I want to be able to see dinosaurs, but from what I've heard, time travel is only possible if you're heading towards the future.
Newbie
I want to be able to see dinosaurs, but from what I've heard, time travel is only possible if you're heading towards the future.
Banned
From what I've read on the BABB/BAUT about time travel, you are right, you won't see the dinosaurs. You will see me yesterday, though. I wish I could tackle this with more expertise, but I will wait for the experts to arrive.
Established Member
There are games one can play with unusual black holes. The math folks say it might be theoretically possible. Of course, if you look at those games, there is no way a human could survive the trip. Your individual particles might arrive in the past, but the sense of order they have right now that defines YOU sure wouldn't.
Order of Kilopi
Probably one should distinguish between "seeing" the past, and "being in" the past. You can see dinosaurs if you can get the light they emitted to bounce off something 100 million light years away and come back (in principle!). But can you actually take an action that affects the past? My speculations on that are no better than anyone else's, but one must distinguish between whether it is possible in principle, versus whether it is practical, and I agree with adiffer that there does not appear to be any reason to think it's practical (plus if it were practical, we'd most likely have ample historical evidence of it by now! Not to mention the logical paradoxes.) You'd be better off shooting for the Jurassic Park scenario if you want to actually walk amongst dinosaurs (and look what happened to those people!)
Order of Kilopi
I'd have to say no, because the past no longer exists.
Well, actually the past does exist, but it's now the present. In other words, the past did once exist as the past, but it no longer does; it now exists as the present, and one day it will exist as the future. I hope that's clear.
Newbie
Scientific truth can be a *****, can't it?Originally Posted by Ken G
Established Member
Thanks, now I've gone all crosseyed!
Order of Kilopi
Serious note: I really should look into what theorists really have to say on theoretical time travel. Personally, I'm skeptical of such ideas, but I'm too lazy to do a lot of reading on it.
Silly note: The Hitchhiker's Guide to the Galaxy had something to say on time travel. To paraphrase: The problem isn't with being your own father/mother. Any well-adjusted family can overcome that problem... The problem is with grammatical references, such as future-past-future participle phrase...
In the webcomic "Bob and George", they put it the best way.
"I hate time travel"
Order of Kilopi
Look at this:
http://news.bbc.co.uk/1/hi/sci/tech/4097258.stm
"Quantum behaviour is governed by probabilities. Before something has actually been observed, there are a number of possibilities regarding its state. But once its state has been measured those possibilities shrink to one - uncertainty is eliminated.
So, if you know the present, you cannot change it. If, for example, you know your father is alive today, the laws of the quantum universe state that there is no possibility of him being killed in the past. "
Order of Kilopi
There is a difference between scientific possibility and logic. Time travel may be physically possible (assuming current physical theories are correct) but it violates logic, and therefore I do not believe it is possible.
Moderator
This is just another presentation of The Chronology Protection Conjecture
Order of Kilopi
(I need to ask people how they usually do their quotes)
I find this statement amusing. If our pasts changed, would we really notice? This seems to make that assumption - that every change would be noticeable. I mean, if history was changed, why should anyone in the future recognize that change? Since, for us, the future is different, but for the future, the past is normal for them...From BBC NEWS
Clearly, the present never is changed by mischievous time-travellers: people don't suddenly fade into the ether because a rerun of events has prevented their births - that much is obvious.
In short, for all we know, our pasts are changing every second of the day. But we might well NEVER KNOW, for our memories can very well be changing to fit that!
Now, this is something that irks me. This is almost like backwards destiny - that, even if you could go back to the past, some "hand of <insert something here>" would affect you and your personal choices in order to get things into an orderly fashion.From Professor Greenberger
You go back to kill your father, but you'd arrive after he'd left the room, you wouldn't find him, or you'd change your mind
That... well, it suggests something, for sure, and it fits nothing that I care to believe.
Established Member
If a violation of some dialect of mathematics were enough to make something physically impossible, we would get trapped pretty fast. We used to think there was one kind of geometry and discovered later an amazingly rich field of possibilities. The same applies to logic, so don't cling to it too much.
Mathematicians are bright people. They come up with all sorts of crazy constructs that enable us to comprehend and speak the patterns we observe in reality. Time travel ideas are tricky ones because we are used to languages with verbs that have built in time senses. Drop that bias and time is easier to understand. Was, Is, and Will Be are all the same thing that way.
Order of Kilopi
And then there's the parallel universe idea, which is that you can go back in time but you won't actually find the same thread that is your own past. To do so would be like finding a needle in a haystack. Instead you'll find some other thread where things could be quite different, and the future of that time could be radically altered by your presence, but that future would be distinct from your own past. Still, I say if it were practical, we'd have seen it by now. Sort of the same argument against interstellar space travel, but I guess that's another "thread".
Order of Kilopi
I seem to remember that Hawking has a bet with someone, forget who, about whether time travel is possible.
Order of Kilopi
I've heard of a bet where Hawking claimed that black holes, via creation and evaporation, could cause information to disappear, in apparent violation of the second law that says information (i.e., entropy) must not decrease. Is that related to the time-travel idea you refer to? Perhaps it is, via the issue of entropy defining an arrow of time. This is really tough sledding, because you have to unite gravity theory with quantum mechanics, and the reference frames are really hard to keep track of as well. It makes my head hurt. Hawking has since changed his opinion, but no one really understands why yet. But let's face it, this is all angels-on-the-head-of-a-black-hole stuff, I don't think I'm out on a limb to claim that reversing time's arrow, in the sense of being able to affect one's own past, is not a possibility in humanity's present future.
