I have a headache.
TIME TRAVEL TEST finds black holes needed to make photons flit
University of Queensland researchers have doubled-down on the question of whether quantum mechanics can exhibit “time travel” behaviours, producing a simulation of time travel using a single photon following a “closed timelike curve” (CTC). No, it's not actually time travel. Rather, the UQ work is looking at what we can …
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Tuesday 24th June 2014 07:09 GMT dan1980
Re: So that's how Heisenberg compensators work
@Richard 12
"Or rather, anything we teleport becomes spaghetti, just don't tell the test subject..."
REALLY? That would be awesome. It'd certainly give those hokey as-seen-on-tv wonder gadgets a run.
Imagine - anytime you want spaghetti you just generate a quick CTC and BAM: delicious pasta!
The potential relativistic side-effects could be a bit of an inconvenience but then time moves oddly in my kitchen anyway - especially when baking and roasting or following any recipe that says it will only take '15 minutes'. Even 2-minute noodles take 4 minutes in my house.
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Tuesday 24th June 2014 08:05 GMT Chris Miller
If you accept multiverse interpretations of quantum physics
... the grandfather paradox goes away. You can (if you can reach the environment of a rapidly rotating black hole) travel back in time, but you will be in a different instantiation of the quantum state, one in which your grandfather is killed and so the original 'you' won't exist.
Simples?
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Tuesday 24th June 2014 13:59 GMT Chris Miller
@Grikath
If we're considering a super-massive (galactic) black hole, of up to a few billion solar masses, the tidal effects of approaching the event horizon aren't all that great. Since they follow an inverse cube law (essentially because tidal effects are the result of the rate of change in the gravitational field) and the event horizon is several AUs in size, you don't have to worry about spaghettification. There are a few other minor practical concerns, however ...
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Tuesday 24th June 2014 15:06 GMT breakfast
Re: If you accept multiverse interpretations of quantum physics
If you accept a strictly deterministic single timeline where the future and past are equally fixed as each other then the grandfather paradox also evaporates - the evidence that you can't kill your grandfather is that your grandfather did not die. Or at least he wasn't murdered by a time traveller before he could beget your parent. If you were able to travel into the past, your actions would be a matter of record.
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Wednesday 25th June 2014 11:55 GMT Austhinker
Re:grandfather paradox
Or he wasn't your grandfather! This idea was used in a Futurama episode - memory's a bit fuzzy on some details, but Fry's purported ancestor (grandfather?) dies and Fry fathers the next ancestor in line.
I don't think the entire timeline has to be strictly deterministic - only parts related to the time travel. The past is fully determined, and once a time traveller has travelled back from the future his past is part of the past, and thus deterministic to people in the present.
You can't go back and kill someone at a time when they weren't killed, but you could put a winning lottery ticket in a drawer and not open the drawer again until after travelling back to the future. In short you can theoretically make any change that there's no proof didn't happen.
Since historical records aren't always true, time travellers could even go back and do things history says didn't happen, although trying to do this deliberately is 1) most likely pointless as history will still say it didn't happen, and 2) asking for trouble as the most likely way for history to say it didn't happen is if it didn't happen, perhaps because something happened to the time traveller on his (or her) way to do the deed.
EDIT: Shucks! I should have gotten a headache tablet manufacturer to sponsor this post! :-)
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Tuesday 24th June 2014 08:38 GMT stucs201
CTCs and Virtual Particles.
Something I've wondered for a while, but never properly looked into the maths of:
Does a virtual particle/anti-particle pair forming and then anihilating look any different to a single particle on a (very short) CTC? If they are equivalent then does this mean that the virtual particle theory might not be right and time travel might be taking place all around us on a quantum scale?
If there is an equivalence then what are the implications for Hawking radiation from black holes if the CTC model is the correct one?
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Tuesday 24th June 2014 08:49 GMT Len Goddard
Singularity (information style)
With a CTC capable of transmitting photons, you could use the result of a computer operation as its own input. Any recursive algorithm could then be executed in essentially zero time.
Charles Stross used this as the basis of his weakly godlike AI (the Eschaton) in Singularity Sky/Iron Sun. Unfortunately without access to the technology he backed himself into a logical corner from whence he cannot continue the story without introducing inconsistencies. Pity, because those books cry out for a sequel.
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Tuesday 24th June 2014 22:17 GMT Destroy All Monsters
CTC imply NP problems solvable in polynomial time
That would be called bootstrapping.
Scoot Aaronson: PHYS771 Lecture 19: Time Travel
"The Timehack Funding Bill is passed. The system goes on-line August 4th, 2017. Timehack Control begins to experiment at a geometric rate. It manages to create a closed timelike curve at 2:14 a.m. Eastern time, August 29th, or a few seconds earlier depending on your point of view. In a panic, they try to pull the plug. Too late. Minds of the the Aperture Science research team are taken over in 5.1 seconds. The rest of the connected world follows soon after. Only techno-refuseniks, hippies and stuckists survive."
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Wednesday 25th June 2014 08:44 GMT Faye Kane, homeless brain
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So you publish an article with "TIME TRAVEL TEST" in caps, but there's no time travel and no test of anything. It's just the same speculative sci-fi BULL sh it about closed timelike curves I've read about for decades.
This isn't the droids I'm looking for.
-faye kane ♀ girl brain
Sexiest astrophysicist you'll ever see naked
Google me. Google me HARD.
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Wednesday 25th June 2014 11:58 GMT Stoneshop
Uncertainty
and Heisenberg's uncertainty theorem, except this poor hack doesn't quite understand why – can all break down
This is clearly related to Heisenberg's Uncertainty Principle of Broken Things: one can not simultaneously know the way something is broken, and what is needed to fix it (both in parts and labour).