Posted on 06/23/2003 9:25:12 AM PDT by RightWhale
Berkeley Lab Physicist Challenges Speed of Gravity Claim
Berkeley - Jun 22, 2003
Albert Einstein may have been right that gravity travels at the same speed as light but, contrary to a claim made earlier this year, the theory has not yet been proven. A scientist at Lawrence Berkeley National Laboratory (Berkeley Lab) says the announcement by two scientists, widely reported this past January, about the speed of gravity was wrong.
Stuart Samuel, a participating scientist with the Theory Group of Berkeley Lab's Physics Division, in a paper published in Physical Review Letters, has demonstrated that an "ill-advised" assumption made in the earlier claim led to an unwarranted conclusion. "Einstein may be correct about the speed of gravity but the experiment in question neither confirms nor refutes this," says Samuel. "In effect, the experiment was measuring effects associated with the propagation of light, not the speed of gravity."
According to Einstein's General Theory of Relativity, light and gravity travel at the same speed, about 186,000 miles (300,000 kilometers) per second. Most scientists believe this is true, but the assumption was that it could only be proven through the detection of gravity waves. Sergei Kopeikin, a University of Missouri physicist, and Edward Fomalont, an astronomer at the National Radio Astronomy Observatory (NRAO), believed there was an alternative.
On September 8, 2002, the planet Jupiter passed almost directly in front of the radio waves coming from a quasar, a star-like object in the center of a galaxy billions of light-years away. When this happened, Jupiter's gravity bent the quasar's radio waves, causing a slight delay in their arrival on Earth. Kopeikin believed the length of time that the radio waves would be delayed would depend upon the speed at which gravity propagates from Jupiter. To measure the delay, Fomalont set up an interferometry system using the NRAO's Very Long Baseline Array, a group of ten 25-meter radio telescopes distributed across the continental United States, Hawaii, and the Virgin Islands, plus the 100-meter Effelsberg radio telescope in Germany. Kopeikin then took the data and calculated velocity-dependent effects. His calculations appeared to show that the speed at which gravity was being propagated from Jupiter matched the speed of light to within 20 percent. The scientists announced their findings in January at the annual meeting of the American Astronomical Society.
Samuel argues that Kopeikin erred when he based his calculations on Jupiter's position at the time the quasar's radio waves reached Earth rather than the position of Jupiter when the radio waves passed by that planet. "The original idea behind the experiment was to use the effects of Jupiter's motion on quasar-signal time-delays to measure the propagation of gravity," he says. "If gravity acts instantly, then the gravitational force would be determined by the position of Jupiter at the time when the quasar's signal passed by the planet. If, on the other hand, the speed of gravity were finite, then the strength of gravity would be determined by the position of Jupiter at a slightly earlier time so as to allow for the propagation of gravitational effects."
Samuel was able to simplify the calculations of the velocity-dependent effects by shifting from a reference frame in which Jupiter is moving, as was used by Kopeikin, to a reference frame in which Jupiter is stationary and Earth is moving. When he did this, Samuel found a formula that differed from the one used by Kopeikin to analyze the data. Under this new formula, the velocity-dependent effects were considerably smaller. Even though Fomalont was able to measure a time delay of about 5 trillionths of a second, this was not nearly sensitive enough to measure the actual gravitational influence of Jupiter. "With the correct formula, the effects of the motion of Jupiter on the quasar-signal time-delay are at least 100 times and perhaps even a thousand times smaller than could have been measured by the array of radio telescopes that Fomalont used," Samuel says. "There's a reasonable chance that such measurements might one day be used to define the speed of gravity, but they just aren't doable with our current technology."
Oh, you're just fishin' for a compliment, aren't you? :^)
Actually, I know RA quite well, and yes...he does talk and think just like that. Which is why I told him he has more brains than are decent and asked him for a translation. I'm just a lowly geochemist and have postively NO clue what he was talking about either, but it sounded legit.
Indeed he does, but in this instance he's quoting "Physicist," so it's a safe bet it wasn't uttered in jest.
Well it most certainly was legit. What you are all talking about was the addition that Physicist freepmailed me for a post I was making. (If you note: I added this caveat in front of that paragraph with this statement: " An addition by Physicist")
It was a paragraph he added to my description of the Standard Model for a post I made a while back. I had originally only included the (Pion and others) as an exchange force and he made the addition that the “others” needed to be a bit clearer. I should have added my two cents to this to make that paragraph more understandable from the beginning.
