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Time paradoxes and alternate universes
March 12, 2009 1:19 AM   Subscribe

These subjects still fascinate me after a lifetime of interest: faster-than-light speed, alternate time streams, parallel universes, time travel, antiparticles moving backward in time, time loops, and the recurring themes of paradox -- all serious but astonishing ideas of science. Something about them inspires infinite possibilities. Am I not alone?
posted by ember (64 comments total) 10 users marked this as a favorite

 
You are not alone: these are interesting topics for science and fiction and may well change how we interpret the universe around us and I hope they do, for very practical purposes. That said, smart money is on relativity at the moment.
posted by christhelongtimelurker at 1:37 AM on March 12, 2009


Scientists have declared it possible for a post to be simultaneously not right for MetaFilter, not right for MetaTalk, and not right for AskMetaFilter. Congratulations for confirming they're correct.
posted by Mapes at 1:38 AM on March 12, 2009 [4 favorites]


This post is a double. Not now, but some time in the future.
posted by twoleftfeet at 1:39 AM on March 12, 2009 [2 favorites]


I already posted this last week from now.
posted by codswallop at 1:49 AM on March 12, 2009 [1 favorite]


Thankfully, I'm in this post's light cone, or causality would go all to hell.
posted by eriko at 2:26 AM on March 12, 2009


Part of me thinks there is a strong case not to be interested in alternate time streams, parallel universes, and disrupting fundamental linear streams of cause and effect.

In a brave new world where such things are possible, the ethical dilemmas are almost as mindboggling, if not more so, than the physics. The changes to "life" as we know it would be so complete as to make us aliens to our native environment. The impact of such technological developments, in the case either that they were available to an elite few or made mass market would herald such a land grab that seismic levels of conflict would be inevitable.

The other part of me hopes fervently for teleportation technology that cut out my punishing commute, and time travel technology that allowed me to undrink the morning after the last two drinks the night before that have changed a mild headache into a full-blown hangover.
posted by MuffinMan at 2:34 AM on March 12, 2009


On when didden not re-posted this last unweek?
posted by loquacious at 2:34 AM on March 12, 2009 [10 favorites]


Yep. Pretty sure you're alone there, champ.
posted by koeselitz at 2:37 AM on March 12, 2009


I love those subjects too, ember. But just putting four links together because they interest you isn't really right for Metafilter. (It's more of a blog post, imo.) If you posted about one thing and found a number of other interesting links that really explored the subject, that would probably get a better reception.
posted by Kevin Street at 2:39 AM on March 12, 2009


The universe is like a big pancake. A big pancake balanced on the head of a rabbit. And don't ask what the rabbit is standing on.
posted by pracowity at 2:41 AM on March 12, 2009


In a thousand years, Metafilter will be destroyed. A thousand years ago, Metafilter will be saved and what can't be avoided will be.
posted by autodidact at 2:41 AM on March 12, 2009 [1 favorite]


I'll just watch this post speed by from the event horizon.
posted by Mblue at 3:06 AM on March 12, 2009


I don't like posts that end with a question mark.
posted by marxchivist at 3:07 AM on March 12, 2009


Wow, the "alternate time streams" link is awful. That writer, as much as one can say this when discussing time travel, has no idea what in the hell they're talking about. For example: In his discussion of "Flight of the Navigator", he confuses the fact that ASCII uses 8 bits to store characters with the idea of an 8-bit/16-bit/32-bit/64-bit processor, which as I understand it refers not to how individual characters are stored, but to the number of bits allocated to a memory address.

