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Science

Speed of Gravity Experiment Challenged 63

Posted by michael from the dueling-banjos dept.
An anonymous reader writes "The previous hoopla over the discovery of the speed of gravity has an opponent from the Lawrence Berkeley National Laboratory. Read about the latest calculations."
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Speed of Gravity Experiment Challenged More

Speed of Gravity Experiment Challenged

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  • Gravity (Score:5, Funny)

    by ArmorFiend ( 151674 ) on Tuesday June 24, 2003 @02:09PM (#6286494) Homepage Journal
    Gravity: we all know it sucks, we just don't know how fast.

    • Re:Gravity (Score:1, Offtopic)

      by KDan ( 90353 )
      Scanning for not-so-astonishingly-bad-that-it-makes-you-want-to -kill-yourself-very-painfully-right-now-joke... scanning... still scanning. Nothing found, captain.

      ;-)

      Daniel
      • Vulcans don't have a sense of humour, this one would make mass suicide the only logical thing to do in a galaxy that produces such kind of joke (the parent and the grandparent posts, I mean)

        • Re:Luckily... (Score:3, Funny)

          by KDan ( 90353 )
          You wouldn't believe it, but I've been told a bad sense of humour is the most dangerous thing that can happen to a galaxy. Where do you think all those giant active galactic nuclei (which are in fact black holes) came from? They're all the result of astonishingly bad jokes being left out of check, causing the implosion of a galaxy. My invisible friend also mentioned that ours is due for a collapse any time soon, if the quality of posting here keeps on getting worse.

          Daniel

    • Re:Gravity (Score:3, Funny)

      by bobbozzo ( 622815 )
      But does it swallow?
      • But does it swallow?

        Depends on whether unladen [armory.com] or not. If unladen, it will be different for Africa and Europe.

        I sig therefore I am.

  • Repurcussions (Score:4, Interesting)

    by geek42 ( 592158 ) on Tuesday June 24, 2003 @04:09PM (#6287869)
    What do you suppose the repurcussions would be if it could be shown that gravity was instantaneous, rather than propagating at the speed of light? Could we use that to transmit information instantaneously? Would that violate causality?

    • Re:Repurcussions (Score:3, Insightful)

      by confused one ( 671304 )
      short answers: Ugly, no, yes.

      • How's that? (Score:3, Insightful)

        by JMZero ( 449047 )
        If gravity was instantaneous, how is it that we couldn't use it to transmit information? Surely it would be difficult in practice, but it seems pretty simple in theory.

        "When we're ready, I'll start moving this ball'o'mass towards and away from you."

        What's impossible? Moving the mass around, detecting the mass in motion, or detecting it instantaneously?
        • I'm with you on this one. Measuring and manipulating gravity are both easy enough - they're both just a matter of, well, matter! I think this conclusion, along with the agreement that instantaneously transmitting information would violate causality, is a pretty good hint that gravity must go at the speed of light (or slower - why not?!).

          Too bad it looks like the experiment was bunk... it'd be nice to know for sure. And what if it did go slower than the speed of light....? ;\

      • Re:Repurcussions (Score:4, Interesting)

        by shadowbearer ( 554144 ) on Wednesday June 25, 2003 @12:06AM (#6291448) Homepage Journal
        It's been shown (reference, help! :-) that no matter how fast the propogation medium, information propogation is still limited to c. I believe the latest was in the quantum experiments with electrons which were simultaneously created yet still "knew" what the others' state was.

        God, it's late, and I'm tired, someone help me out on this one? I know I've read it over and over :-( just don't remember the specifics.

        SB

        • Re:Repurcussions (Score:2, Informative)

          by masterkool ( 550633 )
          Quantum entanglement [stanford.edu] would be a possible way to have relativity hold true, yet allow superluminal information transport. Essentially, the states of two similar particles become, for a lack of a more definate word: "entangled" and changes made to one of the particles occurs instantaneously with the second.

          • Re:Repurcussions (Score:3, Interesting)

            by KDan ( 90353 )
            I'm sorry, but your post shows remarkable lack of understanding for what relativity means when it says "nothing can move faster than light". The movement of anything faster than light is mathematically equivalent to it moving backwards in time. That holds true for information as well.

            Do not try to understand this by imagining a universe with an absolute time frame. That is the very understandable mistake that led you to the above post in the first place. The point of relativity is that there is no such fr
            • Thank you, that was well put. I like your dice analogy, have to remember that one.

