Difference between revisions of "Talk:Essay:Quantifying Order"

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(Mercury anomaly data)
(And about that Will paper)
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So the Einstein prediction is within the margin of error of those four radar-ranging measurements of the Mercury anomaly. I'm sure there've been more recent studies, but I don't have them literally sitting in front of my face at the moment, so those are the ones I'm citing. Can I see your numbers that say the Einstein prediction is outside the margin? More recent data than what I have in my hand here maybe? (This Pijpers paper is [http://arxiv.org/pdf/astro-ph/9804258v1 on ARXIV], by the way, if you want to check it out.)--[[User:KSorenson|KSorenson]] 21:17, 14 November 2009 (EST)
 
So the Einstein prediction is within the margin of error of those four radar-ranging measurements of the Mercury anomaly. I'm sure there've been more recent studies, but I don't have them literally sitting in front of my face at the moment, so those are the ones I'm citing. Can I see your numbers that say the Einstein prediction is outside the margin? More recent data than what I have in my hand here maybe? (This Pijpers paper is [http://arxiv.org/pdf/astro-ph/9804258v1 on ARXIV], by the way, if you want to check it out.)--[[User:KSorenson|KSorenson]] 21:17, 14 November 2009 (EST)
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Oh, and just incidentally? Will didn't leave Mercury out of his paper; he just talked about it in really jargony physics-paper language.
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:Three decades of experiments, ranging from the standard light-deflection and perihelion-shift tests to lunar laser ranging, planetary and satellite tracking, and geophysical and astronomical observations, have placed bounds on the PPN parameters consistent with general relativity.
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"PPN" is the ''parameterized post-Newton" formalism, a rewriting of the law of universal gravitation to include coefficients derived from general relativity. The Einstein field equations are nightmarish to solve, so PPN was created as a middle-ground approximation between the (good but not good enough in some contexts) Newton approximation and the agonizing pain of having to actually ''solve'' the Einstein field equations every time you want to calculate the delta-vee required during a solar slingshot maneuver for a planetary probe. What Will said in that paper is the PPN approximation has been tested ''against general relativity'' and supported by 30 years of experiments.
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This is really getting into the tall grass, and I know how you hate wasting time. Maybe we can bring this conversation to a conclusion? --[[User:KSorenson|KSorenson]] 21:38, 14 November 2009 (EST)

Revision as of 20:38, 14 November 2009

"Subsequently, however, more accurate measurements with more sophisticated technology have determined this precession to be 55 arc-seconds per century, nearly 30% off the number provided by relativity."

Please provide a citation in the article for this. I'm shocked that I somehow missed the news. Thanks much. --KSorenson 17:48, 14 November 2009 (EST)

I'm urging you to look beyond what you're taught. I went through the same physics curriculum as others, and it is what isn't taught that matters. Earnestly.--Andy Schlafly 17:53, 14 November 2009 (EST)
Okay. Let's find a way of making that point without quoting an incorrect value for the Mercury anomaly then? Cause putting in a number that's not actually supported by observations just to make a philosophical point seems kind of … I dunno. Deceptive? --KSorenson 17:58, 14 November 2009 (EST)
Kate, if I can call you that, I have no reason to lie about this. I'm not applying for any grants. I'm not trying to get a PhD from liberal professors. I'm not worried about what my colleagues might say. Like the Bible, I'm just telling the truth, and trying to learn more of it.
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?--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.--KSorenson 19:11, 14 November 2009 (EST)
Your point is an excellent one. Thank you. The 30% figure was wrong for the reasons you provide.
But the underlying point in this entry remains correct: due to advances in precision in measurement, the prediction of relativity no longer matches the data on the precession. The discrepancy is much greater than the margin of error, which is all that matters from a logical perspective. The entry has been updated accordingly, and I welcome further comments you may have.--Andy Schlafly 19:44, 14 November 2009 (EST)

(Unindent) I'm not sure you're going to welcome these comments, sir. Because you're just flat-out, provably, unequivocally wrong on this one. The observed value of the precession of Mercury hasn't been changed in a hundred years, because it's a direct observation. We measured it with telescopes, and those were just fine at that scale a century ago.

I'm afraid your edit made the offending section paragraph even more misleading than it was. Predicted value of the precession (via Newton) in 1915: 5,557. Observed value in 1915? 5,600. Difference? 43. Predicted value from the Einstein equations? 5,600. Observed value today? Still 5,600. Difference? Ridiculously small. I know you're actively working on this essay, and I feel really bad about beating you up over this, but you wouldn't have the paragraph in there unless you thought it had value.

