Time Travel Paradox Ideas - Except Grandfather

[Viru.universe]

Hey guyies, can i get some really interesting and crazy paradoxes, except the grandfather one, thank you

 

[Bandersnatch]

At some point in human history the solution to Y is developed. The chrononaut takes it back in time and uses it to solve Y in the past, preventing the development of the solution.

Y might be a disease, mortality, global warming, poverty, whatnot.

 

[brenan]

All time travel paradoxes are the grandfather paradox just expressed differently.
With the possible exception of if you meet yourself. I'm not sure if the entire human body
is regrown over time or just parts of it (maybe someone here can say?)

If the entire body is regrown over time I guess there is no paradox.
If it isn't - that may constitute one?

 

[ModusPwnd]

Time travel is physically impossible.

Is there a difference between physically impossible and just impossible? I don't understand what "physically" has to do with it... ?

 

[skeptic2]

My favorite is the fire alarm (pop quiz) paradox. An announcement is made that there will be a surprise fire alarm next week but the exact day will be a surprise. Obviously it can't be on Friday because if it hasn't been on any of the previous days it wouldn't be a surprise on Friday. That means it can't be on Thursday either because if it can't be on Friday and it hasn't been on Monday Tuesday or Wednesday, it wouldn't be a surprise on Thursday. The same reasoning is repeated for Wednesday, Tuesday and Monday.

 

[Viru.universe]

@skeptic2,
wow that's a nice one!
But on thursday, the students don't know whether the test will be today or tomorrow, that is they are not 100% confirmed, so if the test in on thursday, it'll be a surprise right?

 

[Fredrik]

Hey guyies, can i get some really interesting and crazy paradoxes, except the grandfather one, thank you

My favorite is from Bill & Ted's excellent adventure. Their time machine had the strange property that the return trip has to be the same "length" (in time) as the trip. So if they go back 100 years, spend 5 minutes there, and then go "home", they will end up in the place they left, 5 minutes after they left it.

Early in the movie, Bill mentioned that the key to his father's car had been missing for a week, and that the father was sure that Bill had taken it.

(The quotes below aren't actual quotes; I'm paraphrasing).

Here's the paradox: Near the end of the movie, Bill and Ted need to go to school to take a test. To get there in time, they need to take the car. But the keys are missing. So Ted suggests "let's go back in time a week and take the keys". Bill answers "we don't have time" (because they have to leave immediately to not be late). So Ted says "OK, so how about this. We take the car to school and take the test. Then we go back in time a week, take the keys, and put them...under that rock". Bill agrees, so they walk up to the rock, lift it, and grab the keys from under it. As they're walking to the car, Bill says "Your dad was right. It was you who took the keys".

There are also some great paradoxes in the Doctor Who episode "Blink". It's a great episode, and you can see it even if you haven't seen any others. There's more than one paradox in the episode. The best one is the video conversation between The Doctor (David Tennant) and Sally Sparrow (Carey Mulligan).

 

[BobG]

Pool ball is sent into the corner pocket. The corner pocket is the entrance to a time machine. The exit from the time machine is the side pocket.

The time machine only sends the pool ball far enough back in time that it hits the pool ball headed towards the corner pocket.

If neither the original pool ball nor the time traveled pool ball enter the corner pocket after the collision, then there is no pool ball to be ejected from the side pocket, the collision can't occur, and the original pool ball is never deflected. In which case it enters the corner pocket ... You have an unstable reality that can't exist unless it doesn't exist.

If the time travel pool ball deflects the original pool ball, but not enough for it to not go in the corner pocket, then you have a stable reality. No problem.

If the time travel pool ball deflects the original pool away from the pocket, but then enters the pocket itself, you also have a stable reality. Except now you have a loop created entirely by the time travel pool ball.

The last was supposed to be the concept of the movie "Looper", but it was badly done. In other words, by the end, you had an unstable reality that couldn't possibly exist unless it didn't exist, etc.

 

[Bandersnatch]

The last was supposed to be the concept of the movie "Looper", but it was badly done. In other words, by the end, you had an unstable reality that couldn't possibly exist unless it didn't exist, etc.

It was much better realized in Chris Smith's "Triangle"(2009).

 

[brenan]

It was much better realized in Chris Smith's "Triangle"(2009).

A quite underrated movie. I loved that one.

