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Oddities of science and time-travel - Synchronicity swirls and other foolishness

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November 7th, 2008


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10:29 pm - Oddities of science and time-travel
This article about a physicist interested in time-travel is fascinating and cool (here's an article going a (tiny) bit more into the science). I've run into the idea of a time machine only being able to send things back to when it was first turned on, and this idea likely comes from Dr. Mallett's earlier work. In any case, I wish him luck, since even this sort of time travel would definitely make the world a far more interesting place. I'm also once again deeply amused at the primary objection to time travel by physicists who don't accept it as being possible ultimately comes down to aesthetics. I happen to like the sort of messy and complex universe that the existence of retrocausality would produce. Of course, this makes much sense given my general philosophical and cosmological outlook.

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Comments:


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From:mindstalk
Date:November 8th, 2008 06:55 am (UTC)
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Huh, seems not as crackpotted as I'd assumed from rumors. Sounds like there's at least an interesting if suprisingly expensive experiment. (Well, surprising given the initial description of just some lasers and a neutron... I guess manipulating a single neutron is pretty hard. Anyway.) Could be interesting even if it fails, which I expect it will, because I'm skeptical of free lunches plus this sounds like a case where quantum could step in to modify relativity. But finding a experiment where quantum and relativity measurably interact would be worth a Nobel by itself.

Also your retrocausality link is broken.
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From:heron61
Date:November 8th, 2008 11:07 am (UTC)
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But finding a experiment where quantum and relativity measurably interact would be worth a Nobel by itself.

Indeed. I'd be exceptionally pleased if this idea worked, but suspect that our universe isn't quite that interesting. However, I expect something useful or informative might happen if it was tried.
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From:mindstalk
Date:November 8th, 2008 03:59 pm (UTC)
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Oh, forgot something. The idea that a time machine only works back to the point of its own creation is familiar to me as well, from Tipler Time Cylinders. I suspect it's a basic idea, easily re-discoverable.
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From:heron61
Date:November 8th, 2008 07:25 pm (UTC)
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Ah, I never knew that those were supposed to work that way too.
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From:heron61
Date:November 8th, 2008 07:29 pm (UTC)
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As a side note, the initial experiment would be very odd, essentially you'd turn it on and see if a neutron mysteriously appears. Then, of course there's the question of what happens if you decide to not send one back...
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From:mindstalk
Date:November 8th, 2008 08:18 pm (UTC)
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I was wondering how they were going to tell if a neutron went back in time.
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From:aekiy
Date:November 9th, 2008 01:04 am (UTC)
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They can record the reception time and the transmission time, and see if the former shows as being a fraction of a second prior to the latter. The same is true of Cramer's experiment.
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From:spoonless
Date:November 9th, 2008 09:02 am (UTC)
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But finding a experiment where quantum and relativity measurably interact would be worth a Nobel by itself.

Any experiment involving photons requires both quantum mechanics and relativity to explain (at least, special relativity).

Richard Feynman and others got the Nobel Prize for unifying quantum mechanics with relativity to form what's now known as "quantum field theory" (or for the specific case of photons "quantum electrodynamics", or QED). It's necessary to describe any sort of particle physics that's done in the lab today.
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From:mindstalk
Date:November 9th, 2008 09:06 am (UTC)
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Yeah, but time travel via spacetime warping involves general relativity, which has been the hard nut to reconcile with quantum, or to measure together.
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From:spoonless
Date:November 9th, 2008 10:30 am (UTC)
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True.

I guess I'm used to the word "relativity" by itself meaning "special relativity" unless there is a "general" before it. That's usually the convention.

But no experiment you could do with lasers in a lab could possibly have anything to do with general relativity, because you don't have nearly enough energy density around to warp spacetime by a noticeable amount. That's one of the really basic problems with what this guy is claiming.
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From:aekiy
Date:November 8th, 2008 09:03 am (UTC)
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Oh, ya! So Mallett is his name. I was aware of his ideas, but not who he was. I'm more aware of John Cramer, who's daughter's blog I follow. I got that retrocausality article rolling after reading an article about him, I think, in New Scientist a couple years ago. (Someone actually started the article itself a couple days after I'd noticed it wasn't there; it was just garbage, though, so I turned it into a stub.)

Both their experiments involve light and lasers, though they're grounded in different principles. Cramer's has more to do with quantum mechanics and is grounded in the notion that quantum entanglement may actually be the result of particles emitting energy both forward and backward in time simultaneously. (I think of it more as simply emitting energy in all directions, including any and all temporal directions, but "back and forward" simplifies the concept to fit with the common linear view of time.)

Edited at 2008-11-08 09:04 am (UTC)
From:jake_richmond
Date:November 8th, 2008 05:05 pm (UTC)
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awesome. Thanks.
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From:b00jum
Date:November 8th, 2008 06:12 pm (UTC)
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If you haven't - see the movie Primer. It starts to make sense after the 3rd or 4th time you see it, but its well worth the time.
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From:heron61
Date:November 8th, 2008 07:23 pm (UTC)
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I have indeed seen it, it's fascinating, if also not the easiest movie to figure out (to say the least).
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From:b00jum
Date:November 8th, 2008 07:30 pm (UTC)
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That is what I love about this film, the 'solution' is not given to you on a platter like so many movies. Its great when you start to figure out which time layer you're viewing.
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From:spoonless
Date:November 9th, 2008 08:52 am (UTC)
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These guys have an explanation of why his idea has nothing to do with reality:
http://arxiv.org/abs/gr-qc/0410078

Basically, he starts with a fictitious spacetime, that is different from the one we live in, then adds a circulating beam of light, and gets closed timelike curves (things that allow retrocausality). You would never get something like that by starting out with the real spacetime that we live in. And even if you could, it would take a laser far more powerful than anything on earth... as well as an infinitely long cylinder (which is what he uses to do it). For some reason, he ignores all of this when he talks to the press... hmmm.

It's usually a good tipoff that someone is a crackpot when he has to resort to getting funding from people who get excited about crackpot ideas but know nothing about physics... rather than convincing the government, or other scientists to fund it based on the actual merits of his ideas:

http://www.phys.uconn.edu/~mallett/main/funding.htm

Stephen Hawking has already proven that you can't do what he's claiming to do, unless you had a strange form of "exotic matter" that is not known to exist.

John Cramer is probably more of an idiot overall, but neither of them will ever contribute anything important to science.

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