cargrrl82, lindseyp

Does my time travel thought make any sense? (since you seem to have a handle on the same things).


2005-05-02 03:22:52 PM BojanglesPaladin

BojanglesPaladin:

The REAL problem with that theory is that sooner or later you will have to do a massive cross-over Called Crisis on Infinite Earths or something and end up killing the Flash and Super Girl. Ad No one want to go through that again.

No one wants to, but it is only a matter of time before the DC universe is so farked that the writers need to hit the reset button once again...

PLEASE all read up on the Uncertainty Principle. I think everyone is a bit off.

I'm far more than a bit off. But for the purposes of a fark discussion of time travel, I like to think I'm all right.

St.Alfonzo

AI=Artificial Intelligence. As for physics knowledge, I know a bit but like Richard Feynman once said "No one really understands quantum theory". And anyone up for superconductors? Which though it's under the heading of condensed matter physics actually involves quantum physics quite a bit. But black holes, the big bang and inflation, string theory, quark muon plasma, table top fusion, and all the rest, also good fun stuff.

GhostFish

I gave up on them long. long ago. Even without continuity problems, the writing was almost universally crap. (Vertigo excepted of course).

2005-05-02 05:39:28 PM BojanglesPaladin

The REALLY freaky stuff is what cargrrl82 and lindseyp are talking about.

See. the thing is (apparently) that with or without the 'detector' actually detecting, the results still shift. There is no 'interference in the system' at all. Which would suggest that the act of observation alone can affect quantum states.

As I understand it.
.

Well, it's the same stuff. The billiard ball idea is just an analogy of how it is impossible to measure something without affecting it; that's not what is going on in quantum mechanics when they talk about measurement infulencing a system. The effect that is particular to quantum physics is superposition - the idea that a thing can be in more than one state at the same time, and it doesn't choose one until you look at it.

The two-slit interference stuff is a great, simple way to illustrate it, and show how real it is.

Various Farkers

You're all confusing cycles with time. We are all culturally programmed to think in linear patterns (a + b = c) but nature doesn't work like that. The planet doesn't know it's May 2, it's just orbitting the sun, same as always. Sure, we're born, we grow old and we die and we see that as the passage of time because we are small, but in the bigger picture we just die and are instantly replaced, and so the cycle continues and everything carries on as normal. Time was only invented so that you could get to work at 9:00 am.

PLEASE all read up on the Uncertainty Principle. I think everyone is a bit off.

Is that the part in J-Park when the Macintosh guy is getting all grabby-wabby with the Worldcom guy's chick?

St.Alfonso
The billiard ball idea is just an analogy of how it is impossible to measure something without affecting it; that's not what is going on in quantum mechanics

Ah. Then we are on the same.........(wait for it)........wavelength.

St.Alfonzo:

the idea that a thing can be in more than one state at the same time, and it doesn't choose one until you look at it.


This sounds suspiciously like the old standby "If a tree falls in a forest"...

Badfysh
You're all confusing cycles with time

I think your brush is too broad there. In fact it seems the only mention being made about the 'mental construct' of time is being made by people like yourself who are arguing a point no one is making.

No one discussing time travel is confusing time minutes on clocks. Any more than one would confuse gravity for pounds on a scale.

blogwhore on this topic...

If I were a time traveler, I'd definitely attend this thing, but I'd come in full-on tinfoil hat regalia and spew nonsense. You know. Just to keep my cover intact while giggling at all the noobs. And then I'd toss out one or two totally true tidbits about the future, but things so outrageous that no one would believe them.

"Then tell me, 'future boy', who is president in the United States in 1985?"
"Ronald Reagan."
"Ronald Reagan? The actor?" Who's Vice President? Jerry Lewis...? I suppose Jane Wyman is the first lady. And Jack Benny is secretary of the treasury. I've had enough practical jokes for one evening. Good night, future boy."

Jamespoon

I'd go back in time and nail Natalie Portman before she was famous

You mean when she was like, eleven..?

