Charlottesville Man Discovers Speed of Gravity

In what qualifies as Very Very Big News in the science world, Charlottesville astronomer Ed Fomalont (who works with the National Radio Astronomy Observatory, which headquartered in Charlottesville) has confirmed Einstein’s theory of relativity by demonstrating that the speed of gravity is roughly the same as the speed of light. In September, Fomalont monitored the light from a quasar as it was eclipsed by Jupter. If the speed of gravity were infinite, as some thought that it might be (notably Newton), the quasar would have appeared as a circle; if gravity were finite, the quasar would have appeared distorted. Fomalont worked with University of Missouri’s Sergei Kopeikin on the project. Kate Andrews has the story in today’s Progress, though a more detailed article can be read in New Scientist.

14 Responses to “Charlottesville Man Discovers Speed of Gravity”


  • The only thing I don’t like about the coverage of this story is that it took place before the peer review process was complete.

    Several scientists believe, and I agree with them, that this experiment was flawed. That they in fact did not measure the speed of the propogation of gravitic force, but that they instead measured the speed of light. Which happened to be *gasp shock* the speed of light. Some believe that at best, they measured the speed of gravitational waves (which are different than gravitic force).

    One particular scientist, Hideki Asada, believes that the effect that actually accounts for their measurements is the light-cone effect. You can read more about that here.

    Hideki Asada is (arguably) the world’s foremost expert on gravitic lensing, and so I’d tend to put a bit more stock into his explanation than that of the experimentors.

    Now, it could actually be that these fellows are correct, and they did measure the speed of gravity. Or it could be that they were incorrect, but that gravity does propogate at the speed of light. It could also be that gravity propogates instantly (there are some good arguments for this). However, we won’t be able to be even fairly certain what this experiment is telling us until after the peer review process is complete.

  • Not a delay on the first. Hopefully, the coverage generally notes the doubts (though probably not).

    I think that the story is essentially unimportant for most readers of general news (excluding those sophisticated enough in science to know of peer review, etc.) that it is mostly just a human interest story at this point.

  • This Washington Post story mentions the critiques, albeit briefly:

    A researcher in Japan has contended that the technique actually measured the speed of light, not gravity, but his interpretation is not attracting support.

  • MSNBC took a similar track. Notice that the Post doesn’t include names or credentials of those that oppose, at least MSNBC went that far.

    From the DP story, it seems that these guys were conducting their research and preparation in "secret", before the big event. And then tried to make a "splash" with their discovery.

    This is not the way to do good science. I’m still not saying they aren’t correct, but they, and the media, are jumping the gun.

  • Did this experiment confirm the theory of relativity, or merely one facet of that theory? I’m thinking the latter.

    Have the Raelians chimed in on this one yet to establish its validity? I’m just saying.

  • *sigh* I dont see why we hold so tightly to the ideas of general and special relativity. Science took a wrong turn at some point, and no matter how hard we try to pull it back on course, some guy with a radio telescope array tries to stand in our way.

    Lorentzian relativity is an experimentally viable model for the relativity of motion that nullifies the “proof” that nothing can propagate faster than light in forward time. The most common interpretation of GR is that the speed of gravity is the speed of light. This interpretation is based on a misunderstanding of the implications of aberration and confusion between the meanings of gravitational force variations and gravitational waves.

    There have been 6 major experiments that show gravitational forces to travel faster than light speed. To avoid direct violation of the causality principle, the propagation delay of gravitational forces must be finite. Large, but finite. One of these experiments, obesrving binary pulsars, showed that the position, velocity, and acceleration of each mass is anticipated in much less than the light-time between the masses. The calculations placed the speed of gravity to 2 x 10^10 C.

    I can’t present an argument that their expermient was flawed. I simply do not understand their experiment. I wouldn’t be suprised if they confused the as yet undiscovered gravity waves resulting from the inertial mass of jupiter with the gravitational fields (force variations) of jupiter.

  • *sigh* I dont see why we hold so tightly to the ideas of general and special relativity. Science took a wrong turn at some point, and no matter how hard we try to pull it back on course, some guy with a radio telescope array tries to stand in our way.

