"Time Travel" and Hawking

[mooeypoo]

Hey guys,

 

Recently I've heard a layman explanation to what Hawking used to "solve" the grandfather-paradox. I am not too versed in this, but the way I understood it, Hawking solves the paradox by saying that nature will "disallow" the travelling to the past in such sense to create the opportunity of the paradox.

 

That got me thinking.

 

Is it valid to say that on Nature? Doesn't that assumption (that nature will "prevent" -- or rather, laws of nature will accumulate to somehow prevent time travel) puts nature with a consciousness?

 

I mean.. if time travel is theoretically valid through relativity (and it is my understanding that if "exotic matter" is used, it theoretically is valid), then saying nature will prevent it still because we - humans - thought of a paradox is.. well, weird in my taste. Nature is not conscious, it's an accumulation of laws.

 

I hope I am not just rambling through this, and that you guys get my point here.. I'm.. again.. not too well versed in this subject.

 

btw, I wasn't sure if this should be here or in pseudoscience and speculations, so apologies if it doesn't belong.

 

~moo

[Sayonara]

Why should a natural law preventing a paradox have any special status, as opposed to, say, the laws that make gravity such a drag?

[theCPE]

Besides obvious implications from relativity that allow time travel FORWARD, I am unaware of what theories allow travel into the past.

 

Aside from garden variety theories that have no emperical evidence such as "well if you rotate a massive cylinder fast"....or wormholes...etc.

 

That being said, I think there is a difference between saying there is a natural law that would prevent travel into the past, as opposed to saying nature would stop the grandfather paradox if someone did travel into the past, the later sounding quite silly.

[Spyman]

The chronology protection conjecture is a conjecture by the physicist Professor Stephen Hawking that the laws of physics are such as to prevent time travel on all but sub-microscopic scales. Mathematically, the permissibility of time travel is represented by the existence of closed timelike curves.

 

In a 1992 paper, Hawking uses the metaphorical device of a "Chronology Protection Agency" as a personification of the aspects of physics which make time travel impossible at macroscopic scales, thus apparently preventing time paradoxes. He says:

 

It seems that there is a Chronology Protection Agency which prevents the appearance of closed timelike curves and so makes the universe safe for historians.

http://en.wikipedia.org/wiki/Chronology_protection_conjecture

 

I don't think Hawking meant that Nature would make deliberate decisions to prevent us from making a paradox...

IMO He suspects and argues for a natural law of physics preventing the appearance of closed timelike curves.

 

(More or less what Sayonara³ said.)

[mooeypoo]

Why should a natural law preventing a paradox have any special status, as opposed to, say, the laws that make gravity such a drag?

 

Well, if you explain it as "Drag is nature's "assurance" that we can't reach high speeds" it's not quite .. scientific?

 

Besides, drag is an effect, and we discovered it after gravity, speed and acceleration (if i am not mistaken). It's not like we said "There must be an effect because Nature wouldn't "allow" something".

 

I guess my problem is setting a standard on Nature to "solve" our own paradoxes. A paradox may just be created by our HUMAN limitation, and stating that Nature just may have means to prevent our own imagination-flaws sound a bit unscientific.

 

But again, I may be wrong - and odds are I just simply did not understand correctly what he said.

 

 

~moo

[Sayonara]

Now it sounds like you are saying that describing a law in a non-scientific way robs it of its effects.

 

I understand where you are coming from though; I think the problem here is that you are listening to something that Hawking said, instead of doing something more interesting.

[foodchain]

Well, if you explain it as "Drag is nature's "assurance" that we can't reach high speeds" it's not quite .. scientific?

 

Besides, drag is an effect, and we discovered it after gravity, speed and acceleration (if i am not mistaken). I guess my problem is setting a standard on Nature to "solve" our own paradoxes. A paradox may just be created by our HUMAN limitation, and stating that Nature just may have means to prevent our own imagination-flaws sound a bit unscientific.

 

But again, I may be wrong - and odds are I just simply did not understand correctly what he said.

 

 

~moo

 

I would suggest on reading about natural kinds and the entire ordeal if making science free from human fallacy. Not to say your idea put forward is fallacy, just more on the point to follow. For instance, why do you think people looked for the big bang, because something that started should have an ending or vice versa, or was it purely from an I wonder perspective. Its drastically difficult to cut away the human part of human thought you know, such is why math was invented, as an attempt basically to cut down on the ease in which human thought can corrupt if you will. Regardless of person, you have to view something from you perception, its not some scientific fact of an extreme nature as much as its not everyone has the same favorite sports team or team for that matter. Such as for me, I worry about the level of corruption that even math can offer. Geophysicists and related methods and technology labeled various boundaries when it came to the earths structure, when actually went to in the form of physically being there, sometimes there boundaries could be off by more then a thousand feet, so its not so much that the methods are wrong, but if it were just up to the math and no one went to see, well what else could that apply to.

 

So yes, human corruption in the form of fallacy is a major issue, probably inevitable and only overcome by science of humans being social to a certain extent. How about nature just is a word that giving any specific person in its own right can be relative. If you spend any length of time trying to think about nature per say and our understanding of it in terms of anything purely philosophical, it quickly falls apart unless you favor things like logical gymnastics and other unholy acts. Science is about the only chance due to method, but as pointed out to me on this board already many times its an extremely slow process in regards to human lifetimes. Though I do love to debate philosophy at times, its always funny trying to use the subjective to gain some objective victory.

[someguy]

I don't know.. Einstein i don't believe practiced classical science as in isolating variables and testing. certainly observation but also imagination. imagining scenarios he could test within his own mind and postulating scenarios where he could logically come to certain conclusions. for example, he didn't discover gravity could bend light by actually bending light with gravity or observing light being bent by gravity, he figured it out by knowing certain principles and imagining a scenario using them and he ended up coming to the conclusion that gravity must bend light. it wasn't until later that we had the proper equipment to observe what he predicted.

 

as for the natural limit to going back in time: people usually think of the twin paradox in terms of as you accelerate time for you slows down. I think a better way to look at it is that as you move faster you are carried through time at a faster rate, just like you are carried through space at a faster rate. so the slower you go the slower you move through time, in relation to other objects of course, until you reach a point where you are in sync with them and time is the same for you and the other moving body you are in sync with. now if you want to go in reverse time, wouldn't you need to move "slower" than the body you want to travel back in time from? this is impossible, you must either move or not move in relation to an object. either still, or slow or fast or faster, you can't anti move you can't unmove, or demove whatever you wanna call it. there's no speed slower than 0. so then i don't see how moving back in time could be possible just by nature of how the universe is. The only way i can see it would be possible is if you could anti-move by traveling into some other dimension, but that seems far fetched and untidy to me.

 

as for math, ya i know what you mean that math is logic in its purest form but i don't think it can help the human error portion of science. I say this because math doesn't really describe something we can understand it just is numbers. we could look all day at formulas that function in 4 dimensions, plot them draw them out as much is possible and still never clue in that the 4th dimension is time. it never says that in the math. so though formulas can never be wrong, and can predict events if we know what the math represents, finding what it represents is truly the tricky part, or representing what we observe with it whichever way around it happens. That is where you can easily find human error, translating the math to describe reality. Personally I find this is where post Einsteinian physics is kind of weak, they're great in the math aspect and if you understand the math then there's information to look at but as for actually describing the universe i think it is lacking. but what's for sure is that if any theory is to hold up it must comply with math, it must be able to be described mathematically and for that math is a very useful tool.