Anyone got the time?

February 10, 2003 4:09 PM

Just how plausable is time travel? Could you go back in time and kill your own grandfather?. Would you want to? Time travel is a popular subject for films, but do the writers work out exactly what is happening? Current opinion seems to be that time travel is only possible to the future, and is only one way, by travelling at near light speed. However despite this, time machines seem to already be on sale.
posted by Orange Goblin (53 comments total)

The most important question is definately "would you want to?".
posted by Pretty_Generic at 4:25 PM on February 10, 2003

i would definitely want to.
posted by folktrash at 4:31 PM on February 10, 2003

Pretty_Generic: Yes! And this is why (form the last link): If you have ever had difficulties astral projecting then this device can help you to succeed. ... The time coil headband sends the vibrational energy of that time into your third eye. After this is done for 5-10 minutes, you meditate and your astral body should be transported to the date and time you chose. If you have done the procedure on a grid point [Do they mean the power grid? I have to try that!] or vortex, you may even be physically transported in time. The unit comes with complete written instructions for proper use.
posted by MzB at 4:33 PM on February 10, 2003

Can't someone just buy one of those Hyper Dimensional Resonator's and tell us if it works??? I don't have $500 bucks to blow.
posted by banished at 4:35 PM on February 10, 2003

nice article (first link), but is the final comment about bell's paradox correct? this article (sci.physics faq) says it's still an open problem (but the article is 10 years old).
posted by andrew cooke at 4:38 PM on February 10, 2003

Only $497.00 for that gizmo. I'll take 10! But wait - it says "For Research Purposes Only". That shoots my business plan all to hell.
posted by dragstroke at 4:52 PM on February 10, 2003

I'm having trouble conceptualizing this... someone please help me out. When I time travel a day into the future leaving my friend behind, how is it that my friend catches up to me? Wouldn't I always be a day ahead of him? Time is still passing for me and I will be on to the next day before my friend catches up won't I? This is the problem I didn't understand in Back to the Future 1 when he sends his dog 1 minute into the future and somehow explains why they catch up with each other.
posted by banished at 5:07 PM on February 10, 2003

This guy claims that all you need is the right music.

http://www.circlevilleherald.com/action.lasso?-response=/1editorialbody.lasso&-token.folder=2002-03-18&-token.story=46114.111111&-token.quiz=&-token.pagelink=&-token.sectionads=Features&-token.thread=&-token.section=/editorial/2003-02-10/Featuresmini.html&-nothing
posted by metameme at 5:14 PM on February 10, 2003

When you go a day into the future, your friend will be there, already caught up with you.
posted by redfoxtail at 5:38 PM on February 10, 2003

banished: imagine yourself standing next to some train tracks. A train approaches you from behind at the speed of light and rushes onward in the direction you are facing.

That train represents time.

Now, the faster you run, the less rapidly the train (time) is moving past you.

So in the example of Back to the Future, when the dog (Einy) jumps forward in time, he travels in space at we'll arbitrarily say is just 1/1000th of the speed of light shy of the speed of light for what he feels is 1/1000th of a minute - effectively keeping pace with the train during that time. The end result is that relative to the rest of the world time passes him only 1/1000th of its normal speed, but relative to him everyone is experiencing time 1000x faster. So that 1/1000th of a minute he experiences passes 1000 times faster, and the rest of the world ages 1 minute in the time he ages 1/20th of a second.

So if you travel from star A to star B, a distance of 100 light years, at 99% of the speed of light, you will age 1 year while the rest of the people age 100 years.

I was fortunate enough to read an Einstein biography at age 8 which included the 'train rushing past you' model which really helps you visualize what is going on. I've probably explained this poorly but I hope that helps.
posted by Ryvar at 5:41 PM on February 10, 2003

But could you kill yourself?
posted by atom128 at 5:42 PM on February 10, 2003

Not really because information cannot propagate that way.

Except *maybe* via quantum entanglement, but I'm really getting out of my depth here in a subject I haven't touched for years.