 

[FlexGunship]

I'll throw my two cents in:

Read Heinlein's short story called "--All You Zombies--" (http://en.wikipedia.org/wiki/"—All_You_Zombies—"). It probably sets the world record for best time travel story ever. I never quite figured it all out, but I'm pretty confident that every character in the story is the same person. If I recall, it's only 10-20 pages long. Read it. It's worth it.

Here's the full story:
http://faculty.uca.edu/rnovy/Heinlein--All%20you%20zombies.htm

 

[skeptic2]

In ninth grade I read Heinlein's Time For The Stars and I recommended it to a friend. The book was about the twin paradox. He read it and used it for a book report for English. The English teacher knew nothing of relativity and gave him an F because the story didn't make any sense.

 

[Viru.universe]

I'll throw my two cents in:

Read Heinlein's short story called "--All You Zombies--" (http://en.wikipedia.org/wiki/"—All_You_Zombies—"). It probably sets the world record for best time travel story ever. I never quite figured it all out, but I'm pretty confident that every character in the story is the same person. If I recall, it's only 10-20 pages long. Read it. It's worth it.

Here's the full story:
http://faculty.uca.edu/rnovy/Heinlein--All%20you%20zombies.htm

oh ya! I know this one
its the craziest story i ever read

 

[BobG]

If the time travel pool ball deflects the original pool away from the pocket, but then enters the pocket itself, you also have a stable reality. Except now you have a loop created entirely by the time travel pool ball.

Actually, this would still be a paradox. From the time traveling pool ball's perspective, it would spend an eternity being involved in pool ball collisions. Eventually, the accumulated stress will shatter it. Then what?

It would be an even bigger paradox for a human in this time loop. They would soon die of dehydration and starvation and their body would eventually decay. Even if that problem were overcome, they'd age.

From the point of view of a person not in the loop, you can't say what they'd see.

 

[skeptic2]

Pool ball is sent into the corner pocket. The corner pocket is the entrance to a time machine. The exit from the time machine is the side pocket.

The time machine only sends the pool ball far enough back in time that it hits the pool ball headed towards the corner pocket.

If the time travel pool ball deflects the original pool ball, but not enough for it to not go in the corner pocket, then you have a stable reality. No problem.

There may be a problem with this scenario too. If the time travel pool ball deflects the original pool ball, it too will be deflected slightly. It will enter the corner pocket and emerge from the side pocket with a slightly altered trajectory and momentum. After a number of loops it will either miss the original ball or miss the corner pocket.

 

[Fredrik]

I like the version that goes like this: You shoot a pool ball towards the middle of the short edge of the table. Now two things can happen.

1. Nothing interesting.
2. An older version of the pool ball emerges from the side pocket and hits the side of the younger ball, deflecting its path into the corner pocket.

The cool thing about this is that neither alternative is a paradox.

 

[brenan]

Pool ball is sent into the corner pocket. The corner pocket is the entrance to a time machine. The exit from the time machine is the side pocket.
...
The time machine only sends the pool ball far enough back in time that it hits the pool ball headed towards the corner pocket.

This is the grandfather paradox again.

 

[Jobrag]

I'll throw my two cents in:

Read Heinlein's short story called "--All You Zombies--" (http://en.wikipedia.org/wiki/"—All_You_Zombies—"). It probably sets the world record for best time travel story ever. I never quite figured it all out, but I'm pretty confident that every character in the story is the same person. If I recall, it's only 10-20 pages long. Read it. It's worth it.

Here's the full story:
http://faculty.uca.edu/rnovy/Heinlein--All%20you%20zombies.htm

Also by Heinlein "By His Bootstraps" another short story

 

[FlexGunship]

I've always felt that Heinlein's treatment of time travel was always the most intellectually rigorous. He never proposed simultaneous alternate histories (a la Back to the Future) but instead always stuck to the idea of "one dimension of time."

As a result, there were never any "paradoxes" per se; just very interesting causal loops.

Essentially, Heinlein's take on the grandfather paradox is this: "You already know that you haven't killed your grandfather. You might not know why or how you've failed, but you know that you have."

Spoiler

In the case of Heinlein's Time Enough for Love Lazarus Long became the strange man whom his mother loved and then went off to war and died. He wasn't his own father, but he was a part of his own childhood memories.

 

[skeptic2]

I like the version that goes like this: You shoot a pool ball towards the middle of the short edge of the table. Now two things can happen.

