Will the speed of light always be a barrier?

Air and Space Magaine. Vol # 1 March 1978 | March 1978 | Editorial Staff w/ Melvin B. Zistein

[vannrox]

Berkeley Lab Physicist Challenges Speed Of Gravity Claim

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 light 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 radiowaves 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 radiowaves, causing a slight delay in their arrival on Earth. Kopeikin believed the length of time that the radiowaves 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 radiowaves reached Earth rather than the position of Jupiter when the radiowaves 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."

[righttackle44]

"But I doublt that it will be in my lifetime."

Have you NEVER watched the Roadrunner? Or the Tasmanian Devil?

[vannrox]

"... (HOWEVER) Even though these new results represent a significant improvement in our knowledge of the possible (non-) variation of one of the fundamental physical constants, the present set of data would in principle still allow variations that are comparatively large compared to those resulting from the measurements from the Oklo natural reactor.

Nevertheless, further progress in this field is expected with the new very-high-accuracy radial velocity spectrometer HARPS on ESO's 3.6-m telescope at the La Silla Observatory (Chile). This spectrograph works at the limit of modern technology and is mostly used to detect new planets around stars other than the Sun - it may provide an order of magnitude improvement on the determination of the variation of alpha..."

Hum, it doesn't seem that this is lock-on solid proof that c is a constant. Not at all.

[Sam Cree]

looks interesting, read later.

[Willie Green]

Perhaps some day we might be able to travel faster than light. It certainly would be cool. But I doublt that it will be in my lifetime.

Maglev is a step in the right direction.
And the technology is available NOW!!!

[dread78645]

Hum, it doesn't seem that this is lock-on solid proof that c is a constant. Not at all.

The ground state oscillation of Cesium-133 has a frequency of 9,192,631,770 Hz, which is used to define the second.
The meter is defined as the distance that light travel in 1/299,792,458 of a second, in vacuum.
A change in the speed (distance / time) necessitates changing the length (distance) of a meter, so c is constant by definition.

Pedantry aside, no one has seemed to be able to repeat Webb's observation, and some question his methodology. While it is possible that Webb is correct and everybody else is wrong ... but I wouldn't bet the rent on it.

ESO PR Photo 07/04 shows measured values of the relative change of alpha from the sample of absorption systems studied by Hum Chand and his colleagues, plotted as a function of the redshift and the corresponding look-back time. The open circle is the measurement from the Oklo natural reactor. The horizontal long dashed lines show the area of the previous claim of variation of the fine structure constant. Clearly, the new UVES data are inconsistent with this range.

[Fester Chugabrew]

Their first attempts to publish a technical paper on the subject, however, ran into what Magueijo characterizes as condescension and purely political opposition. Indeed, the childish, personal nature of these arguments will shock anyone who imagines disinterested scientists searching together for truth.

Why am I not surprised?

[FireTrack]

They probably should be able to get some useful data. I can't remember if the pioneers are moving faster or slower than they should be moving distance wise.

The same anomaly appears to be affecting both craft. Both are heading out in opposite directions I believe.

Another thing, our solar system is traveling around the galaxy at much faster velocities than NASA deals with. I don't recall reading anywhere calculations of this effect on propulsion efficiencies.

Some forces may indeed travel faster than light. Gravity for instance. Black holes have gravitational attraction yet light can not escape. I believe entanglement observations has been shown to be practically instantaneous.

How can there be wave shifts without a median that regulates the speed of light even if in a local frame of reference.

There is much that is not understood. So I'm not convinced that one cannot exceed the speed of light, relatively speaking.

[SunkenCiv]

Good topic VR. Just a ping, FO and SM.

[Swordmaker]

Re: Speed of light...

If it is the ultimate speed limit, how do black holes leak???

[SunkenCiv]

:') Must be related to the speed of dark. ;')

[Swordmaker]

:') Must be related to the speed of dark. ;')

With Black Holes it's probably more related to the speed of heavy...

[SunkenCiv]

He's not heavy, he's just a star's dark companion.

[SunkenCiv]

Will Spacecraft ever Go Faster than the speed of Light?
Various - See Text | 16 FEB 2003 | Various
Posted on 02/16/2003 2:16:44 PM PST by vannrox
http://www.freerepublic.com/focus/f-news/844807/posts

[freepatriot32]

ok youll probably know the answer to this over the next 150 baseball seasons do the cubs win the world series ? :-)

[benjaminjjones]

Hey, D-Bag, aerosynamicist amoung

Merriam-Webster Suggestions for aerosynamicist

Merriam-Webster Suggestions for amoung