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Ravenous
2001-Nov-15, 06:44 AM
Possible or not?

I tend to think this: The paradoxes it would create make it impossible. For example, what would happen if you traveled back to before you were born and killed your mother? Would you immediately blink out of existance? What if you killed Hitler? Would the world's population of Jews suddenly EXPLODE?

James
2001-Nov-15, 11:55 AM
I've heard that, in one theory about time travel, it wouldn't be possible to go back before the time machine itself was invented.

Donnie B.
2001-Nov-15, 12:46 PM
Another is that you can travel back in time, but not into your past, but into a parallel one -- so there's no paradox. Kill your grandfather there, and that universe's "you" is never born. No problem.

The big problem with time travel is physics. Imagine a time traveler appears in front of you. Where did he come from? From your perspective, his mass did not exist until he showed up. Serious violation of mass-energy conservation.

One clever s/f story I've read had a time-travel scheme that avoided a lot of these problems. You could travel into the past, but not physically. Instead, you could briefly "posess" the body of a person from the time you wanted to visit. You couldn't choose the individual, so you were much more likely to be a stable boy than a duchess. And if you didn't get "recalled" in time, you'd forget who you were and revert to your host's personality. Minimal likelihood of changing history. Good concept, eh?

GrapesOfWrath
2001-Nov-15, 01:22 PM
Here's an interesting thought that occurred to me a couple days ago.

We exist in a universe of ::mumble:: space and time dimensions, and each particle exists at a particular point of that spacetime. No matter what happens, each particle can only move a positive distance from that particular point.

We are used to the cartesian system of describing space in terms of plus and minus x, y, and z directions--and the concept doesn't seem to extend to the t, time, dimension. But is is true that the square root of x^2+y^2+z^2 is always positive, and that concept does extend to our perception of time.

Of course, x^2+y^2+z^2-t^2 is the invariant quantity for relativity, but who cares about that?

<font size=-1>[Fixed italics html]</font>

<font size=-1>[ This Message was edited by: GrapesOfWrath on 2001-11-15 08:23 ]</font>

Mr. X
2001-Nov-15, 10:41 PM
I don't know what Grapesofwrath is saying since he's mumbling things /phpBB/images/smiles/icon_biggrin.gif , but talking with a friend in philosophy we used to have this idea.

There's no proof of it, just wishful thinking, because we prefered the universe not to be a fatalist one back in philosphy. Also because we were led in that direction by the teacher, maybe just a little. /phpBB/images/smiles/icon_smile.gif

So we used to think that there is an infinite number of parallel universes, that every possibility, even if there is an infinity of possibilities, is mapped, an infinite number of ramifications. Meaning it just goes as deeply as to how one molecule bounces off another anywhere in the universe. Cause and effect. And I'd like to think that by going back in time even if you do absolutely nothing you create branches, an infinite number of ramifications, simply because you impact on how every little part will interact with the other by being there. So everytime there is any infinitely small event, branches are created for every eventuality.

Or I am just insane. This is the only thing everyone seems to agree on. /phpBB/images/smiles/icon_smile.gif

On a more official note I read that "the experts" are at a stage too early to decide whether or not this is possible. At this point there is no way of deciding one way or another.

Enjoy it while you can, you'll think back to days like this in the future when we dreamed about it and it will be a big no-no at that point. /phpBB/images/smiles/icon_smile.gif

If you want to hear more of the raving delusions of a madman, go on, ask and you'll get!

The Rat
2001-Nov-16, 02:44 AM
I tend to think this: The paradoxes it would create make it impossible.

The great Larry Niven wrote on this subject, and came up with a strange sounding but simple rule; If the physics of a universe allow time travel, then time travel will not exist in that universe. In other words, the paradoxes negate the possibility.

Let me go on record as saying that I hate most time travel stories simply because of the paradox problem. I don't care how cleverly they are written, they are impossible!

Ducost
2001-Nov-16, 09:33 AM
On 2001-11-15 21:44, The Rat wrote:

Let me go on record as saying that I hate most time travel stories simply because of the paradox problem. I don't care how cleverly they are written, they are impossible!



Some science fiction do a great job of handeling the paradox problem. Sphere is a good example. The paradox was avoided because all parties involved either died or forgot what happened, therefor the future was not changed. 12 Monkeys also did a good job of eliminating paradox by using false memory of the actual events.

Kaptain K
2001-Nov-16, 10:10 AM
Mr.X,
The very best science fiction story I have ever read concerning time travel and parallel time lines is "The Proteus Operation" by James P. Hogan. It starts in 1975 in a world where the Nazis won WWII and goes back to back to the start of the war as the characters try to change history. It is even better than "The Number of the Beast" by Robert A. Heinlein and you won't catch me ranking Heinlein second to anything very often! /phpBB/images/smiles/icon_eek.gif

David Hall
2001-Nov-16, 11:02 AM
Speaking of Heinlein (again /phpBB/images/smiles/icon_smile.gif).

I never got a chance to read "The Number of the Beast", but he does a great job of time travel in "The Door into Summer". It avoids any paradox by making sure the characters were never able to do anything that could cause a paradox. They could walk all over and do almost anything, but whatever they did was incorporated into the normal timeline, and events would conspire to make sure nothing paradoxical happened. I especially remember that the main character kept on just missing himself everywhere he went. It was as if everything was fixed and couldn't happen any other way.

James
2001-Nov-16, 11:44 AM
On 2001-11-16 06:02, David Hall wrote:
Speaking of Heinlein (again /phpBB/images/smiles/icon_smile.gif).

I never got a chance to read "The Number of the Beast", but he does a great job of time travel in "The Door into Summer". It avoids any paradox by making sure the characters were never able to do anything that could cause a paradox. They could walk all over and do almost anything, but whatever they did was incorporated into the normal timeline, and events would conspire to make sure nothing paradoxical happened. I especially remember that the main character kept on just missing himself everywhere he went. It was as if everything was fixed and couldn't happen any other way.



So it was as though time had already been written in stone? There's another theory, as well.

Speaking of books, I remember reading one story that took place in the future that was about this company that(illegally, of course) helped people go back in time, to see the dinosaurs, for example. What they would do is they would go back and create an area that, no matter what anyone did, the future wouldn't be affected. Anyway, a customer went on this trip and went off the path. When the customer got back to his time, things had changed dramatically. It was a very good story.

ToSeek
2001-Nov-16, 12:52 PM
On 2001-11-16 06:44, James wrote:

Speaking of books, I remember reading one story that took place in the future that was about this company that(illegally, of course) helped people go back in time, to see the dinosaurs, for example. What they would do is they would go back and create an area that, no matter what anyone did, the future wouldn't be affected. Anyway, a customer went on this trip and went off the path. When the customer got back to his time, things had changed dramatically. It was a very good story.



Ray Bradbury's "A Sound of Thunder." A classic.

NottyImp
2001-Nov-16, 01:43 PM
"One clever s/f story I've read had a time-travel scheme that avoided a lot of these problems. You could travel into the past, but not physically. Instead, you could briefly "posess" the body of a person from the time you wanted to visit."

Sound a bit like "Quantum Leap"? Although I bet the story came first!

<font size=-1>[ This Message was edited by: NottyImp on 2001-11-16 08:44 ]</font>

NottyImp
2001-Nov-16, 01:49 PM
An interesting link here, if you have the time:

http://setis.library.usyd.edu.au/stanford/entries/time-travel-phys/

Mr. X
2001-Nov-16, 02:05 PM
And in an episode of the outer limits you could only see a short period of time in the future, about 15 minutes and move around in a "virtual reality" suit, but impossible to interact with anything, just see things. Nobody could see you either.

NottyImp
2001-Nov-16, 02:07 PM
But "just seeing" is interacting, as photons must travel from the future and impact on your retina. This means there has to be a physical - and hence causal - connection. OK, it's only a story...

_________________
Up the Imps!

<font size=-1>[ This Message was edited by: NottyImp on 2001-11-16 09:16 ]</font>

Kaptain K
2001-Nov-16, 02:35 PM
Speaking of Heinlein (again ).
... and time travel (again /phpBB/images/smiles/icon_smile.gif ), one of his weirdest stories is "All you Zombies". Closed loop time travel.

Mr. X
2001-Nov-16, 02:43 PM
On 2001-11-16 09:07, NottyImp wrote:
But "just seeing" is interacting, as photons must travel from the future and impact on your retina. This means there has to be a physical - and hence causal - connection. OK, it's only a story...


Okay, but what if, IF, I had some sort of retina in the future, but, it was only a "virtual" area shaped like a retina, and in some way, the photons are counted and measured, but go straight through? You could have a picture, right? And you wouldn't interact? Right?

Okay, I'm now certifiably insane, thanks to you, Nuttyimp! /phpBB/images/smiles/icon_biggrin.gif

dgavin
2001-Nov-16, 07:28 PM
I can't remember who wrote about this, (read about it some 20 years ago), but thought it was an intresting take on time.

He was proposing as a part of dimensional theroy, that time was the fourth dimension.
And following the postulates of dimensional theroy, a dimension higher on the ladder can effect one below, but not vis versa.

For example he put forward, that a three dimensional object, casts a 2 dimesional shadow, that could be seen by a two dimensional creature, if such a thing existed, and if it was in the correct intersection plane.

A 3 dim. subject, if a creature, could however see the 2 dim. creature, and directly influance it, upto and including moving it to other locations on it's intersection plane, or other intersection planes.