Most important to remember, though: time and space are fundamentally the same thing. One light-second away is one second away.
posted by Ryvar at 6:07 PM on February 10, 2003

I hate temporal mechanics.
posted by DakotaPaul at 6:15 PM on February 10, 2003

I think time travel to the past is possible, and any paradox created by one's interfering with or observation of historical events is nullified by the creation a divergent timestream. For every action there's an equal and opposite reaction, don't ya know. I also like the definition of infinity implied by a multiverse ... if it can be experienced (or perhaps more relevant to quantum entaglement, communicated), then it must be experienced/communicated. Somewhere.

However, none of that makes up for the fact that even could I fulfill a long-standing wish and travel back in time to visit Ancient Rome and hobnob with Caesar Augustus, some damn bug or other blight would probably kill me the second I appeared.

(semi-frivolous) Disclaimer: Everything I know about this and other diverse topics comes from comic books. I love Hypertime.
posted by WolfDaddy at 6:31 PM on February 10, 2003

I also like the definition of infinity implied by a multiverse ...

I want to be The One.
posted by bwg at 7:04 PM on February 10, 2003

The only problem is, I can't kick ass like Jet Li.
posted by bwg at 9:00 PM on February 10, 2003

Has anyone ever considered that time travel backwards in time contradicts the first law of thermodynamics? "First Law of Thermodynamics: Energy can be changed from one form to another, but it cannot be created or destroyed." Well, if mass and energy are basically interchangable, ala e=mc^2, then travelling back in time adds mass to a system that should have a set mass. That is, if I travel back in time to a day ago and meet myself, there are now two of me where there should only be one. I have created matter out of, effectively, nothing. This is my main problem with backwards time travel.

The other, slightly smaller problem I have is the whole idea of time streams. If I go backwards and change something, then go forwards again, the history that is created from my actions are relative to myself. So, a friend in 2003 that doesn't go back experiences life as usual, while when I return I get a whole 'nother universe, so to speak. So what are the implications of this? Is the existance of time streams just in our minds?

Ack, getting too metaphysical. Time to recharge my chakra with some energy crystals.
posted by Civil_Disobedient at 9:31 PM on February 10, 2003

Thanks for that explanation, Ryvar. That's a much clearer metaphor than I've ever heard on the subject.
posted by ttrendel at 9:34 PM on February 10, 2003

Penn and Teller are doing a weekly show right now on Showtime. It's called (elegantly) "Bullshit". That web page with the experiemental time machine should be submitted ...
posted by MidasMulligan at 10:13 PM on February 10, 2003

I wonder how moral relativism relates to relativity. *ducks*

Damn you Einstein! Damn you mostly nameless mostly faceless hordes of quantum physicists! You're doing more damage than every religion ever! Damn you to helllllllllllllll!
posted by WolfDaddy at 10:16 PM on February 10, 2003

While I don't have anything to contibute about time travel, in refreshing my understanding of special relativity I did find this nifty chart showing how many years it would take to travel to various locations in the universe at nearly the speed of light. According to the chart, at a constant acceleration of 2g's we could make it to the Andromeda galaxy in about 15 years*. That sounds even cooler than time travel to me.

*of course, 2.2 million years would pass on earth during that time
posted by boltman at 11:23 PM on February 10, 2003

Andrew Cooke: Regarding Bell's Inequality, it seems to be the standard view that it does show fundamental nonlocality. Or at least that's what my undergrad quantum textbook says. However, I've learned that as far as the still-debated physics goes, you can't always trust textbooks. It does raise an interesting question to ask next time I talk with the prof, though.
posted by Schismatic at 1:13 AM on February 11, 2003

When I was a very little kid, I astounded myself by coming up with the old "either back-in-time travel is impossible, or mankind vanishes before becoming advanced enough to make it possible, because there is no evidence that anyone from the future has ever visited us."

I was very proud of myself.

