I see you read Slashdot too!

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Microsoft is over if you want it.

The bar has been lowered for the promotion of ATM ideas; the bar for the acceptance of ATM ideas must remain high.

Oh, I go way back to the underpants gnomes on South Park. I didn't even realize their business model made it big on the internet!

This is where your argument went wrong. Nothing after this statement matters.

Albedo is a measure of the ability of a surface to reflect light. It depends on the composition of the surface (cloudy atmosphere? liquid ocean? ice? dirt? soot?) and the condition of the surface (smooth? rough?). The Earth would exhibit the same albedo whether its core was made of osmium or creamy nougat.

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Microsoft is over if you want it.

The bar has been lowered for the promotion of ATM ideas; the bar for the acceptance of ATM ideas must remain high.

You have to start somewhere. That answer is not as flippant as it sounds
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Why would the 4 rocky planets be the same density? You must think there's a lot of idiots in this place for us to just drift past that assumption un-noticed. How, exactly, could the density (and thus, I presume you infer the bulk composition) of Mercury be the same as Mars when they formed in places two orders of magnitude different in solar radiation.
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You are assuming that the solar system condensed from a dusty ring, I'm assuming it did not. If Newton and Einstein are correct gravity is geometric and basically unstable, you almost have to start with dusty rings to get circular orbits. If on the other hand you reject the relativistic solution for Mercury's procession, it is helpful to have some explanation for Mercury's procession; and the best answer I have today is that a combination of resonant and resistive effects dampens and circularizes orbits.

You mentioned several posts ago that Bouguer anomalies are the difference between the measured gravity and the expected gravity, assuming a body is spherical. That is a simple Bouguer anomaly. The Bouguer anomaly charts of Venus and Mars are based upon the orbitally measured gravity residual after correcting for topographic relief, and assuming a constent density of crustal elements.

Mars volcanic mountains appear to be quite grossly over-dense (compared to the Earth), while the mountains of Venus are measurably under-dense. The deep rifts and lowlands of Mars have measured under-densities - for a while it was speculated that this is because of the presences of water; although both the atmospheric physics and visual observations are not consistent with than explanation. Meanwhile, all the chasma of Venus are over-dense. There may be geological explanations for these oddities, but they are conditions that must be observed if the Newtonian equivalence principle is faulty.

The Earths density is 5.52g/cm^3, the Moon is 3.34 g/cm^3. The combined mass and volume of the Earth and the Moon result in a density of 5.47g/cm^3 (figures below) Why do you cite a figure of 4.47, roughly, the average of the two? Why is that a valid number in this instance? It's not the density of the Earth Moon system as a whole.[/quote]
No its not. It is the (Earth+Moon)densities/2 but we both agree that number is likely meaningless - as I said, I did a best-fit curve from Mercury to Pluto, and the earth and moon straddle it; and if you assume the densities of the Earth and Moon are most likely to be the best determined masses in the solar system, the curve fit slices though at a density of 4.47 - I would be happier if the mean were 5.47g/cc^2; but nature is rarely that accomidating.

Watch Messenger and Mercury - if the topography, as modeled from orbit doesn't come off completely skewed (very under dense mountains, very overdense lowlands) you can deep six my model yesterday.

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jwj

The Reluctant Cosmologist

Wrong assumption about the justification for my assumptions.

I threw out the small icy moons with high albedos because they are most likely very icy - I didn't throw out Europa - as I said, this was a curve fitting exercise based upon the assumptions 1) Newtonian mechanics don't work. 2) If the solar system is a system of captured planets rather than an accretion ring, the average density of all of the planets should be about the same. I was shocked when the curve fit so well, I was even more shocked when I realized how many of the Mars probes appear to have fallen very fast.

I can't stress enough how important the gravity anomaly data is: If you get very close to a moon or planet, the acceleration due to local gravity is is more perturbed by variations in the local gravity field. If you over-or-under estimate the mass of the planet as a whole, you will miscalculate the mass distribution, based upon orbital gravitational harmonics. That's what is happening - Messenger's quick look at Mercury is just the short version.

I have stated that I think that the mass of Mars is ~14% greater than Newtonian estimates. The moment of inertia determined for Mars is 0.366 compared to that of the Earth: 0.3308 That's 111%; which basically assumes a lighter core and heavier crust. That is not unreasonable if you assume Mars cooled faster than the Earth, but it does not explain how or why the surface of Mars under rifts and such should be ultra light, as flyby data indicate. Venus has a moment of Inertia that is slightly less than the earth's, 0.2%; so when you look at the over-dense chasma, you have to ask why the moment of inertia is not higher, too.

