You were criticizing general relativity, not string theory

Post #251,406 by ben_tilly 4/8/06 12:21:14 PM Reply	You were criticizing general relativity, not string theory It is GR that predicts that one can travel backwards in time. Not string theory. It is just that this is a consequence of GR that we can't test. (Just like we can't really tell that the stars are light years away. Admittedly we have better tests of that than GR, but the principle is the same.) I agree that this article was overstated. However the project is truly fascinating in its own right. Part of the problem with unifying GR and QM is that it is extremely hard to produce experiments that show effects due to GR at a level where QM comes into play. I know of a handful that mixed gravity and QM, but none tested gravitational effects that require full GR. Let alone one where the gravitational effects are being produced by subatomic particles. It sounds like he has come up with exactly that. If it works, this is Nobel prize material. Incidentally if one just wants a subatomic particle travelling backwards in time, that is blase. According to QM, a positron is an electron travelling backwards in time. Nothing more, nothing less. :-) Cheers, Ben I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
Post #251,407 by Another Scott 4/8/06 12:50:08 PM Reply	We have measured the distance to over 8000 stars: Parallax. [link\|http://www.bpccs.com/lcas/Articles/telehist.htm\|Lake County Astronomical Society]: The development of large refractors came to an abrupt end with Yerkes [site of the 40" refractor telescope - still the world's largest]. But not all the telescopes of the past have been relegated to serving as museum pieces. Some are still used for important research work where image quality is especially important. In studies of the cosmic distance scale, traditional measurements of the distances to stars are unreliable beyond 100 light years. Trigonometric parallax is the most precise method of measurement, and the rest of the distance scale is built off it. At this scale, angles are very difficult to measure, so the Allegheny Observatory 30-inch Thaw refractor has been fitted with equipment for multichannel astrometric photometry in order to measure parallax to an unprecedented accuracy of 1 milliarcsecond. The Yerkes 40-inch has done spectroscopic work and photometry, which is the direct measurement of photons to create intensity traces that are used to measure star magnitudes precisely to 0.01 magnitude. The 40-inch has also re-photographed stars that were originally photographed around 1910 to see how much they have moved in the intervening years. By using the same telescope over a long span of years, the image scale remains the same so that the positions of stars can be measured with significantly higher precision. Emphasis added. A good summary on the advancement of precision in measuring the distance to stars over time is [link\|http://msc.caltech.edu/workshop/2005/presentations/McAlister.pdf\|here] (47 page .pdf). See slides 9 and 10 for the basics. The distance falls out of geometry (to get the angle) and Newton's laws (to get the diameter of Earth's orbit). Over 8000 stars have had their parallax measured (as of 1995). Cheers, Scott.
Post #251,411 by ben_tilly 4/8/06 3:03:09 PM Reply	But only indirectly We've never been there. Absurdly speaking, there could be a big hologram just outside the Oort cloud, and we wouldn't know. More realistically, in deep space light could propagate by different rules than it does here. Therefore our conclusions are based on chains of hypotheses, only some of which we can test. True, the alternate options seem so absurd that no reasonable person would argue for them. (Which is exactly why I used that example.) However our current theory requires us to believe that the rules we've measured in our incredibly small corner of the universe work in a much larger volume. Who knows [link\|http://en.wikipedia.org/wiki/Pioneer_anomaly\|what] unpredicted effects are out there? Cheers, Ben PS Actual parallax calculations are more complex than that paragraph indicates. The biggest confounding factor is stellar aberration, which happens because the motion of the Earth causes light to appear to be coming from an angle. In the same way that raindrops falling straight down do not appear to be falling straight down if you are in a car. I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
Post #251,412 by drewk 4/8/06 3:45:44 PM Reply	Show me where I did that? All the theories I've seen for time travel ... General Relativity is not a theory of time travel. It is a theory of the relationship among time, space, matter and energy. It is an attempt to describe a physical law. Time travel is a hypothetical activity that (some people hope) could be based on that law. The exciting thing about this experiment ... Again, not addressing GR, but addressing this experiment. Right now there are descriptions of experiments ... Addressing experiments or proposed experiments. ... the article talked about "travelling through time". Addressing what the article said. I've been consistently saying that the experiment as described doesn't actually present a way to show what the article says it will show. It appears, at most, to be a way to demonstrate on a small scale that time progresses more slowly in the vicinity of a high-velocity beam. This is IMO nowhere close to "Time Travel This Century". === Purveyor of Doc Hope's [link\|http://DocHope.com\|fresh-baked dog biscuits and pet treats]. [link\|http://DocHope.com\|http://DocHope.com]