And that's not even touching his awful article about Twelve Monkeys.
posted by vernondalhart at 3:21 AM on March 12, 2009


Hey ember? You got any more of that stuff, man? Take 2 puffs and pass.
posted by chillmost at 3:33 AM on March 12, 2009


We need time travel. I'm not asking for much... like, say, 2007? I've got some stocks and a fuckin' house to sell.
posted by gman at 3:52 AM on March 12, 2009 [3 favorites]


See also: What makes a good front page post to MetaFilter?
posted by dunkadunc at 3:53 AM on March 12, 2009


"What you call the present we call the past; so you can see you guys are way behind."
posted by maxwelton at 3:58 AM on March 12, 2009 [2 favorites]


Present time is Christmas time. Which is not only in the future, but also in the past.
posted by popcassady at 4:13 AM on March 12, 2009


"And don't ask what the rabbit is standing on."

You're very clever, pracowity, very clever. But it's rabbits all the way down.
posted by The Tensor at 4:15 AM on March 12, 2009


IT IS NOT IMMORAL TO DELETE BASTARD POSTS
posted by atrazine at 4:25 AM on March 12, 2009


Sure, this isn't the best post, but I don't understand why the ragging has come here when SLYT posts now pass by without a murmur.
posted by MuffinMan at 4:33 AM on March 12, 2009 [2 favorites]


That's not true. Some SLYT posts are ragged on (even deleted), while others are simply better than this post.
posted by gman at 4:40 AM on March 12, 2009


Have you ever really looked at your hand?
posted by DU at 4:53 AM on March 12, 2009


clearly you need to get your hands on some spice
posted by incompressible at 4:59 AM on March 12, 2009


After 1,435,112 posts about the F***ing US elections, I think this post is great!

If we could just find out Obama's stance on time travel, everyone would love it.
posted by the_very_hungry_caterpillar at 5:05 AM on March 12, 2009


These internetz are not the best of the webz.
posted by IvoShandor at 5:16 AM on March 12, 2009


I'm with you on this Ember- that stuff is inspiring to think about.
Ignore all the haters and purveyors of weak jokes.
posted by Liquidwolf at 5:42 AM on March 12, 2009


That's not true. Some SLYT posts are ragged on (even deleted), while others are simply better than this post.

It depends on who's doing the ragging. N00bs get thrashed, oldsters get a pass (hint: usually starts with "D" and is usually the third comment in every.single.goddamn.metafilter.post). Being MetaFilter's Sweetheart helps too.

Anyways, to the point:

In a brave new world where such things are possible, the ethical dilemmas are almost as mindboggling, if not more so, than the physics.

Stepping into the universe next door where everything pretty much goes my way doesn't pose any ethical dilemmas for me.
posted by sidereal at 5:44 AM on March 12, 2009


Sigh I looked at the links and thought this post was interesting.... grant it, it could have had breasts somewhere in it but it was interesting to say the least. But OH NOOOES it ended in a question mark.... Delete it ASAP MODS!!!!

Seriously if we can have 2 open threads about the racism of RES 5 then this can stay.
posted by Mastercheddaar at 6:02 AM on March 12, 2009


Parallel universes and solipsism are two strong tastes that are great together, but I am alone in that.
posted by Free word order! at 6:15 AM on March 12, 2009


... but I like the weak jokes...
posted by Drasher at 6:19 AM on March 12, 2009


Not so long ago, I got into an argument with another scientist. This guy's pretty unusual, but this was extreme even for him. He was arguing that peer review was a bad idea. He had been trying to publish a few papers for several years. From what I could tell, they were fine, but they rubbed a few people the wrong way, and those people had been randomly chosen as the reviewers. So his career got disrupted and/or killed. At the time, my inclination was to argue rationally with him. Yes, you got hosed. Yes, there's lots of things that suck about it. But it's necessary. In retrospect, I should have just said, "the internet", and looked at him with a single raised eyebrow.
posted by Humanzee at 6:27 AM on March 12, 2009 [1 favorite]


Boo haters!