However at best, the 2 dim. creature, could only get a vauge idea of what the 3 dim. creature was. It could measure it's shawdow, so to speak, and perhaps produce get and idea of shape, and using abstrat thinking, postulate about debth.

Appling this dimasional law to us, we can in a sense, see the effects of time, and in a way understand what time might be. But we will never be able to interact, or influance it, without the assistance of something from the dimension of time itself.

In essense, time travel will be impossible, as people can only see the effect of time, not interact directly with it. Time travel would require more understanding of the fourth dimension, (and possible even going to it), then any being from the third dimension could comprehend.

Again this was an old theroy I read once, and not sure with the advent of quantum mechanics and other sciences if it's even applicable anymore.

But i'm guessing it is applicable in one sence. -If- time is a dimension (so to speak) above our, were basically out of luck, in trying to influance it.

Silas
2001-Nov-16, 07:32 PM
Okay, but what if, IF, I had some sort of retina in the future, but, it was only a "virtual" area shaped like a retina, and in some way, the photons are counted and measured, but go straight through? You could have a picture, right? And you wouldn't interact? Right?

It's a lovely notion, and, hey, who knows? But it violates the rules of quantum uncertainty (as we know them at this time.) You can't "detect" a particle without altering its position and momentum. Doing that would interfere with history, at least at a very trivial level. Likely enough, intercepting a few photons would not create a causality paradox... But it *might*...



Okay, I'm now certifiably insane, thanks to you, Nuttyimp! /phpBB/images/smiles/icon_biggrin.gif


Quantum weirdness is enough to drive anyone insane (let alone complex arithmetic... the square root of negative one? AIEEE!)

Silas

Ravi Pinjala
2001-Nov-17, 01:10 AM
I'm pretty sure Larry Niven wrote a short story in which time travel was impossible, and the time machines went to a fantasy world where time travel was possible-along with unicorns and other fun stuff.

Donnie B.
2001-Nov-17, 02:14 AM
On 2001-11-16 20:10, Ravi Pinjala wrote:
I'm pretty sure Larry Niven wrote a short story in which time travel was impossible, and the time machines went to a fantasy world where time travel was possible-along with unicorns and other fun stuff.


A whole series of stories, actually, collected in "The Flight of the Horse". Pretty good, but not my favorite Niven stuff.

Donnie B.
2001-Nov-17, 02:16 AM
On 2001-11-16 08:43, NottyImp wrote:
"One clever s/f story I've read had a time-travel scheme that avoided a lot of these problems. You could travel into the past, but not physically. Instead, you could briefly "posess" the body of a person from the time you wanted to visit."

Sound a bit like "Quantum Leap"? Although I bet the story came first!

<font size=-1>[ This Message was edited by: NottyImp on 2001-11-16 08:44 ]</font>


Now that you mention it, Quantum Leap did use that idea. The story did indeed come first. Wish I could remember the name...

Hauteden
2001-Nov-17, 03:24 AM
Time Travel - Y'gotta'luv'it.

Here's a interesting idea I came up with Time Travel. What if Time wasn't linear per se but rather a series of points. (I know that a series of points can be a line but stay with me here) Like a 'choose-your-own' adventure novel only certian points are available to be "jumped" to from specific points. The kicker is ALL possiblities exist but you may not be able to reach them from you present position.

One rule is that you can only go from one specific point to another specific point once or to any other point in the chain. For example, Given points A,B,C,D,E & F if you follow this series of points A-> B-> C-> A-> X-> X the next point could not be B or C or even A. Which means you would need to head to D,E,or F following one of those you could then head to any point but you could not continue up the "chain" that may have already been established.

Now it must be understood that there is and infinite number of points accounting for every conceivable situation including paradoxes. (But some of those may never be attainable.) Since all points exist with their respective matter and energy you couldn't add or subtract matter or energy from a specific point.

That is a short version of one of the ideas I play around with sometimes. I think time travel should be left to the experts like The Doctor and possibly the writers of Star Trek /phpBB/images/smiles/icon_wink.gif

Hauteden

NottyImp
2001-Nov-21, 12:18 PM
"Okay, but what if, IF, I had some sort of retina in the future, but, it was only a "virtual" area shaped like a retina, and in some way, the photons are counted and measured, but go straight through? You could have a picture, right? And you wouldn't interact? Right?

Okay, I'm now certifiably insane, thanks to you, Nuttyimp!"

How do you count photons without them (or the detector) being affected? That violates all sorts of quantum principles and wouldn't work. Your insanity must be yet more ingenious, I'm afraid...

Mr. X
2001-Nov-21, 03:13 PM
My insanity could get more ingenious!

Tell you what, you build all that crazy stuff and tell me if it works or not!

At least I'm thoroughly crazy, not like those half-insane people. /phpBB/images/smiles/icon_biggrin.gif

<font size=-1>[ This Message was edited by: Mr. X on 2001-11-21 10:22 ]</font>

NottyImp
2001-Nov-22, 11:11 AM
Unfortunately, as Joseph Heller conclusively demonstrated in "Catch 22", you can't be completely mad, Mr X., because if you were, you would of course assert that you weren't in the least bit crazy at all.

Mr. X
2001-Nov-22, 04:11 PM
Oh but I am not! I am a misunderstood genius! /phpBB/images/smiles/icon_smile.gif

I'm only saying what your misguided brain has been telling you! /phpBB/images/smiles/icon_biggrin.gif

MowerMan
2001-Nov-24, 02:41 AM
Not possible. The universe would not be stable if it were possible (as in the stability of it's own existance, and even in our infinitesimal time slice of personal observation, we can garner a lot of data of the universe's structure). Time is universal, but the measuirement of time varies a lot. The "speed of light" only holds true within the frame of the source.

Time travel defies entropy and conservation of energy.

Lusion
2001-Nov-24, 03:45 PM
Time travel defies entropy and conservation of energy.


What if conservation of energy is merely an approximation, though, of a more fundamental law?

It's my understanding that time travel actually does happen, on a QM level--at least for short periods of time. I think most of the thread's point, however, is to contemplate time travel on the scale of humans--and, for that matter, to contemplate time travel into the past (the future isn't too hard, from a physics standpoint anyway)

Kaptain K
2001-Nov-24, 04:27 PM
...the future isn't too hard...
Try not to! /phpBB/images/smiles/icon_biggrin.gif I'm doing it right now. /phpBB/images/smiles/icon_eek.gif

Lusion
2001-Nov-24, 05:55 PM
On 2001-11-24 11:27, Kaptain K wrote:

...the future isn't too hard...Try not to! /phpBB/images/smiles/icon_biggrin.gif I'm doing it right now. /phpBB/images/smiles/icon_eek.gif

Yeah, but are you actually going anywhere? :b

Of course, what I meant was to travel into the future--or, make time go faster. It's just a "simple" matter of having an enormous amount of energy at your disposal and being able to survive the accelerations (and the trip itself).

Kaptain K
2001-Nov-24, 07:52 PM
Yeah, but are you actually going anywhere?
Yep! I'm going into the future. /phpBB/images/smiles/icon_biggrin.gif
Unless, of course, I am standing still and it is time that is moving into the past.

MowerMan
2001-Nov-25, 07:28 PM
Changes in matter do not necessarily constitute alterations of time itself. There is actually no proof of time dilation either, as using matter (in any form, from the period of a hydrogen electron, to a pendulum) is not an accurate methodology to measure true time (as matter is affected by natural occurances such as acceleration and/or gravity). It is the matter that changes, not time.

So the question would still be "Did you go anywhere?".

Lusion
2001-Nov-26, 05:50 AM
On 2001-11-25 14:28, MowerMan wrote:
Changes in matter do not necessarily constitute alterations of time itself.
...

I think too often we take for granted, probably because of our own experiences with spatial dimensions, that there exists some form of absolute measure along a line. What I mean is this. Let's say there are no rulers beforehand--they have all been lost. Now let's say you want to measure, oh, the length of a house. You need to invent a measurement, so maybe you take a stick and call it 1 unit long. To measure the house, then, you just move the stick along, 1 stick-length at a time.

When you move the stick down the line 1 "Stick", that is a translation. It's very easy to translate with sticks, because we can physically move it. We can rotate the stick 90 degrees as well (obviously, a "rotation"--btw, I'm going to ignore angles during this article as well) and start measuring the other side of the house with the same units. Thus, we can do things like sensibly answer the question: "Is the house longer than it is wide?"

Enter time, and suddenly, we can't measure in sticks any more (without some other reference, like c, which I'm explicitely ignoring for now). We need a new type of stick. Ignoring problems with time dialations at the moment, we can use, say, a fraction of a day.

Now, we can ask ourselves a similar question that we ask about the house: Is the house wider than the time it takes for a ball to fall from the roof and hit the ground? This question isn't as sensible. It's easy to say that 30 sticks is less than 65 sticks, but we can't really compare 30 sticks to 10 microdays.

Now, what I'm going to do is use this type of analogy to pose a question. To do this, though, I'm going to throw away time altogether, and I'll stick with just measuring the house. Hopefully you'll see the analogy.

Let's say that I have two sticks. One of them is really a rod made up of magnetic Galeczkium (a currently unknown substance), and the other is made up of crystalized Einstonium (another unknown substance--not to be confused with Einsteinium).