1. Nothing interesting.
2. An older version of the pool ball emerges from the side pocket and hits the side of the younger ball, deflecting its path into the corner pocket.

The cool thing about this is that neither alternative is a paradox.

With regard to option number 2, and with backwards time travel in general, there always is a causality violation.

 

[BobG]

It was much better realized in Chris Smith's "Triangle"(2009).

I watched that movie recently and it is good!

But what the heck is with the main character's shoes!? I have to admit they're nice and all, but for sailing? And she never lost them while swimming? Or fighting? Do they have some sort of symbolic meaning?

 

[HallsofIvy]

In "the Man Who Folded Himself", a young man finds a time machine and uses it to move back and forth in time to the extent that there are a huge number of "copies" of himself all around. Finally, when he is so old (in his "own" time frame) he knows he will die soon, he takes the time machine back to the same time and place he found it. So where did the time machine come from?

Another "closed time loop" occurs in "Star Trek- the Voyage Home". Back in twentieth century Kirk raises the money they need by selling a pair of antique glasses. When Spock protests that the glasses were a gift from McCoy, Kirk says "That's the beauty part- they will be again", implying that McCoy will buy these specific glasses and give them to Kirk in the future. So when, if ever, were the glasses actually made?

And I am going to take this opportunity to vent: In order to be able to build a container for the whales, and all the water, they need to make "transparent aluminum". They go to a plant that where, apparently a variety of things are fabricated and shows the supervisor there the formula for "transparent aluminum". (After realizing that he can't just talk to the computer, he immediately types what must be instructions to draw the formula. Isn't it lovely that he knew the system and instructions to do that. But that's not mu point.

After Scott gives the supervisor enough information to make "transparent aluminum", Kirk protests that they could be changing the past. Scott responds "How do we know that he wasn't the inventor of transparent aluminum?" Excuse me? As long as we don't know what happened in the past its alright to do whatever we want? And, any way, Scott, being the well educated engineer that he is certainly should know who created transparent aluminum. It would have made much more sense if Scott had said "But captain, he did invent transparent aluminum". That would still be a "closed time loop" but would have made more sense.

 

[Bandersnatch]

But what the heck is with the main character's shoes!? I have to admit they're nice and all, but for sailing?

The memories of the film are a bit hazy, no thanks to the plot being a (charmingly intriguing)bastard child of a contortionist and a schizophrenic, but I would assume she was not exactly thinking about going sailing when she had put them on.

 

[BobG]

After realizing that he can't just talk to the computer...

Totally off topic and silly, but my daughter's workplace got a new copier. Someone made up a really nice looking sign (they even laminated it) to post above the copier announcing the workplace's new voice activated copier.

Amazing how long people will talk to the copier, trying to figure out just how the darn thing works, occasionally cursing the lack of an operator's manual.

 

[Ibix]

After Scott gives the supervisor enough information to make "transparent aluminum", Kirk protests that they could be changing the past. Scott responds "How do we know that he wasn't the inventor of transparent aluminum?" Excuse me? As long as we don't know what happened in the past its alright to do whatever we want? And, any way, Scott, being the well educated engineer that he is certainly should know who created transparent aluminum. It would have made much more sense if Scott had said "But captain, he did invent transparent aluminum". That would still be a "closed time loop" but would have made more sense.

McCoy, I think, rather than Kirk. Kirk is off flirting with the lady marine biologist. In the novelisation, though, the scene plays out more or less as you suggest. Scott is massively impressed to be meeting the guy, much to the poor man's confusion. Scott initially thinks he's got another man of the same name (Marcus something?), but the penny drops about half way through the conversation.

 

[azzo]

if you think parallel universes, a travel to the past could be a travel to a universe identical but delayed in "time"

 

[Viracocha]

Time travel seems logically impossible as well as physically impossible, since, even if you did it, it produces so many paradoxes

 

[StrayCatalyst]

Heinlein's careful poke at time travel was what you'd expect of an engineer with imagination - All You Zombies was beautifully recursive. All the characters who drove the story, were the same person at different ages, but only the oldest (if the word applies - it's somewhat inaccurate!) knew what was going on, and made the arrangements for his/her younger self to meet his/her much younger self... leading to his/her own birth.

Heinlein had some serious blind spots (cam-drive rocket autopilots, world-wide theocracies, SSTO starships that you could buy like a used car, etc) but this story was brilliant.