Check out this Radiolab interview with physicist Brian Greene. He makes compelling arguments for the ideas that there are an infinite number of exact replicas of you and I, free will is an illusion, and it's likely that we are living in a computer simulation! I thought it was fascinating, and I'm neither on drugs nor typing from a college dormroom.
posted by diogenes at 6:59 AM on March 12, 2009


It depends on who's doing the ragging. N00bs get thrashed, oldsters get a pass (hint: usually starts with "D" and is usually the third comment in every.single.goddamn.metafilter.post). Being MetaFilter's Sweetheart helps too.
posted by sidereal at 7:44 AM on March 12


You know, I had thought that once the floodgates opened, and Metafilter became more open (albeit with a small entrance fee) that this effect would lessen, but it seems to be as much as it ever was. I mean, we were at 17k for many years, now we're up to somewhere over 80k, maybe close to 90k by now.

As for this post, I cannot for the life of me understand what is wrong with it. People post "something they find interesting" every day. I'm not sure at its most basic level there could be any OTHER criteria for a post besides "I found this interesting, perhaps you will too".

From the metafilter posting guide:

A good post to MetaFilter is something that meets the following criteria: most people haven't seen it before, there is something interesting about the content on the page, and it might warrant discussion from others.

I don't think mjyoung.net or mindbluff.com are daily reading for most mefites. I think any "typical" reader of MeFi would find these topics interesting. I think it clearly might warrant discussion from others.
posted by Ynoxas at 7:04 AM on March 12, 2009 [4 favorites]


Maybe the mathematical models which use "time" for computational purposes say less about the human experience of material change than we'd like to believe.
posted by clockzero at 8:13 AM on March 12, 2009 [1 favorite]


maybe you should read these
posted by Drasher at 8:19 AM on March 12, 2009 [1 favorite]


thanks for the Flo & Eddie link, pracowity! That was take me back, alright.
posted by sneebler at 8:26 AM on March 12, 2009


There's no such thing as time-travel, because there's no such thing as time -- at least not as a physical dimension. It's just a convention for comparing change, a benchmark. For example: with no change, there is no "time" -- not the other way around.

Parallel universes and alternate time streams? Things that could-have-happened-but-didn't. They don't exist because they... didn't happen. What-ifs are fun to think about, but you can't just go *poof* over to them.

Faster-than-light travel... I think it's possible, but will take too much energy to ever be feasible and would squish any human who tried it from the acceleration. Gotta control gravity to counteract those forces, and, again, that too much energy.

So sayeth the spider.
posted by LordSludge at 8:33 AM on March 12, 2009


Excuse me, Rorschach. I'm informing Laurie ninety seconds ago...I-I'm sorry. It's these tachyons. They're muddling things up.
posted by Guy_Inamonkeysuit at 8:34 AM on March 12, 2009 [2 favorites]


FQXI (a fundamental questions in science institute, founded by the controversial late Templeton of the Templeton foundation of science and religion) recently announced the winners of their essay contest on the nature of time. Some interesting papers there. Also, one of these things does not belong with the others. I don't think antimatter being matter going backwards in time is not as controversial or speculative, though at some point in fundamental physics one seems to lose the distinction between "real" and "a good metaphor for the mathematics".
posted by Schmucko at 8:37 AM on March 12, 2009


A Soviet professor's site on Time Travel.

From Omsk University--not far from where the Tunguska blast occurred, which several science fiction books suggest can be used for time travel.
posted by eye of newt at 8:54 AM on March 12, 2009


Gonna be tough for that Soviet professor to be taken seriously if he insists on having that animated GIF of the Enterprise there...
posted by Guy_Inamonkeysuit at 9:04 AM on March 12, 2009


I always like to solve for time in different equations and then substitute freely. For example:
Interestsimple = Principal x Rate1 x ( Distance / Rate2)
posted by Fezboy! at 9:05 AM on March 12, 2009


Keeping in mind that according to Einstein's relativity theory, time travel and FTL travel are two terms for the same exact thing.

The old bromide is "Causality, Relativity, FTL travel: chose any two."
posted by Nyrath at 9:08 AM on March 12, 2009


eriko : Thankfully, I'm in this post's light cone, or causality would go all to hell.