I measure the house's width and length with the Einstonium rod, and discover that it is 30 Einstons wide and 65 Einstons long. Now I measure the house's width with the Galeczkium rod, and see that it is 45 Galeczki's wide and 40 Galeczki's long.

Confused, I do the experiment again, with the same results. Then I notice that as I translate both rods, they seem to vary a little in relative lengths (although every single time I measure it, they measure consistent numbers for the length of the house--we'll even say, hypothetically, for all houses). When I rotate the rods 90 degrees, they change length dramatically in a different way.

So, here's my question. Can we still sensibly answer the question, is the house wider than it is long?

If need be, assume that most of the matter around us (sticks, rocks, shoes, etc) measure the same basic dimensional ratios as the Einstonium rod, although there are a few other things (neutronium rods?) that measure the same dimensional ratios as the Galecskium rod.

SAMU
2001-Nov-27, 09:48 PM
Here's one for you.

You travel in space and land on a planet on 10/22/2002 1:05 PM. The planet is identical to Earth exept that there are no people and all the clocks have stopped. When you read the newspaper it is dated 10/22/2002 and when you check the clocks they read 1:05 pm. When you start any of their clocks you see that they measure time in the same length years, months, weeks, days, minutes and seconds as we do.

The question is, can you tell exatly when, according to your clock, did their clocks stop? How long ago did their Armstrong walk on the Moon? If yes, how? If no why not?

SAMU

Ravenous
2001-Nov-27, 10:05 PM
I haven't the slightest clue. I am responding merely to make sure that there is an answer (and that you've got it) as opposed to it being just something to ponder.

Silas
2001-Nov-27, 10:31 PM
On 2001-11-27 16:48, SAMU wrote:
Here's one for you.

You travel in space and land on a planet on 10/22/2002 1:05 PM. The planet is identical to Earth exept that there are no people and all the clocks have stopped. When you read the newspaper it is dated 10/22/2002 and when you check the clocks they read 1:05 pm. When you start any of their clocks you see that they measure time in the same length years, months, weeks, days, minutes and seconds as we do.

The question is, can you tell exatly when, according to your clock, did their clocks stop? How long ago did their Armstrong walk on the Moon? If yes, how? If no why not?

SAMU

Fun question! I have (as often I do) two answers:

Is there any means by which time can be measured? For instance, have the trees in my backyard (on this new world) grown a year's worth? Is there a year's worth of dust on my back porch? Have the winter's rains broken a few windows? etc. etc.

If yes: then, yes, time has passed in a meaningful sense, and the "real" time can be determined.

If no: then, no, the world was apparently "frozen" in some sort of "stasis" and might have been in that state for a day or a billion years...

This is a lovely variant of the truism, "A difference that makes no difference is no difference." (I wonder if all the people in Sleeping Beauty's Castle, after awakening, got into fights over "what year it is.")

Silas

James
2001-Nov-28, 01:03 AM
(I wonder if all the people in Sleeping Beauty's Castle, after awakening, got into fights over "what year it is."

I thought only Sleeping Beauty fell asleep...or couldn't have the prince told her what year it was?

Mr. X
2001-Nov-28, 03:03 AM
On 2001-11-27 16:48, SAMU wrote:
Here's one for you.

You travel in space and land on a planet on 10/22/2002 1:05 PM. The planet is identical to Earth exept that there are no people and all the clocks have stopped. When you read the newspaper it is dated 10/22/2002 and when you check the clocks they read 1:05 pm. When you start any of their clocks you see that they measure time in the same length years, months, weeks, days, minutes and seconds as we do.

The question is, can you tell exatly when, according to your clock, did their clocks stop? How long ago did their Armstrong walk on the Moon? If yes, how? If no why not?

SAMU


Kind of reminds me of that movie The Langoliers for some reason.

Call me a sadomasochist, but for weirdness sakes that is something I would like to (temporarily for a short moment /phpBB/images/smiles/icon_smile.gif ) experience once in my life. /phpBB/images/smiles/icon_biggrin.gif

Silas
2001-Nov-28, 03:13 AM
I thought only Sleeping Beauty fell asleep...or couldn't have the prince told her what year it was?


Hoo boy, is this off topic! In the Disney version, the whole castle -- guards and noblemen and advisors and troubadors -- all fall asleep.

Time passes (who knows how long?) and then, with the usual heroic triumph, the princess is rescued...

So: I'm a landlord: can I charge rent from my tenants for all the time that has passed?

BTW, this is why this might just possibly be on topic... In the early 1700's, when England accepted the Gregorian calendar, there actually were rent riots, when people objected to paying a full month's rent for "only" 20 days.

Time really is money!

Silas

SAMU
2001-Nov-28, 05:14 AM
In answer to Silas' question. Yes, the winter rains have come, some dust has settled and some windows have broken. Can you determine to an accuracy of within a week when the clocks stopped? In fact you see in the paper the headline is how bad "yesterday's" rain was. Problem is it's raining when you land.

Also there are aliens going around and kidnapping whole planets of people and the way they do it leaves all the clocks stopped. If you can determine when they did it you can follow their trail through "subspace" and catch them and put an end to their villany.

SAMU



<font size=-1>[ This Message was edited by: SAMU on 2001-11-28 00:26 ]</font>

Ravenous
2001-Nov-28, 05:39 AM
Will there eventually be answer, SAMU?

NottyImp
2001-Nov-28, 12:18 PM
"BTW, this is why this might just possibly be on topic... In the early 1700's, when England accepted the Gregorian calendar, there actually were rent riots, when people objected to paying a full month's rent for "only" 20 days."

I know somebody over here in Blighty who worked a night-shift when the clocks went back (i.e. come mid-night, it's only 11 pm again), and hence did a thirteen-hour shift. He doesn't get paid for the extra hour, as his boss tells him he'll do one less hour when they go forward again - except that he's not doing a night-shift on that day. Isn't life a ***** sometimes?

David Hall
2001-Nov-28, 12:35 PM
On 2001-11-27 16:48, SAMU wrote:
Here's one for you.

You travel in space and land on a planet on 10/22/2002 1:05 PM. The planet is identical to Earth exept that there are no people and all the clocks have stopped. When you read the newspaper it is dated 10/22/2002 and when you check the clocks they read 1:05 pm. When you start any of their clocks you see that they measure time in the same length years, months, weeks, days, minutes and seconds as we do.

The question is, can you tell exatly when, according to your clock, did their clocks stop? How long ago did their Armstrong walk on the Moon? If yes, how? If no why not?

SAMU


Actually, from the description, it can only have happened at exactly the time you landed. Because your clocks and date exactly match their clocks and date. Unless of course this is just an incredible coincidence, and the date and time of the event as measured in their calendar just happened to exactly match the date and time of landing in yours. Boy, talk about stretching believablity.

But is this unbelievable coincidence is the case, then we have no way of knowing absolutely if or in what way their system matches our own. For example, we know it happened on October 22nd, but we couldn't be sure if October is autumn, or spring, or the dead of summer. Since we can't directly relate the two calendars, the question has to be how long ago from now that this event happened.

How can we do that? Well, we have to use the same methods historians and archeologists use today to date past events, and with the same margins for error. It's of course obviously easy to determine if the event happened very recently or sometime in the past. Check for dust. Find someone's refrigerator and see if the milk's gone bad.

So if it's been a while, then how long ago was it? It might be possible, for example, to find a library and discover whether October is really the fall. Then we would have better idea of how long ago it was by comparing it to the current season. If you also used other means to determine if it's been less than a year or not, then you could place the event to within a few weeks.

In any case, I see two possible ways to determine the time. First, if the event had some effect other than evaporating the humans and stopping clocks we might be able to determine when it happened by the direct effect it had on the environment. If it scorched the bark on some (still living) trees for example, we can measure how much they've grown since the event. This sounds like an unlikely avenue of approach though, as the original problem suggests that there weren't any direct effects.

If the event left no trace on it's own, then we'd have to use more indirect evidence. Specifically, we would have to find something the inhabitants did to alter the environment preferably on a continual basis, and then determine how long it's been since the effect last occurred. Measuring the accumulation of dust inside a room might work, for example, if you could determine the average rate of dust accumulation.

Accumulation rates, erosion rates, seasonal effects, plant growth, aging of materials; I suppose all of these are possible, but the accuracy and appropriateness would vary according to the details of the situation. I'm not going to go into any detail here, as I'm no expert in dating methods though. I'll just say that the best guess we could get would depend on what method gave the answer with the least margin for error. I doubt that accuracy could be determined to within a week in most cases. But I don't know. Take it up with archeological experts for more details.

Oh, but if my first guess is right, we'd better watch our behinds, because the aliens might just reach out and grab us too while we're fooling around with the clocks.

David Hall
2001-Nov-28, 12:47 PM
I just had another thought. The clocks say 1:05pm. But it doesn't say what time zone. So assuming as in my first post that it's not just an incredible coincidence, the event could have happened up to, but no more than, 24 hours ago, if you landed in a different time zone from the one synchronized with your clock.

SAMU
2001-Nov-28, 05:10 PM
Since they're the ones who are trying to answer, does Silas and David Hall really want a hint? The answer has an accuracy to the minute.

SAMU

Mr. X
2001-Nov-28, 06:16 PM
On 2001-11-28 12:10, SAMU wrote:
Since they're the ones who are trying to answer, does Silas and David Hall really want a hint? The answer has an accuracy to the minute.

