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Space Science

Cassini Experiment Confirms General Relativity 58

Posted by michael from the it's-all-relative dept.
MikeZilla writes "An experiment by Italian scientists using data from NASA's Cassini spacecraft, currently en route to Saturn, confirms Einstein's theory of general relativity with a precision that is 50 times greater than previous measurements."
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Cassini Experiment Confirms General Relativity More

Cassini Experiment Confirms General Relativity

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  • It seems that, according to scientific philosophy today (and I say this as an observer, not a scientist), you still can't really believe this is _the_ truth about something. You have to keep thinking, "it might _not_ be true". I hear how a hypothesis must be "falsifiable"--what does that mean? So if science is a search for truth, how can you find it? And how does this experiment matter? I mean, didn't people already believe that relativity was (mostly, apparently, seemingly) true?
    • Scientists know that there is always more. Once you find an answer to a question, you will open to the door to 3 more questions about something else. It is the way advances are made. You create a theory, which you test, and from those results you come up with more theories.

      With this particular test, they wanted to rerun test that have been run before to see if the results from the Viking Mission hold up with the more accurate equipment available now.

      Truth is only as good as the information you have. A
      • > You create a theory, which you test, and from those results you come up with more theories.

        You left off the first bit! You *first* observe. Theory did not come first! It came from observations, and wondering how the universe works.
        e.g.

        1. Observe (natural, or man-made expirements)
        2. Theorize
        3. Test
        repeat

        > Truth is only as good as the information you have.

        Physical truth, yes. Meta-physical truth, I disagree. But that is a discussion for another time.

        Truth doesn't change, but your perception and
        • Sorry, I forgot to observe my tiredness when writing this morning...

          Meta agree physical truth is waaaaaayyyyy OT for this story.

          I think of the truth as a blob, it may stretch and move and change shape, but it is still a blob. And on a perticular day, I might see it differently. So I agree with you again.

        • You left off the first bit! You *first* observe.

          No, you have to have a (possibly primitive) theory before you can "observe" anything. If you don't have a theory, you don't know what part of the world you are observing is relevant and what isn't. You need a theory to guide your observations, to filter out the signal from the noise. Karl Popper (aptly) talked about "searchlight theories" without which there can be no observation.

          JP

    • Another part of the problem is that once you find a truth, it is soon recognisable that it only holds true under certain circumstances. Bridging the gap between the large, where certain rules apply, and the small, where other rules apply, for example, is an awkward one. we know that a certain law holds true under x circumstances, and then along comes Y and the whole thing gets thrown out. So there either has to be a way to take up the slack ( a formulaic work-around of sorts), or a new description for what
    • "It seems that, according to scientific philosophy today (and I say this as an observer, not a scientist), you still can't really believe this is _the_ truth about something. You have to keep thinking, "it might _not_ be true"."

      I think basically that's right, it's just a matter of what theories we decide to keep testing to the limit to try to find any inconsistencies. For instance, when a new method of atomic mass spectroscopy is invented no one says 'hey I bet we could use this to test Dalton's [hypermart.net] theory of

    • Re:Help Me Here--some novice Questions (Score:1, Interesting)

      by Anonymous Coward
      There's a great quote answering your question in the article:

      "The question is not whether general relativity is true or false, but at which level of accuracy it ceases to describe gravity in a realistic way."

  • Cute, but (Score:5, Interesting)

    by CheshireCatCO ( 185193 ) on Saturday October 04, 2003 @12:17PM (#7132712) Homepage
    Nice measurement, no doubt. But the article is a bit misleading. This isn't the most precise measurement of GR, just the most precise mesurement of this prediction. It sounds like they got this measurement to an error of one part per fifty thousand. If memeory serves, the measurements of the orbit on pulsar 1933+16 (the one that netted Taylor and Hulse the Nobel Prize about a decade ago) are precise to one part in something lik ten to the eleventh. And they agree with GR.

    One some level it amazes me that GR passes every test we throw at it with such flying colors. On another level, I agree with Albert: the theory is too beautiful *not* to be true.
  • longer wavelength?

    Cassini's experiment

    The researchers measured how much the Sun's gravity bent an electromagnetic beam, in this case the radio signal transmitted by the spacecraft and received by the ground stations.

    1919 Eclipse

    Probably the most important eclipse in the history of science occurred on 29 May 1919. Just six months after the end of World War I, British astronomers used it to test a new idea that came from Germany in 1915. The proposition was that gravity affected light, space a

  • the usual misstatement (Score:3, Insightful)

    by penguin7of9 ( 697383 ) on Saturday October 04, 2003 @06:20PM (#7134473)
    It's misleading to say that this experiment "confirms" General Relativity. What it does is fail to falsify GR. That's nothing to sneeze at. But it tests such a small part of GR that one really can't say that it "confirms" GR. These kinds of delays are part of many alternative theories as well. If you say that this experiment "confirms" GR, then it also "confirms" many theories that otherwise wildly disagree with GR.
    • Yes, it falsifies Newtonian mechanics, which came before, though.

      I have a mate, who when we play 9-ball, if he racks the balls himself can _always_ pot the 9 on he break. I believe, or theorise, that he has a special way of racking up, and of breaking.

      Every time he does it, does it fail to falsify my beliefs, or does it confirm them. It takes a brave man to say it _only_ fails to falsify.

      So yup, it's just another data point to give a bit more confidence in theories that are previously held with reasonabl
      • That's why the other guy always racks for the guy who breaks!
      • Yes, it falsifies Newtonian mechanics, which came before, though.

        That is correct. But we already knew that Newtonian mechanics was wrong, both experimentally and because it is logically inconsistent.

        So yup, it's just another data point to give a bit more confidence in theories that are previously held with reasonable conviction anyway.

        Confidence compared to what? What alternative theories was this experiment designed to rule out? If you don't have any alternative theories, you don't gain any infor
        • """
          you don't gain any information from an experiment whose results agree with your theory
          """

          Taking that logic to the extreme no scientist need ever take more than one measurement.

          I was under the impression that you'd find scientists trying to reproduce their and other's results, but maybe the scientific world has become fat and lazy in recent years.

          YAW.

          • """you don't gain any information from an experiment whose results agree with your theory
            """

            Taking that logic to the extreme no scientist need ever take more than one measurement.

            You are quoting out of context. What I wrote was:

            If you don't have any alternative theories, you don't gain any information from an experiment whose results agree with your theory.

            Notice that there are two conditions: (1) you don't have an alternative theory (i.e. one that predicts a different outcome and hasn't already been

    • If you say that this experiment "confirms" GR, then it also "confirms" many theories that otherwise wildly disagree with GR.

      I would concur.

      The assumption is often that, since a particular mechanism was proposed along with a particular equation, that if the equation is right, the mechanism has to be.

      That simply doesn't have to be the case, any more than deriving an equation describing the falling activity of Slashdot threads would lend 100% credence to my hypothesis that the light from the Slashdot h

  • [snip] confirms Einstein's theory of general relativity [snip]

    Good to see the word "confirms" used as opposed to "proves".

    Remember, a theory can never be proved, only disproved/discounted.

  • So this didn't not un-de-falsify the "theory" of "relativity!"

    (This post has been rewritten to conform to the Slashdot Scientific Grammar Police Code.)

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