

What Movies Get Wrong About Time Travel - edw519
http://www.slate.com/id/2225223/pagenum/all/#p2

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cgs
For a real mindfuck, check out Primer:
<http://en.wikipedia.org/wiki/Primer_%28film%29>

~~~
ivankirigin
I highly recommend you stop recommending Primer when time travel is brought
up. The movie is better viewed not knowing anything about it. It could be a
character drama before the weird shit starts going on. By the way, this is an
awesome timeline <http://neuwanstein.fw.hu/primer_timeline.html>

~~~
clistctrl
awesome, on another note i have a 30" computer monitor and i still had to
scroll left

~~~
eurokc98
37" and still needed to scroll. Who's next?

~~~
ivankirigin
pixels matter, bro. 30" mac display is 2560x1600

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AndrewDucker
Oh for goodness sake. Time Travel _does not exist_. Therefore you can't get
anything wrong about it, except including it in the first place.

If you're allowing them to have time travel then you can only quibble about
internal inconsistencies, not inconsistencies with the real world.

~~~
sho
You sound awfully sure of yourself.

~~~
pg
There is a class of things it's possible to be very sure of.

For example, I feel very sure there's no such thing as blue weight. The
expression "blue weight" is syntactically legal, but that doesn't mean it
refers to anything. "Time travel" appears to be in the same category.
Syntactically legal, but you find that if you try to express precisely what
you mean by it, you can't. It's effectively a type error, like asking for the
square root of a stream.

Incoherence as a concept is a different sort of impossible from mere
technological "impossibility," like e.g. a pill you could take that would let
you survive in outer space without a suit. You can say what that means, even
if you can't do it. I have never heard a coherent explanation of what "time
travel" could even refer to.

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ivankirigin
We're travelling through time right now, and not even at a fixed velocity
given relativity. That makes the question whether you can control your
velocity, not whether you can travel.

~~~
lg
So we can change the velocity at which we travel through time? To what, 2
seconds per second?

~~~
ivankirigin
Yes, you can travel two seconds forward in time for what appears to be one
second to you. It depends on reference frames and velocities.

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TrevorJ
Can somebody clear this up for me?

Relativity states that time slows down as you approach the speed of light.
Given that fact, lets say I hop in a spaceship and zip around the earth at
near light speed for several years (Yes, I know there are problems with this
in terms of increased mass, energy needed, etc.) Ok, so after several years I
slow down and land. For me, it seems as if I've traveled into the future
becasue the people on earth have experienced more time than I have.

How is that not time travel, at least in a functional sense? I get that by
strict definition it may not be, but the result would be the same. It seems
like in this sense time travel is not only possible but proven.

~~~
quizbiz
I fail to understand how time can slow. So way beyond me as an HS grad.

If two people program 60 lines of code per hour, one does so in a spaceship
traveling nearly the speed of light and one does so on earth... after 1
year/365 days/8760 hrs they make a report on their progress and they don't
have the same results? If a watch ticks every second, the faster you go the
slower it ticks? Why? How?

Will people be buying a 2100 model Bugatti, hiring a driver, and working in
the passenger seat to be more productive?

~~~
roundsquare
So you got person A on earth writing code and person B going around REALLY
fast (very close to the speed of light lets say) writing the same code.

When person A finishes (say a week later) and comes back, he'll find that
person B finished "a long time ago." That is, person B finished, and then
waited till person A came back (say for a year, depending on how fast person B
was going).

What happened? Time went at different speeds for each person. They each took a
week from their own point of view!

Which one is right? Both of them. Thats what relativity says. There is not one
thing called "time" but that its "relative" (hence the name).

