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Cassini Experiment Confirms General Relativity

Posted by michael on 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."

58 comments

  1. ANother FP for Cradle of Filth??? by Anonymous Coward · · Score: -1, Offtopic

    w00t!

    Thirteen Autumns and her Widow

    w00t

  2. Hmm by anthony_dipierro · · Score: 0

    Somehow I suspect they're using Einstein's equations to prove his predictions. From the article: "They precisely measured the change in the round-trip light time of the radio signal as it traveled close to the Sun." But round-trip time is not enough. You must also precisely measure the distance, and you can't measure that without using Einstein's equations.

    1. Re:Hmm by cryptor3 · · Score: 1

      I don't think that's necessarily a problem. What they're showing is that he is using a consistent model for how the universe works (which, as the article states later, is not exactly the issue; they're actually after more subtle questions).

    2. Re:Hmm by CheshireCatCO · · Score: 1

      Presumably they did measure the distance: you can get the round-trip signal when the path to Cassini is far from the Sun. That, along with the fact that Cassini is itself far from any significant gravitational source means that it's easy to know exactly where Cassini is right now. (In this limit, Newton and Einstein are pretty much identical. You can argue that this theory is incorrect, but that's a pretty difficult argument to make, given how often it has worked quite well.)

      So, no, they don't really need to use GR to get the distance.

    3. Re:Hmm by anthony_dipierro · · Score: 0

      Presumably they did measure the distance: you can get the round-trip signal when the path to Cassini is far from the Sun.

      But that's not the same distance as when it's near the sun. And you have to factor in the fact that both objects are in accelerated motion around the sun, which of course uses Einstein's equations.

      Obviously we're both merely speculating without seeing the actual calculations, though.

    4. Re:Hmm by Smallpond · · Score: 1

      Measuring the distance only requires you know the speed of light in a vacuum, which is fairly easy to measure. They were repeating Eddington's 1919 measurement of the deflection by a massive body. As Eddington wrote while developing the plates in Brazil:

      Oh leave the Wise our measures to collate
      One thing at least is certain, light has weight
      One thing is certain and the rest debate
      Light rays, when near the Sun, do not go straight.

    5. Re:Hmm by CheshireCatCO · · Score: 1

      Cassini is never near the Sun. The signal sometimes passes near the Sun, but Cassini never does.

      Cassini is on a well-measured orbit far from the Sun. As I said, in this limit, Newtonian gravity is all you need to get the trajectory. (Newton agrees with GR, and no one doubts the validity of either in this regime)

    6. Re:Hmm by anthony_dipierro · · Score: 0

      Cassini is never near the Sun. The signal sometimes passes near the Sun, but Cassini never does.

      Yeah yeah, that's what I meant :).

      Cassini is on a well-measured orbit far from the Sun.

      What means are used? The orbit isn't measured with rulers. It's measured by people living on an accelerated platform, the Earth.

      As I said, in this limit, Newtonian gravity is all you need to get the trajectory. (Newton agrees with GR, and no one doubts the validity of either in this regime)

      And in the limit there is no effect by the gravity of the sun. When we're talking about confirming something to "20 parts per million" this certainly needs to be factored in.

    7. Re:Hmm by Alsee · · Score: 1

      you have to factor in the fact that both objects are in accelerated motion around the sun, which of course uses Einstein's equations.

      Given suitable equipment, Issac Newton himself could calculate the precise, simple, and smooth ellipse of the orbit. There is no relativity involved in this step.

      As Cassini passes directly behind the sun there is a fairly rapid anomolous bump in the radio-measured distance. The apparent bump in distance is caused by the part of the path that passes very close to the sun.

      By measuring the bump they measure just the breif anomoly caused by relativity.

      -

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    8. Re:Hmm by anthony_dipierro · · Score: 1

      Given suitable equipment, Issac Newton himself could calculate the precise, simple, and smooth ellipse of the orbit.

      Sure, you can calculate the elipse of the orbit. But that's not the same as calulating the round-trip distance between two accelerated objects.

    9. Re:Hmm by Alsee · · Score: 1

      calulating the round-trip distance between two accelerated objects.

      (1) There is zero relativisic effect on the probe at these low speeds and at the probe's distance from the sun. The probe's path is purely classical.

      (2) There is no need to calculate the actual distance. The earth is following a perfectly smooth orbit. The probe is following a perfectly smooth orbit. The distance to the probe must follow a perfectly smooth curve. You don't need to know the distance to know the signal timing should follow a smooth curve. Scientists can simply watch and draw that curve as it happens. As the probe passes behind the sun the curve will get an anomolous bump on it. The curve is pure classical and the bump is relativity. Just draw in the smooth curve under the bump and measure the size of the bump.

