I, for one, welcome our time-travelling Borg overlords..

St.Alfonzo

The uncertainty principle states that you can't measure the position and momentum at the same time to infinite precision.

I'm afraid you're wrong. Here is a sanity check: take a look the statement of the uncertainty principle. They are talking about variance. What good is a statement about variance unless you can repeat trials?

Sorry, won't be attending. You bore us.

Unavailable for comment.

ymagynatyf

I understand your point (at least I presume so).

But in the same way that we understand mass, and velocity, and momentum, and friction, and all the other 'perceptions' that 'define' a speeding truck about to run us over, we also understand time. There is a perceivable, real world moment when the truck is heading toward me. There is a percievable real world moment when I have been hit by the truck. The results of the collision are empirically very noticeable - I am all broken, where a moment ago I was not. Were I to be completely oblivious to the oncoming truck, I would nonetheless be hit. And it would nonetheless have moved through time as it did so.

If we understand that the truck is not a 'cognative construct', ( i.e. if Kant was quite as sure of the objective existence of the "truck" as you or I.) then how can it's transition from 'about to hit me' and 'did hit me' somehow be?

If we accept that we can 'understand' gravity by watching an apple fall, how can we not then 'understand' time by watching the transition between not falling and fell?

If one of the attendees can help me travel back in time to stop the production of that God foresaken Rosie O' Donnell made for TV retard movie then, for the benefit of all mankind, I'm there.


This didn't have to happen and, with a little help, it won't.

ymagynatyf

Apologies. I would REALLY like to get into this, but I have a previous engagement, and I don't have the....err....time.

Will try to check back in later.

sigdiamond2000

"it's a jumpsuit." futureman, nice. did you ever read the original script which included a reference to WHY bob's brother (played by the other wilson brother, andrew, of course)...

DIGNAN: So who's going to know?

BOB: My brother.

ANTHONY: Future Man.

BOB: Who?

ANTHONY: Future Man. You know. Cause he
looks like he's from the future.

DIGNAN: He looks like he was designed by
scientists. For desert warfare.

/the lawn wranglers

time travel isnt possible..get over it.

lindseyp

But the observer outside the box does not affect what happened inside the box BEFORE the observation took place. It's not as though opening the box collapsed the wave function of the initial radioactive decay, since that was done by the photon detector right after the emission.

Ok, here is a description of the system at a time just after the internal observer saw the gun fired, from the point of view of the outside observer. From the point of view of the outside observer, the complete system is in a superposition of two classical possibilities:

- The cat is dead, and the observer inside saw the cat die
- The cat is alive, and the observer inside saw the cat live.

So you see, from the point of view of every observer, everything is still consistent. How exactly this all comes about is not clear, but your objection has not been overlooked by physicists.

Dammit, and I've gotta be out of town this weekend.

Funny that this comes up, though, as I was just thinking of a new theory about time travel.

Everyone knows the grandfather paradox: go back in time, kill your grandpa, shouldn't you no longer exist? One of the proposed solutions is that if you tried to go back in time to kill your grandfather, you would necessarily fail, because it has already happened. Basically, you can't succeed, because you've already failed. Similarly, you can't go back in time and save JFK from the assassin. You could try, but your efforts will fail, and might even contribute to the assassination.

However, this leads to an interesting line of thought. If you go back in time, the only things you can do are those things that have already occurred. For instance, if a friend got his car stolen in the past, yet he was unaware of the identity of the thief, you could theoretically go back in time, put on a disguise, and steal the car. That is, the only actions you can undertake after travelling to the past are those that fill in the holes of the truest records of history, not those which contradict them.

Conclusion: You can't go back in time to save JFK, but you can go back in time to kill him.



Guilty as charged?
Framed by the government?
Or is he a time travelling bounty hunter?
...or framed by one?

Heh, if I get a time machine, maybe I could sell tickets to people who want a shot at killing JFK. I could sell as many tickets as I want, whenever I want, renting out silenced sniper rifles and directions to the book depository. The great thing is that everyone who tries it will claim they got the winning shot, while everyone who hasn't tried it will be right in thinking they still have a chance, so there's nothing to stop the customers!

Then again, there is the risk that some customers might bring something back from the past. It would explain a lot of unsolved cases of robbery and missing persons, but I'd still have to ask them to put them back where they got them. And you just know someone will get the idea to pick up Oswald before the shooting to try to stop it. Then again, maybe I could sell Oswald a ticket before sending him back...