Post #251,416 by ben_tilly 4/8/06 5:59:22 PM Reply	OK... Right around [link\|http://z.iwethey.org/forums/render/content/show?contentid=251317\|here]. General Relativity predicts that one can set up configurations which will result in backwards time travel happening. The underlying theory is testable. (In fact specific effects involved, like frame dragging, are being tested.) The physical requirements are calculable. They are just..impractical. That doesn't make the process of doing those calculations into religion. It is science. Theoretical science, sure. But no different in principle than, say, attempting to calculate what sets of atomic reactions will go on in stars, and therefore calculate the predicted proportions of various elements in the universe. (Did you know that this is how Fred Hoyle made his reputation?) Or attempting to calculate the amount of mass it would take to have self-gravitation cause atoms to collapse. The answer for a white dwarf, incidentally, is about 1.4 solar masses and figuring out this number made Subrahmanyan Chandrasekhar's reputation. Hoyle's figures are testable, and since the theoretical proportions of elements (and isotopes of elements) match his theory, we're pretty sure that we know what happens inside of stars. Chandrasekhar's Limit is not testable by any science we're likely to have in the foreseeable future, but it is critical for our understanding of stellar evolution. The contrast with string theory is that string theory is a family of theories that have been put forth, none of which have ever produced a tested prediction, none of which have produced a prediction that anyone is seriously thinking of trying to test, and the only criteria for exploring the subject is the aesthetics of the theory. That is religion. Cheers, Ben I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
Post #251,418 by drewk 4/8/06 7:00:03 PM Reply	Like I said, we just set the bar at different levels You say there are experiments. They're just impractical to perform. ID proponents could say the same about offering to sacrifice your son, to see if God comes down to stop you. When someone comes up with a practical (for suitably loose values of "practical") experiment to prove or disprove the theory that you can travel backwards in time, then I'll call it science. Until then, any statement stronger than, "The rest of the math suggests that this might happen," is IMO religion. === Purveyor of Doc Hope's [link\|http://DocHope.com\|fresh-baked dog biscuits and pet treats]. [link\|http://DocHope.com\|http://DocHope.com]
Post #251,420 by ben_tilly 4/8/06 11:08:06 PM Reply	Yet you believe that stars are lighted by fusion and... they are light years away. Yet those statements rest on beliefs that cannot be subjected to experiment. What makes one science, and the other not science? Cheers, Ben PS Note that science is not the accumulation of facts. It is the accumulation of theories about the universe which are generated and tested in a particular way. Very frequently science leads to lots of wrong statements. That they are wrong doesn't make them not science - it is the process that matters. I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
Post #251,443 by drewk 4/9/06 11:54:54 AM Reply	Now you're telling me what I believe? Yup, you sound just like a fundamentalist. Look, you've spent a lot more time reading the "sacred texts" of science then I have. You believe some things that I find a bit far-fetched. You believe if I only spent enough time reading the same books you have, I would believe the same things you do. Think about who usually talks like that. But yes, I do believe stars are lighted by fusion. We can do fusion experiments. We can produce things that look pretty much like what the sun does. We know that the sun, from the distance of some of our probes, looks just like other stars. So there's nothing really stretching plausibility. But travelling backwards in time is one of those extrordinary claims that is going to require some extrordinary evidence. We can't do anything like that. And it seems too intuitively implausible for me to accept it without some evidence. I'm not saying it won't someday be demonstrated. I'm saying that just because the math suggests that it should be possible is not nearly enough for me to think it's likely. === Purveyor of Doc Hope's [link\|http://DocHope.com\|fresh-baked dog biscuits and pet treats]. [link\|http://DocHope.com\|http://DocHope.com]
Post #251,446 by ben_tilly 4/9/06 2:33:05 PM Reply	And I was right, too! I said that you believed it, and in point of fact, you do! Shall we call it coincidence? However when it came time to stating my beliefs, you mangled it. Pretty badly. Sorry. I don't believe that we have a way of travelling backwards in time if we can just build it. I do have the following beliefs though: There is a theory that predicts that we can travel backwards in time. That theory is scientific. In the long run, science tends to wind up with accurate statements. Science is often wrong. Science is often spectacularly right. It is possible that science is right in predicting that travel backwards in time should be possible. Which is why I replied to [link\|http://z.iwethey.org/forums/render/content/show?contentid=251205\|http://z.iwethey.org...?contentid=251205] and pointed out that there is a theory that you've seen which allows backwards time travel. And in point of fact this is true. You claimed that theory was religion. I disagree that the theory is religion. I'm not saying that the theory is true, just that it is not religion. As for whether I'm a fundamentalist, I highly doubt it. Were I a fundamentalist, I doubt I would spend as much energy as I do carefully drawing shades of gray. Cheers, Ben I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