Until I told my Dad (who is both German and mathematician, for chrissake). He very gently loosened my childish grip on reality, and then we had ice cream (or at least some of us did, somewhere, I think).
posted by Opus Dark at 1:13 AM on February 11, 2003

I decided to post this because I was doing some 'research' into time travel theory for a film I'm writing, and came up with a load of good stuff that deserved a FPP. I'd decided to have the main character rewind time (literally - he uses a VCR remote...). Of course, to advance the film, he has to remain his future (or rather, present) self whilst in the past. However, this doesn't work, because if time is being rewound, the future he is rewinding from does not yet exist, thus he can't be his future self, only his past self.

Basically, I'm stumped.
posted by Orange Goblin at 2:44 AM on February 11, 2003

Erm... seriously, you don't want to give out the premise for a film you're writing, mon frere.
posted by Pretty_Generic at 2:50 AM on February 11, 2003

You're not "stumped" - you're "paused".
posted by Opus Dark at 2:52 AM on February 11, 2003

Metafilter: loosens your childish grip on reality, and then there's ice cream!
posted by WolfDaddy at 5:43 AM on February 11, 2003

orange goblin - if i understand what you're saying then isn't the standard ruse to have the time machine travel with the user? so the video and remote travel back through time too.
posted by andrew cooke at 5:54 AM on February 11, 2003

If I travel in time and murder myself, will I go to hell?
posted by Dick Paris at 6:01 AM on February 11, 2003

If I travel in time and murder myself, will I go to hell?
no way man, after i go back in time and kill god there won't BE any hell.
posted by quonsar at 6:39 AM on February 11, 2003

Shadowkeeper wrote an excellent piece on his work with time travel. Myself, I swore off the stuff after I screwed things so badly that the British rebels won that colonial uprising in the 1700s and hundreds of years later some other guy invented Metafilter, instead of Keanu Reeves.
posted by Yogurt at 7:36 AM on February 11, 2003

"Having a time machine means never having to say you're sorry" - me
posted by dyaseen at 8:07 AM on February 11, 2003

When we use the phrase "time travel," we always seem to imply traveling with our physical, causal presence. But what if - even if that turns out to be impossible - observational time travel is possible? In other words, you could go back and watch your grandfather being raised from infancy, but would be powerless to change anything in that stream? You would move through the past like a spectre, but would be able to see what was going on? This avoids the grandfather paradox, the multiple timestreams, and the second law of thermodynamics. It also means people may have already come back from the future and we haven't noticed. I think we need to build high-powered detection instruments, if only for department store changing rooms.

Seriously, though, I think observational time travel will happen, if only through the inevitable archiving of most of (public) reality which will create a huge database into which we can dive. Give it a decade or so.
posted by soyjoy at 8:57 AM on February 11, 2003

Another problem I have with time travel has to do with the wave functions of our particles staying continuous... Time and space being the same thing, it seems to me that there'd have to be a break in the wave functions if you went spontaneously from one space/time coordinate to another... it's like teleportation.

Also, if you were traveling in time, you'd have to account for the movement fo the earth and sun, or else you'd wind up in empty space.

And dammit, Yogurt, were you the one who convinced Jerry Lewis not to run in '68?
posted by COBRA! at 9:04 AM on February 11, 2003

Re: oberservational time travel; see Pastwatch, by Orson Scott Card (and probably other stories and books as well, but this is one I know of).
posted by yhbc at 9:05 AM on February 11, 2003

yhbc - thanks, that looks like a good read - from the descriptions, reminds me a little of a couple of Philip K. Dick's.

What I'm talking about, though, is not so much using recording machinery to "see" into the past, but to record it now. For instance, if we started a camera on one public spot right now (say, at a frame every couple seconds) and were able to archive it into perpetuity in a searchable database, there would be one "spot" (ignoring COBRA's sun & earth variance, of course) where people a decade from now would be able to travel to, would be able to travel back to right now, when we started the camera. Let's get it going! Or has somebody?...
posted by soyjoy at 9:31 AM on February 11, 2003

I have created matter out of, effectively, nothing.