 

[remmeler]

More simple paradox

Traveling 5 days back in time and for some reason not being able to travel forward except in the normal way of 1 day at a time.

There would be two of you existing in that time, but in 5 days your original self would travel back again and now there would be two of you who have traveled back and so forth.

The only way it could happen would be that you traveled back in time and ended up in that part of the multi universe where you traveled back in time.

Also there is the problem that no one has ever met someone that had information that would prove that they traveled back in time.

Just a little stupid thought I had, just to see if anyone has any thoughts on it.

I actually think that Space-Time is a misnomer. Times is really just the measurement of event that happen in space. If nothing, absolutely nothing happens in space, then does time even exist. Time is always expressed in relation to an event. How many heartbeats, how many sunrises, etc.

 

[raunaqrox]

Is there a difference between physically impossible and just impossible? I don't understand what "physically" has to do with it... ?

Time travel is theoritically kind of possible , I am not expert but here are the possible ways to time travel,

1.Move very close to the speed of light , when you stop you reach your future(as time for you , let us say 5 hours where as outside time passed much faster (depending on how close to the speed of light).
2.Move fast around a very dense object , like black hole or a very heavy planet. Again when you come back to Earth it will be your future on earth.
3.All around us small worm holes , so small it we don't see it, if we are able to stabalise them then we can do the time travel for real.

All these are beyond our current technological possibilities.


------------
now the paradox,
You switch on your time machine > assemble a gun>go in time before you assemble the gun>and shoot yourself.

 

[aa1bb2cc]

I'll throw my two cents in:

Read Heinlein's short story called "--All You Zombies--" (http://en.wikipedia.org/wiki/"—All_You_Zombies—"). It probably sets the world record for best time travel story ever. I never quite figured it all out, but I'm pretty confident that every character in the story is the same person. If I recall, it's only 10-20 pages long. Read it. It's worth it.

Here's the full story:
http://faculty.uca.edu/rnovy/Heinlein--All%20you%20zombies.htm

There is a movie based on this story. Its called "Predestination" staring Ethan Hawke.
Its really a good movie with very little cinematic liberty. A must watch

 

[chasrob]

I read this interesting arXiv paper--http://arxiv.org/abs/1505.07489 that helped me understand FTL is time travel. Me, who is mathematically challenged--it has high school algebra equations--mostly heh, heh..

It had 2 pads for the space ship; one launch pad and a landing pad. Weird stuff going on when the flight was superluminal. Ships returning while its optical replica? was taking off, ships returning to the landing pad days before they took off from the launch pad, views from telescopes on Earth showing the ship approaching and leaving the destination at the same time, even the pair meeting at the destination and disappearing... what the ...?

 

[BastianQuinn]

In my experience, a paradox isn't some kind of magical error in space-time that can be harnessed by the plot of a scifi story like "pure chaos" or "reversing the polarity." A paradox generally only signifies that the person performing the thought experiment lacks the knowledge to complete it. (that person is often me)

An example of this is Zeno's paradox which says that crossing a distance is technically crossing half the remaining distance repeatedly (paraphrasing) and claims that there should always be more distance to halve, so it should be impossible to cross any distance. This is a paradox because of the assumptions made in constructing the model. In reality, halving the distance also shortens the time ad infinitum, the kind of thought process that makes integration possible.

All that the grandfather paradox shows is that the assumptions made in constructing that model of time travel are incomplete. Any model of time travel where the actions of the traveler(t_n) could theoretically change the traveler before traveling(t₀) are incomplete. This is why savvy time travel authors come up with rules which preclude a grandfather paradox.

The other "paradox" is said to be meeting yourself, this is said to be related to the Pauli exclusion principal, which is misquoted as stating that "the same matter cannot occupy the same space-time twice." This is a misunderstanding of quantum physics. As I understand it, (and I understand it poorly) even if it had anything to do with time travel, it would be prohibitively difficult to intentionally attempt to have two identical fermions "touch." In layman's terms, this theorem is kind of a mathematical proof that electrons in the same orbital have opposite spins.

Oh, but here's another paradox I have heard. When we move along space, we accelerate and decelerate. If time is a comparable dimension, traversal of it would follow similar rules. (faulty model construction) However, if we attempt to decelerate in order to move backwards in time, when we reach 0 time-velocity, we would be parked at a point in space-time where future-us is constantly arriving, and be unable to pass through the wall of past-us. An infinite number of us would suddenly occupy the same point in space-time, creating a black hole.