              As I understand it, the effective transmission bandwidth(and therefore the amount of info that can be exchanged / function of time) is constrained in some way by the speed of light.
              It's been a long time since I read it, and I don't really pretend to understand the math involved (although I do understand GR and SR from a conceptual viewpoint; higher calculus has never been my strongest subject :-).

              But I did remember the

        • It's been shown (reference, help! :-) that no matter how fast the propogation medium, information propogation is still limited to c. I believe the latest was in the quantum experiments with electrons which were simultaneously created yet still "knew" what the others' state was.

          IIRC they managed to created linked particles and by examining the signal log could tell which bits of the movement of the particle were the data but only after the fact, in other words they could not transmit data that way. In

          • More or less my understanding of it is that while the linked particle exchange happened more or less instantaneously, any data exchanged would have a an effective bandwidth (ok, amount of info / second) limited to a value determined to be under/at the speed of light. As I recall that was tied to GR theory.

            I may be wrong, tho, it's been a while since I read it.

            More stuff to reread. Sigh.

            SB
            • You are mixing things up, though. The bandwidth is not determined by the speed of light, the propagation time is. Now maybe the latency is related to some wavelength of light, and that's what you're thinking, or something else totally different...
              • There seems to be a lot of difference of opinion on this.

                See here [ernet.in]

                Quote:


                There are two conservative ways, and, third, a non-conservative way, to respond to EPR:

                accede that nonlocal superluminal influences are possible. This violates Einstein locality ("state vector collapse should occur instantaneously at all point in configuration space") but does not violate signal locality ("no usable signal can be communicated faster than light's speed").
                Another is that |Y> is not an intrinsic property of the qu
    • Ain't gonna happen. But if gravity was shown to be instantaneous, the repurcussions would be a whole lot of people going back to the drawing board. We could probably figure out some way to use that to transmit information instantaneously, and yes, that would certainly violate causality, which is ugly.

    • Re:Repurcussions (Score:2, Insightful)

      by Izago909 ( 637084 )
      What about quantum intertwining? Create 2 nanoscopic black holes at opposite ends of the earth. Then find ways to alter the âspinâ(TM) of one, and the other should instantly alter to match. There are all sorts of weird and spooky things that we know little or nothing about.

      Teleportation is simple, in theory. Just get 2 massive superconducting plates (a metal, for example) and place them very close together, just close enough that you can still walk between them. Then repeat at opposite end of t
      • Umm, where the hell did you pull that second paragraph out of? It seems like complete and utter nonsense. I don't see what superconducting plates have to do with teleportation (except in bad science fiction).

        Daniel
        • It's rather complex, but I was over-simplifying. So to make myself clearer, I will simplify some more. Keep in mind this is all being stated in a very analogous and rather unscientific way in order to demonstrate a currently unproven theory.

          If it were possible to look so deeply into space and matter, so far that you could not âoezoomâ in any further, it might resemble something like a bubbling liquid. Now, assume you could charge 2 separate planes (most any sort of matter), which are in near pr

          • Discover how to find the square root of a negative and I'll make sure you become the most famous person in human history.

            Imaginary numbers? That's the way to solve everything: When in doubt, make it up.

          • Well mate, I'm sorry to say, but I did a Masters in Physics and what you're saying still sounds like complete mumbo-jumbo. Maybe you want to go into a short mathematical explanation for me because I still don't get what you're saying. All you would get by charging two separate planes (assuming you charge them with opposite charges) that are very close together is a very steep E-field gradient, no matter the scale (if it gets too small and there isn't a perfect void in between you'll get a discharge, but tha
    • If that violated causality, we wouldn't have to take a piss after drinking too much wine... but that would cut off the opportunity to meet a nice blond who just had orgasm-dissert.
  • The time it takes to 'get' a joke.
  • Teacher:
    So as you can see, young Mr Kopeikin, the ability to measure gravity waves is dependant on your frame of reference. As Stuart (Look at what I can do) Samual points out, when you take into account the position of Jupiter and rotate your frame of reference, you cannot accurately measure the propigation effects of gravity with todays measurement instruments.

    Mr Kopeikin:

    Why do we have to learn this? We aren't really going to need this stuff outside school right? Like I'm really going to g

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