Dissenter of Dearth

Well there's Schrodinger's cat. Put a cat in a sealed box, so that you can't hear the cat or detect any movement from the cat. Now take a gun and shoot one bullet into the box. Open the box. Observe that the cat is dead. Now, could you say the cat was dead before you opened the box? After all until you observed the cat in its dead state you did not have the information to know that it was the state of the cat. You could assign some probability to the cat being dead and some probability to it being alive. But you can never state that probability is 100% that it is dead. So until you open the box all that can be said is that there's some probability the cat is dead. It is only once you open the box and observe the cat that it actually can be said to be dead.

And then there's what Stephen Hawking said about Schrodinger's cat, "Every time someone mentions Schrodinger's cat I reach for my gun".

Time travel? If you care to travel in time, you should go back to 1787 to talk to this guy, Immanuel Kant:



While you're there, you can read up on his Kritik der reinen Vernunft (Critique of Pure Reason), which provided the best argument demonstrating that time is nothing more than the a priori synthetic condition of apperception and judgment.

Put simply, time is not "out there." It is not something like a big hallway you can go "back" and "forward" in. Time, and space, are the fundamental organizing forms by which our minds intuit and apperceive the physical world. You can't go "back in time" for the simple reason that we impose temporal (and spatial) cognition on the world, not vice-versa.

Could there be multiple spatial dimensions beyond the three we perceive? Sure. We wil just never perceive them, because that's not how we're built. And while it is conceptually consistent to talk about the existence of prior or posterior arrangements of the underlying physical correlates of our sensual perception, we simply would never be able to perceive them outside of the unidimensional temporal framework of our cognitive structure.

(What is more interesting, IMO, is to posit the existence and perception of multidimensional time: what would it be like to perceive 2- or 3-dimensional time?)

Regardless, you can't "go back in time" because there's no "there" to "go back" to. Time is the condition of our perception, not the container of it.

If you are a religious believer, then, you can have faith in the a-temporal plenitude of the aeternum, the world beyond time and beyond the limitations of the conditions of our a priori synthetic judgments. If not, then you are left with the void of the imperceivable ding an sich... go talk to Schopenhauer!

/that is all, class dismissed.

All this time travel speculation is useless unless we identify what kind of universe we live in.

http://www.xibalba.demon.co.uk/jbr/chrono.html

2005-05-02 05:46:42 PM cargrrl82

AI=Artificial Intelligence.

I know, I was just kidding;)


As for physics knowledge, I know a bit but like Richard Feynman once said "No one really understands quantum theory".

That's true. You can understand it in it's own terms, and even become comfortable enough with it that you develop a similar kind of intuition for it that you might have with classical physics, but at a really fundamental level, it never ceases to be mind-boggling.

The Heisenberg uncertainty principle is a much stronger statement than you guys (and girls) are making it out to be.


You are saying that if you put a particle into a certain quantum state once, and measure its position and momentum once, then there is uncertainty in the outcome. The uncertainty principle implies that, if you reproduce a certain particle in a quantum state 2 billion times, measure its position on the first billion trials, and measure its momentum on the second billion trials, then you will STILL be unable to pin down the particle's position and momentum.

A stasis room can solve all of our problems.

"A stasis room creates a static field of time. Just as x-rays cant pass through lead, time can not penetrate the stasis field. So, although you exist, you no longer exist in time, and for you, time its self doesnt exist. You see although you are still a mass, you are no longer an event in space time. You are a non event mass with a quantum probability of zero."

some of y'all need to stop being so linear...

/you know who you are

lindseyp: Observation isn't a human privilege


Exactly, how would you explain Causality otherwise?

ymagynatyf

I don;t know about that. Time can be measured by means outside of our cognative perception of it. (see atomic clocks at sea level and on spacecraft). It can be objectively measured. Now it's true there is no such thing as a 'second', but that is not the same thing as time. It is simply a mental construct by which we can quantify time. In that sense Kant is correct. We can only understand time by means of an arbitrary quantification: a clock.

Think of Gravity. It cannot be seen, felt, touched, heard, smelled or in anyway directly percieved. We can only become aware of gravity's existance through being able to percieve the affect of gravity on other things, not by percieving gravity itself.

Now if you push it further to the point of saying that gravity is also "nothing more than the a priori synthetic condition of apperception and judgment", (as Kant was prone to do) then you enter into the metaphysical realm of questioning the objective reality of reality itself. And at that point, discussing reality, gravity, or time all becomes pointless anyway as nothing can be proven outside our abilty to 'understand' the proof.