Post #251,448 by drewk 4/9/06 3:39:14 PM Reply	I'll simplify Do you believe, as Mallett predicts, that we will have "human time travel this century"? If you do, that's religion. If you don't, you're disagreeing with the position you'd like me to have, not the one I actually stated. === Purveyor of Doc Hope's [link\|http://DocHope.com\|fresh-baked dog biscuits and pet treats]. [link\|http://DocHope.com\|http://DocHope.com]
Post #251,450 by ben_tilly 4/9/06 3:48:23 PM Reply	I'll complexify Where in our discussion did "this century" ever show up as a qualifier? In fact where was there a qualifier in our discussion saying that "likely human time travel" was what was under discussion? Nowhere until you just said it. Again, in [link\|http://z.iwethey.org/forums/render/content/show?contentid=251205\|http://z.iwethey.org...?contentid=251205] you said that all theories for time travel that you've seen are ways to go to the future. My point was, and still is, that there is a theory for time travel that allows travel to the past. I've never claimed that time travel in either direction (other than the prosaic means of just living) was going to happen or be feasible within any given time frame. In short I'm disagreeing with the position that you actually stated, and not the position that you likely have. Cheers, Ben PS To bring this full circle, I felt at the start that you'd probably stated a position that was somewhat different from the one that you have. Which is why in [link\|http://z.iwethey.org/forums/render/content/show?contentid=251313\|http://z.iwethey.org...?contentid=251313] I made the comment about People Who Know This Stuff But Weren't Paying Close Attention 101. I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
Post #251,451 by drewk 4/9/06 4:00:01 PM Reply	I'll simplify some more READ THE FUCKING ARTICLE! You know, the one at the top of this thread. The one with a headline of Professor Predicts Human Time Travel This Century Did you see it? Good. Now, given that my first post -- the first content in this thread that wasn't a quote from that article -- was in reference to and in the context of that statement; and given that my first response to you was to refer you back to that article; do you finally see why I'm not the one missing the point? === Purveyor of Doc Hope's [link\|http://DocHope.com\|fresh-baked dog biscuits and pet treats]. [link\|http://DocHope.com\|http://DocHope.com]
Post #251,462 by boxley 4/9/06 6:28:40 PM Reply	I have to read the article to disagree with you? why? Any opinions expressed by me are mine alone, posted from my home computer, on my own time as a free american and do not reflect the opinions of any person or company that I have had professional relations with in the past 50 years. meep
Post #251,464 by drewk 4/9/06 6:39:44 PM Reply	The specific disagreement he made, yes When I say, "The position put forth in the article is bogus," to say that I'm wrong it would help to know what it is the article says. === Purveyor of Doc Hope's [link\|http://DocHope.com\|fresh-baked dog biscuits and pet treats]. [link\|http://DocHope.com\|http://DocHope.com]
Post #251,465 by broomberg 4/9/06 6:49:21 PM Reply	But.... If a time traveler from the distant future travels to the timeframe specified within the article, wouldn't that satisfy the prediction?
Post #251,466 by drewk 4/9/06 7:04:46 PM Reply	That'll work, but kind of hard to perform that experiment === Purveyor of Doc Hope's [link\|http://DocHope.com\|fresh-baked dog biscuits and pet treats]. [link\|http://DocHope.com\|http://DocHope.com]
Post #251,471 by Another Scott 4/9/06 8:01:19 PM Reply	It's been done. [link\|http://www.msnbc.msn.com/id/12208638/\|MSNBC] via [link\|http://www.theinquirer.net/\|The Inquirer]: Chiropractor claims to travel through time Updated: 4:16 p.m. ET April 7, 2006 COLUMBUS, Ohio - A chiropractor who claims he can treat anyone by reaching back in time to when an injury occurred has attracted the attention of state regulators. The Ohio State Chiropractic Board, in a notice of hearing, has accused James Burda of Athens of being "unable to practice chiropractic according to acceptable and prevailing standards of care due to mental illness, specifically, Delusional Disorder, Grandiose Type." Burda denied that he is mentally ill. He said he possesses a skill he discovered by accident while driving six years ago. [...] Cheers, Scott.
Post #251,484 by ben_tilly 4/10/06 12:03:10 AM Reply	This is getting silly Drew, I read the article. I understand it. And I agree with your current criticism. However your current criticism has nothing to do with your initial comments. And my reaction to your original comments still stands. We could go through a bunch more rounds of this, with your trying to yell louder and louder, and me pointing out that what you're yelling about has nothing to do with the start of our conversation. But I'll make this the last round because I see no point in continuing to repeat myself. So go ahead. Yell again. Call me names. Whatever you like. The last word is yours. Cheers, Ben I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
Post #251,494 by Ashton 4/10/06 5:49:36 AM Reply	Still, in Bertie's words - (Russell) Mathematics may be defined as the subject in which we never know what we are talking about, nor whether what we are saying is true. (That is - too - when speaking of 'the arrow of time' etc. etc. via means of mathematical manipulations of formulae ... such exercises probably are covered in that blanket statement: which neatly slips in the Biggest bugaboo of all (?) an idea of the true. The whole topic IMO is squarely akin to all published essays on 'causality' - ie you/theProf are in metaphysics territory; love it or leave it. ;-) :-\ufffd

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