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jwj

The Reluctant Cosmologist

Wrong. Newtonian mechanics works quite well on Earth (done any experiments in a lab lately that show otherwise?) and in the Solar System. Only in the case of Mercury is the need for Einstein's amendment strongly needed; and the remaining flyby and Pioneer anomalies are both quite small.
A non sequitur if I ever saw one. Even granting the premise (which I do not) the consequent just does not follow from it.
How about trying some other curves? Exponentials, third-degree polynomials, etc. Bet some of them will fit as well. What justification do you have for the one that you actually chose?
Which sounds impressive (ooh! 111% ooh!) but really is not. A uniform sphere has a moment of inertia of 0.4; a real body will be less because more of the mass is concentrated in a core.
Given your faulty argument starting with albedo, I must find your reasoning about the flyby data equally suspect.

__________________
Microsoft is over if you want it.

The bar has been lowered for the promotion of ATM ideas; the bar for the acceptance of ATM ideas must remain high.

Further utterly foundation-less assumptions. Even if it were proven that the planets are all captured ( which it isn't ), then why would the density be the same for all of them? That's just so hideously wrong it's not even funny Jerry. You're making utterly unjustifiable assumptions simply to fit your model. What you should be doing is looking at the DATA and then working from there, not cooking up a model, and making up the data to fit it.

And again - please explain why you believe the 'average' density of the Earth and the Moon is an accurate figure in any way whatsoever? Why should the moon, a tiny body in mass terms compared to the Earth contribute half the density figure for the Earth Moon system. It shouldnt. You've just made a figure up so it fits your graph. THAT IS NOT SCIENCE. STOP PRETENDING IT IS.

Wrong. Check out Tensors numbers for Icarus:

That's impressive enough to have me believing in relativity! If only every relativity-base prediction worked this well! But then we would have dark matter particles identified, we would be observing gravitational waves; and we could even have seen the edge of the universe with the last generation of telescopes, not the next one.

Yes, there are many mathematical equations that can be matched quite well with our observations - I rest my case on that issue! Mathematically, you can model anything! What I continue to argue is that our observations don't agree with what our theories predicted, and adhering to wrong basic premises has lead to extremely convoluted mathematical models, full of all kinds of darkness... In empty space (dark energy); In galaxies (dark matter) and on Titan (dark stuff).

If you want to see some light, start with some new basic assumptions. Uniform density within the solar system is just one of many possible new basic assumptions. Try some others, and see if you can find one that might work better.

If the moment of inertia of Mars was the same as the Earths, and if the deep ravines of Mars were full of ice, or if they had measurable densities from altitude that is consistent with the crustal density; we would not be having this discussion, because I would be throwing this hypthesis as far as I could chuck it. I have stayed with this concept because I can't null it. I can use it explain why mountains on Mars appear to be much heavier than the Martian crust, even though they really are not.

Given Newton's argument for spontanious generation or Darwin's arguments about use and dissuse, you could use the same grounds for - you get the point: I get to be wrong, at least I am trying.

We have good reasons to believe our planets were once part of a supernova. Is it such a big stretch to assume that they have similar evolutionary histories? Similar compositions> Similar densities? That said, It is possible that the masses very a lot, and that the densities of the outer planets are generally lower than the inner ones. The model I have in my hands says Titan has a mass more than twice that allowed by Newtonian physics, and as long as the surface of Titan looks like sand and is described as 'dark stuff', my answer is as good as anybodies.

Supernova researchers are assuming there is no Malmquist bias in observed supernova, even though we know supernova Ia type events vary as much as 2.5 magnitudes fairly locally. I find that utterly unjustifiable; and grounds for completely new models.

New basic assumptions are a painful, but necessary choice when we don't have a working model of the universe. Make an assumption, prove that it is wrong, make another new assumption.
Assume we drilled cores to the center of the earth and moon from enough locations to conclude that the average density of all the materials found in both the moon and the Earth is 4.47g/cc.

We would need a new theory for gravity that doesn't include the Newtonian Equivalence Principle; and a new set of love numbers, a revised distribution of mass within both the earth and the moon. Possible? Maybe. Likely? NO!

My 'All bodies have the same density' assumption does not work well for the Earth and the moon. I concede that. But if we keep finding iron and pyrenes on bodies in the outer solar system, and if Iapitus turns out to be white-on-black rather than 'dark stuff' on white; and the best physical match for the sands of Titan turns out to be silicate sand and other refractory materials (as grainy particulate usually is); new basic assumptions will be needed; and Dark Energy will not cut it.

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jwj

The Reluctant Cosmologist

Why would I make that assumption? To fit your model? Are you now stating our knowledge of the mass of the Earth and Moon could both wrong by 25% , but in opposite directions?