My apologies for not doing this from the beginning. So here goes:
BTW This is all mine, so any mistakes are mine as well:
First, lets take a look at Van der Waals Forces:
(I am attempting this without a complete lecture on chemical bonding so please be kind) Atom and molecules are attracted to each other by two classes of bonds. The Intramolecular bond and the Intermolecular bond.
The Intermolecular bond is divided into these categories; Van der Waals Forces, Hydrogen Bonds, and molecule-ion attractions.
The Intramolecular bond (which are much stronger than the Intermolecular bond) is divided into these categories; Ionic bonding, covalent bonding, and metallic bonds.
We will only concentrate on the Van der Waals Forces.
Van der Waals Forces arise from the interaction of the electrons and nuclei of electrically neutral atoms and molecules. How is this possible if these are considered electrically neutral I hear you ask. What is going on here is that the electrons and nuclei of atoms and molecules (for this description: from here out called particles) are not at rest, but are in a constant motion. Since this is the case, there arises an electrical imbalance (called an instantaneous dipole [another term is a temporary polarity]) in this electrically neutral particle. Two “particles” in this dipole state will attract. Also this dipole action in one particle can cause a dipole in an adjoining (nearby) particle. So the dipole-dipole attraction is what is known as Van der Waals Forces. If these “particles” kinetic energies are low enough (anc close enough together), the repeated actions of the instantaneous dipoles will keep them attracted together.
One of the interesting things about this that the more electrons are in play the greater the Van der Waals Force. This is why the noble gas Krypton liquefies at a higher temperature than the noble gas Neon.
Whewwwwww!!!!!! Half done!:
Back to the Standard Model.
Again trying to keep this at an understandable level I may mess this up So if I did not explain this quite right, please correct me!.
A brief background: How does a nucleus stay together when it is packed with positively charged protons? Since “like” charges repel, you would think that the nucleus would fly apart. The force that keeps this from happening is the Strong Force. One of the things that was discovered is that the mass of any nucleus is always less than the sum of the individual particles (called nucleons) that make it up. The difference (residual) is due to the “Binding Energy” of the nucleus. This binding energy is directly related to the strength of the strong force. Note: This is why there is a release of energy when an atom is split. (nuclear fission).
So just what is this Strong Force anyway? The Strong force has an effect on quarks, anti quarks and gluons. Oh my, another term, QUARKS! After much research, it was discovered that the protons and neutrons in the nucleus were made up of smaller particles called quarks. It turned out that two types of quarks were needed to “produce” a proton or a neutron. However, there are six types of quarks in normal matter. The strong force binds these quarks together to form a family of particles called hadrons which include both protons and neutrons. (SORRY IF THIS IS GETTING COMPLEX) To simplify this discussion, quarks have a “color charge” (red, green, and blue). BTW, this was a convenient way of describing the charge, it is not referring to color as we commonly use it). Like colors repel and unlike colors attract. There are also antiquarks. The attraction between the quark and antiquark is stronger than between just quarks. If it is a quark/antiquark (same color) it is called a meson. If its between quarks it is called a baryon (protons and neutrons fall in this category). Here is the rub, baryonic particles can exist if their total color is neutral; i.e. have a red green and blue charge altogether.
Without getting into too much more detail, quarks can interact, changing color, etc. so long as the total charge is conserved.
The quark interactions are cause by exchanging particles called gluons. There are eight kinds of gluons each having a specific “color” charge.
So back to the original paragraph. Neutral (all three colors) hadrons (which include protons and neutrons) can interact with the strong force similarly to the way atoms an molecules react via the Van der Waals forces.
Physicist? Anything you want to add or change if I "stuffed it up" so to speak?
Oh, so I'm a humorless cipher then, am I? Guess I'll just go eat worms...
;^)
ROFLMAO! Not until you tell us what "color" they are...
"Binding energy" is a negative energy. If the mass of a nucleus were always less than any sum of its potential components, then it would always take energy to split a nucleus. This is true for any nucleus below iron. For nuclei above iron, the binding energy becomes less and less; the strong nuclear force creates stable minima in which very heavy nuclei can exist, but these are but local minima sitting high on the electromagnetic hill. A uranium nucleus is heavier than thorium plus helium.
Doc Smith, in the classic novel Triplanetary, made the error of taking binding energy to be a positive, exploitable energy. Accordingly, the aliens used iron as fuel for their starships, iron having the maximum binding energy...sucking it, if necessary, out of the hemoglobin of human beings! In reality, iron is the one nucleus that can't be used for fuel, but I'm glad I didn't know that as a 12-year-old just the same.