As someone who started life in an alternate future controlled by fascist bipedal reptiles, who had to time-travel to the distant past to kill as many of their ancestors as I could, to bring about the present we are all living in, I can honestly say, "Fuck causality!"
posted by quin at 9:11 AM on March 12, 2009 [1 favorite]


I think the most perturbing concept is the statistical likelihood that we are mere simulations, based on the projected amounts of computing power that would be available to an advanced civilization. If there are billions or trillions of "subjective real-time" simulations running on the quantum computers of the future, then it is extremely unlikely that you are a real, flesh-and-blood human being. Even more horrifying than The Matrix, where at least there is a body that belongs to you floating in a tank somewhere.. in actuality, your existence is likely constituted as an entry in a database.
posted by autodidact at 9:52 AM on March 12, 2009


"There's no such thing as time-travel, because there's no such thing as time -- at least not as a physical dimension. It's just a convention for comparing change, a benchmark. For example: with no change, there is no "time" -- not the other way around."

Um, entropy only runs one way.
posted by klangklangston at 10:01 AM on March 12, 2009


In a parallel universe, your evil goatee-wearing doppelganger was too busy plotting with his supervisor's mistress to assassinate and replace his boss to post this.
posted by Halloween Jack at 10:18 AM on March 12, 2009


Correction: a look at Google maps shows that Omsk is, in fact, pretty far away from where the Tunguska blast occurred. Siberia is frigging huge.
posted by eye of newt at 10:44 AM on March 12, 2009


You know what stinks about metafilter? There's nowhere to discuss whether or not a post is good enough for the blue.
--This post brought to you by MetaTalk: The Choice of the Bitchers and Moaners
posted by inigo2 at 11:01 AM on March 12, 2009


I think the most perturbing concept is the statistical likelihood that we are mere simulations

I remember the "we're all in a computer" story a little while back.

There are a couple of major problems with that however.

The primary, and by far most important is simply "so what". If the theory were true, even if we were TOLD it were true, it would be indistinguishable from any other reality, and we could do nothing about it, even if we were aware of the fact. If I hand you an apple, and I tell you it's not really an apple, it is a rock, but you are able to see, touch, smell, taste, and digest it just like an apple, well then... apple is just another word for rock, or vice versa. You have a definitional problem, not a reality problem.

Any discussion of "free will" has the same problem. Even if you somehow are able to tell me definitively that I have no free will, I can't do anything with that information because I still have to do whatever it is I do, free or not. It makes no difference whether I really do have free will or not, because the way the world works, it is indistinguishable from my vantage point. And most non-religious discussions about free will fall into, again, definitional problems, not reality problems.

The second problem is that a simulation would have no value after its denizens were made aware it was a simulation. Basically, once the first person thought "hey, this is all a simulation", then it would immediately blink out of existence, because it is no longer simulating anything. "I disbelieve the illusion" and everything goes black.

I believe this same argument helps define the constraints of any time travel. If you could travel back in time, someone would have by now. We would see them every day. And every day of our life leading up till now. It would be commonplace.

It has always seemed to make sense to me that you could only time travel forwards, if at all. Basically, if it takes 500,000 years to get to a certain star, and I can bend space and get there in a week, I have effectively time traveled forward. And that is really only an illusion. Remember the "you leave on a rocket, and when you get back home, you are a day older, but a little baby has turned into an old man".

I did get a feeling for relativity once in a dream. I had a very vivid dream once where I lived an entire life during the dream. I spoke a different language, lived in a different time and place, and had what I would guess was a 60-70 year lifespan during the course of a dream that probably didn't last but a few moments "here".

Very strange. Very strange indeed.
posted by Ynoxas at 11:20 AM on March 12, 2009


A simple self-referential argument disposes of all "we are living in a computer" claims.

Where does the computer live?