 

[skeptic2]

The thing that all backward time travel stories have in common is that the time traveler himself doesn't regress in time, everything else around him does. If the traveler were to regress in time he would get younger and lose his later memories. He would never meet a younger version of himself because he would be that younger version. Unfortunately this doesn't make for an interesting plot. It seems that this split direction of time travel in which the time traveler continues to travel forward in time, i.e. he gets older and accumulates memories, but everything else travels backwards in time, is the crux of the paradox.

 

[BastianQuinn]

The thing that all backward time travel stories have in come is that the time traveler himself doesn't regress in time, everything else around him does. If the traveler were to regress in time he would get younger and lose his later memories. He would never meet a younger version of himself because he would be that younger version. Unfortunately this doesn't make for an interesting plot. It seems that this split direction of time travel in which the time traveler continues to travel forward in time, i.e. he gets older and accumulates memories, but everything else travels backwards in time, is the crux of the paradox.

This is true. Time travel generally fails to specify what exactly is being transported through time, and the more detail a story gives about what is being transported, the more obvious it is that it would not work... at least not as described.

Most instantaneous time traveling such as Back to the Future begs the question: "how does the car know where to come out?" The Earth rotates, the Earth orbits, the Earth's orbit has apsidal precession, the sun moves through the galaxy, etc. etc. etc. The two inertial frames differ wildly, yet the car appears to maintain velocity as if it "blinked" from one point in space-time to another.

Space-time bubble devices like the eponymous Time Machine give the impression of acceleration and deceleration through time, which is problematic as described above.

Situations where the traveler "wakes up in a younger self" ask more questions than they answer. Did the character's mature brain travel back to inhabit his immature skull? So many how.

Then there is what's perceived as the simple solution: the threshold of death. Even if air pressure was somehow a non-issue, it sounds to me like a good way to reintroduce smallpox, the bubonic plague, and polio into the modern world.

In the face of these criticisms, even Terminator logic seems plausible.

 

[rootone]

Transporting matter (in human or other form) into the past, increases the total mass-energy content of the past, and decreases the mass energy content of the future.
I think this could get problematic after a few iterations.

 

[BastianQuinn]

Transporting matter (in human or other form) into the past, increases the total mass-energy content of the past, and decreases the mass energy content of the future.
I think this could get problematic after a few iterations.

Wow... I think this might be the only example of a loop which will always close itself. The source of the extra energy is the point in the future, which will have been a universe with the extra mass-energy to spare, because it manifested when it came from the future. If T_p is the moment in the past that the traveling stuff emerges from the future, and T_f is the moment in the future it leaves for the past, then the mass-energy content of the universe at T_p-1 and T_f+1 are equal. There's nothing extra, just folded through space-time. Mass-energy doesn't age or die, and doesn't care if it's "the same stuff". There is no question of where this extra mass-energy comes from or goes, it does not have to stay in the same form, and the equation will always be balanced. This is merely a method of temporarily increasing the mass-energy content of the universe. Similarly, jumping forward in time reduces the mass-energy content temporarily.

I mean, yeah. doing so might be problematic, as you said, but I was surprised to find such a cleanly closed loop in a time travel model.

 

[cpscdave]

In Stephen Baxters Exultant they have FTL drives, and its possible depending on your FTL path to travel back in time. This causes the main character to travel back in time to before he was sent on a doomed mission.
Like many of the other examples listed this results in 2 versions of himself existing.

Later in the book Humans use these FTL loops to create a computer that can solve any problem instantly. It does this by using the time travel loops.
It first checks the time travel result register, if its empty it processes 1 step of the algorithm. If the step produces the answer it sends the result back in time, otherwise it repeats.
One of the engineers remarks that they can build the computer using very cheap components cause they will never actually do any work.
Always thought this was a fun application of time travel :D

 

[Khashishi]

Pool ball is sent into the corner pocket. The corner pocket is the entrance to a time machine. The exit from the time machine is the side pocket...
If the time travel pool ball deflects the original pool away from the pocket, but then enters the pocket itself, you also have a stable reality. Except now you have a loop created entirely by the time travel pool ball.

Maybe this paper is on your mind:
http://journals.aps.org/prd/abstract/10.1103/PhysRevD.44.1077