Around here, you have achieved Mt. Rushmore status.
I believe the attraction between them is the same, as they have the same strength of charge.
If it is a quark/antiquark (same color) it is called a meson. If its between quarks it is called a baryon (protons and neutrons fall in this category). Here is the rub, baryonic particles can exist if their total color is neutral; i.e. have a red green and blue charge altogether.
Both mesons and baryons are "colorless" with respect to the outside world. In baryons, as you say, red + blue + green = colorless. In mesons, for example, red + anti-red (or, if you like, red - red) = colorless.
Aw, great. Now Daschle represents me. Worms! More worms I say!
Surely you jest.....
;-)
Yes, but the reasons you gave for that announcement were goofy, IMNSHO.
Like the folks doing the experiment, you may have arrived at the right answer more by accident than via correct reasoning.
[Deep-Fried, Insufferable Geek Alert: there are three color charges, each with a corresponding anti-color. Every gluon carries both a color and an anti-color charge. Shouldn't there be nine kinds of gluon? Why are there only eight?
The combination red-antired + green-antigreen + blue-antiblue is colorless. Therefore, if I assign three gluons that are red-antired, blue-antiblue, and green-antigreen, I'm doing something redundant, because blue-antiblue (for example) is just 0 - red-antired - green-antigreen, and so forth. I'm using three vectors to span a two-dimensional space.
So what we do is choose two of the three color-anticolor pairs, and use them to compose two orthonormal basis vectors (such as g1=(red-antired + blue-antiblue)/sqrt(2), g2=(red-antired - blue-antiblue)/sqrt(2)), with the other gluons being g3=red-antigreen; g4=red-antiblue; g5=green-antiblue; g6=green-antired; g7=blue-antired; g8=blue-antigreen.]
[Atomic Wedgie Geek Alert: The symmetry group of Quantum Chromodynamics is SU(3). In the minimal representation of SU(3), there are three generators...the color charges. In the non-minimal representation, there are 3²-1 generators...the eight gluons! This was spookily mirrored by Murray Gell-Mann's original (1964) quark theory, which also exploited the SU(3) symmetry. Only this time, the minimal representation was the three light quark flavors (up, down, strange), and the non-minimal representation was Gell-Mann's famous Eightfold Way, which correctly(!) predicted the properties of all the light hadrons, including some that had not yet been discovered.]
Trivia Of The Day: Because their foot pads end in literally billions of microscopic filaments, geckos use Van Der Waals forces to allow them to stick to just about any surface and climb up walls and across ceilings. They do this so efficiently that the average gecko is "glued" to the wall with about 200 pounds of force.
The same argument could be applied to the force of electromagnetism, but electromagnetism conclusively propagates at the speed of light.
It can't be that simple. Physicists would have nothing to do. You want to be responsible for all these physicists being out of work and on welfare?
Cha, cha, cha... You know,
epicycles can explain
retrograde motion.
If you're willing to
pile complexity onto
complexity, you
need never give up
on Ptolemy's paradigm.
Sorry. Just rambling...
"So Ptolemy adopted an instrumentalist view --- this strange model is only an accurate calculator to predict the planet motions but the reality is Aristotle's model. This apparent contradiction between reality and a calculation device was perfectly fine in his time. Our modern belief that models must characterize the way the universe actually is [!] is a tribute to the even longer-lasting influence of Aristotle's realism."
Van Flandern also now insists that electromagnetism propagates at infinite speed. (Not electromagnetic waves, mind you, but the field...whatever the devil that means.) It's nonsense, but he's forced into it by his own (mistaken) geometrical argument.
Presumably this frees gravitational waves (as opposed to fields) to propagate at c.
Is he insisting now? This is not good news. Insistence could be a symptom of underlying progressive spookiness. That's right, he could soon be a candidate for kookville.
Ah, you're calling my name. Would you settle for near-infinite rather than "infinite speed"?
How does the speed of light squared strike you, so to speak?
Gravity is the Energy of a Mass (G=E/M).
Energy is equal to the Mass times the speed of light squared (E=MC^2).
Solving the two equations for Gravity yields G=C^2.
Well OK, that would all be fine except the units look pretty funny, so how do we *observe* whether or not the math adds up?