No self-respecting time traveler I know would go to MIT when Rammstein is on tour, Amsterdam and New Orleans are still above water, cigarettes and chewing gum are still legal, and women are still so sexually inhibited that they have orgasms at the drop of a pant.

Plus you don't need a license to kill Taliban, gasoline is cheaper than beer, and there *is* beer!

The future has no beer. It is Hell. Goddamn Hillary.

FlyingLizardOfDoom
The Encyclopedia Galactica has much to say on the theory and practice of time travel, most of which is incomprehensible to anyone who ...

I think you ment the Hitchhikers Guide. The time travel part of the Encyclopedia Galactica was censored by the 2nd Foundation. Or maybe R Daneel Olivaw. I forget which.

Mr. Titor went into hiding after his delivery of anti-psychotic medications came through.

As soon as time travel is invented I'm going to a Def Leppard concert.

I feel like it's my duty just to say:
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEERRRRRR RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDSSSSSSSSSSSSSSS SSSSSSSSSSSSS

lindseyp

But that's totally not the point of Schrodinger's thought experiment.

Huh, what? Did I say "This is the point of the thought experiment" somewhere? I think what I said was "your objection to cats being alive and dead is not sufficiently justified"

I can tell you the point of the experiment; it is to consider the consequences of quantum mechanics to our objective views of reality.

NiteClerk: Or maybe R Daneel Olivaw

Did you know that R. Daneel Olivaw can be rearranged to form
Drew. Oval Elian

/Scrabble Fiend

You know, before I answer any more questions there's something I wanted to say. Having received all your letters over the years, and I've spoken to many of you, and some of you have traveled... y'know... hundreds of miles to be here, I'd just like to say... GET A LIFE, will you people? I mean, for crying out loud, it's just a TV show! I mean, look at you, look at the way you're dressed! You've turned an enjoyable little job, that I did as a lark for a few years, into a COLOSSAL WASTE OF TIME!

I mean, how old are you people? What have you done with yourselves? You, you must be almost 30... have you ever kissed a girl?

NEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEERDSSSSSS

Why don't we call this new theory, "Time Travel" ?

murray208:

2005-05-02 06:43:00 PM murray208

St.Alfonzo

The uncertainty principle states that you can't measure the position and momentum at the same time to infinite precision.

I'm afraid you're wrong. Here is a sanity check: take a look the statement of the uncertainty principle. They are talking about variance. What good is a statement about variance unless you can repeat trials?

A statement about precision is a statement about repeated trials.

/zing

Marcus Aurelius:
Everyone ignores that the bacteria within the cat observed the cat's demise, and would therefore colapse the wave equation all by themselves. Most of the cat's affected tissues would also collapse the wave function.

Indeed the cat seems like a bad example since the model presumes that the cat is insufficiently aware (and the bacteria, etc) so as to affect waveform collapse.

It does seem kind of interesting the the universe starts to fall apart, or at least become something quite different, in the absence of awareness.

TIME TRAVEL DISCUSSION AND NOBODY mENTIONS THE JOURNEYMAN PROJECT???!!!!



I'm really suprised this wasn't mentioned yet.

i donated $3 to their refreshments fund.

I am a time traveler, but unfortunately my gear box is messed up and I can only move slowly forward at the rate of 1day/24hours.

KrustAsian

> Time travel is impossible because time itself doesn't really exist. It's just a man made system for measuring cycles. If we hadn't invented clocks and calendars we would have no concept of travelling backwards and forwards in time. So there.

Humans only invented the *measure* of time, but not time itself. By your logic life itself doesn't even exist because humans invented scales to weigh people, for example.

I don't follow your assertion that if humans cannot be weighed, then they cannot exist. What about a human in a gravity-free environment? No weight, so therefore he doesn't exist?

My take on this argument is there is no way to prove time exists without using some kind of man-made measurement device, where all the rules for measurement are made-up by whoever is doing the measuring. Even observing sunrises and sunsets is arbitrary.

I, instead, believe in causality as the closest thing to the passage of time that we can observe without imposing our own measurement devices. Event A happens, and produces Result A, which sets up Event B, and so on.

As for time travel... it would be possible if parallel universes existed that were on their own "schedule" or "timeline" for causality. If we manage to forge a connection between two nearly identical universes, Universe A may have already had the first moon landing, but Universe B is just building up to it. So time travel is possible in a sense, but then tampering with the events in Universe B would not affect Universe A.

Again, this is supposing that multiple universes exist. I'm no scientist, just a layman with ideas.

Has anyone seen the movie primer? Seriously, this deals with this issue in quite an interesting way.

http://www.primermovie.com/

Check it out.