      Have you taken calculus? It's a lot like that, you don't know the +C term of a function, but you can work with the exact derivative.

      Many science experiments use this sort of method - you ignore the actual value of something, but you make precise measurements of the size of changes in that value.

      -

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    10. Re:Hmm by CheshireCatCO · · Score: 1

      Actually, I doubt you need to factor in GR for that kind of accuracy. GR rapidly goes to Netowian mechanics as you move away from the Sun. Look at Mercury: the anomalous perihelion shift is 43 seconds of arc per *century*. Mercury itself will have orbited though more than 10 million times that angle in only one century. The GR correct, even there, is minute. Out between Jupiter and Saturn it isn't worth taking into account. NASA has guided several spacecraft out to that part of the solar system with very high accuracy without using GR.

      Given all of that, I think it's up to you to show that they need to use GR to get this position. You're welcomed to show me the math and convince me that it matters. But until you do, you're just guessing, and guessing against the evidence at that.

    11. Re:Hmm by anthony_dipierro · · Score: 1

      Given all of that, I think it's up to you to show that they need to use GR to get this position.

      I'm not sure it's possible to show that they must use GR to get this position. There's always a possibility that they found some way around it, I just don't see what it is.

    12. Re:Hmm by CheshireCatCO · · Score: 1

      But that's what you are asserting: that they need to take GR into account. You'd better believe that you can show that that is the case (or not the case, either way).
      All *you* have to do (or them, to prove that they don't need GR) is to work out the GR correction from the Newtonian ephemeris for Cassini. You would have to show that it affects the position enough to significantly affect the measurement in question. They just need to show that the affect is too small to be important at their level of precision.

    13. Re:Hmm by anthony_dipierro · · Score: 1

      But that's what you are asserting: that they need to take GR into account.

      No, I never made that assertion.

    14. Re:Hmm by CheshireCatCO · · Score: 1

      "You must also precisely measure the distance, and you can't measure that without using Einstein's equations."

      Sounds like you are asserting that to me.

      In any event, this has become futile. You either don't understand, don't want to understand, or are simply trolling. In any case, I'm out of here.

    15. Re:Hmm by anthony_dipierro · · Score: 0, Troll

      "You must also precisely measure the distance, and you can't measure that without using Einstein's equations."

      Sounds like you are asserting that to me.

      Well, that's true. You don't deny that fact, do you?

      In any event, this has become futile. You either don't understand, don't want to understand, or are simply trolling. In any case, I'm out of here.

      Cya.

  3. Help Me Here--some novice Questions by jazman_777 · · Score: 2, Interesting

    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?

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    1. Re:Help Me Here--some novice Questions by ZoneKagen · · Score: 0

      Falsifiable, simply put, means that you have to be able to prove something wrong in theory. The implications of this is, however, not clear to me.

      --
      - Dost thou think because thou art virtuous, there shall be no more cakes and ale?
    2. Re:Help Me Here--some novice Questions by Unholy_Kingfish · · Score: 3, Insightful

      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. At first there was earth wind fire and water (no jokes please). Then there were atoms. Then the atoms where broke down to electrons proton and neutrons. Then those particles where broke down into quarks. Then quarks where broke down into mueons. Each time, they add to the new truth.

      The fundamental philosophy of that truth doesn't change, just the details showing it is.

      --
      Fear Is the Only God
    3. Re:Help Me Here--some novice Questions by deglr6328 · · Score: 2, Informative

      "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 theory of atoms down to the fraction of an AMU!', even though it could very well be used to do that. The reason we don't is because no one expects to find anything that would invalidate the atomic theory of elements. We know, however, that there must be something "beyond" Einstein's relativity in the same way that the orbit of mercury reveals a breakdown of Newtonian Physics. This experiment with Cassini was in a way looking for Einstein's 'Mercury problem'. The fact that it has not found any inconsistency with GR (along with countless other experiments done in the past century) is a testament to, not only our lack of tools to measure with extreme enough precision the physical phenomena effected by GR but also to the greatness of the theory of General Relativity itself. We will continue to test Einstein though, in December Gravity Probe B will be launched, using ultrahigh precision quartz sphere gyroscopes, it will be able to measure certain effects of GR to the parts per million range. Science is a search for ever greater truth.

      --
      - "Hear that?! The percolations are imminent! Cease your ingress!"
    4. Re:Help Me Here--some novice Questions by UnknownSoldier · · Score: 2, Insightful

      > 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 knowledge of it does.