SAMU

Wait wait wait, does it involve relativity and physics, or is it a riddle, because I like riddles, and if it is a riddle could you post the situation and all the facts needed in one post?

Silas
2001-Nov-28, 07:14 PM
On 2001-11-28 12:10, SAMU wrote:
Since they're the ones who are trying to answer, does Silas and David Hall really want a hint? The answer has an accuracy to the minute.

SAMU


A hint would be nice... I was afraid that it was like most scientific puzzles: there isn't really an answer, just a whole lot of approaches that might produce better and better approximations...

Um... Is there a radioactive process that would "start" when people disappear? For instance, could you look at the reactor in a nuclear submarine and know when it was last fueled by how much the fuel has decayed?

(I'm presuming that clock-like devices have also stopped? Such as the cpu clock in a computer, the "time module" in certain hand calculators, etc.?)

This is fun, but I suspect I'm treeing up the wrong bark...

Silas

Mr. X
2001-Nov-28, 10:16 PM
I tend to think like David.

But do we assume that if it is exactly the same planet as Earth wouldn't it mean it revolves around a star identical to the sun, in the exact same amount of time, at the exact same distances, that there is a copy of me there doing the exact same thing, that they have witnessed the birth of Christ and have started counting years the same way we did (the ancient astronomers witnessed the same sky, same planets, same moon, same stars!?)!?

**Music starts**
Oh my God, I was wrong, it was Earth all along, you've finally made a monkey...
..yes we finally made a monkey...
...Yes you finally made a monkey out of me!
**Music ends**

Maybe there's some trick to it, maybe rephrasing the problem, because it really leads, at least me and David, to that conclusion.

SAMU
2001-Nov-29, 02:01 AM
Gee Mr X,

I hate to give you a hint, you're getting so close.

Oops, that was a hint wasn't it?

SAMU

<font size=-1>[ This Message was edited by: SAMU on 2001-11-28 21:03 ]</font>

Ravenous
2001-Nov-29, 02:54 AM
Perhaps it is Earth itself and we merely travelled in a large galactic circle..

Lusion
2001-Nov-29, 05:20 AM
I think the answer he's looking for is to simply go to the nearest library and thumb through the astronomy section for anything describing how to calculate the location of the planets, which presumably you already know about or else you wouldn't have been driving your spaceship. The big clue he gave was talking about "their Armstrong", which suggests that you are to assume this is very, very much like earth (so that it has a solar system).

It's a bit different from my point, which was simply that there's no such thing as "true time" except in relation to something, like, oh, all normal matter. If you find some sort of exotic matter (which I named based on a borrowed reference from another thread) that's able to measure time a different way, then you merely have two different kinds of measurements, and saying that either is the "real time metric" is a bit too Platonic for my tastes.

Ducost
2001-Nov-29, 07:16 AM
On 2001-11-27 16:48, SAMU wrote:
Here's one for you.

You travel in space and land on a planet on 10/22/2002 1:05 PM. The planet is identical to Earth exept that there are no people and all the clocks have stopped. When you read the newspaper it is dated 10/22/2002 and when you check the clocks they read 1:05 pm. When you start any of their clocks you see that they measure time in the same length years, months, weeks, days, minutes and seconds as we do.

The question is, can you tell exatly when, according to your clock, did their clocks stop? How long ago did their Armstrong walk on the Moon? If yes, how? If no why not?

SAMU

You can tell when their clocks stopped by looking at them.
Their clocks stopped on 10/22/2002 at 1:05 pm
You then take the difference between the years, 2002 - 1969, you get how long ago they walked on the moon.
They walked on the moon 33 years earlier
That is assuming that they are exactly like earth.

I think i might have misread something







<font size=-1>[ This Message was edited by: Ducost on 2001-11-29 02:19 ]</font>

SAMU
2001-Nov-29, 11:35 AM
You missed this

Quote:

"The question is, can you tell exatly when, according to YOUR CLOCK, did their clocks stop?

Answer at 5:PM today.

Last hint.

Some of you probably know it already and will remember it when you hear it.

SAMU


Meawhile,(off topic)
You've heard of the pot of gold at the end of the rainbow. That,s a myth. But do you know how to feel a rainbow? And whats at the center of a rainbow? It may surprise you.
Answer at 5:00.

SAMU
2001-Nov-30, 12:33 AM
The answer is

You go to the library and check their almanac for where the planets are for the time their clocks stopped. Then you compare that to where the planets are now. that gives you the date. Then you check their table of Galiean ephemerals and then you go to a planetarium and look at the Galiean satelites. When the satelites cross the terminator you note the time and that gives you the correct time now to the minute according to their clocks. You subtract what their stopped clocks read from what they should read and that tells you when their clocks stopped according to your clock.

At the center of a rainbow is a shadow of your head. Whether it's a rainbow in the sky or a rainbow you make with the spray from your garden hose you can look at the center and see a shadow of your head. When you look at the shadow of your head you can feel the rainbow in your eyes. It feels like when you've been swimming too long and you look at lights and there is a halo arount them, that's what what it feels like.

SAMU

GrapesOfWrath
2001-Nov-30, 11:26 AM
I don't think their library would be very reliable if their clocks aren't. JMO.

ToSeek
2001-Nov-30, 12:57 PM
On 2001-11-29 19:33, SAMU wrote:

At the center of a rainbow is a shadow of your head. Whether it's a rainbow in the sky or a rainbow you make with the spray from your garden hose you can look at the center and see a shadow of your head.


This is true. People in airplanes have reported seeing full-circle rainbows, and at the center of the rainbow is the shadow of the airplane.

Here's an imperfect example:
http://www.nadn.navy.mil/Users/oceano/raylee/RainbowBridge/RB_images/Fig8_1.GIF

<font size=-1>[ This Message was edited by: ToSeek on 2001-11-30 07:58 ]</font>

Silas
2001-Nov-30, 03:29 PM
Good One, SAMU! I was getting close, then, with radioactive decay and other "clocklike" processes... I just forget the planetary clockworks!

(I tend more to physics than astronomy... Maybe I should compete with Phil with a "Bad Physics" site...)

Gotta remember to look *up* more often!

Silas

David Hall
2001-Nov-30, 03:46 PM
Hey, I was close too. I even suggested going to a library. I just didn't get far enough into the idea to check planetary alignments.

Actually, I was starting to think it was one of those "trick" questions, where something in the wording of the puzzle gives a clue to the answer. So I kind of went off track again after that.

Lusion
2001-Nov-30, 03:47 PM
WRT Samu's puzzle, guys, scroll up and check my post (and note that it's not edited). And while you're at it, read the second paragraph! (No comments required, unless you're driven to respond.)

Kaptain K
2001-Nov-30, 09:14 PM
To Seek said:
This is true. People in airplanes have reported seeing full-circle rainbows, and at the center of the rainbow is the shadow of the airplane.
This phenomenon is known as a "glory".

ToSeek
2001-Nov-30, 09:49 PM
On 2001-11-30 16:14, Kaptain K wrote:
This phenomenon is known as a "glory".



Not true! A "glory" is something separate. You can actually see a glory in the photo I supplied as the small circle about the same size as the airplane's shadow. The rainbow is farther out.

SAMU
2001-Dec-01, 05:03 AM
This time question could make for a cool computer game. I'm thinking it could run in a browser. You start as comander of a spacecraft exploring where no man has gone before. You are in orbit above the planet when Command (Star Fleet?) warns you to be on the lookout for the kidnaping villans and gives you some details of what to look for and how to track them. Ie find the time the people disapeared and the clocks stopped and backtrack the planets path through space to find the right subspace trail to follow and blast the villans. Done with simple fast loading GIF format image maps and clicking on the wrong link sends you to a cyclical set of pages or a message like "can't land there the air is poisonous". Clicking on the right link takes you further down the line. There would have to be hints in the game layout like there's a clock that runs in the control panel of the ship but the clocks where the ship lands is not running, the ship lands across the street from the library and down the road is the observatory. Course I'm thinking of more detail to add to it. Think it would be too intelectual?

SAMU



<font size=-1>[ This Message was edited by: SAMU on 2001-12-01 00:08 ]</font>

Mr. X
2001-Dec-01, 06:31 AM
Uh, actually I think it would make for a very good and weird movie, with only one character, a man that somehow winds up there, remake of the planet of the apes like, and struggles to get back, and uncover what happened, the planet being identical to Earth.

As I said kinda reminds me of the langoliers for some reason.

Pi Man
2002-Jun-28, 11:56 PM
I heard somewhere(It might have been on Stephen Hawkings lectures) that one cannot travel back into time unless they have already arrived in the past and have not disturbed anything enough to create grandfather paradox situations(Your actions in the past preventing you from going back into the past in the first place.) So, not only do you have to arrive before you leave, but the effect has to give the ok before the cause can happen.

beskeptical
2002-Jun-30, 04:23 AM
If you picture time as a dimension. Take a stream of photons. These photons represent the time dimension. If we could travel around in time, we should be able to go forward and backward along that stream. So what would happen?

If we went backwards along the stream coming to us, we would be seeing the stream that hadn't gotten to us yet. Whatever we did in that world would affect the future, but not the past.

If we went forward, ahead of the stream that had already passed us, we would be going back in time. But whatever we did in that world would not necessarily make the photons that had already passed us go back and pass us again.

So if our universe is like in the Langoliers, if we go faster than light and get ahead of time, thereby going back in time, we would reach nothingness.