So, if your going to choose to hire one of them... you'd hire person B
(assuming your business is on Earth).

~~~
run4yourlives
You got it backwards... person A's week is much faster than the dude in the
spaceship. (Hence person B "travels into the future")

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danteembermage
This is the time travel I like to think about: Suppose we actually are
simulated ancestors of an advanced civilization. Then time travel can take all
sorts of interesting forms.

For example, suppose our simulation is run sequentially. Then someone
traveling back in time would travel back to an earlier state in the simulation
that is already out of "RAM" and stored. This agent is "dead", the simulator
does not bother to re-simulate the past just for them, they just disappear.

Suppose instead the simulator is more flexible; then there's no reason they
couldn't "fork" the timeline and let the gal do whatever she felt like and
change the past going forward on their own. Since this would take vast
computational resources, it would only be worth doing if you changed something
_big_ so maybe time travel wouldn't work unless your plans were grand enough.

This also resolves the grandfather paradox; your grandpa is dead, you are
never born in this timeline, but your simulated agent is just fine since it
was copied from a different code base. You live out your life, reproduce,
share technology, do whatever you want to do and life goes forward normally.
In fact, it'd be likely they wouldn't bother simulating the whole world but
just pull a Truman Show kind of thing and only propagate the changes, and copy
from old data elsewhere.

I'm sure there are even more interesting kinds of time-travel you could come
up with given a simulated universe. It actually could be fun to write some sci
fi short stories with this in the background, unexplained.

~~~
derefr
> I'm sure there are even more interesting kinds of time-travel you could come
> up with given a simulated universe. It actually could be fun to write some
> sci fi short stories with this in the background, unexplained.

I'm actually working with this exact idea, more or less, for a [roughly
proposed] series of books, the first of which I'm procrastinating upon as I
type this. :) Time travel, though, is a rather small part of what is possible
with my metaverse model. I assume that the simulations are infinitely stacked,
and each one has a 0:1 time-passage correspondence, so that for a "parent"
simulation, the "child" simulation runs instantaneously, no matter the in-sim
execution time, thus making Hypercomputation and such possible. All sorts of
fun-with-philosophy falls out of that:

The protagonists are Star Trek-style "everything is science" types, who
discover that magic exists (for "magic," read "simulation runtime bugs.") They
go on "Hard Science-based Fantasy" adventures using said magic for ten or
twelve books, before figuring out that it was (very complicated) science all
along. They then care for their own sim for a while, hacking it to fix some
kinks (such as the inevitable existence, given probability, of a malevolent
entity who has the root password.) Bored of that, they proceed to "break out"
of their simulation, repeatedly, visiting "higher planes" that each have
radically different physics and sometimes even logic, but that all share the
property that Turing machines can be constructed within them. Eventually, they
get to the "root" universe (really just a chroot jail) and meet God—that is to
say, an AI who was left to run for an infinite time on an analogue computer
and thus became omniscient merely by evaluating all possible states of all
possible universes (that it could detect from within the chroot.)

And that's only the first half of the sequence. 's called "Infinity's Tale",
by the way. :)

~~~
danteembermage
Now _that's_ singularity fiction; I think speculative fiction really does well
when there's a case for a truth or a worldview underneath, and like you said
there are lots of "fun-with-philosophy" implications here. Good luck shipping!

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Ygor
The point of this article isn't so much to prove some theories incorrect or
impossible. As time travel doesn't really exist we cannot say anything about
it and say its a fact. Its about logic. If you are making a movie about time
travel, than do it the way it makes sense.

There are to many movies this days that employ some kind of time traveling
mechanics which make no sense at all. Instead of using time travel as a good
plot device, it is more and more used as a deus ex. Writers aren't able to
think of better ways to resolve the plot. Don't you just hate it when that
happens. Oh, no, the main character died, its all over, the ship is destroyed
and the world has ended. But no, wait! What's that? Oh, its OK. We managed to
go back in time and prevent the tragedy, and now we can all go on with our
lives forgeting that we just found a way to travel through time.

Now that i think about it, there is not a single movie including time
traveling that hasn't got some kind of a plot hole. But that's ok, as you
said, its a movie and it doesn't have to be all real. But it has to have some
sense and meaning. Using time travel as a main plot device where it is not
necessary or even sane, is a serious crime.

The actual act of time traveling isn't that important, or the science behind
it. There are many theories and no one can say one is the best. A far far more
important aspect is how you handle the story and the world after the actual
act. Its easy to think of a functional super cool futuristic time machine, but
it is hard to think of what to do with it once it is actually there.

------
riffic
1) movies are works of fiction.

~~~
Timothee
I would put a spoiler alert on this.

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jp_sc
I prefer the theory of the parallel universes over the self-correction of the
time.