      Cheers

      --
      "I want to move to theory, everything works in theory." - John Cash

    5. Re:Help Me Here--some novice Questions by Unholy_Kingfish · · Score: 1

      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.

      --
      Fear Is the Only God
    6. Re:Help Me Here--some novice Questions by Anonymous Coward · · Score: 0
      1. Observe (natural, or man-made expirements)
      2. Theorize
      3. Test
      repeat
      You forgot:
      4. ...
      5. Profit!!!
    7. Re:Help Me Here--some novice Questions by Anonymous Coward · · Score: 1, Interesting

      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."

    8. Re:Help Me Here--some novice Questions by jpkunst · · Score: 1

      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

  4. Cute, but by CheshireCatCO · · Score: 4, Interesting

    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.

    1. Re:Cute, but by Unholy_Kingfish · · Score: 1

      It is misleading for the overall measurement. This is for a manmade signal transmitted to earth in a controlled environment.

      --
      Fear Is the Only God
  5. some novice thoughts by SolemnDragon · · Score: 1
    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's going on.

    Theories frequently turn into paradoxes, because bits are missing from the description that are necessary to the theory's application to more than one set of circumstances. So the theory sits in limbo for awhile until somebody starts asking the right questions. Einstein recognised this several times, although i think he'd be spinning at the thought of what's happening with his work now.

    My favourite Einstein quote got translated several times, but the best one (provided by Eistein himself, in later years) comes out to, "God's slick, but he ain't mean."

    That sentence always comes to mind when stuff like this comes up.

    --
    "I'd say 'Have a good time,' but arson is still illegal.
  6. Same experiment... by OneOver137 · · Score: 1
    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 and time itself, and as a result the Sun would deflect starlight passing by it. Changes in the apparent direction of stars in the sky, seen close to the Sun during a total eclipse, could confirm the idea.
    source: http://www.esa.int/esaSC/SEM7I9R1VED_index_0.html
    1. Re:Same experiment... by Anonymous Coward · · Score: 0

      yes

  7. Theory by BortQ · · Score: -1, Troll
    What a lot of people don't seem to know is that the fact that it is still called the 'theory' of relativity means that it hasn't been accepted as gospel by scientists yet.

    Contrast this with the 'law' of gravity, which has.

    It's true that as time goes by and the evidence stacks up on its side relativity appears to be on its way to becoming a 'law', but it could still take a number of decades.

    --

    A Multiplayer Strategy Game for Mac OS X, Windows, and Linux
    1. Re:Theory by OneOver137 · · Score: 1

      Sure it's a theory, but this "theory" was used to prove the "laws" of Newtonian mechanics were wrong and not all-encompassing--they are just good approximations to what we observe as humans during our daily routines.

    2. Re:Theory by Narchie+Troll · · Score: 4, Insightful

      That's not really true. "Law" is something of a layman's term. In mathematics and science, there are no absolute facts, just postulates and theorems. General relativity is basically identical to Newton's theory of gravity in basic situations, but it differs when you're working with high speeds and large scales. In fact, Newtonian physics is proven wrong for many planetary-scale gravitational effects.

      It's a "law" because it seems immovable to us.

    3. Re:Theory by Alsee · · Score: 4, Insightful

      What a lot of people don't seem to know is that the fact that it is still called the 'theory' of relativity means that it hasn't been accepted as gospel by scientists yet.

      That's not a very good description of the situation.

      Contrast this with the 'law' of gravity, which has.

      Actually the 'law' of gravity have been proven incorrect. It has been superceded by relativity. The common usage of 'theory' and 'law' don't quite match up with the scientific usage :)

      According to the "law of gravity" the results from this measurement should have been zero. Relativity says the value isn't zero, and the value given by relativity is at least a 99.998% match for the measured value. The remaining 0.002% doesn't indicate a problem with relativity, it is just the limit of the accuracy of devices they used to make the measurement.

      Relativity has been challenged with the most stringent scientific testing ever devised in countless ways. Actually part of the "problem" is that relativity is "too good". Absolutely everything it describes it does so with unbelievable accuracy. The irony is that you can't learn anything new when every single measurements exactly matches your predictions. It leaves them without anything to grab on to to try to explore the things that relativity doesn't explain.

      -

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    4. Re:Theory by Tablizer · · Score: 1

      That's not really true. "Law" is something of a layman's term. In mathematics and science, there are no absolute facts, just postulates and theorems.

      I view it more as a probability. The more evidence that backs something, the higher its probability of being the proper theory. But, nothing is 100% certain, except may death and taxes.

      In fact, Newtonian physics is proven wrong for many planetary-scale gravitational effects.

