Changes
The Mercury anomaly
:::The physics journals all seem to require payment for access. But type this into a Google search: 5599.7 Mercury. You'll then see what the liberal physics professors won't tell you, as Google returns fragments from limited-access journals. Then, please, pause for a moment and ask yourself: why didn't they tell you this so you could decide for yourself, rather than being told what to think?--[[User:Aschlafly|Andy Schlafly]] 18:40, 14 November 2009 (EST)
::::Oh, okay. I see where you made an honest mistake.
::::There are two numbers at play here: there's the ''observed'' precession of Mercury's orbit, and then there's the ''anomaly.'' The anomaly is the amount by which the observed precession differs from the mathematically predicted precession. What you did was quote a figure for the ''anomaly'' using the figure for the ''observed'' precession. Hang on, lemme splain.
::::The precession of an orbit is the sum of several effects. Newton's approximation for gravity predicted three different effects: axial precession of 5,025 arc seconds per century, 530 additional arc seconds per century from the gravitational effects of the other planets, and a tiny amount, less than one arc second per century, due to the fact that the sun isn't a perfect sphere. (Those numbers are all rounded off; the precise figures are trivially googlable.)
::::If you add up the precession predicted by Newton's approximation, you get exactly 5,557.02 arc seconds per century.
::::But if you run the numbers using the Einstein equations instead of the Newton equations — using the same constants for things like the mass and shape of the sun — you get a precession of exactly 5,600±0.04 arc seconds per century. It's really weird that it would be a round number like that, but that's how the math works out.
::::The observed precession of Mercury's orbit? It's 5,599.7 arc seconds per century. Which is where you got your number from. And that means the general relativity prediction was accurate to within (deep breath) one half of one one hundredth of one percent.
::::That's like shooting an arrow from Los Angeles and hitting the bullseye in Melbourne.
::::Would you be a dear and remove the incorrect anomaly figure from your essay now? I know it's a work in progress and I hate nitpickers, but somebody could stumble across that and be misinformed.--[[User:KSorenson|KSorenson]] 19:11, 14 November 2009 (EST)