Most movies go that way too, since otherwise, the plot would be fatalistic
(eg: '12 monkeys'). So they aren't really wrong.

~~~
dkersten
I'm too tired to explain it here, but I like the explanation of time travel in
the book Cowl: <http://en.wikipedia.org/wiki/Cowl_(novel)>

~~~
run4yourlives
Sounds like a good book... thoughts on the story?

~~~
dkersten
I personally really liked the story. It had some interesting ideas and the
author seems (IMHO) quite good. I'd reccomend it.

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ewjordan
IMO the simplest resolution of things like the grandfather paradox are
obtained by including quantum mechanics in the equation.

Usually in quantum mechanics we find that waves are quantized because they
must be periodic over very tiny reaches of space, and the quantization comes
about because only certain frequencies of wave can meet themselves over these
distances.

But if we have time loops, it's pretty much the same thing, except the
consistency conditions can be experienced on arbitrarily large scales - the
quantum state where I kill my own grandfather is not a self-consistent loop,
and won't exist as a solution to the wave equations. In essence, the "wave"
that describes me killing my grandfather will interfere with itself over the
time loop, and will eventually (hopefully? I don't have a proof...) converge
on a wave that _does_ reinforce itself, and ends up consistent. This may
require a pretty serious divergence from what we'd usually assume about
classical physics, even at the macroscopic scale.

So quantization is the _real_ reason we shouldn't worry about the grandfather
paradox; any solution to the equations of QM will _have to be_ self consistent
over a closed timelike loop, even if the results are ridiculous as far as
classical mechanics is concerned.

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pmichaud
Dismissing Everitt branches by saying "there is no evidence," is totally off
base. There's a mountain of math that practically demands that it's true.

~~~
Kadin
Theory != Evidence

"Evidence" is by definition empirical; it's generally described as 'the result
of empirical observation' or something substantially similar.

~~~
rw
It's more of a gradient, not a strict inequality; cf. argument from parsimony,
inference vs. deduction.

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pronoiac
He's arguing for a non-forking timeline, which is nice, but I like soft
science fiction with stories rather than people spending much of the story
monkeying around with technology so that it's consistent with what we
currently know about science.

I'll quote something I wrote elsewhere: The two major time travel literary
views are forking & non-forking timelines:

* The game Achron has forking with merges via non-instantaneous time waves, sorta like Back to the Future.

* Lost is not forking. I think.

* The original Terminator's non-forking, but the sequels & series have forking timelines.

* Forking: Primer, The Butterfly Effect.

* Non-forking: 12 Monkeys, Slaughterhouse Five, Bill & Ted, All You Zombies.

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mattmichielsen
I'm really surprised that guy hasn't seen Primer.

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rimantas
The book on time travel describing model which made most sense to me for
years: <http://en.wikipedia.org/wiki/The_Technicolor_Time_Machine>

_This novel presents a clear use of the restricted action resolution of the
Grandfather paradox. The actions of the characters can not have changed the
past because the past is what their actions brought about._

~~~
ars
It makes sense on a social level, but not on a physical one. No matter what
you do, you change things - you ate, you breathed.

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doki_pen
Is it just me, or does the concept of "near speed of light" not make any
sense? I was under the impression that light travels at a constant speed no
matter how you are moving. And also, since there are no absolute coordinates,
the concept of moving only make sense in relation to other things. Isn't it
impossible to move "near speed of light"? Isn't light always going to move C
faster then you?

~~~
evgen
"Near the speed of light" carries with it the implicit disclaimer of "relative
to a stationary observer" (that is why the theory has the word "relativity" in
its name :)

Light travels at C (through a vacuum) regardless of your frame of reference,
so it used as the comparator for speed/velocity among different frames of
reference.

~~~
pbhjpbhj
The speed of light in a vacuum being [constantly and universally] constant is
an axiom (ie assumption, belief) of special relativity so it applies to
inertial frames of reference.

So, strictly it is not "regardless of your frame of reference". Accelerating
frames, eg rotating or accelerating (eg under gravity where General relativity
applies) require special treatments.

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humbledrone
I always thought the moniker "time travel" was not specific enough. I'm
traveling through time right now. I can't help but travel through time. Maybe
a more appropriate term would be "time navigator."