      I think gravity is called a "law" because for the vast majority of things people deal with it, it works well and predicts dead-on. But astronomers may not find it as useful. By the way, the interplanetary space probe gravity anomally is indeed odd. It may trigger a revolution in gravity theory together with solving "dark matter" problems.

      --
      Table-ized A.I.
    5. Re:Theory by bcrowell · · Score: 1
      What a lot of people don't seem to know is that the fact that it is still called the 'theory' of relativity means that ...
      Oh please. I keep telling myself I should stop reading the comments on science articles on /. because there are so many people who, like you, think they know a hundred times more than they really do.

      Scienctists do not consistently use "law" and "theory" to mean two different things.

      ...it hasn't been accepted as gospel by scientists yet
      Science doesn't have gospels. Science has testable theories/laws.

      Contrast this with the 'law' of gravity, which has.
      Actually Newton's universal law of gravitation has been definitively disproved. It just happens to be a very good approximation under certain conditions.

      --
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    6. Re:Theory by Scarblac · · Score: 2, Informative

      There's no difference between a "theory", a "theorem", a "law", etc in science. They're all just synonyms for theory, to give them different names. Science deals with theories. Math deals with theorems.

      I've remarked before, it's only Americans that have this idea that a "law" is better than a "theory", etc.

      Can someone explain to me why that is? Is this taught in schools? Is it caused by Creationists (another US phenomenon) trying to muddy the waters by suggesting "evolution theory" hasn't made it to "law status" yet?

      --
      I believe posters are recognized by their sig. So I made one.
    7. Re:Theory by Feztaa · · Score: 1

      Can someone explain to me why that is?

      My guess would be that a lot of people think a law is absolutely correct and immutable (due to the legal system?), while they think a theory is just a vague set of guesses.

      The truth, of course, is more the opposite. A law tends to be a detailed observation, while a theory is the best explanation we can come up with given the evidence we have to work with.

      Laws are ultimately useless, because they don't really give us anything to work with. A theory, on the other hand, can be incrementally improved or completely disproved and replaced, and the process of improving theories allows us to gain a better understanding of the universe.

    8. Re:Theory by You're+All+Wrong · · Score: 1

      """
      I've remarked before, it's only Americans that have this idea that a "law" is better than a "theory", etc.
      Can someone explain to me why that is? Is this taught in schools? Is it caused by Creationists...?
      """

      They don't have laws, they have commandments!

      YAW.

      --
      Your head of state is a corrupt weasel, I hope you're happy.
    9. Re:Theory by 00420 · · Score: 2, Informative

      I've remarked before, it's only Americans that have this idea that a "law" is better than a "theory", etc.
      Can someone explain to me why that is? Is this taught in schools?

      Yes. I was tought this in middle school. I was told the steps of the Scientific Method were:
      1. Observe
      2. Hypothosize
      3. Experiment
      4. Theory
      5. More experiments
      6. Law

      Not only that but I was told that in order for something to become a law it had to hold up 100% of the time!

      I was quite suprised when I got to college and learned that this was not true.

      --
      Have you tried Linux yet?
    10. Re:Theory by Anonymous Coward · · Score: 0

      Actually, there is a difference between a theory and a theorem. A theorem can be mathematically proved, starting from a given set of assumptions. Meanwhile, you can't really prove a (scientific) theory in any sort of rigorous way, just show experimentally that it seems to be predictively accurate.

  8. Are you trolling? by Spamalamadingdong · · Score: 1
    Sure, you can calculate the elipse of the orbit. But that's not the same as calulating the round-trip distance between two accelerated objects.
    On the chance that you might not be, I'll answer you:
    1. The orbit of Cassini is independent of the path its signal takes to Earth.
    2. The influence of the curvature of space around the Sun can be separated from anything which changes the orbit of Cassini (or the Earth) by measuring the delay properties of the signal path when the signal passes nearer or further from the Sun.
    We can also make very precise measurements of other signal paths, such as the timing of signals from pulsars. We can even do this at the same time as we measure the signal from Cassini....

    If you want to take issue with the results (and be taken seriously), you need to make an effort to understand those results and the previous work which underpins it. This is not the same as repeating buzzwords; it takes much more in the way of both effort and raw intelligence.

    --
    Scientists restrict study to entire physical universe; creationist
    1. Re:Are you trolling? by anthony_dipierro · · Score: 0

      If you want to take issue with the results (and be taken seriously), you need to make an effort to understand those results and the previous work which underpins it.

      I obviously am not taking issue with the results, as I have not seen them. You, on the other hand, seem to be defending them without having seen them either.