    I would differ with you, but only slightly.

    We do hold too tightly to general and special relativity. We already know that there are some parts of relativity that need serious overhauls. And we know that other parts seem to be rock solid.

    Where the danger lies is ignoring significant data in favor of wishful thinking, as may be the case here. They wanted to see this part of GR proven, and so they weren’t as rigorous as they needed to be in interpreting the results.

    There have been 6 major experiments that show gravitational forces to travel faster than light speed.

    I remembered something about this as well, and now cannot find a link to one of them for the life of me. I must be Googly-challenged. One specific experiment, that seemed pretty cut and dried to me, involved a gravitometer and the moon, that seemed to show (within a reasonable amount of error) that the moon’s gravitational pull preceeded its image in the sky. Again, though, I couldn’t seem to find a link to a page describing this experiment anywhere. Do you happen to have any links?

  • I found the paper describing their experiment!!!

    Testing Relativistic Effect of Propagation of Gravity by Very-Long Baseline Interferometry

    You’re not googally challenged, its just hard to find scientific papers online. I think the porn has smushed it all to the boundaries of existance already.

    Since the scientific community is so inbred and institutional, you are expected to pay $1000/yr for some little magazine. Apparently its worth all this money to kill trees. More likely, the publishers of journals want you to believe if its on the internet, it couldn’t possibly be true.

    This is the best I can find, it describes the existing experiments fairly well.

    T. Van Flandern, The Speed of Gravity – What the Experiments Say

    They are, as I understand them:

    1. A modern updating of the classical Laplace experiment based on the absence of any change in the angular momentum of the Earth’s orbit (a necessary accompaniment of any propagation delay for gravity even in a static field)

    2. An extension of this angular momentum argument to binary pulsars, showing that the position, velocity, and acceleration of each mass is anticipated in much less than the light-time between the masses.

    3. A non-null three-body experiment involving solar eclipses in the Sun-Earth-Moon system, showing that optical and “gravitational” eclipses do not coincide

    4. Planetary radar ranging data showing that the direction of Earth’s gravitational acceleration toward the Sun does not coincide with the direction of arriving solar photons.

    5. Neutron interferometer experiments, showing a dependence of acceleration on mass, and therefore a violation of the weak equivalence principle (the geometric interpretation of gravitation)

    6. The Walker-Dual experiment, showing in theory that changes in both gravitational and electrostatic fields propagate faster than the speed of light, c, a result reportedly given preliminary confirmation in a laboratory experiment.

    The biggest problem for such experiments is that we can’t turn sources of gravitational force on and off like we can say, a lightbulb. The sun simply isn’t going to dissappear without a trace. I’m going to have to mull over the very-long baseline interferometry experiment before I can knock on this guys door and laugh in his face. Sorry guys… It is however interesting to note that all he did was point an array at the right coordinates in the sky and take a picture. He’s a photographer not a physicist. So this is sooooo not charlottesville related… infact, the nearest radio telescope is in WV. *licks thumbs* come on! Bring it on NRAO boy! Its ON yo! What you got? *bobs, weaves*

  • Thanks for the link to Van Flandern’s paper. I had seen that at one point, but no longer had the reference to it.

    I’ve still had no luck coming up with on-line documentation of the other experiments.

    The biggest problem for such experiments is that we can’t turn sources of gravitational force on and off like we can say, a lightbulb.

    Except that maybe we can. Hopefully.

    The above linked experiment leads me to again wonder if gravity isn’t a repulsive force rather than an attractive one… hmmm. One thing is for certain, there’s a lot more that we don’t know about gravity than there is that we do!

  • Speed of the "influence of gravity" is the key phrase here.

    I see no reason to stop thinking of gravity as a spatial dimension with no speed of its own, much like time. (Balls rest on the fabric of space-time stretched tightly on a frame; gravity is the downward direction, toward the bottom of the depressions)

    What travels at the speed of light are the ripples on the fabric of space-time, not gravity itself. The ripples were what was measured here.

    And who knows how elastic the fabric is. Maybe the depression left by a Sun that suddenly disappeared, for example, takes a little longer

    to resolve (on account of its length of time spent resting on and stretching out the fabric)

  • Speed of the “influence of gravity” is the key phrase here.