I've been thinking about this for awhile, and the 'system' in the case of time travel into the past would have to be Creation in its entireity, from beginning to end. By going back twenty years, yeah, I'm adding mass to 1983, but I've removed an equal amount of mass from 2003. Books are balanced. God's an accountant.

Now, however, the information my brain contains in 1983 is just a subset of the information my brain contains in 2003. Information can, apparently, on some levels, be exchanged at a cost of zero mass, so any information I transfer from my present-self to my past-self has to be balanced out somehow ... however, the creation of a divergent timeline seems horribly wasteful. Unless that divergent timeline already exists. Which means that someone afore me has conceived the possibility that I would time travel, and made allowances for it, and thus do I really have any free will and ... my head hurts.

Another idea that sprang from my cogitations: if a cataclysmic event can warp space in a small area, wouldn't it also warp time in both directions? So wouldn't information about a cataclysmic event that occurs, from our perception, in the future, be able to be discerned today, if we just knew where and how to look? I believe Miss Cleo should have seen it coming.
posted by WolfDaddy at 10:06 AM on February 11, 2003

Erm... seriously, you don't want to give out the premise for a film you're writing, mon frere.

If I had anything that wasn't a rehash of Bill and Ted/Back to the Future/Groundhog day, I'd be worried.

if i understand what you're saying then isn't the standard ruse to have the time machine travel with the user? so the video and remote travel back through time too.

You've miss understood, but thats because my explanation was very poor. The problem is not that the VCR remote doesn't travel. Imagine the stream of time as a video tape. You watch half of the film, and then decide you didn't quite understand the beginning, so you rewind to the start of the tape. Now, the characters in the film don't know what is going to happen during the course of the film, because for them it hasn't happened. However, you, as the observer, know what is going to happen because you've already seen it.

This is all fine and dandy, but this is 'observational time travel', as mentioned above by soyjoy. You can have no bearing on the outcome of the story, no matter how many times you rewind the tape. If, however you your self are on the tape (remember, the tape represents the stream of time), rewinding the tape will mean rewinding yourself. If you let the tape run for an hour, and then rewind that hour, you lose all the experiences of that hour.

This means that using the model of time as a video tape just doesn't work, and the film falls apart.
posted by Orange Goblin at 10:08 AM on February 11, 2003

Shadowkeeper wrote an excellent piece on his work with time travel.

That entry was inspired by a post at Cardhouse:

02apr08. I've thought of a much easier way to smuggle drugs into the U.S. First, smuggle tons of drugs from the U.S. into Mexico. This is much easier, you'll get no hassle at all. Then, reverse time.

posted by Shadowkeeper at 10:10 AM on February 11, 2003

Just noticed this - Also, if you were traveling in time, you'd have to account for the movement fo the earth and sun, or else you'd wind up in empty space.

Yeh, thats a point that always bugs me, films never take it into account, which is what I was trying to do with the video tape model described above. Maybe time machines are just assumed to travel in 4 dimensions, rather than the one :p
posted by Orange Goblin at 10:12 AM on February 11, 2003

The only problem with observational time travel is that observing something without interacting with it (at least on the level of photons and such) seems to be impossible. If we could do that, even in our own time, the Uncertainty Principle would be voided, and that doesn't seem to be happening any time soon.

Of course, as the premise for stories (namely Pastwatch), it's a great one.
posted by Schismatic at 10:16 AM on February 11, 2003

I thought the Uncertainty Principle only applied at subatomic levels? It seems silly to apply it to things on a larger scale - for example, if I read a MeFi thread without commenting, am I not observing without interacting?
posted by Orange Goblin at 10:24 AM on February 11, 2003

Orange Goblin: The film is fine, you just remake Memento, only with time travel! (see also 12 Monkeys).
posted by wobh at 10:33 AM on February 11, 2003

Here's another thing. Perhaps the playback isn't guaranteed to be exactly the same. There might be some temporal entropy in the rewinding such that particles aren't *exactly* in the same place afterwards. Which might mean, (via Butterfly Effect) you could get a Run, Lola Run situation out of this device. The guy in control of the machine may or may not know of the price he will have to pay for rewinding (losing the experience he had and not being assured that the outcome will be any better for him). But this is a dramatic problem, not one inherent in the device itself.