But, if our universe really exists in a time dimension that has a physical presense, then the future and the past would exist at the same time, and that would mean an infinite number of universes. So if you change the past, you would be changing a different past than the one you originated in.

Then what? The whole thing might explode or disappear because if the future and past are out of synch it could mess the whole thing up. Or, all of the universes might be different, in which case the paradox of changing the world and then not existing to change the world would not occur. Or???

And, if there were an infinite number of universes, it could explain why a time traveler of the future had not gotten to our exact spot. But you might have one heck of a time trying to get back to the exact instant you came from.

If you weren't exact you'd end up in a universe where another one of you also existed. And, you would disappear from the world you left. Which might make the people in that world think you didn't make it and others might not want to try again.

Bad Engineer
2002-Jul-02, 01:44 PM
I love what Stephen Hawking had to say about the subject of time travel. It was something like this:

"If time travel will be possible some day, then why aren't we inundated by time travelers from the future?"

I think he has a point there


B.E.

SeanF
2002-Jul-02, 02:15 PM
On 2002-07-02 09:44, Bad Engineer wrote:
I love what Stephen Hawking had to say about the subject of time travel. It was something like this:

"If time travel will be possible some day, then why aren't we inundated by time travelers from the future?"

I think he has a point there


B.E.


Answer #1: Because of the Temporal Prime Directive, which says they can't intefere with the past. As such, they don't make themselves known when they're here.

Answer #2: If you could go visit any time in the History of the World, would you pick now? /phpBB/images/smiles/icon_wink.gif

Wiley
2002-Jul-02, 05:08 PM
On 2002-07-02 10:15, SeanF wrote:


On 2002-07-02 09:44, Bad Engineer wrote:
I love what Stephen Hawking had to say about the subject of time travel. It was something like this:

"If time travel will be possible some day, then why aren't we inundated by time travelers from the future?"

I think he has a point there


B.E.


Answer #1: Because of the Temporal Prime Directive, which says they can't intefere with the past. As such, they don't make themselves known when they're here.

Answer #2: If you could go visit any time in the History of the World, would you pick now? /phpBB/images/smiles/icon_wink.gif



Misanthropic & pessimistic answer #3: Humanity destroyed itself before inventing time travel.

<font size=-1>[ This Message was edited by: Wiley on 2002-07-02 13:08 ]</font>

Argos
2002-Jul-02, 06:55 PM
Something much more feasible than large scale time travel would be small scale time distortion, and it would open interesting possibilities as well. Imagine that you can decelerate time at a particular region, a small region. Time would flow normally, from your point of view, within that region. For the outsiders it would appear that you moved in accelerated motion. You would see things almost frozen in time. People frozen in strange poses, moving at almost undetectable speeds. A It would avoid the paradoxes raised by the averted direction in time. Time would still flow to the future, at a lower rate.

Arthur C. Clarke once wrote a short story, named, if I can remember, ”All The Time In The World” (I read it in an anthology, in portuguese), in which aliens, masters of time, knowing of our fate, come to Earth in the last hour of its existence and take away all the treasures of all nations, few minutes before the explosion of a test bomb which would wipe out all life on our planet. They used a bracelet around which time flowed in a slow pace. It’s funny. Do look for to read it. I won’t play mr. Killjoy and tell you the end.

beskeptical
2002-Jul-02, 07:32 PM
On 2002-07-02 09:44, Bad Engineer wrote: I love what Stephen Hawking had to say about the subject of time travel:

"If time travel will be possible some day, then why aren't we inundated by time travelers from the future?"

I think he has a point there.
B.E.


On 2002-07-02 10:15, SeanF wrote:

Answer #1: Because of the Temporal Prime Directive, which says they can't intefere with the past. As such, they don't make themselves known when they're here.

Answer #2: If you could go visit any time in the History of the World, would you pick now? /phpBB/images/smiles/icon_wink.gif


On 2002-07-02 13:08, Wiley wrote:

Misanthropic & pessimistic

answer #3: Humanity destroyed itself before inventing time travel.

Re #1: I doubt humans will evolve to a point where we evoke 'the Temporal Prime Directive'. You've been watching too much Star Trek. /phpBB/images/smiles/icon_biggrin.gif Besides, if a butterfly flapping its wings could affect major rearranging of weather patterns, you couldn't arrive without changing the future anyway.

Re #2: But if you had picked any historical time before now, shouldn't it be in recorded history?

Re #3: Can't you imagine at least a few of us surviving? Couldn't we go on to a future future and invent time travel and go back and save a few more and so on. Otherwise, there should be enough time before the Sun glows red to evolve technology again. Maybe they'd be nicer.

I'm waiting to see what becomes of the quantum experiments where some Germans sent Mozart music through a solid object and it arrived before the Mozart music that wasn't blocked by the object, (IE it went faster than light).

And then there's that one at a time photons going through the slits that act as if they were all going through at the same time.

These are my favorite current mysteries. /phpBB/images/smiles/icon_biggrin.gif

SeanF
2002-Jul-02, 09:50 PM
On 2002-07-02 15:32, beskeptical wrote:
Re #1: I doubt humans will evolve to a point where we evoke 'the Temporal Prime Directive'. You've been watching too much Star Trek. /phpBB/images/smiles/icon_biggrin.gif Besides, if a butterfly flapping its wings could affect major rearranging of weather patterns, you couldn't arrive without changing the future anyway.


While it's true that just travelling into the past would have some minor effects, one would think you'd still want to avoid any major changes, and that means hiding your . . . um . . . "futurisity." /phpBB/images/smiles/icon_smile.gif

And BTW, there is no such thing as "too much" Star Trek! /phpBB/images/smiles/icon_wink.gif

g99
2002-Jul-02, 09:57 PM
How would you travel back in time in the fiorst place? Disreguard the whole paradox thing because if only one person goes back in time, the whole human race and the universe is probobly screwed. And what is back in time anyways? Is it going to a parallel dimension that has the same exact laws and occurences as our dimension except the big bang(or whatever created it) happened that may years later. Or is it like a stream and all you have to do is "swim" backwards against the stream and you are back in time? Also what about going forwards in time? that is easy, all you have to do is travel to near the spead of light and time will slow down for you. They have shown this on the space shuttle, where their clock will be a VERY VERY minute amount slower than our "normal" time. But then you have a problem of going back in time.

I remember reading a novel a long time ago (i forget the name and the author) about a girl who gets on a long duration colony ship or something like that. Well, the whole crew is killed in a accident and the engines malfunction by constantly accelerating. She breaks the light barier and continues to accelerate. Well due to time dilation the whole universe continues to evolve and finally she sees it collapse back into a small point of mass and cause another big bang. She is then able to slow it down and stop the ship. She finds out thet she has gone full circle and the universe has progressed to a point that she has been born again(in the new universe). She then stops herself from going on the trip in the first place. thus this form of "time travel" does not have to account for paradoxes.

What do you think?


Also, I just read a good novel called "chronospace" by Allen Steele. It posed an interesting theory. Basically they said that time travel has been inventer and that they disguize all og the ships as alien space craft "flying saucers" So basically he is saying that all of the alien spacecraft that we saa are time travelers.

Wiley
2002-Jul-02, 10:46 PM
On 2002-07-02 15:32, beskeptical wrote:

Re #3: Can't you imagine at least a few of us surviving? Couldn't we go on to a future future and invent time travel and go back and save a few more and so on. Otherwise, there should be enough time before the Sun glows red to evolve technology again. Maybe they'd be nicer.



Certainly, I can imagine a few people surviving the upcoming revolution. Now the question was "If time travel will be possible some day, then why aren't we inundated by time travelers from the future?" The misanthropic and pessimistic answer, the human race kills itself before getting a chance to invent a time machine, is a viable and arguably the most probable answer. Now I suppose the rosy, "always look on the bright side of life" answer would be that mankind finally learns that just because we can do something does not mean we should. We realize the traveling back in time would most likely destroy civilization, and we don't do it. Wisdom prevails.

The few who do survive the upcoming revolution, wearing red and green liberation jumpsuits they have been saving for just the proper occasion, are wise. They have learned optimism from Gene Roddenberry and respect from Stanley Kubrik; they will not make the same mistakes previous generations have made. They know that man will never have dominion over nature until man has dominion over himself, because man is part of nature. They are the Wise.

With that, I think I'll have a cigerette and go to bed. /phpBB/images/smiles/icon_smile.gif

<font size=-1>[ This Message was edited by: Wiley on 2002-07-02 18:47 ]</font>

Donnie B.
2002-Jul-03, 02:20 AM
One of my favorite time travel stories was about a physicist who discovered she could "twist" the four dimensions of spacetime, so that she experienced the time dimension as one of the space dimensions. All she had to do to travel in time was walk forward into a sort of mist to get to the future, or backward into the past.

But there was a catch, because when she tried to demonstrate the technique by walking into the past, she walked and walked but never seemed to get anywhere. When she finally gave up and made it back to the "present", exhausted, she realized that the time dimension was scaled at 300 million kilometers to the second...

roidspop
2002-Jul-03, 06:17 AM
"If time travel will be possible some day, then why aren't we inundated by time travelers from the future?"