Just so you know, I've got some feedback on your paragraph on quantum mechanics as well. For starters, the position and momentum of a particle is exactly as uncertain after an observation as it is before, because reducing uncertainty of the position increases uncertainty of the momentum and vice versa. They're intrinsically linked. Maybe that's not your point; measuring a particle does, I suppose, bring about a sort of philosophical order that was previously absent — we know where the particle is now — but at the cost of reducing our knowledge about another aspect of the particle's motion. But your essay isn't fleshed out enough for me to really see yet what you're getting at, so that might be irrelevant to your point. --KSorenson 20:00, 14 November 2009 (EST)

Kate, I don't have an ax to grind about this. General Relativity was developed to explain the Mercury precession, so the theory certainly should fit the data. I expected that it would. But the fit isn't there anymore, due to more precise measurements. It's beyond the margin of error, and logically that's all that matters. You're using rounding above that obscures what the margin of error is. Professor Will does not even include this test in his recent summary of all the evidence for GR, and we can now see why. Those are the facts, and logic applied to the facts. Anyone has free will to accept or deny it. I accept the facts and logic as they require.
You make an interesting point about position, but I don't think the essay is incorrect because it says nothing about momentum. Observation can pin down the position, which is relevant to establishing order. But without observation there is disorder. That is the basic point.--Andy Schlafly 20:11, 14 November 2009 (EST)
Right, but there's an error of fact buried in there. It's a totally innocent one, I'm sure; I'm not accusing you of axe-grinding. It's just that the precession of the perihelion of Mercury has not changed since 1916 when the theory was published. It's not that we measured it with telescopes before 1916 and got a rough estimate, and now we measure it with better telescopes and have a much more precise figure. We measured it before 1916 and got a very accurate figure because measuring the motion of Mercury just isn't that hard, and the measurements we make today with better telescopes say only that yup, the older measurements were pretty much spot on.
What we have done since then is to much more precisely measure the oblateness of the sun. There was a big controversy about that back in the … hmm … 80s I think it was? Goldberg and Dicke claimed that the sun was much "fatter" than previously thought, which would have made the predictions from general relativity different from the observed precession. Maybe that's what you're thinking of? For a while there was a lot of disagreement about what shape the sun actually is, but that's been pretty much put to bed with both more accurate ground-based observations in the 90s and helioseismography.
Anyway, saying that the prediction matched the observation in 1916 and doesn't today is simply flat-out false. If your argument depends on it, then you're hurting your argument with this point. If it doesn't, then what's the harm in fixing it?
Thanks for clarifying your point about quantum mechanics. --KSorenson 20:35, 14 November 2009 (EST)
Kate, as I said, I don't care either way, but I am going to tell the truth. GR fit the observed data in 1916 (indeed, GR was developed to fit it), but now (due to more sophisticated measurements) the GR prediction is wrong by more than the margin of error. None of your comments above address the margin of error, which must be the scientific focus. A difference between theory and observation is not "ridiculously small" if it is more than the margin of error, as in this case.--Andy Schlafly 20:47, 14 November 2009 (EST)
Perhaps this is what Mr. Schlafly is referring to. The article states that 5599.7 arc-seconds is the observed value. KSorenson is quoting a value of 5,600 (±0.04). 5600-.04=5599.96. From just those values then yes the relativity value is higher by .26 arc-seconds even factoring in the error. The only thing I ask is what is the error range for the observed value? ameda 21:08, 14 November 2009 (EST)
Presumably the error range for the observed value is no more than .1. Again, note that Professor Will conspicuously omits this famous claim of evidence for GR from his recent comprehensive summary of the evidence for GR, as cited in this entry.--Andy Schlafly 21:12, 14 November 2009 (EST)

(unindent again because I'm lazy with bullets) We can do a heck of a lot better than "presumably," Andy, and as a person who cares deeply about facts and logic, you darned well know that. I happen to have the Pijpers paper from 94 here; I dug it out when I thought you might have been thinking of helioseismography. In it he cites radar ranging studies from 1976 to 1992. Here's the data, with margins of error. Note that these numbers are for the anomaly, and not the precession total, and remember that the figure from the Einstein equation is 42.98 ± 0.04, okay?

  • 43.11 ± 0.21 (Shapiro 76)
  • 42.92 ± 0.20 (Anderson 87)
  • 42.94 ± 0.20 (Anderson 91)
  • 43.13 ± 0.14 (Anderson 92)

So the Einstein prediction is within the margin of error of those four radar-ranging measurements of the Mercury anomaly. I'm sure there've been more recent studies, but I don't have them literally sitting in front of my face at the moment, so those are the ones I'm citing. Can I see your numbers that say the Einstein prediction is outside the margin? More recent data than what I have in my hand here maybe? (This Pijpers paper is on ARXIV, by the way, if you want to check it out.)--KSorenson 21:17, 14 November 2009 (EST)

Oh, and just incidentally? Will didn't leave Mercury out of his paper; he just talked about it in really jargony physics-paper language.

Three decades of experiments, ranging from the standard light-deflection and perihelion-shift tests to lunar laser ranging, planetary and satellite tracking, and geophysical and astronomical observations, have placed bounds on the PPN parameters consistent with general relativity.

"PPN" is the parameterized post-Newton" formalism, a rewriting of the law of universal gravitation to include coefficients derived from general relativity. The Einstein field equations are nightmarish to solve, so PPN was created as a middle-ground approximation between the (good but not good enough in some contexts) Newton approximation and the agonizing pain of having to actually solve the Einstein field equations every time you want to calculate the delta-vee required during a solar slingshot maneuver for a planetary probe. What Will said in that paper is the PPN approximation has been tested against general relativity and supported by 30 years of experiments.

This is really getting into the tall grass, and I know how you hate wasting time. Maybe we can bring this conversation to a conclusion? --KSorenson 21:38, 14 November 2009 (EST)