Order of Kilopi
If Everett's "many worlds" scenario is correct, you can go back to the past, change what you like without changing the present, because you fork out into another universe.
Order of Kilopi
Which presupposed that the simple act of going back in time won't cause you to fork into a different past to begin with, which would be a forking nuisance.
Banned
From Brian Greenes The Fabric Of The Cosmos, he states no to Time Travel to the Past.
He lists a ton of names for the earliest relativity papers with relevance for time machines.
- 1937 by the Scottish physicist W.J. van Stockum
- 1949 by a colleague of Einsteins at the Institute for Advanced Study, Kurt Gödel.
- 1970s, Frank Tipler reanalyzed and refined van Stockums solution.
- 1991, Richard Gott of Princeton University discovered another method for building a time machine making use of so-called cosmic strings (hypothetical, infinitely long, filamentary remnants of phase transitions in the early universe).
- Recently, Kip Thorne and his students at the California Institute of Technology make use of wormholes.
Greenes books are great for the layman!
Order of Kilopi
Kip Thorne
Same Guy, he Made The Penthouse, Black Hole Bet, with ...
Established Member
I liked your first post, Ken.
Just a thought I've been mulling over for several days. I've been considering the implications of intense artificial gravity to counter the move into the future caused by sustained relativistic speeds. However, if you didn't just exactly balance movement into the future, but insted used additional gravity, then you might indeed be able to to move into the past. Be there; not just see it. It brings up though a host of issues, not the least is what we mean by time, and what happens to causality.
Order of Kilopi
The Only Issue Is, you Still Have to Accelerate, ALL, Of That Simulated Mass.
This Would Tend to Bring It, Into The Same Reference Frame; Thus Negating The Buffering Effect.
Also, Natural Gravitational Fields, Don't 'Cause Time-Like Curves, Except Through Massive Curvature; Why Should Artificial Fields, Be Any Different?
Order of Kilopi
It is possible that the only way to really understand time would be to actually go back in it and see what happens, if that is in fact possible. Inasmuch as going back in time would represent a totally new experiment, it is likely that none of our present theories could predict the result with confidence. The more important issue is will we ever know enough to build the technology that can do it, and then see what happens next. My money says nope, but that shouldn't deter the intrepid dreamer.
Moderator
When I was younger I did a sci fi serial on our main frame, where I had the idea of using some device that would react certain particles to produce accelerated anti-chronons. which would radiate outside of a defined sphere. The universe outside the bubble would then be driven backwards, whilst those inside the bubble continue to go forward as normal. Hence you effectively have a bubble moving backwards using some form of temporal Newtons third law of motion.
In the story line the device itself stayed in the present, so the hero had to track down the earliy experimental device, create a bubble outside of which accelerated chronons out into the universe, to overdrive it back to the present.
You can obviously rip that mechanism to shreds, but at the time it seemed as good as any, and the story line was to get as many in jokes ans side swipes out as possible.
wrt paradoxes, I used the idea of the predestination paradox, i.e the original history only unfolded as it did because of the person travelling to the past. A bit like that scene in the third Harry Potter movie where the Harry Potter who travels into the past creates the shock wave that takes out the wraiths, that he had thought his father had done, sort of.
Order of Kilopi
How do you know that?
Time is a dimension. We can travel around in the 3 spatial dimensions and haven't yet traveled backward in the time dimension. But does that mean the past side of the time dimension isn't there? We can see back in time when we look at the light that left the past.
I consider future time as the edge of the Universe everyone usually thinks of as non-existent. Past time gets us to the center of the Universe which also doesn't exist apparently within the 3 spatial dimensions. Viewed in that conceptual version, whose to say exceeding the speed of light won't allow you to travel in the time dimension?
Order of Kilopi
The problem that I have with travel to the future involves the fact that I don't like the idea of destiny.
My problem with travelling to the past, is that a lot of people like to make it a "reverse destiny" - as if there's no real way you can alter things there because something stops you somehow.
Maybe mathemeticians and physicists really can predict that we can go into the past or the future in a reasonable way. Heck, in my science fiction story ideas, I investigate my own imagination of time/dimensional travel (though in a fictional sence). Still, a lot of times, the ideas by theoretical physicists can be misinterpreted and misrepresented, and I'm VERY skeptical in general when it comes to time travel.
Order of Kilopi
Yes, by a strong G field, for instance. Many people (me, me and me) believe that gravitational mirrors are possible, exactly like gravitational lenses.
Established Member
This morning I had Cheerios for breakfast. I made the decision to eat the Cheerios. Tomorrow when I wake up I will make a choice about what I will eat for breakfast. What will it be? It is my choice. Is it any less of a choice because it was made in the past rather than the future? Regardless of when I make a decision it is still *my* choice. It doesn't matter when it was made, or even if it is changable.
Order of Kilopi
I invented a commercially practical time machine, but my first customer turned out to have a prior patent.
Order of Kilopi
Same HERE!!!
Turned Out, To Be, My Future Self!!!!
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