Why are we hung up on linearity? Why must these travelers come from the future? Transtemporal travelers may be popping in all the time. We have good reason to believe interstellar travel would be extremely difficult, energy-intensive and slow; so, maybe cross-time travel is no more difficult and you're at least assured of (probably) arriving at a livable target planet when you emerge from the dimensional soup. So all these (oddly humanoid) critters we keep hearing about in their snappy inertia-ignoring vehicles are just visiting from Earths not so far away (but I challenge you to POINT in that direction), not from Out There. In a Universe that permitted that sort of travel, could you ever go home again? Niven thought not. So, our visitors are from here, elsewhen. Stranded. Green card, please?

Bad Engineer
2002-Jul-03, 12:05 PM
I probably won't start thinking too seriously about the possibility of time travel until I begin to see physicists winning the lottery on a regular basis.

B.E.

Chuck
2002-Jul-03, 02:39 PM
The thing to look for is someone who wins a big lottery and invests the money in a few small companies that grow quickly. That's probably the best way to get rich quick if you know the future.

g99
2002-Jul-03, 05:50 PM
the best way to make money, is to take some future technology and take it back in time and "invent it" before it was concieved. Thus making yourself billions of dollars HAHAHAHAHAHAHAHAHAH!!!!!!!!! /phpBB/images/smiles/icon_smile.gif I will be rich, i will take back the recipea for the Twinky to the 19th century and make billions!!!! HAHAHAHAHAHA I will rule the world!!! (BANG...G99's head suddenly explodes from his overexagerated ego) Ahh that better, sorry....

Can anyone think of some good examples of technology or ideas that seem to come out of nowhere? Hmm..Penecillin? T.V.? Radio? Cheesburgers? makes you think doesn't it?

Roy Batty
2002-Jul-03, 06:01 PM
The 1st 3 didn't exactly come out of nowhere, & as for cheeseburgers, i'm quite happy for them to go back there... /phpBB/images/smiles/icon_smile.gif /phpBB/images/smiles/icon_biggrin.gif

g99
2002-Jul-03, 06:38 PM
i know that the first 3 came from somewhere, it was only a joke. I was just tyring to activate some neurons. But i still think cheesburgurs came from the future.

David Hall
2002-Jul-03, 06:49 PM
Hey, don't go dissin' cheseburgers here. Them's God's gift to mankind. Why just yesterday I gorged myself on a birthday burger (Hickory BBQ) at the Hard Rock. I'm still suffering for it now, but it was worth it. /phpBB/images/smiles/icon_biggrin.gif

g99
2002-Jul-03, 11:28 PM
i'm not dissing a cheesburger, im saying that thye are so close to perfection, that they must be from the future.

beskeptical
2002-Jul-04, 12:39 AM
Don't eat hamburger unless you burn it yourself. It's not worth the risk. E-coli 0157 H7 is becoming much more common. Do you want to trust your life to the new hire down at the burger place?

I'm drawing a blank on the the name of the BBC show with the characters on the spaceship stranded in space after a million years or so, but they go back and invent "bubble wrap" and get rich. /phpBB/images/smiles/icon_lol.gif

nebularain
2002-Jul-04, 02:48 AM
On 2002-07-03 20:39, beskeptical wrote:

I'm drawing a blank on the the name of the BBC show with the characters on the spaceship stranded in space after a million years or so, but they go back and invent "bubble wrap" and get rich. /phpBB/images/smiles/icon_lol.gif



Sounds like Red Dwarf - yep! Definantly sounds like Red Dwarf!

David Hall
2002-Jul-04, 05:45 AM
Sorry g99, not talking to you. I agree with you. It's that Batty guy above you I'm targeting. /phpBB/images/smiles/icon_wink.gif /phpBB/images/smiles/icon_biggrin.gif

beskeptical
2002-Jul-04, 08:32 PM
On 2002-07-03 22:48, nebularain wrote:
Sounds like Red Dwarf - yep! Definantly sounds like Red Dwarf!



Yes. I thought of it last night. I kept thinking Red Devil or something and I knew that wasn't right.

g99
2002-Jul-04, 08:58 PM
On 2002-07-04 01:45, David Hall wrote:
Sorry g99, not talking to you. I agree with you. It's that Batty guy above you I'm targeting. /phpBB/images/smiles/icon_wink.gif /phpBB/images/smiles/icon_biggrin.gif



no problem
/phpBB/images/smiles/icon_smile.gif

Pi Man
2002-Jul-09, 09:41 PM
I second SeanF's statement that says, "There is no such thing as too much Star Trek"(even if it does have a little bit of Bad Astronomy here and there!)

g99
2002-Jul-09, 10:14 PM
I second my own statement

2002-Jul-13, 02:29 PM
http://www.badastronomy.com/phpBB/viewtopic.php?topic=1713&forum=1&0
MY baINdex (http://www.badastronomy.com/phpBB/viewtopic.php?topic=183&forum=1#LOCKTHRD)
anyway my "TIME TRAVEL" came at the END of my ride

in the Gravity Wave POD..and i did the transition
from inside a Gravity Wave POD to the TIME/space frame
of the ASR-7. the way i saw events: WAS that events
slowed in the POD {giving photons of light More time to activate the retnia}
So things could be seen in very fine focus at high detail {very pleasant}
anyway at end transition the time had to compress [Violently] see later post on violent end's

ZaphodBeeblebrox
2002-Jul-17, 03:25 AM
On 2002-07-02 22:20, Donnie B. wrote:
One of my favorite time travel stories was about a physicist who discovered she could "twist" the four dimensions of spacetime, so that she experienced the time dimension as one of the space dimensions. All she had to do to travel in time was walk forward into a sort of mist to get to the future, or backward into the past.

But there was a catch, because when she tried to demonstrate the technique by walking into the past, she walked and walked but never seemed to get anywhere. When she finally gave up and made it back to the "present", exhausted, she realized that the time dimension was scaled at 300 million kilometers to the second...


One Problem, though, does Time Pass while you're Passing Through Time?

If not, then The Answer is Simple, just Pre-Set and Go!

A related Idea that I'm working on, for a Novel that I'm in the Earliest Stages of Writing, is The Swapping of a Space Dimension for a Time Dimension.

Does anybody know if that's Even Possible, and If So, How?

Kaptain K
2002-Jul-18, 10:33 AM
A related Idea that I'm working on, for a Novel that I'm in the Earliest Stages of Writing, is The Swapping of a Space Dimension for a Time Dimension.

Does anybody know if that's Even Possible, and If So, How?
For a fairly extensive treatment of the idea, see "The Number of the Beast" by Robert A. Heinlein.

GrapesOfWrath
2002-Jul-18, 10:54 AM
On 2002-07-16 23:25, ZaphodBeeblebrox wrote:
Does anybody know if that's Even Possible, and If So, How?

Well, there's this tiny shack at Langley that seems like it's been there forever...

therealdeal
2002-Jul-21, 06:28 AM
the other day i visited myself from the future and gave myself a time machine. all i have to do is give it back to myself later. I saw the future and it is real cool. i am going to get all sorts of patents for inventions i saw and become really rich and my wife is damn hot! the future is awesome!

ZaphodBeeblebrox
2002-Jul-21, 09:09 PM
On 2002-07-21 02:28, therealdeal wrote:
the other day i visited myself from the future and gave myself a time machine. all i have to do is give it back to myself later. I saw the future and it is real cool. i am going to get all sorts of patents for inventions i saw and become really rich and my wife is damn hot! the future is awesome!


Uh-Huh, and Next Week's Powerball Numbers are, what exactly?

You know, that, or who'll win the Next World Series, don't say The Yankees!

g99
2002-Jul-22, 08:45 PM
I can't release the jackpot nuymbers because i have already won the jackpot. Also next year Florida will break off into the sea and become a new nation of old geezers and young hippy spring breakers. The nation will then fall into poverty becuse noone will work and then they will all die of alcohol intoxification and choke on their early-bird specials.

LONEGUNMEN33
2002-Jul-25, 07:42 AM
Ok im jumping in really late but...Not sure who said it first but i know there was a twilight zone about it,,something about "even if one was to travel back in time the laws of physics would disallow that person from changing anything. since everything has already happened there is no way to change whats already occured"...In the twilight zone episode some guy was sent back to assinate hitler...he rented some hotel room with a clear shot at hitler.. people kept interrupting him b4 he could shoot and his gun would jam,,at the end they find the gun in his room and arrest him... (something like that i havent seen it in yrs)..I dunno bout you guys but reading these posts makes me wanna watch terminator one and 2...still dont get how kyle reese is john connors dad if connor was the one who sent him back...weird......

Manchurian Taikonaut
2004-Mar-19, 06:18 PM
Even if it is possible it is something we will not achieve in our next thousand years, the understanding of science and technology is just not even anywhere near this level

milli360
2004-Mar-19, 06:35 PM
Even if it is possible it is something we will not achieve in our next thousand years, the understanding of science and technology is just not even anywhere near this level
We know how to go to the moon, but we don't do it anymore because it is too expensive. We'll find the same about time travel, soon.

Chuck
2004-Mar-20, 04:42 AM
http://www.unitedmedia.com/comics/reality/archive/images/reality2004034066713.gif

sidmel
2004-Mar-22, 02:47 PM
I watched an interesting TV program that went into the possibility of time travel, may have been a bunch of bunk, but interesting non-the-less. First off, they stated that there is nothing to Einstein’s equations that necessarily prohibits time travel, which I find interesting.