    2. Re:Are you trolling? by Spamalamadingdong · · Score: 1
      I obviously am not taking issue with the results, as I have not seen them. You, on the other hand, seem to be defending them without having seen them either.
      Wrong on both counts.
      1. I am not defending the results, but the integrity of the scientists against your groundless assertions.
      2. You certainly did question the validity of the results.
      Here's what you said to begin the thread:
      But round-trip time is not enough. You must also precisely measure the distance, and you can't measure that without using Einstein's equations.
      You are asserting that the experimenters did not do their homework. If you have grounds for that assertion, you've not even hinted at them; if you have no grounds for that assertion, you shouldn't be posting.
      --
      Scientists restrict study to entire physical universe; creationist
    3. Re:Are you trolling? by anthony_dipierro · · Score: 0

      You have completely misunderstood me. Get some rest and try reading what I wrote again some othehr time.

  9. the usual misstatement by penguin7of9 · · Score: 2, Insightful

    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.

    1. Re:the usual misstatement by You're+All+Wrong · · Score: 1

      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 reasonable conviction anyway. However, fairly generated data points that are not to be sniffed at (if you're a proponent of the theory).

      YAW.

      --
      Your head of state is a corrupt weasel, I hope you're happy.
    2. Re:the usual misstatement by dnahelix · · Score: 1

      That's why the other guy always racks for the guy who breaks!

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      I Hate \.
    3. Re:the usual misstatement by penguin7of9 · · Score: 1

      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 information from an experiment whose results agree with your theory.

    4. Re:the usual misstatement by You're+All+Wrong · · Score: 1

      """
      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.

      --
      Your head of state is a corrupt weasel, I hope you're happy.
    5. Re:the usual misstatement by nimblebrain · · Score: 1

      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 home page casts light evenly on the topics, and thus causes activity, until they pass beyond the Oldnewsii Shell at some distance and get progressively more shielded from the light by other articles. :)

      There are plenty of means to get to the same sorts of relationships as GR presents in terms of light bending. Etheric, tired light, and other particle, flux, or field-based theories can arrive at the same observations.

      Sometimes it's a primacy (who got there first) or popularity contest. That's perhaps sad in a way, but the devil is really in the anomalies - sometimes brushed away as 'error', other times requiring some other body acting on it (that can lead to discovering Pluto, or a need for dark matter). The anomalies are where alternate explanations might really prove their mettle.

      Here's an example:

      There are anomalies in the in-track acceleration of the LAGEOS satellites.

      Do you try for the General Relativity solution (section 3.7.3)? Or something "wilder" (near the bottom)?

      I guess it's easier to say "X confirms GR" than "X confirms list of equations here", but it does imply that much more in physics has been 'set in stone' than actually has been.

      --
      Binary geeks can count to 1,023 on their fingers :)
    6. Re:the usual misstatement by penguin7of9 · · Score: 1
      """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 ruled out by other experiments) and (2) your experimental results agreed with the predictions your theory already makes. In that case, and only in that case, you do not learn anything from the experiment. These measurements satisfy both conditions.

      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.

      It makes a lot of sense to try to reproduce results because of the possibility of fraud, logical inconsistencies in the formulation of a theory, or unexpected phenomena. But,fraud and logical inconsistencies aren't an issue anymore in the theory of GR (at least when it comes to this simple aspect of the theory) and the results agree with prediction, so you don't learn anything from them.
  10. Good use of words... by BladeMelbourne · · Score: 1
    [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.

  11. Special vs. general relativity by Anonymous Coward · · Score: 0
    Bear in mind that this is about general relativity, which makes predictions that are hard to confirm. Special relativity predicts lots of clearly detectable phenomena that can and have been confirmed experimentally many times.

    General relativity remains iffy, because it's incompatible with quantum mechanics. Someday, somebody will pull the two together in an experimentally testable way, and will go down in history with Einstein and Newton. But not yet.

    1. Re:Special vs. general relativity by CheshireCatCO · · Score: 1

      "General relativity remains iffy,"

      Given that GR has been more precisely tested (passing all tests) than any other theory, including QM, I'm not sure that "iffy" is really a good way to describe it. Especially since the incompatability could point to flaws in either theory (or both). Frankly, and I admit to being something of a heratic here, I'm more expecting QM to fall down before GR.

  12. Wrong. by Grog6 · · Score: 1

    The precession of the apogee/Perigee of Mercury's orbit does not agree well with Newton or Einstein. There is yet a discrepancy that is currently unexplained.

    --
    Truth isn't Truth - Guliani
  13. Excellent! by The+Gline · · Score: 1

    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.)

    --
    Honorary Member of Jackie Chan's Kung Fu Process Servers