2005-05-02 05:52:29 PM Dissenter of Dearth

the idea that a thing can be in more than one state at the same time, and it doesn't choose one until you look at it.


This sounds suspiciously like the old standby "If a tree falls in a forest"...

It does, and yet you can go into just about any college undergraduate physics lab in the world an actually see the two slit experiment done right before your eyes. The sensation is a lot like watching a tree fall over, and not make any noise.

quagaar1

Sounds familiar - Red Dwarf?

lindseyp

True that, I replaced the radioactive part with a gun just because it's a clearer example. Also shows how what may seem intuitively true even obvious doesn't hold in quantum theory. No matter how much you argue the cat is absolutely positively dead before you open the box, there's always a chance it isn't. And you can't know that it is or isn't until you actually observe the cat.

Badfysh

Yes,Im surprised anyone recognized it. That was quick.

If one were able to go back in time to the past you'd find yourself quite alone because the universe isn't there anymore, it's here, in the present. The past only exists in our memories and fossils and drawings. It doesn't exist anymore as a place, you can't go there. All this talk about alternate universes and quantum theory is just clerical hand waving. We are all just stuck here.

I always thought a good movie would involve an individual going back in time to say the late 19th century and accidentally changing a few key events that led up to our reality, like WWI, II, and present day terrorist situation. The plot would be that what we're living right now, and everything thing we know wasn't really supposed to be, but because of the time travelers screw up 100 yrs ago, we were left with all the world wars and the current threat of terrorism. A little twist on a regular idea.

2005-05-02 06:03:16 PM murray208

Don't confuse the uncertainty principle with the superposition principle.

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

you can certainly measure a particle's position exactly, if you want, but then the momentum is completetly unknown - it's uncertainty becomes infinite. That is to say, it is in a superposition off all possible momentum states.

You can then measure it's momentum exactly, if you wan't. The wavefunction collapses to a single momentum state when you do, and it's position becomes a superposition of all possible states -- your previous position measurement is now useless.

If you measure position again, you will (likely) get a different answer than last time.

Anything a time traveller could do in the timeline has already happened. It's imperative that time travellers do effect the timeline so past events will unfold as we know them to unfold.

/the time travel thing kinda makes head hurt

DAR: /can't believe no John Titor jokes yet!


Ok, here goes;


Paging Mr. Titor, Mr. John Titor. Please pick up the courtesy phone.

cargrrl82

But then what does the cat see? And what happens if you do the double-slit experiment on a scale of light-years but with people instead of electrons? It gets confusing, very, very fast. And I'm a physics major.

What, no references to "All you Zombies?" I am ashamed of you people.

No, wait, that's too literary for Fark.

What, no references to "Bill and Ted?" I am ashamed of you people.

"Whoa! Hey, it WAS me who stole my dad's keys!"

--Nosy

/P.S. Duck!

Yeah, but.. even before you observe it. it's either dead or it isn't. Some Schrodinger enthusiasts insist that it is neither, because you haven't observed it. Hence my statement about observation not being a human privilege

But that's not true either. Double slit experiment is a counterexample. The particle does not go through slit 1 or slit 2 until you look at it.

lindseyp: Yea, but Hawking's all talk and no action.

Again - Ouch.

As for Schrodinger's cat, I always thought of that experiment as being about the limitations of human knowledge more than anything else.


cargrrl82:

No matter how much you argue the cat is absolutely positively dead before you open the box, there's always a chance it isn't. And you can't know that it is or isn't until you actually observe the cat.

Agreed. I'm inclined to believe the cat is dead, but I'm not about to chuck the box onto the fire without looking first. Kind of makes me wonder how doctors, psychologists, and politicians can so readily make decisions based on phenomena that can only be observed indirectly.

cfreak:

My feeling is, if time travel is ever invented, we don't see the effects because when people travel back in time and change something it puts them in a different reality than our own. In other words, in some reality WWII was stopped, but in our own it wasn't because its already happened.

This follows the view of "reality" that every possible outcome of everything occurs simultaniously, but we live in one particular one.