Their proposal was that time was represented as a wav form, i.e. a sine wave or similar. If someone/something traveled back in time that would create a paradox, the wave form would collapse and reform into the next likeliest scenario. So if you went back in time to shoot and kill your grandfather, the wave form would reconfigure itself so that you might miss, the gun jam or most likely, you didn’t travel back at all. Something similar to this is present by Steve Hawkings, who said it word prevent time travel all together.

As far as doing the actual travel, I believe the more popular theory right now is using worm holes which might connect to a black hole/s in differing time references.

squeak
2004-Mar-23, 11:19 AM
Having read all this conjecture about time travel, I do have a quite obvious flaw with the feasibility of time travel that would make it 99.9999% (underlining since I lack the ability to add the repeat notation) impossible to affect the timeline *period* that I'm surprised nobody has mentioned.

While an advanced civilization capable of manipulating spacetime would probably have mastered the art of folding space, trying to move throughout all *4* dimensions simulatenously (x, y, z, *and* time) would probably prove the largest challenge of all.

Assuming that someone could get a craft to travel either backwards or forwards in time, the possibility of ending up on earth again is nearly infintesimal.

The earth rotates on it's axis, which *does* wobble every 26,000 years. Earth then rotates around the sun, which rotates around the center of the galaxy, which rotates around the center of the cluster, which rotates around the center of the supercluster, which rotates around god knows what, at god knows what speeds.

You'd have to know these velocity and orbital constants, as well as variations in all the above-mentioned orbits (via immense gravitational effect calculations) *precisely*, and then command your vessel to not only move you through time, but also to fold space and get you to the same *relative* (in terms of position on the planet) point in space that you were in to begin with. The calculations involved, assuming one knows all the above information, would be enormous, as well as invite a *massive* margin of error.

Lacking that information, it would probably *also* prove impossible without detailed charting of the *entire universe*--once having moved backwards or forwards in time--to then calculate a spacewarp which would deposit you even *remotely* close to your destination.

This is of course assuming that spacetime itself has some impossibly undiscoverable static composition. And even assuming an advanced civilization has the ability to manipulate spacetime in the way necessary to travel in this manner, there are just too many variables and too much information that must be known precisely for it to be at all likely. In fact, the amount of information needed might very well be infinite.

In my opinion.

PhantomWolf
2004-Mar-23, 12:30 PM
Of course the simplist explanation is that if you could figure out the x,y,z,and t co-ordinates to get back in time, then the past is set already and you would have already been in the past and done whatever you planned to do and it was either successful or failed and hence would again regardless of any fore knowledge. If that makes sense :-?

worzel
2004-Mar-23, 04:32 PM
the best way to make money, is to take some future technology and take it back in time and "invent it" before it was concieved.
Maybe this is why Einstein worked at a patent office. Maybe he was hoping to identify a time traveller and ask him some questions about physics.

granolaeater
2004-Mar-24, 02:13 PM
I think a big problem with many ways to prevent time travel problems is that I can create time travel paradoxes without travelling in time myself.

Lets assume this: I am sitting at my desk and suddenly beseides me a little time machine pops out of nothing. Inside is no person but only a letter from next week. It states the numbers of coming saturdays lottery. So it bet with these numbers on saturday win the jackpot and use the money to buy a very expensive time machine. I put a letter with the winning numbers into it and send it back into last week.

Ok this works. But what prevents me from playing foul and not buying the time machine from my new won money but to travel to hawai and make a lazy day?
what prevents me from making a mistake while writing down the numbers and so accidently send back the false numbers.
What has prevented me in the past from ignoring the letter?
How could this letter or my knowledge of it determine the outcome of the lottery? The way the numbers were chosen was inherently non determined and there was no physical connection between the letter or me and the lottery machine before the numbers where chosen.

Looks a little bit like magic to me to use some kind of 'impossibility to interfere' or predestination here.

informant
2004-Mar-24, 02:25 PM
OK, but then the machine would have travelled through time. Not someone, but something.

granolaeater
2004-Mar-24, 02:40 PM
OK, but then the machine would have travelled through time. Not someone, but something.

Yes of course. But here the one (or thing) who traveled in time and the one who makes the 'forbidden action' are to different persons.
This makes it much harder to say after time travel into the past I am restricted in my possible actions there.
But here I did not travel, so what mechanism makes me more restricted in my actions then other persons?
And even worse, what restricts the lottery machine in its actions? It had not even contact with someone who had knowledge about the time travel!

informant
2004-Mar-24, 02:59 PM
But here the one (or thing) who traveled in time and the one who makes the 'forbidden action' are to different persons.
This makes it much harder to say after time travel into the past I am restricted in my possible actions there.
But here I did not travel, so what mechanism makes me more restricted in my actions then other persons?
I think the idea is not that you, the time traveller, become restricted in your actions "after" having travelled to the past. I think it's the whole universe -- and everyone in it -- that is "restricted" to non-paradoxical scenarios. (Suppose you bring a sports alamanac from 2015 to 1955, and someone steals it from you. Then, although that person did not travel in time, he or she is also bound not to violate causality.) To put it in another way, only consistent histories are allowed to be real. Everything that happens is predestined in such a way that there are no paradoxes.

(Edited for clarity.)

granolaeater
2004-Mar-24, 03:26 PM
But here the one (or thing) who traveled in time and the one who makes the 'forbidden action' are to different persons.
This makes it much harder to say after time travel into the past I am restricted in my possible actions there.
But here I did not travel, so what mechanism makes me more restricted in my actions then other persons?
I think the idea is not that you, the time traveller, become restricted in your actions "after" having travelled to the past. I think it's the whole universe -- and everyone in it -- that is "restricted" to non-paradoxical scenarios. (Suppose you bring a sports alamanac from 2015 to 1955, and someone steals it from you. Then, although that person did not travel in time, he or she is also bound not to violate causality.)

Yeah, and all the people who are mentioned in that almanac, too. Like the lottery machine in my example


To put it in another way, only consistent histories are allowed to be real. Everything that happens is predestined in such a way that there are no paradoxes.

This is the problem. If you think this way predestination occurs not only in some restricted little area in connection with the time travel, but on a much larger range.
But on the other hand there is quantum mechanics. Here the outcome of an experiment is considered not to be determined until you measure it. And chaos processes carry this up to macroscopic processes. So very much of the things to happen in this world should not be determined at all. How does this fit with predestination?

informant
2004-Mar-24, 03:45 PM
Good question. Any idea about the answer? :)

Emspak
2004-Mar-24, 09:23 PM
Stephen Baxter (I haven't paged through the entire thread, forgive me if I erpeat something) talks a lot about the "many worlds" hypothesis ni his books.

He just posits that if you go back in time, the mass you have isn't really destroyed or created -- if you move back in time and end up in the same universe and meet yourself, the net amount of mass and energy you represent is the same because it disappeared from your future. So the amount of energy in the system (the universe) is X minus one person in the year 3000 and X plus one person in the year 2000 -- since you disappeared from 3000 it balances out.

In that sense, if I go back in time and change somethign it doesn't matter -- it just gets worked into the timeline as a "normal" event. You don't disappear if you kill your dad (though you obviously have some psychological issues to deal with) -- things just go on "normally."

Lusion
2004-Mar-25, 06:21 AM
Stephen Baxter ... posits that if you go back in time, the mass you have isn't really destroyed or created -- if you move back in time and end up in the same universe and meet yourself, the net amount of mass and energy you represent is the same because it disappeared from your future.


I don't think this theory carries much weight for a number of reasons.

First, keep in mind that just because you retain your own psychological identity throughout time doesn't mean that you represent the same matter. Eating, respiration, perspiration, etc are all forms of exchanging matter with the environment. The matter comprising a human just plain changes over time.

Second, I don't agree that mass would be conserved during time travel cases. Keep in mind that time travel can be thought of as equivalent to faster-than-c travel. Based on my naive understanding of QM, faster-than-c travel actually occurs on tiny scales, and what happens in such cases usually depends on your perspective--in one reference frame, it looks like something travelled back in time--in another frame, it doesn't. If mass is conserved in the latter time frames, it will definitely appear in other time frames that it is not conserved.


So the amount of energy in the system (the universe) is X minus one person in the year 3000 and X plus one person in the year 2000 -- since you disappeared from 3000 it balances out.


...and in this case, I don't think the explanation is quite right--your explanation makes it look like the 100kg time traveller's mass just goes away in the year 3000.

Immortal baby A exists in the year 2000, and 1000 years pass. Now he has grown into an immortal time traveller B, at which point in time he travels back 1000 years. Now immortal time travellee C and immortal baby A both exist in the year 2000, but the person who disappeared in the year 3000 is immortal baby A, not immortal time travellee C... instead, immortal time travellee C simply ages during the next millenium becoming immortal old wise man D in the year 3000.

Now, assuming my first objection were false and we treat all of these entities as the same mass (say the weight is 100kg), what happens is that in the year 2000, there is a "triplication" of mass consisting of: 100 kg immortal A, 100 kg of time traveller B (going backwards in time), and 100 kg of time travellee C. Immortal time traveller B (going backwards in time) can be considered antimatter, but antimatter still has positive mass, so the act of travelling back in time adds 200kg to the mix. All this is assuming that the time travel is not accomplished by a "shortcut" like a wormhole, in which case there is only the duplication of mass, and is also assuming that you are in such a time frame as to observe this as time travel.

If you treat the antimatter as negative energy and don't take "shortcuts" back in time, then you can say in this sense that the total amount of energy in the universe doesn't change, but you would have to adjust your explanation (it's X minus the energy in the antitraveller back in time from the year 3000 plus the energy in the travellee going forward in time to 3000).