This argument also destroys Intelligent Design, because the entire justification for ID is that life is too obviously too complex to have just happened, yet IDers explain it by invoking the existence of something infinitely more complex which had to have just happened (in order to avoid infinite regress).
posted by jamjam at 12:20 PM on March 12, 2009


Star Trek: TNG + Time/ Space Oddities
My fab 5

Contagion
Cause and Effect
The Inner Light
Timescape
The Chase
posted by Glibpaxman at 12:32 PM on March 12, 2009


The second problem is that a simulation would have no value after its denizens were made aware it was a simulation.

I don't follow this argument. Why would you think they'd simply blink out of existence?

My consciousness is based on neurons built out of atoms. Okay. Or: my consciousness is based on neurons simulated within a ginormous computation machine of some kind. Okay. Either way, cheeseburgers will continue to be delicious, simulated or not.

Hell, what we know about the underlying mechanics of reality is already so weird and counterintuitive that "it's all a simulation" would actually be something of a relief.

I don't think there's any measurable difference between a sufficiently complex simulation and "reality," at least to those inside. Somebody (was it Searles?) made the anti-AI argument that "a simulation of a hurricane won't get you wet" -- but a simulation of a math equation still gives you the correct answer. I believe that consciousness is more like math than like a hurricane, so it literally doesn't matter what is the underlying substrate it's based in.
posted by ook at 12:35 PM on March 12, 2009


A simple self-referential argument disposes of all "we are living in a computer" claims.

Where does the computer live?


This is just a restatement of "it's turtles all the way down"; it doesn't dispose of anything. Reality A could be a simulation within reality B, which is a simulation within reality C, which is within reality A. And "but which came first?" doesn't make that impossible, because none of them have to share (or even have) a timelike dimension.
posted by ook at 12:41 PM on March 12, 2009


Reverse psychology, eh? OK, I give. And since it doesn't look like this will be deleted...

vernondalhart: Wow, the "alternate time streams" link is awful. That writer, as much as one can say this when discussing time travel, has no idea what in the hell they're talking about...

He's neat, though, because he takes his central idea, and tries to fit it onto a whole bunch of different movies that weren't written with consistency in mind. The fun comes from following the contortions he has to go through to nail down all those disparate details and occasional sloppy plot holes into a single belief system. It's like the arguments fans have after the release of any science fiction movie, but extended to cover a wide range of films and carried out with a vigor that would exhaust most people.

diogenes: Check out this Radiolab interview with physicist Brian Greene. He makes compelling arguments for the ideas that there are an infinite number of exact replicas of you and I, free will is an illusion, and it's likely that we are living in a computer simulation! I thought it was fascinating, and I'm neither on drugs nor typing from a college dormroom.

There's a pretty mindblowing argument for the existence of infinite clones of you and I, and it doesn't depend upon any alternate universes or anything outside of our own reality. Supposedly, all it needs to be valid is the presupposition that the universe is infinite in size.

It goes like this: In an infinite universe, there's an infinite amount of matter and energy. However, our little chunk of the cosmos, the observable universe, is not inifinite. Within the boundary of what we can perceive (defined by a giant sphere centered on us), there's a limited number of things: only so many stars, planets, galaxies, and so on. It's possible to count the number of atoms and quantify the amount of energy within the observable universe.

But if the universe is infinite there's lots more stuff out there beyond that boundary, invisible to us. You could even imagine an infinite cosmos broken up into little bubbles, where each bubble is an observable universe. There must be an infinite number of these bubbles, each containing a finite amount of matter and energy.

But a finite amount of matter and energy can only be arranged in a finite number of configurations. (Because it's quantized.) Our observable universe is one such configuration, and if there's an infinite number of other bubbles out there past the pulsars, it stands to reason that every possible configuration of matter and energy (possible within the laws of physics) must occur, somewhere. Because the sample size we're talking about here is infinity.

