to a certain Michael Crichton book (I believe it was Timeline). Using this book's system, you might decide to send someone back in time for five hours. In this case, you'll press the button, wait five hours, and then bring them back. The person you send back in time will also experience five hours of time before they are returned to the present. It is assumed to be impossible to change the events of the past enough that the present is altered to the point where you were never sent back.

I believe Crichton uses time travel based on the string theory. You don't travel "back" in time/space rather you are sent as individual photons across space to an event destination. I think it's called quantum teleportation.
However you are sent to an alternate dimension and not "back in time." In this sense, no paradox is possiible since your actions will not effect your autochthonous reality. In effect you create an alternate reality.

 

[Perfection]

Impossible. Time doesn't really exist.

I'm bemused by this whole silly "time dodesn't exist" thing. Time sure as hell exists, just as much as space or electrons. Your usage of time based language shows how you don't actually believe that time doesn't exist.

 

[Turner]

However you are sent to an alternate dimension and not "back in time." In this sense, no paradox is possiible since your actions will not effect your autochthonous reality. In effect you create an alternate reality.

That's not how I remember Timeline. Didn't they find the professor's glasses in an excavation?

 

[Chandrasekhar]

That's not how I remember Timeline. Didn't they find the professor's glasses in an excavation?

Yes, they also found a statue of that one dude that stayed behind. Though alternate dimensions might be an interesting thing to base time travel off... it would be mostly for scientific historical experiments. What would WWII have turned out like if Hitler had been assassinated midway through? What if FDR hadn't died before the A-bomb? What if the Japanese never attacked Pearl Harbor? Of course, you'd have to have a ridiculous level of scientific detachment to play around with whole alternate planets without regard for the hundreds of milllions of people living there.

Hm... sounds like a good book.

 

[BasketCase]

One of the big problems with the mechanism of time travel is when the time machine goes "poof" and appears out of thin air in the past.

Why should a real time machine act that way?

When you're driving your car on the freeway, you're basically in a time machine moving the other direction: into the future (at the convenient pace of one second per second ). You get on the 405 from Pine Street, drive north for one minute, then exit at Grant Boulevard. You don't simply go "poof" and then appear out of thin air at Grant Boulevard.

Hop in a time machine and go backwards, and you're doing the same thing, except in the other direction. You move back in time at a steady pace. Naturally, sci-fi novels and movies always assume the space occupied by the time machine is vacant so that the time machine can pass through it; what's likely to happen in reality is this:

You start up your time machine (which you decided to set up in a vacant spot in your garage) and set it for a week ago. Anybody who looks into the garage will see you sitting there in the machine--and living backwards. Then, three days back, the machine crashes into something and stops moving back in time. Turns out your roommate removed that bookshelf from the garage three days ago, so that space had been vacant when you started your trip backwards. When you reach the point just before your roommate removed the shelf--CRASH! Better hope you've got spare parts to fix the machine.

Edit: I should note that you would actually be three days in the past, just AFTER your rommate removed the bookshelf. You can't actually go back in time to the point when the bookshelf was there--because every time you try, the time machine will bump into the bookshelf from just "ahead" of it in time. Or, maybe your time machine will smash the bookshelf to bits and keep going backwards until you arrive at one week ago?

 

[Chandrasekhar]

You start up your time machine (which you decided to set up in a vacant spot in your garage) and set it for a week ago. Anybody who looks into the garage will see you sitting there in the machine--and living backwards. Then, three days back, the machine crashes into something and stops moving back in time. Turns out your roommate removed that bookshelf from the garage three days ago, so that space had been vacant when you started your trip backwards. When you reach the point just before your roommate removed the shelf--CRASH! Better hope you've got spare parts to fix the machine.

Actually, something like that was one of the major concerns with the Pastwatch crew. They dropped the one of the people on a beach because they were afraid that he'd appear inside a tree, the part of the tree that they overlapped with would be destroyed, and the top of the tree would... well, let's just say that at least the natives wouldn't recognize any sort of time traveller.

 

[Mott1]

That's not how I remember Timeline. Didn't they find the professor's glasses in an excavation?

Well thats the logical flaw in his book. According to Crichton's story, people are not traveling back in time rather they are teleporting to an alternate reality or parallel universe. So the professor's eyeglasses could never have been found by his understudies at the dig site.
He's simply using the theory of quantum teleportation as the vessel for time travel to advance his storyline.

 

[Chandrasekhar]

That seems too big to be overlooked in his storyboard. Then again, maybe he takes a much more haphazard approach to his storylines than I'm used to, I don't know.

 

[Pegasos]

If someone invented a time machine, it would not be much of use if you couldn´t change the location too. The Earth moves very fast through the space, and if you travelled only 5 minutes forwards or backwards, you would be far out in space, smaller jumps can lead you under the peel of Earth where is, um... pretty warm.

 

[Winner]

I agree that the first statement is more likely. What I hate is that it sort of validate Doc's theory in Back to the future 2, the silly drawing with parallel lines, but hey... can't have it all.
So yes, going back in time actually puts you on a different space-time than where you started from, meaning your impacts can not affect your original timeline - and also you can not go back to that original timeline.

What if you move to the future?

Say I move from 2006 to 2058. I like it there, so I stay, but then, humanity is almost wiped up in nuclear war I accidentally caused by insulting the US president in front of his wife (I know it is silly). So I get into my time machine and move back to 2006, just after I left for the future. No I am back in my original timeline and the alternate timeline I created don't start until 2058.

 

[Winner]

There is one thing I'd like to discuss:

say that you move back in time with numbers that won in lottery a day ago. You are a cheater, so you decide to move two days back, kill your "past-yourself" and bet on these numbers you've brought from the future.

But will they really win again? Aren't such events random, as chaos theory says? If you move back, you'll create an alternate timeline, where events you know from your timeline may happen differently or not happen at all.

Time travel would become completely different if that was true. You'd move back to witness the Fall of Rome, but because of some random events would end up differently, the Battle of Adrianople would end with crushing Roman victory and no Fall would come. You'd be disappointed

 

[Chandrasekhar]

There is one thing I'd like to discuss:

say that you move back in time with numbers that won in lottery a day ago. You are a cheater, so you decide to move two days back, kill your "past-yourself" and bet on these numbers you've brought from the future.

But will they really win again? Aren't such events random, as chaos theory says? If you move back, you'll create an alternate timeline, where events you know from your timeline may happen differently or not happen at all.

Time travel would become completely different if that was true. You'd move back to witness the Fall of Rome, but because of some random events would end up differently, the Battle of Adrianople would end with crushing Roman victory and no Fall would come. You'd be disappointed

Absolutely. The minor random factors influenced by your coming before the lotto numbers were picked could easily change what they are. Same thing for the fall of Rome, though that might require some more active intervention. And you'd only be disappointed by the lack of a fall of Rome if you were a sociopath.