    Do you mean the gravitic force? Or gravitational waves? Gravitic force seems to propogate at infinite speed. Gravitational waves seem to propogate at about the speed of light.

    I see no reason to stop thinking of gravity as a spatial dimension with no speed of its own, much like time. (Balls rest on the fabric of space-time stretched tightly on a frame; gravity is the downward direction, toward the bottom of the depressions)

    The only problem I have with that analogy of gravity is that it still doesn’t explain the force itself. Sure, if 3D space is imagined to be a flat surface, and you put a dimple in it, then a gravity-like force will cause balls to roll into those dimples. But that’s just a description of how things react to the force… it doesn’t explain the causality. Imagine being in orbit, and warping a 2D fabric and setting a ball upon it. Will the ball roll into any dimples? Nope. So what causes us to move towards large masses?

    If we could answer that question before anyone else, I bet we could get rich. ;)

    What travels at the speed of light are the ripples on the fabric of space-time, not gravity itself. The ripples were what was measured here.

    I believe you may be correct, which still wouldn’t match the media reports that these fellows measure the speed of “gravity”.

  • Attractive, repulsive, whatever. Change the spin on a quantum graviton and it carries an anti-force. Poof. Warp drive anyone?

    Gravity is SOOO poorly understood. It is the least understood of the forces, and also the weakest. The people working on quantum theories of gravity are WHACK at the moment. They’re so determined to come up with a quantum model that they have thrown physics out the window and embraced only math. Math has internal dependancies and doesn’t have to answer to nature.

    Keep in mind, that while general relativity took a few months of Einsteins time in his early 20’s, a theory of quanta took up his ENTIRE LIFE, and was unfinished. So don’t beat yourself up if you don’t have a nobel prize yet.

    There is a big bruhaha right now in sci.physics about quantum gravity. Worth a read.

  • "I see no reason to stop thinking of gravity as a spatial dimension with no speed of its own, much like time. (Balls rest on the fabric of space-time stretched tightly on a frame; gravity is the downward direction, toward the bottom of the depressions)"

    Relativity (and to some extent your ultra-simple 2-d model of it) is usefull for APPROXIMATING the effects of the gravitational force on matter.

    One good reason to not think of gravity as a dimension is that you just presented a model with a time dimension, a space dimention, and a fixed value for gravity for any given combination of time and space. I.E. you cant specify a coordinate for gravity that doesn’t fall on that "fabric" you have stretched out. You have 2 degrees of freedom, not 3. A dimension must allow for a range of values, not a value that is the result of a function of space and time.

    When you get down to VERY small scales (on the order of the Plank scale) there is no way to calculate the volume of spacetime. You can’t pin down the location of an electron in an "electron cloud", you have to treat it as a volume of anywhere the electron "could be". This is due to the uncertainty principle. Spacetime can be reduced to units of space that contain a finite amount of volume. You can’t determine where in that volume matter is, but you know that it is in that black box somewhere. For all practical purposes it is "everywhere" within that volume. Just like an electron is "everywhere" it could possibly be. This inherant uncertainty makes general relativity useless, since it is a deterministic equation, for given inputs you should be able to predict the curvature for a given point. Which simply is not possible on the quantum scale. Back to the drawing board.

    A wire is full of electrons, when you shove one in the end, one pops out the other end at near light speed. But its a DIFFERENT electron. One that was hanging out near the end of wire already. If you were to trace the path of the orginal electron you put in, it would travel at only a few inches per second. Such is the twisting of spacetime. As mass affects spacetime, changes are propagated at what is observed to be EXTREEMLY high speeds (2×10^10 c) much like we observe electrical force to be traveling at light speed, when the individual electrons are traveling MUCH slower. The individual gravitons are leaping from quantized volume to quantized volume at "only" near light speed, when the overall effect is that a "stream" of gravitons reaches the destination MUCH faster.

  • I don’t know if anyone is still reading this story, but some of the back-lash is catching up to these guys in the physics community now.

    And their first attempt to publish their papers in a scientific journal has been balked.

    Space.com story here.

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