Back to the future - the movie

  • #26
JesseM
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Danger said:
While I'm somewhat familiar with the concept from the perspective of ring singularities, split event horizons, antimatter time-reversal invariance and whatnot
I was thinking of stable wormholes, held open by exotic matter--this is the most common scenario when discussing time travel in GR. Travelling through a ring singularity might take you some unknown region of spacetime, but there's no reason to think it would be your own past...time-reversal invariance has nothing to do with time travel (after all, Newtonian laws are time-reversible too), and I'm not familiar with the term "split event horizons". (a google search only turns up 19 hits, are you sure you have the term right?)
Danger said:
I don't believe that it will ever be technologically possible to transfer anything macroscopic into the past in any condition to affect causality. I'm not sure about that, of course, but it seems extremely unlikely to me.
But when you were talking about paradoxes and the impossibility of time travel, it seemed like you were using "impossible" in the sense of what's allowed by the laws of nature, not in terms of practical engineering issues. If something leads to a genuine paradox, it must be logically impossible, not just impossible in practice.
 
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  • #27
Danger
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JesseM said:
I was thinking of stable wormholes, held open by exotic matter
As I understand it, an impossible amount of negative energy, rather than exotic matter, would be required to maintain a wormhole.

JesseM said:
Travelling through a ring singularity might take you some unknown region of spacetime, but there's no reason to think it would be your own past
When I was informally trying to study up on this stuff almost 30 years ago, there was no mention of ring singularities. The split event horizon was at the time considered to be the consequence of excessive spin or charge on a black hole. It would essentially allow one to cross the event horizon, but miss the singularity to emerge in either a different time or a different region of space. The instantaneous travel to another place was also considered to be backward movement in time equal to the forward movement through space, so that you get there at the same time that you left. Since I never really got back into it, it's quite possible that the ring singularity is the replacement model for the split horizon.

JesseM said:
time-reversal invariance has nothing to do with time travel
I'm aware of that; I was actually using that example to support your case about travel being theoretically possible on the quantum level. Since particle interactions going forward are identical to antiparticle ones going backward with parity upheld either way, it might be argued that antimatter is in fact travelling backward in time. On the macroscopic level, of course, causality would cut in to screw it up.

JesseM said:
But when you were talking about paradoxes and the impossibility of time travel, it seemed like you were using "impossible" in the sense of what's allowed by the laws of nature, not in terms of practical engineering issues. If something leads to a genuine paradox, it must be logically impossible, not just impossible in practice.
That's not exactly what I meant, but pretty close. I don't believe that backward time travel of a macroscopic object can physically occur, regardless of how theoretically possible it might be.
I'm going to hold off on any more comment until Space Tiger or someone else weighs in. This is getting over my head. :redface:
 
  • #28
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Danger said:
As I understand it, an impossible amount of negative energy, rather than exotic matter, would be required to maintain a wormhole.
matter:energy::exotic matter:negative energy
 
  • #29
cronxeh
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Jesse/Danger

Why would you even want to transform matter over a wormhole? Its too far, not in your lifetime, etc.

If you would agree that consciousness is separate from your body, then it is weightless and capable of traveling through time. Nostradamus did it. And you can do it today with certain chemicals. Its highly debatable but people do it and have OOB experiences. Some end up spending a great chunk of time in some place they dont recognize having intelligent conversations with creatures that dont exist, while their bodies are like zombies and walking around the house on their own. Far fetched? I know it happens, because it happened to me.
 
  • #30
StatusX
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The only thing from back to the future that's even remotely accurate is that if you see your future-self in the future, the universe will collapse on itself. It's true, but no one knows why.
 
  • #31
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StatusX said:
The only thing from back to the future that's even remotely accurate is that if you see your future-self in the future, the universe will collapse on itself. It's true, but no one knows why.
I would have to disagree. We don't know enough to make any assumptions like that.
 
  • #32
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StatusX said:
The only thing from back to the future that's even remotely accurate is that if you see your future-self in the future, the universe will collapse on itself. It's true, but no one knows why.


That's a load of hogwash.

If a particle takes a four dimensional path (as all particles do) the only restrictions would be against faster than light travel (which amounts to travelling backwards in time) and having the path intersect itself (have a particle at the same time and place, twice, would violate the Pauli Exclusion Principle, so obviously I'm talking about fermions). So let's say a fermion went forward in time, and passed near its own path, the particle equivalent of seeing future-self in the future. What would possibly necessitate the collapse of the universe?

Unless you were joking, in which case :redface:
 
  • #33
JesseM
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StatusX said:
The only thing from back to the future that's even remotely accurate is that if you see your future-self in the future, the universe will collapse on itself. It's true, but no one knows why.
You're kidding, right?
 
  • #34
StatusX
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Well, that's the last time I try to be funny. Thanks everybody.
 
  • #35
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StatusX said:
Well, that's the last time I try to be funny. Thanks everybody.


As I said, in that case :redface:

I should add that my humour detector regularly malfunctions. Just ask tribdog and Danger.
 
  • #36
Janus
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StatusX said:
The only thing from back to the future that's even remotely accurate is that if you see your future-self in the future, the universe will collapse on itself. It's true, but no one knows why.

That's a worse case scenerio, the actual effect could be quite localized; limited to merely our own galaxy.
 
