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Double Pulsar Discovered

Posted by michael on from the double-your-pleasure dept.

jabberjaw writes "Nature is reporting that a set of two pulsars could be emitting gravitational waves. Einstein predicted the existence of gravitational waves in his general theory of relativity, but a gravitational wave has yet to be detected. Find out more about gravitational waves and pulsars at Eric Weisstein's World of Physics."

11 of 293 comments (clear)

  1. Speed of Gravity by fejikso · · Score: 5, Interesting

    Does someone know if these waves travel at the speed of light? Of course, as predicted by the theory.

    I suppose so... otherwise we could eventually devise faster-than-light communications, and I don't think the Universe is that nice :)

    1. Re:Speed of Gravity by UPAAntilles · · Score: 5, Insightful

      The answer is a resounding...we dunno!

      We have determined that it is at least 2x10^8 m/s, however, it may be as much as 3.6x10^8 (faster than light). We honestly don't know. I'm pretty sure I heard my quantum mecanics professor at the University of Arizona mention something about Einstein's theories requiring light and gravity to equal in speed, but I'm an aerospace engineer, not a quantum physicist. If they do equal...if the sun were to disappear, we would see the light of the sun and still be fine orbit wise for about 8 minutes. Kinda funny to think about.

      As for the faster-than-light communications, we could do that with tangled photons. Einstein was troubled by the fact that quantum entanglment causes an instantaneous change across a large distance. It's been used in a large number of sci-fi novels, including Orson Scott Cards Ender's Game series of books.

    2. Re:Speed of Gravity by DigiShaman · · Score: 5, Interesting

      This was discussed in a NOVA special about String Theory in The Elegant Universe. You can watch all three hours of the program online for free. I think the part about the speed of gravity (as to if it's effect are instant or at the speed of light) are in the first hour of the program. Check it out here

      http://www.pbs.org/wgbh/nova/elegant/program.htm l

      --
      Life is not for the lazy.
    3. Re:Speed of Gravity by sahrss · · Score: 5, Informative

      You can also download the entire thing if you like. I just spent 15 minutes digging all this up, figured I might save someone else that time.
      Some previous Slashdotters showed us how (first link is to the highest quality download).

      I got it to work fine with this (remove the spaces!):
      curl "http://a768.g.akamai.net/5/768/142/3f9e9589/1a1a1 afb6ae049ae214fc034aad839a91985ea187bea5786f362d84 1a61948bf2688f01f87fb6fdf0e7ceb61c22186fb/nova_eu_ 30[12-14]c[01-08]_mp4_300.mov" -o universe#1_#2.mov

    4. Re:Speed of Gravity by TexVex · · Score: 5, Informative

      When calculating the orbits of celestial bodies, it is necessary to assume that gravity is instantaneous. When an object moves, its gravity appears to move with it instantly. The earth appears to orbit the Sun's present position rather than where the sun appears to be due to speed-of-light delay.

      As I understand it, though, there are two ways to look at it. The Earth is approximately 8 light-minutes from the Sun. The Earth is either orbiting the Sun's actual position, or it's orbiting a point that would be about eight minutes in front of the Sun's extrapolated path based on its position and momentum at that given instant.

      It comes down to a question of whether or not gravity is a field or a particle. If it's a particle, then it must travel at some unimaginable speed. If it's a field then it would share some of the properties (like velocity and direction) of the object that generates it, and changes to the field would propagate outward from the object at the speed of light. These changes to an object's field of gravity are thought to produce "gravity waves" that have yet to be detected.

      I could very well be muddled on this subject but I have done some reading on it. Please correct me if I'm wrong.

      --
      Fun with Anagarams! LADS HOST, SHALT DOS. HAS DOLTS. AD SLOTHS, HATS SOLD. ASS HO, LTD.
  2. Question for a physicist by MillionthMonkey · · Score: 5, Funny

    I wonder how many times these two neutron stars could bounce if they were to hit the water at an angle of 20 degrees.

  3. Yes by rebelcool · · Score: 5, Informative

    Article

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  4. Actually not yet, but... by UPAAntilles · · Score: 5, Informative

    Here's a cool kid's site that has some animations

    It's for the LISA (Laser Interferometer Space Antenna). Space.com did a story on it a little while back, and it was in a Scientific American, but I'm not sure which, I have too many lying around. Unfortunantly, it doesn't launch until 2009.

  5. Nobel prize for pulsar discovery by etymxris · · Score: 5, Interesting

    Anybody know why Jocelyn Bell received no credit for actually discovering pulsars, yet her thesis advisor, who actually seemed to do nothing, did?

  6. Maybe Not. by Anonymous Coward · · Score: 5, Interesting

    Article 1, Article 2.

    Some scientists that have inspected the calculations believe the experiment is flawed and that they instead measured the speed of light itself (ie: they probably measured the speed of the light they were using to make their observations with, not the speed of the Jupiter distortion).

    Correct answer: The speed of gravity is not (yet) a scientifically proved and universally accepted fact. Saying anything else is bad science.

  7. Re:detecting gravitational waves? by rokzy · · Score: 5, Funny

    I hate it when physics topics come up on slashdot, there are always annoying people like you who know a few words but don't really have a clue.

    you're the science equivalent of the guy who says his OS is AOL.