Thus a "time machine" at least in the classic sense isn't really possible since just by traveling you would create a new reality, it would really be a "new reality creator" machine.

/or more probably its just us here and its not near that complex!

You have it almost, but not exactly. It would actually be just a dimensional hopper. You move from one form of reality to the next. Since ALL possible realities exist at the same time. There are an infinite number of realities generated infinitly generated at infinite points in time/space.

WigNosy

"All you Zombies"?
"Bill and Ted"?

Nah. too easy. Dig deeper....

, ,

Unfreakable

That is a real ad -- my best friend placed it. Wait til I tell him he's on Fark!!!

lindseyp

Schrodinger's cat is not supposed to be alive OR dead until we open the box to check, but that's crap, because the act of 'observation' in schrodinger's setup was the detection of some radioactive decay which sparked the poison bottle to be broken open (It wasn't a shooting)

Observation isn't a human privilege, it's the act of interaction of ANYTHING with ANY consequence of the event in question.

It doesn't matter. The observer inside the box does not affect the observer outside the box. QMs will predict what the observer inside the box will see, and what the outside observer will see.

It wasnt a very convention, it was disappointing.

I booked my room in Cambridge, MA four years ago, when I first arrived. Meanwhile, I have one more monkey to round up.

BojanglesPaladin
I don;t know about that. Time can be measured by means outside of our cognative perception of it. (see atomic clocks at sea level and on spacecraft). It can be objectively measured.

Think about it. What are all those "measurements" prior to the moment of perception? Well, they're something, sure -- motion, change, instability, energy transfer, shifts in geometry, what have you -- but they acquire no definite status until "perception." Nothing is measured until there is a measurer. For us, that measurer -- our minds -- will always be governed by the fundamental structures of our apperceptive capabilities.

The same goes for gravity. And, of course, for the famous two-slit experiment, which is the best simple demonstration of Kant's epistemological point. In one set of conditions, it's a wave. In another, it's a particle. Well, what is "it"? "It" is what it is. What changes are the conditions of our possible perception of "it." It's physical identity is defined by our ability to perceive it as such. And if we cannot perceive it -- by any physical means -- for us it might as well not be there, even if its existence is not a logical impossibility. (Think virtual-particle pairs, alternate dimensions, etc.) This was also part of Schroedinger's point with the famous "cat in a box" thought-experiment. Until perception -- by any means -- the cat remains in a state of uncertainty which cannot be reduced.

Part of the problem, of course, is that this understanding of the fundamental epistemological structure of our apperception of reality slides too easily into a bad version of faux-Eastern mysticism... "time be time"... "it's all in your head"... "there is nothing that is not perceived"... "if a tree falls in a forest"... etc. etc.

This is not what Kant meant. Kant was quite as sure of the objective existence of the "real world" as you or I. We can't wish away an oncoming truck by asserting "it's all just an a priori synthetic judgment of my perception." The very fact that the physical world appears as "prior" means that it is absolutely objective. But "time" and "space" are not things like trucks and rocks. They are the perceptive categories we bring, unavoidably, to the cognitive perception of the "world" -- or whatever world-frame is our relative environment -- and we cannot escape them. And while we are built to perceive multi-dimensional space, we are not built for multi-dimensional time, which is what "time travel" would require.

But I am, of course, open to correction by any time-travelers who can prove otherwise!

eggrolls:

A long long time ago, I read the best time travel story.

The man who invents time travel is about to pull the switch when Shakespeare shows up. Turns out everybody and their uncle has been waiting for this guy to make the discovery, and he's about to be desended upon by the press, publicists, research fellows, scam artists, etc, etc, all of whom want a piece of his sudden celebrity. After all, he's the man who invents time travel! He's been famous in the future for years. Shakespeare, as it turns out, is an old hand at time travel, since the documentarians, hucksters, researchers and the like have been following him since before he was born (pissed off his mom too). He talks invention-guy down off the ledge, so to speak, and helps him get past the shock of sudden celebrity.

The punchline is Shakespeare's actually there to offer to represent the man who invented time travel. For a small fee, of course.

Anybody else ever read this story?


Read it? I was the reporter for the Filbert Studge Stationer who covered it!
/Isaac Asimov's Science Fiction Magazine, circa 1983