Emspak
2004-Mar-25, 12:18 PM
First, keep in mind that just because you retain your own psychological identity throughout time doesn't mean that you represent the same matter. Eating, respiration, perspiration, etc are all forms of exchanging matter with the environment. The matter comprising a human just plain changes over time.


Wel, I wasn't thinking the mass itself was the same -- take the example of a brick.

Brick goes back in time 1,004 years to year 1000, when it was made. So now there are two bricks. But when you get to 2004 the "original" brick disappears. the one that just time-travelled goes blithely on. The net amount of mass-energy in the universe is unaltered.

With people the situation is similar-- I realize you aren't made up of the same atoms as when you were walking around 10 years ago but the mas is almost the same (I weigh about 80kg, for instance, no matter what I have eaten and such in the past year).

Anyhow, the point of Baxter's speculation is that there are no paradoxes in the way we usually think of them -- histories are like wave functions. Real once observed, but in the meantime pretty flexible, and if I go back in time and kill dad I don't disappear.

If you think of time as just another linear dimension this works. I mean, if I move stuff from one side of a room to the other the net amount of mass-energy in the universe doesn't change. The same could apply to time as well. It's only because we experience it in one direction that it seems odd to do that. It is true some parts of particle physics point to their being a physical "arrow," -- there were some old K particle experiments in the 70s -- but if we treat it as just like any other "direction..."

--Just my wild speculations.

-J

squeak
2004-Mar-25, 10:18 PM
Brick goes back in time 1,004 years to year 1000, when it was made. So now there are two bricks. But when you get to 2004 the "original" brick disappears. the one that just time-travelled goes blithely on. The net amount of mass-energy in the universe is unaltered.


This would be basically collapsing all 4 dimensions (x,y,z and t) down into a closed system in terms of mass/energy conservation, rather than only considering x,y, and z as the basis for said conservation, correct?

Emspak
2004-Mar-25, 10:42 PM
Yeah, that's basically it.

You see, time travel to a point can occur with some solutions to both GR and QM, though the way you get there is a bit different. But I don't know of any GR solutions where mass conservation is even an issue.

In QM there are virtual particles and some with negative mass, (would they travel through time backwards?) and yuo could theoretically open up a wormhole with a lot of negative-mass matter. Take the wormhole in some direction -- doesn't matter where -- at relativistic speed, and return it to the starting point. Since the wormhole connects things instantaneously, you have to account for the fact that time for the second wormhole -- the one you took away -- has slowed down.

So the second wormhole -- say you are carrying it around in a spaceship -- is in a place where guy says "my clock says only a few years went by" and the original wormhole terminus in Space Station Alpha says "no, you were away for 1,000 years."

What happens? Interesting question, but the upshot is you have a wormhole connecting Space Station Alpha and the spaceship that drops you back to whatever time the guy on the ship has on his clock. You also end up with anyone who is on the moving ship -- whose clocks are really slow by the "stationary" wormhole's clock -- being able to zip back home into their future.

Conservation of mass doesn't come into it.

Stephen Hawking gets into this in one of his books with a nice little illustration.

Phobos
2004-Mar-28, 11:14 AM
Time travel, hmm

How about this.

Quantum entanglement has been proven to allow transfer of non-local effects over space (Einstiens's spooky action at a distance). Since space and time are so closely related QE may offer the hope not only of teleportation over space, but time as well.

Let me explain. Teleportation experiments have already taken place that teleport light. The technique involved taking advantage of the non-local effects that come in to play when you perform a measurement on one of a pair of entangled particles. Under normal conditions making a measurement on one of the particles has an instant (and faster than light) affect on the other.

Note I said it affected the other, but I didn't say a signal travelled faster than light. The reason is nothing actually passes through the gap in between the entangled particles - this is why the normal restriction of the light speed limit does not apply here.

OK that covers how teleportation works, but how could this be applied to time travel ? Well, one possibility might be to perform the same experiment with one of the entangled particles artificially aged. Since quantum properties of physics dictate that both particles are affected at the same time, we may have a very interesting result.

Take one entangled particle, and pass it through a particle accelarator. This should result in it having a different age to its twin (see the twins paradox). Being different ages could have a dramatic effect if these particles are now used as part of a teleportation experiment.

My logic is as follows. Imagine the entangled particles were from some radioactive matter that is subject to radioactive decay. As the particles are entangled we should expect both particles to decay at the same time and rate. If one particle is passed through an accelarator then they will decay at different points in time, but the entanglement of the particles should still remain.

So if we perform teleportation using one of the particles (eg. just after radioactive decay had happened), then the result should be observed on it's partner at a different point in time. If the particles were used for teleportation purposes then we could imagine some form of matter or information teleportation would take place not only through space, but also thruough time.

If the idea is correct then strictly this should not be called time travel, but time teleportation. That said I think it's pretty close to what you want.

milli360
2004-Mar-28, 11:36 AM
My logic is as follows. Imagine the entangled particles were from some radioactive matter that is subject to radioactive decay. As the particles are entangled we should expect both particles to decay at the same time and rate. If one particle is passed through an accelarator then they will decay at different points in time, but the entanglement of the particles should still remain.
I would guess that they would not remain entangled.

thejew72
2004-Nov-28, 07:53 PM
i have 550$ and a brand new 4000$ computer to give to whoever can invent a time machine for me....so i can go back 4 weeks and save my girlfriend and i's relationship. a little far off, but i need it. it will be sent to you through ups. all postage paid.

electromagneticpulse
2004-Nov-30, 04:46 PM
i have 550$ and a brand new 4000$ computer to give to whoever can invent a time machine for me....so i can go back 4 weeks and save my girlfriend and i's relationship. a little far off, but i need it. it will be sent to you through ups. all postage paid.

I would surgest the word "sorry", Its a better hope then a time machine.

Welcome to the board.

worzel
2004-Nov-30, 05:44 PM
i have 550$ and a brand new 4000$ computer to give to whoever can invent a time machine for me....so i can go back 4 weeks and save my girlfriend and i's relationship. a little far off, but i need it. it will be sent to you through ups. all postage paid.

I would surgest the word "sorry", Its a better hope then a time machine.

How do you he wasn't too weak and said sorry all the time for things that weren't his fault resulting in her losing respect for him and ultimately dumping him? Maybe he wants to go back and tell her what he really thought at the time.

A Thousand Pardons
2004-Nov-30, 05:50 PM
i have 550$ and a brand new 4000$ computer to give to whoever can invent a time machine for me....so i can go back 4 weeks and save my girlfriend and i's relationship. a little far off, but i need it. it will be sent to you through ups. all postage paid.

I would surgest the word "sorry", Its a better hope then a time machine.

How do you he wasn't too weak and said sorry all the time for things that weren't his fault resulting in her losing respect for him and ultimately dumping him?
How do you know he wasn't on a game show where the clue was "apologetic" and the category was S Words with 5 Letters? And he would have won $256,000, but he said "stupid" instead? And his girlfriend was a materialistic golddigger?

worzel
2004-Nov-30, 06:23 PM
i have 550$ and a brand new 4000$ computer to give to whoever can invent a time machine for me....so i can go back 4 weeks and save my girlfriend and i's relationship. a little far off, but i need it. it will be sent to you through ups. all postage paid.

I would surgest the word "sorry", Its a better hope then a time machine.

How do you he wasn't too weak and said sorry all the time for things that weren't his fault resulting in her losing respect for him and ultimately dumping him?
How do you know he wasn't on a game show where the clue was "apologetic" and the category was S Words with 5 Letters? And he would have won $256,000, but he said "stupid" instead? And his girlfriend was a materialistic golddigger?
Because 'stupid' has got 6 letters :)

A Thousand Pardons
2004-Nov-30, 08:45 PM
exactly my point worzel :)

zebo-the-fat
2004-Dec-02, 04:37 PM
I explained all about how time travel worked next year, didn't you listen? :D

John Dlugosz
2004-Dec-02, 10:09 PM
How do you count photons without them (or the detector) being affected? That violates all sorts of quantum principles and wouldn't work.

The photon is captured by one side of the object, and measured. Then you create a new photon with the same properties and emit it from the other side of the object, so the object is invisible. But how to emit it at the same time the original would have gotten there had you not been in the way? Well, you have time travel, right? The back side could be farther in the past than the front side, for example.

How to measure all the properties of the photon, when normally measuring one thing destroys something else? Keep going back into the past, to the same point in space-time, and measuring it several times.

I postulate that if it is possible to observe the past without affecting it, it will also provide a way to duplicate quantum objects. Observing something normally causes the QM matrix to rotate to an eigenstate (of that observable) at random, thus changing the original quantum object. By postulating that you can observe something without affecting it, you are saying that this won't happen!

John Dlugosz
2004-Dec-02, 10:20 PM
what prevents me from making a mistake while writing down the numbers and so accidently send back the false numbers.
What has prevented me in the past from ignoring the letter?
How could this letter or my knowledge of it determine the outcome of the lottery? The way the numbers were chosen was inherently non determined and there was no physical connection between the letter or me and the lottery machine before the numbers where chosen.



It's the same as any other quantum handshake. If the loop was not self-consistant, the quantum wave function would not have collapsed into that state.

It's the same as any double-slit experiment. If you block one path "after" the photon has gone through the slits, you find that it went through one slit (not both) after all.