Been there, done that.


image source: http://www.gaming-media.com/rpg/Chrono_Trigger/Artwork/crono.jpg

"Have you seen my dad?"

One thing this time-travel guy seems to have overlooked is this: It's simply not necessary for him to explicitly give longitude, latitude and time coordinates for a future time traveler. It's been done zillions of times in the past--scientists have taken countless millions of photographs of suitable landing spots (e.g. empty fields) in which the exact time was also recorded. Plenty of places to land a time machine without having it crash into other objects at the target. (Actually, I use the idea, of sorts, in my epic time-travel book.) So, if retrograde time travel was possible, it would have happened already.

BUT--and that's an even bigger 'but' than Rush Limbaugh's--it may yet be possible. By popping into the past, a time traveler would cause the space-time continuum to 'bifurcate' (i.e. split in two). Perhaps a future time traveler did land in my front yard last February 25th at a little past 2 PM. However, I'm not in that particular continuum, just this boring non-visitor continuum, so I'll never know...

Anyhoo, I'm up to 225 pages of my book and it'll be a time-travel epic if and when I finish. Sorta like H.G. Wells' 'The Time Machine' meets 'Gone With the Wind' and written by a complete lunatic...

Everything is a memory of itself.

harryjrf
My take on this argument is there is no way to prove time exists without using some kind of man-made measurement device, where all the rules for measurement are made-up by whoever is doing the measuring. Even observing sunrises and sunsets is arbitrary.

So, if science cant measure time, its existence is not proven?

I dont think I understand the statement. I know time exists because I exist in the passage of time. No big requirement for science to prove that. Maybe Im thinking of time like some think of God. One would not particularly care if science can prove either, if they have experienced it.

2005-05-02 06:43:00 PM murray208

The uncertainty principle states that you can't measure the position and momentum at the same time to infinite precision.

I'm afraid you're wrong. Here is a sanity check: take a look the statement of the uncertainty principle. They are talking about variance. What good is a statement about variance unless you can repeat trials?


I'm not sure exactly what you think I'm wrong about, or what your point about repeated trials is. True enough, the Heisenberg uncertainty in complementary variables would be reflected in the variance of reapeated sets of measurements.

To make a measurement of x to a known precision I do not have to make repeated measurements. I could for instance confine an electron in a narrow box, and then the size of the box defines the precision of my knowledge of its position.

The uncertainty principle then tells me what the minimum uncertainty in the momentum is. You're right that if I make repeated measurements, that would tell me the minimum variance of my repeated measurements, but that is not just an error in my ability to measure; it's a limit on how well the physical momentum is defined.

It's not actually a principle that applies only to quantum systems; any superposition of any kind of waves -- sound, water, whatever -- has the same ambiguity.

hmmm..............

"Time is an illusion
Lunchtime, doubly so"

btw, how many quantum physicists/mechanics are on this site? since it seems to be a good number

The Ghost of Freedom

Well I'm not officially a quantum physicist, but I know the subject matter, can do the math involved, read the relevant journals and all that. Also up on a few other areas of physics. Main thing as far as time goes is superconductor theory. And also big into aerodynamics/aeronautical engineering, and a few other fun things.

^ is familiar with time travel

2005-05-02 08:34:50 PM The Ghost of Freedom

btw, how many quantum physicists/mechanics are on this site? since it seems to be a good number

I'm actually a physicist, just finished my Ph.D this semester. So I've actually done a lot of quantum mechanics, and the number one thing I've learned about the subject is that there's a whole lot I don't know about it.

/Unavailable for comment

//Obscure?

they're already heard of it and they don't wanna go. they know it'll be boring.

St.Alfonzo

To make a measurement of x to a known precision I do not have to make repeated measurements. I could for instance confine an electron in a narrow box, and then the size of the box defines the precision of my knowledge of its position.

Ok, I see. I think that I may have misunderstood what you said. I thought you were suggesting that your precise measurement of position caused a variance in momentum. In my head it's more like: the conditions under which it is appropriate to make a good position measurement are poor conditions for making a good momentum measurement. Maybe the difference is understood and so is left unmentioned by you physicists.

You can go back in time (and pick your geographic location) for one single day. What do you do?

I would go back to around Sunday, 33 A.D. and hang out with Doubting Thomas, camcorder in hand.

What again? I haven't finished watching Grzthsvlbs Gone Wild from the last one.

Are you saying you invented a time machine... out of a Delorean?

/If you're gonna make a time machine, you might as well do it with some style!
//Plus the aluminium casing makes the flux dispersal....
///LOOK OUT!!!!