Posted on 02/16/2007 11:23:52 PM PST by neverdem
Excellent
It seems to me that my expression of the error in this case is better. The calculation is of the rate of precession of the perihelion and it is the observed rate of it that should be the basis for the calculation.
The precession rate is not directly connected to the orbit per se and is, I think, calculated not by dynamically simulating the orbit of Mercury for 100 years from one perihelion to another 415 revolutions later and noting that the position has advanced 5557 arc seconds, but rather by adding together a set of effects and directly obtain an amount of extra turning.
Oh yes, and on that coolissues site. I am not physicist enough to evaluate that page and dispute it point by point but I am very suspicious. For example, he speaks of and stresses certain "ad hoc" equivalences and of course that's not a good description of the way it works in real life. Such things are guided by the very good physical intuition of these scientists and then checked by evaluating the consequences. For another, he speaks favorably of "speed of gravity" skeptics but their claims have been thoroughly debunked. Yet another is I checked out his Precession of Perihelia page. He says in one place
In the 19th century, the French astronomer Le Verrier found that the perihelion of Mercury advanced by 43 arc- seconds/100yand later says
574.1 arcsec/100y, the observed precession of Mercurywhich are not only contradictory but both are wrong and the first mistakes the Newtonian error in the precession for the actual precession.
I think the guy's a crackpot. Like that theorist who's joined the Baghwan and writes his Unified Field papers.
Both science and wikipedia have become politicized, if you haven't noticed. That's why I avoid wikipedia whenever I can. Wikipedia was a good idea whose time is past, IMHO. There are too many folks with agendas out there.
Thank you! I do consider myself a decent scientist.
Probably more thought than went into the original article :)
It seems to me that my expression of the error in this case is better. The calculation is of the rate of precession of the perihelion and it is the observed rate of it that should be the basis for the calculation.
The precession rate is not directly connected to the orbit per se and is, I think, calculated not by dynamically simulating the orbit of Mercury for 100 years from one perihelion to another 415 revolutions later and noting that the position has advanced 5557 arc seconds, but rather by adding together a set of effects and directly obtain an amount of extra turning.
Hmm, I see it as using Newtons equations to predict the orbital motion for 415 revolutions and simply using the precession point as an identifiable place marker. It is relatively easy for astronomers to find that point. The time frame is very important because if Newton is off by 43 arc seconds in a year, that is very different than being off by 43 arc seconds in 100 years. If I understand you correctly, you are saying that the time frame doesn't matter. I disagree.
Remember the whole point of this was to determine the accuracy of Newtons gravities force equation :) In this particular instance Newtons equations were not very accurate, and Einsteins equations were more accurate.
If we want to really figure out how accurate the equations are, we probably should use them to figure out the masses of the bodies. I think that would be easier, orbital mechanics get messy really fast.
I just brought up the cool issues site because I thought it had some relevance to the Newton/Einstein issue. I prefer skeptical sites rather than boring, this is the way it is sites, even though the skeptics are almost always wrong (in real physics).
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