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Gravitation Anomaly Measured
Rob Riggs writes "Is there a hole in Einstein's Theory of Relativity? A story in The Economist talks about an apparent gravitation anomaly recorded during solar eclipses. According to Chris Duif at the Delft University of Technology, the 'Allais effect' is real, unexplained, and could be linked to another anomaly involving a the Pioneer spacecraft. More detailed information can be found in the paper he has just posted on arXiv.org."
Yes. Syzygy is when the Earth, moon, and the sun are all lined up. Spring tides occur at this time. Spring tides are unusally high tides that occur during syzygy.
I would highly doubt that Einstein's theory is flawed, but then again, they did not study the effects of gravity during a solar eclipse back then.
Not only is this comment not "insightful" but it is just plain wrong. One of the original PROOFS for relativity involved measuring the amount that light is bent during a -- pay attention now -- solar eclipse. To quote the article you so carefully did not read, it was "observations taken during a solar eclipse (of the way that light is bent when it passes close to the sun) which established General Relativity in the first place."
Next.
The "three-body problem" is that there is no known general closed-form solution to Newton's laws if more than two gravitating bodies are involved. In short, you can't derive an equation that will give you the positions of all three objects at any arbitrary point in time.
Instead, iterative solutions are used: given the current masses, positions, and velocities of the objects involved, figure out where they'll be a short time from now. Lather, rinse, repeat. The problem with this is that over long timespans (tens of millions of years), errors build up.
"They redundantly repeated themselves over and over again incessantly without end ad infinitum" -- ibid.
"Photons have mass. "
They don't. They do have momentum though.
I wonder if Gravity Probe B will be able to measure this effect if it is still in working order next time an eclipse rolls around.
(Side note-- I never heard of this probe until I saw it in a magazine. Why not?)
MOND evidently has problems; while dark matter can explain both galactic rotation curves and cosmological behavior, MOND is hard to make consistent with both. (And it's also, I've heard, extremely hard to make consistent with any relativistic theory of gravity.)
As for the "apparent need" for FTL expansion in the early universe, by which I assume you mean inflation, some very specific predictions of inflation are now verified by WMAP, including the structure of the acoustic peaks in the CMBR angular power spectrum.
Wacky as they may seem, dark matter, dark energy, and inflation are the mainstream theories right now for a reason: the alternatives so far simply don't work as well.
The easy explanation as I was given to understand is that the photons propagate in spacetime, ie the wave that they are does. Spacetime is curved by gravity, hence the photons/waves curve with them. According to General relativity, they cannot have mass since they propagate at light speed. Any object with mass obtains infinite mass upon attaining lightspeed, which is impossible. Hence a photon has no mass. Of course, solar sails work so photons can exert pressure which might lead one to suppose they have mass. In sense they do, as energy and matter are equivalent. In the case of a solar sail, it is impulse that is being transferred. It depends on how you measure the presence of the photon. By the way, note that Duif does not cast doubt upon Einstein's theories per se. Rather, he invokes the presence of dark matter (although no one has ever demonstrated its presence unequivocally).
----- One learns to itch where one can scratch.
The Economist is probably the best source of general news available. It is in the same category as Time, Newsweek, US News & World Report, except that where those magazines tend to be 10-20% real news and 80-90% pab, the Economist is the inverse with 80-90% real hard news.
They know it too, and consequently it is very hard to find much of a discount on subscription pricing -- if you can pick it up for under $100/yr you are doing very well. All those other rags can typically be found for pennies on the dollar if you look.
In case you can't tell, I get all my news online - no tv news, no newspaper, maybe a dab of NPR when I'm tired of listening to my music in the car and no magazines, except the Economist. Which I get full access to online by virtue of paying for a paper subscription.
The General Theory of Relativity consists of sixteen coupled differential equations that can be reduced to ten, which when just written out would take hundreds of pages. It is so complex that there are research programs just categorizing possible solutions.
Analytical solutions only exist for two cases: the overall case that describes a homogeneous universe, and the Schwartzschild case that describes a spherical body. There is also a linear approximation that gets gravity waves.
It's a bit premature to say that GR has a hole in it, because nobody has ever explored it fully. Perhaps this will lead to a solution of GR for this case, or perhaps not.
I'm inherently skeptical of any paper first heard of via a website. Call me old fashioned, but I'd rather wait for peer review to run its course and read this in something like the Journal of the AAS. Having said that, I read the paper and it's considerably less sensational than the summary suggests. The author considers it possible, if not probable, that the effects can be ascribed to a combination of experimental error and theorists not having taken into account the circumstances of the situation. He suggests that further research would be useful, but I've never read a paper that didn't...
"'I pass the test,' she said. 'I will diminish, and go into the West, and remain Galadriel.'"
- JRR Tolkien.
You obviously aren't a subscriber or a regular visitor to their website. The Economist is simply the best weekly news print magazine in the world. For example, it's the only news magazine which never makes me cringe when they cover technical subjects I know well like Linux or computing. Same with their culture section, world news, etc. They've been doing this since 1843 and they are bad ass. I highly recommend it to anyone looking to read just one print magazine a week to learn about world news.
:-)
And no I don't work for them.