You might as well say "Assume all planets are made of Brie"

The bulk density of Titan has been calculated via radio science of flybys. We now have a LOT of flybys, which have been used to shape the orbit of Cassini over nearly 4 years. If the bulk density of Titan as we understand is significantly wrong ( as you are now suggesting ) Cassini's mission wouldn't have worked. No debate. Accurate repeated flybys have changed the inclination of the orbit. Now - if you're going to argue that the flawed science of measuring the mass of Titan is the same flawed science used to then use that figure - feel free. But what of the composition of the surface known to be Icy via observations from Cassini. Guess what - we get a density for Titan, and low and behind it appears to be made of the right sort of stuff for that density from observations. Quelle Suprise.

How about an overview, from you, of all the major bodies in the Solar System ( Mercury, Venus, Earth, Moon, Mars, Phobos, Deimos, Ceres, Vesta, Jupiter, The Galileans, Saturn, Titan, Iap, Dione, Enceladus, Uranus, Neptune, Pluto ). How and why do these values : http://en.wikipedia.org/wiki/List_of...bjects_by_mass or other sites citing the known masses of the bodies in the solar system - vary from what YOU think they are. Give us your estimates for values on all those major bodies, citing why you believe their bulk composition to be different to that understood given the variations of density your values will incur.

That was supposed to be a thought experiment: Would you still stick with Newtonian dynamics if the density of the Earth were proven by other means to be less than the Newtonian density, (which is based upon both surface gravity and the Newtonian equivalence principle.

Once again, you are assuming that the equvalence principle is true; you are not allowing for any variability in the mass/inertia relationship. It is a fact that the apparent density of the Titan atmosphere did not thin near the poles (where there was expected to be a gradiant due to thermal condensation.) The atmospheric model did not work! The 'atmospheric drag' model had to be determined by trial-and-error, not using the expected thermodynamics of the Titan atmosphere; including an appropriate gravitational gradient. Remember the disagreement between the density of the upper atmosphere as measured by the INMS; and as experienced by Cassini? More apparent drag means either both the calibration of the INMS is off AND the atmosphere is thicker at altitude than Cassini mission planners had modeled, or the differiential in the gravitational field with respect to altitude is greater-than-expected.

You were not following the threads on the BA board when I was predicting that this would happen - the atmosphere would not appear to thin near the poles as modeled prior to the flybys.

Titan has proven not to be a good case for testing gravity; because if the calibration of the INMS is written off, whatever gradiant is necessary can be penciled in. I will be surprised if in the future, we do not learn than during the close pass of Enceladus, Cassini's momentum towards the moon increased more-than-expected at the moment of closest approach.


But what of the composition of the surface known to be Icy via observations from Cassini. Guess what - we get a density for Titan, and low and behind it appears to be made of the right sort of stuff for that density from observations. Quelle Suprise.

You will find my predictions in the same thread I referenced above:

Potential Threat to the Huygen Mission


The reason for these predictions is simple: I don't think that the Newtonian Equivalence principle is valid; very specifically I think there is a gradient in the path through space that is a function of the local mass; so the path of an orbiting body near the sun is longer (relative to the orbital distance) than the path of an orbiting body at a greater distance from the sun.

Further, I think that since it takes more momentum to complete an orbit nearer to the sun than one further from the sun; A probe such as Messenger to the inner solar system has to lose less energy than expected to park near the orbit of Mercury. I probe lifted to the outer solar system, such as Cassini requires slightly less energy. (In both cases the change in the inertial potential is obviously very small; and in the same direction as the correction for the solar wind.)

Finally, whenever a probe passes near a moon or planet, there is also an inertial gradient that is a function the mass moon or planet; and this very small, but very real gradient must effect the energy budget during a gravitational assist: Generally providing more energy than expected during gravitational boosts, and less gravitational braking than expected when trying to slow the probe down.

If Titan is much more dense than Newtonian physics predicts, the the density gradiant of atmospheric should be tighter: A thicker atmosphere near the surface; and less dispersion of light through the atmosphere than epected: Huygens proved this to be true.

Can you, or anyone else explain why the optical density of the atmosphere on the surface of Titan is only 1.5?

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jwj

The Reluctant Cosmologist

But that doesn't stop you trying eh?

It is very unfortunate that the 'A' channel failure occurred on Huygens: We lost an independent constraint on wind velosity. It is also unfortunate that the solar indexing system could not lock on the sun.

But in view of the way the balance of the data was treated, I don't think it would have made much difference. Although they did not say so at the time; when the first descent profiles were released, mission scientists ignored both channels of the ground truthing radar, and pieced together a descent based upon the time that the ground-sensing probe signal was time stamped, and a bazaar wind profile within Titan's atmosphere. Cassini mission scientists are at it again:

http://planetary.org/news/2008/0320_...Mountains.html

Ok, so Titan is not locked in an orbit that always faces Saturn. Neither is Mercury locked facing the sun, nor the Earth, nor Jupiter, nor Saturn. But what do Cassini scientists conclude from this observational fact?