Good luck.
posted by wobh at 10:54 AM on February 11, 2003

Could you go back in time and kill your own grandfather?.

Not sure, as in Back to the Future, Marty was fading away because he did not exist when he changed his parents fate. But yourself

To kill yourself or even to see yourself, you would have to be omnipresent. I'm not sure if that includes time traveling to one point in time but all at once.

I find the theories of why it does not happen, time travel to be amusing but sad.

Where's the pictures of the future/past, this society loves souvenirs especially of themselves in it.

It's possible to time travel, but the energy needed to do so is never achieved...we die out as a society before that time line is achieved.

I'd decided to have the main character rewind time (literally - he uses a VCR remote...).

Kind of like in Memento, OG? or was that me trying to figure out what was going on...
posted by thomcatspike at 12:11 PM on February 11, 2003

Possibly. I haven't seen Memento..
posted by Orange Goblin at 12:25 PM on February 11, 2003

The uncertainty principle is only interesting on subatomic levels, yeah, but it's only because the energy levels are on the order to be affected significantly by interactions. There's no real difference in the interactions themselves (e.g. a photon hitting an electron or whatnot) at either scale, so observing something big is still more or less the same as observing something small. The important thing to Uncertainty is you can't observe anything without "hitting" it with another particle. Something like the temporal entropy wobh suggested might deal with the problem, though... Probably no physical basis, but interesting.
posted by Schismatic at 2:45 PM on February 11, 2003

The only problem with observational time travel is that observing something without interacting with it (at least on the level of photons and such) seems to be impossible. If we could do that, even in our own time, the Uncertainty Principle would be voided, and that doesn't seem to be happening any time soon.

A weird story has been told about this kind of thing. According to the story, the Vatican has a device called the Chronovisor that allows one to peer into the past. There's a book that's been written about it. It's probably bunk but it may help you with ideas for your story line.
posted by metameme at 3:19 PM on February 11, 2003

Couldnt we theoretically build some sort of telescope to see the images of the past that were transmitted by light, say, 50 years ago, if we looked at those light particles which are 50 light years away from us?
posted by titboy at 7:30 PM on February 11, 2003

No special equipment is needed. If you look at a star 50 light years away with the naked eye, the light you are seeing has taking 50 years to get to you. The star is no longer where you are seeing it, because it has since moved on from the point it was 50 years ago.
posted by Orange Goblin at 5:37 AM on February 12, 2003

OG: what I meant was, observing light that originated here on Earth.
posted by titboy at 11:12 AM on February 12, 2003

Well, that wouldn't work very well, as if we set a telescope up 50 light years away to receive light from Earth, it'll take another 50 years for the pictures to get back...
posted by Orange Goblin at 12:15 PM on February 12, 2003

I think I see where titboy is going with this. You'd first have to assume that everything that happens on the planet generates some "light" in the form of wavelengths that could, at some point in the future and by some process we do not posses yet, be picked up and "read" (or "translated") as images of the event which took place originally. If so, then we could also theoretically put some kind of mirror way far out in space to reflect the same wavelengths back to us. Now, if we put that thing fifty light-years out (ignoring for the moment that it would take us as least fifty years to do so), then the images from 100 years ago (which took 50 years to get out, and 50 to come back) could be viewed here on earth now. It would be like turning on a TV and seeing events taking place in 1903.

If you want to take this farther, and assume that these teeny-tiny wavelengths that everything generates can be reflected back and forth multiple times and still be "translated", then we could put a duplicate mirror here on earth to bounce the wavelengths back and forth between the two. Now, we should theoretically be able to tune in to wavelengths that bounced back and forth ten times and view from them the events that took place 1,000 years ago, in 1003.
posted by yhbc at 12:37 PM on February 12, 2003