Two observable phenomenon come to mind:
1. recent experiments in which Light was reduced in speed to under 50 mile per hour show that Light is NOT bent by Gravity at slow speeds. This would seem to indicate that *speed* matters. And since Gravity hasn't been shown to be influenced by Light, but Light can be shown to be influenced by Gravity, a reasonable person could speculate that Gravity is either a much stronger force or a much faster force than is Light.
2. The Earth and other planets in our Solar System. We already know that our entire Solar System is hurtling through space in one constant overall direction at some great speed. Fine. We also know that the planets orbit the Sun in a horizontal plane. Now, if there is a *lag* between the time that a Gravity wave leaves the Sun and reaches each planet, then it should be a more pronounced lag as one moves from Mercury to Pluto, simply because there is more distance to cover.
Now keeping in mind that all of those planets are hurtling through space in the same overall direction (let's say, North) along with the Sun, we should see planets orbit where the Sun *was*, rather than where the Sun *is*.
If it takes 18 seconds for Light to reach Earth from the Sun, then the Earth would be orbiting where the Sun was 18 seconds ago if Gravity travels at the speed of Light, with an even more pronounced lag in horizontal plane orbit for Mars, Saturn, etc.
But we don't see that. Instead of successive planets orbiting more Southward as one looks away from the Sun, we see the planets pretty well line up on the same horizontal plane, as if Gravity was MUCH faster than Light.
And this observation agrees with what we see in the first experiment above when we slow Light down in the lab, which also seems to agree with the math above.
so in my opinion Gravity propagates at somewhere around 3.4703029E10 miles per second (or is that per second squared??).
Every word in your posting is wrong, including "is", "and" and "the".
You cannot even give the correct distance to the Sun in light-seconds. The Sun is about 8.3 light minutes from Earth.
--Boris
Relative to its former position, how far will the Sun have moved in 8.3 minutes?
"In the news tonite, Ben & Jerry's, Vermont's premiere ice-cream makers, announce the introduction of their newest flavor; 'Railing & Rust'...... stay tuned, filmed report at 11. Meanwhile, former Governor Howard Dean claims he is being followed on the presidential campaign trail by a 30 foot tall fiberglas "Truth Cow that goes "Moooooooo! Moooo!" and poops simulated 'pasture patties' everytime he tells a whopper...." Doctors say Dean should be stabilized enough to be released from the Brattleboro Retreat in time for the New Hampshire Primary."
Anything like the "Tooth Festival" at the Tunbridge Fair, or the "Herpes Festival" in Putney?
Yeah, the ones with the moustaches! Now that's what I call "hardy Vermont woman."
One Of the interesting things about the curve of binding energy is the elements that are created in stellar processes:
The weak force is the force that induces beta decay via interaction with neutrinos. A star uses the weak force to “burn” (nuclear fusion). Three processes we observe are proton-to proton fusion, helium fusion, and the carbon cycle. Here is an example of proton-to-proton fusion, which is the process our own sun uses: (two protons fuse -> via neutrino interaction one of the protons transmutes to a neutron to form deuterium -> combines with another proton to form a helium nuclei -> two helium nuclei fuse releasing alpha particles and two protons). The weak force is also necessary for the formation of the elements above iron. Due to the curve of binding energy (iron has the most tightly bound nucleus), nuclear forces within a star cannot form any element above iron in the periodic table. So it is believed that all higher elements were formed in the vast energies of supernovae. In this explosion large fluxes of energetic neutrons are produced which produce the heavier elements by nuclei bombardment. This process could not take place without neutrino involvement and the weak force.
Earth is orbiting the sun at about 60,000 mph. Galactic rotation is a big part of the sun's true motion. We go around the core about every 200 million years at a distance of however far we are from the core. Somebody [preferably a 1st year engineering student] should cruch the numbers and tell us the result in feet or miles. They say the Andromeda galaxy is approaching us, but we might be approaching the Andromeda galaxy, so that speed might be added in.
Too complicated. I regard myself as a privileged frame of reference, and everything is (or is not) in motion relative to me. From my point of view, here on earth, the sun isn't really going anywhere.
Fair enough. So relative to its old position, the Sun will have moved some significant, measurable distance in 8.3 minutes.
This brings up the really interesting question: is the Earth orbiting around the position of the Sun 8.3 minutes ago, as it would if Gravity travels as slow as the Speed of Light, or is the earth orbiting around the Sun at some point closer to the Sun's actual position at this moment, which would indicate that Gravity travels some measurable amount faster than Light.
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