  • #37
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Plastic Photon said:
I love the dad and the son's laugh. Me and my dad use it all the time to annoy mom. 'Ah Ah Ah Ah Ah'.

My daughter does a laugh that starts as Captain Hook from "Hook", shifts to Ricky Ricardo and ends as George Mcfly.
 
  • #38
Danger
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cronxeh said:
If you would agree that consciousness is separate from your body, then it is weightless and capable of traveling through time. Nostradamus did it.
No offense, cronxeh, but I certainly don't agree with a separate mind. I'm an atheist, remember? And Nostrodamus has been so misinterpreted in order to make his 'predictions' valid that it's a total joke.

StatusX said:
if you see your future-self in the future, the universe will collapse on itself. It's true, but no one knows why.
Where the hell did you come up with that?

franznietzsche said:
I should add that my humour detector regularly malfunctions. Just ask tribdog and Danger.
That's true. Franz's sense of humour is like Richard Simmon's sense of 'macho'.

Janus said:
My daughter does a laugh that starts as Captain Hook from "Hook", shifts to Ricky Ricardo and ends as George Mcfly.
And you didn't drown her before her eyes were open? :bugeye:
 
  • #39
cronxeh
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Danger said:
No offense, cronxeh, but I certainly don't agree with a separate mind. I'm an atheist, remember? And Nostrodamus has been so misinterpreted in order to make his 'predictions' valid that it's a total joke.
Where the hell did you come up with that?
That's true. Franz's sense of humour is like Richard Simmon's sense of 'macho'.
And you didn't drown her before her eyes were open? :bugeye:

So you think consciousness has no value then? I wonder what is the point of living and wondering about the wormholes and in general "reaching out there" via various means if you didnt believe that there was more to life than what is offered by the seemingly obvious?
 
  • #40
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cronxeh said:
So you think consciousness has no value then? I wonder what is the point of living and wondering about the wormholes and in general "reaching out there" via various means if you didnt believe that there was more to life than what is offered by the seemingly obvious?


Its intellectual hedonism.
 
  • #41
cronxeh
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franznietzsche said:
Its intellectual hedonism.

Fair enough. Ignorance is bliss then, and Fox News is your #1 source for the refills.

I just wish there was an outlet of frustration with questions of infinite complexity that keep the rest of us up at night.
 
  • #42
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cronxeh said:
Fair enough. Ignorance is bliss then, and Fox News is your #1 source for the refills.
I just wish there was an outlet of frustration with questions of infinite complexity that keep the rest of us up at night.


Huh? Color me confused now. What are you talking about all of a sudden?

You ask why bother wondering about wormholes and the universe if one believes that there is no god, no soul, and when you're dead, you're really just worm food, right? And I answer Intellectual Hedonism. Knowledge, among other things, is pleasurable. So is problem solving. What can I say. I'm a freak.

So what are you going on about now?
 
  • #43
Danger
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cronxeh said:
So you think consciousness has no value then?
I have absolutely no idea how you could draw a conclusion like that. I'm quite fond of my conciousness, however much I might try to suppress it with beer.
And although I don't quite agree with Franz's assessment, it's not far off.

cronxeh said:
Fair enough. Ignorance is bliss then, and Fox News is your #1 source for the refills.
I just wish there was an outlet of frustration with questions of infinite complexity that keep the rest of us up at night.
Sorry, man, but ignorance is the thing that keeps the likes of Nostradomus out of the dungeon. I've never gotten cable until moving in with N/W a couple of months ago, so I've only seen Fox news once. Seems like typical Yank coverage, so I can't comment about how you folks view it.
And anyone who loses sleep over questions of 'infinite complexity' has issues of some sort that normal people don't worry about. I have infinite curiosity, but I'm certainly not going to lose sleep over what I don't know.
 
  • #44
Danger
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Franz's last post showed up while I was posting that last one of mine. Now that I've seen the elaboration of it, I agree.
 
  • #45
JesseM
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cronxeh said:
So you think consciousness has no value then? I wonder what is the point of living and wondering about the wormholes and in general "reaching out there" via various means if you didnt believe that there was more to life than what is offered by the seemingly obvious?
One needn't believe that consciousness has "no value" just because one doesn't believe in dualism. Suppose we were able to map out a person's brain at the synaptic level and simulate it on a computer, and that the simulated person behaved just like the original--same memories, same creative abilities, same sense of humor, same spirituality, same personality, same emotions, etc. This would pretty well demonstrate that dualism is wrong--would such an experiment cause you to become a nihilist?

Anyway, believing that all events have physical causes does not force you to believe consciousness is some kind of illusion--there's always naturalistic panpsychism, which says that all physical processes could have some sort of inner experience, but which also says that the relationships between mental events obey strict mathematical laws which we normally call the "laws of physics". I've always found this idea intriguing since, unlike dualism, it needn't conflict with any of the findings of modern science, it's more like a philosophical "reinterpretation" of the usual materialist view. See here for some more articles on the subject.
 
  • #46
Danger
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I've never heard of that before, Jesse. Thanks for the input. I'll check out your links tomorrow. N/W just went to bed, and I have a very distinct feeling that I'd better follow right away. (She's jealous of PF!)
Catch you tomorrow.
 
  • #47
Mk
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N/W? What's that?
 
  • #48
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Mk said:
N/W? What's that?


Stands for Not Wife
 

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