So there must be other earths out there, not in some other dimension that we can never get to, but in our own universe. (Just so far away that we can never get to them.) Every possibility must be real, somewhere, beyond the boundaries of what we can see. Planets where fictional characters are real, planets with exact duplicates of you and me, planets where dinosaur lincoln is typing these exact same words. Every possible configuration of matter and energy out there somewhere, if the universe is truly infinite.
posted by Kevin Street at 1:48 PM on March 12, 2009 [2 favorites]


Kevin Street: But a finite amount of matter and energy can only be arranged in a finite number of configurations. (Because it's quantized.) Our observable universe is one such configuration, and if there's an infinite number of other bubbles out there past the pulsars, it stands to reason that every possible configuration of matter and energy (possible within the laws of physics) must occur, somewhere. Because the sample size we're talking about here is infinity.

I don't think this argument works.

For example, does every possible 100 digit span occur in the decimal expansion of Pi? That hasn't been proved. Take as another example, the irrational number defined by:

0.1101001000100001000001... etc.

with the span of 0s between the 1s increasing each time. Any given sequence of any length will never be repeated, because there will never again be a span of a certain number of 0s repeated (other than all 0s, once you get past a certain distance within the decimal). And yet the total number of spans of any length is infinite.

The analogy here is that the information within a spacelike slice of the Universe, or an example within a Multiverse, is some set of information, but there may be some prior set of information sets from which this information is chosen--such that even given infinite such examples, what's in our Universe is not chosen again.
posted by Schmucko at 2:28 PM on March 12, 2009 [4 favorites]


Interesting objection, Schmucko! I've never heard this before, and you may be right. I just spent an hour trying to come up with an objection to your argument, and couldn't find one. That's very cool thinking!

And it wrecks the probability of parallel worlds of any kind, from bearded Spock mirror universes to infinite bubbles in our own universe. Goddamn.
posted by Kevin Street at 3:39 PM on March 12, 2009


For the record I was never ragging on this post. I just never get a chance to break out my time traveler lingo ever since I broke my time machine. So lonely.
posted by loquacious at 3:53 PM on March 12, 2009


Kevin Street might be said to have the Ergodic hypothesis on his side, the hypothesis "that, over long periods of time, the time spent by a particle in some region of the phase space of microstates with the same energy is proportional to the volume of this region, i.e., that all accessible microstates are equally probable over a long period of time." if he combines it with the often tandemly used buttressing hypothesis that sampling many parallel instances of a process is equivalent to sampling one instance of that process at many different times.

However, the Big Bang combined with Dark Energy seems to have put paid to the Ergodic Hypothesis (in the equivalent formulation "that given sufficient time, a system will return to states that it has previously experienced") for the universe as a whole (since DE makes the BB a one way street, probably), and it's striking how much Shmucko's number resembles the universe under the BB, with the 1's (objects) within it increasingly surrounded by the 0's (empty space) as time progresses. To make Schmucko's number a better model for DE, we could make the nth string of zeros n! long, as Liouville did to demonstrate the existence of transcendental numbers.
posted by jamjam at 5:00 PM on March 12, 2009


within a spacelike slice of the Universe, or an example within a Multiverse, is some set of information, but there may be some prior set of information sets from which this information is chosen--such that even given infinite such examples, what's in our Universe is not chosen again.

That's an interesting point, but I prefer to believe that dinosaur Lincoln is out there somewhere :)
posted by diogenes at 6:34 PM on March 12, 2009


quin: 'As someone who started life in an alternate future controlled by fascist bipedal reptiles, who had to time-travel to the distant past to kill as many of their ancestors as I could ...'

Hang on - in my reality you had two n's and no time travel!

It's little clues like this which give it away.

(Not to mention that I'm really Bill Froog, fuel maintenance technician, and only put on this spacesuit to rescue an insane astronaut who'd jumped into a vat of liquid fuel. And his uniforms don't fit me...)
posted by Pinback at 8:02 PM on March 12, 2009


Um, entropy only runs one way.

On this side of the universe sure, but on the other side it runs in the opposite direction. Except for the USA's embassy over there, where machines have been installed so entropy runs the correct American Way.
posted by alejo at 2:39 PM on March 13, 2009


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