The orbit is not sychronized with the rotation of Titan, so there has to be a soft liquid layer and the crust is sliding like a spinning egg? Maybe. But why can't the rotation and orbit not be syncronized for some other reason? Reading on:

Except that the data does not come even close to agreeing with this hypotheses spawned before the Cassini mission! Neither Cassini nor Huygens has measured significant quantities of ammonia, a very small, volatile molecule that should have been detected in the atmosphere, if there is a lot of it on or near the surface!

Finally:
Say what? The wind direction - as exposed by the drift patterns, is exactly opposite the direction necessary to paddle the orbital rotation of Titan in the direction it is rotating? What kind of physical model of the planet can cause that? This is absurb!

Restating theories about the Titan system that have been around since long before Cassini, and then drawing conclusions that are consistent with these preconceptions, but directly contradicted by the evidence presented by Cassini is very bad science! It is offensive to the heart of this mission, and what this wonderful probe is trying to tell us: The preconceptions of what Titan is or should be are all wrong.

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jwj

The Reluctant Cosmologist

Thanks for the Titan’s Winds article Jerry. There may be other factors involved in planetary spin, though the idea of a movable crust is intriguing. However, the article’s explanation does not seem to hold water, since the winds are shifting.

Okay, we could live with this, that there is a prevailing EAST-WEST wind, though seasonality may affect this. But then it says further down in the same article: So now the prevailing wind is WEST-EAST, or opposite, depending on the seasons? This sounds like a ‘zero sum’ game to me. So I must agree with Jerry’s: What kind of modeling is that? The same with wind caused ‘sand dunes’ where the explanation offered is murky. In effect, this article really offers no explanation.

OTOH, I realize the ‘turkey timer’ is about to go off (tomorrow?), so here’s my recap of what I think was ‘value added’ in this discussion, thanks to Jerry and all who participated:

1. Testing for ‘anomalies’ that keep cropping up in astronomical observations, regardless of theory, demands critical examination.
2. There are many such anomalies, explored without mercy on ATM discussions, enough to warrant possible revisions in MS cosmology theories.
3. Theories are ‘models’ no matter how internally consistent, or mathematically elegant, so they should not hold greater value than empirical observations, no matter how anomalous those observations turn out to be (or how 'elegant' the theory challenged), where new theory may be called for to better explain anomalies found.
4. To defend theory based on historicity of its effectiveness in describing cosmological observations does not override anomalous observations that keep challenging such theories.
5. It is possible our scientific theoretical understandings based upon current cosmology modeling may be wrong enough to overturn some cherished MS ideas, such as: distant light redshifts as space-expansion (and BBT), Type II 1a standard candles for distance and time, gravitational anomalies such as Pioneers et al, distant body mass and density anomalies (even within the Earth’s crust) especially for Pluto and Charon system where they may be no more than dirty snow and ice balls, anomalous atmospheres on gas giants and moons, flat rotation curves for galaxies (MOND), extreme gravity at galaxy centers (black holes), extreme fast rotation for neutron stars, cometary comas defying the ‘dirty snow ball’ hypothesis, why looking back through Hubble telescope nearly 13 billion years we find fully formed galaxies, and non-falsifiable Dark Matter/Dark Energy, including non-observance of ‘gravity waves’.
6. To test for alternative theoretical models to explain this growing list of cosmology anomalies may require abandoning some presently accepted theories to make room for new ones.

On both sides of the aisle were arguments, where on one side were those arguing for holding current theory and looking to better explain such anomalous observations within context of known astrophysical models (sometimes rigorously defended with MS theories), and the other side calling for major rejections of some aspects of modern theory models and look for new ones. The demise argument in "Demise of ATM Discussions" would favor the first argument, that we need to better study and understand current cosmology rather than challenging it, especially by those not really qualified to do so; while those who favor a non-demise of ATM call for more questioning and brain-storming to find new theoretical explanations that better fit the patterns of anomalous observations streaming in from the latest data. That’s about where I think we are right now, but mine is only an opinion of one. I vote for ATM’s non-demise, and welcome participants to take their positions as far as they can go, arguing for what they think they understand, even if it means sometimes not having the necessary tools to make a full case robust enough to stand up to MS. But keep trying and do not feel bullied because those who argue on the basis of scientific ‘historicity’ had done this before, and in the end theirs were the theories that failed. The Copernican revolution was the end result of new modeling that completely overturned the old. We may now be entering a period in astrophysics that will dramatically change what we had come to accept as seen through General Relativity and supersymmetry. There may be a better way, one that will combine not only strange anamolies but eventually explain Maxwellian theory with a better model down to the Quantum level. And when that happens, when and if it happens, a whole new world of scientific discoveries, and possibly a whole new means of space exploration with new forms of propulsion (beyond rocket science) may take what is today ATM into the Mainstream.

Thanks Jerry, and all who participated in this very interesting seminal discussion.

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Wait. "Always generally"?

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Gillian

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