Prediction results

[Jerry]

It has been a while, and it is fair to look back and see how I did:

There are a few interesting things coming down in the next 18 months or so: Direct observations by NEAR in the asteroid belt; Stardust pays a visit to the Deep Impact target, Tempel 2. Messenger goes into orbit about Mercury and Hayabusa returns. Lots of excitement.

Tempel II: Mission scientists expect to see a gaping hole carved by the Deep Impact probe. I expect an unobservable-to-barely observable surface-wound feature. The difference depends upon whether Tempel II is a dense object, or an object with a density of less than 0.2g/cc, as Deep Impact scientists calculated. I think that is absurd.

Messenger: With a successful orbit, Messenger will be able to measure the gravity fields of Mercury. We won't know right away, but over time, a painful discrepancy will emerge: the high regions will map out as being unphysically underdense, while the low regions will map extremely over-dense. Expect a delay of at least six years in the release of the data: It is hard to release data that is not understood. (The oddball changing color of Pluto was first observed eight years before this was published.)

Near: Just as engineers had a devil of a time figuring out how near Hayabusa was to Itokawa; Near is going to find navigation very close to asteroids highly problematic. Expect results as terse as the first atmospheric braking exercises in the Martian orbiters - a lot of trial-and-error.

Starting with Deep Impact: This prediction is spot on, although it would have helped if I would have quantified with numbers - the Deep impact site was barely discernable, a modest 100 meter diameter crater with no only a few meters of discernable depth - about what an impact of an object on the moon would have created.

It is clear from Mark's blogs entries at planetary.org the approach was a trial-and-error exercise. I hoped, as meticulously as he details the mission, he would have reported the nature of the challenge; but he instead focused on how well the software adjusted to the challenge.

Finally Mercury: Yes, they are having a devil of a time modeling the surface, the Newtonian dynamics require a thin skin, flowing mantle very close to the surface. This should have led to mascons much like what we see on/in the moon, but so far, there is little evidence of mascons. So it is curious.

As for the predictions of under-dense peaks and over-dense low-lands; preliminary data seem to indicate exactly the opposite - so it is back to the drawing board.

[Jerry]

The predictions, by the way, are almost observationally derived. We keep seeing heavy metals in places we do not expect them: On and in comets; and on some of the moons of Saturn. Moons of Saturn; according to Newtonian principles, must be very low in density - made up primarily of water-ice and such. In the formation of such a moon, it is rational (using other Newtonian rules) to assume most of the heavy metals settled into cores. Cassini fly-bys of Titan seem to indicate the moon is virtually undifferentiated. Likewise, we now know that Newtonian dynamics require a very large mantle in Mercury; which should not be true if normal thermaldynamic processes led to passive cooling. There are similar problems with the IR signatures of the outer planets: They are too warm.

There are plenty of reasons to assume something is wrong with the basic physical rules we think govern planetary motions, compositions and histories: The temperatures are wrong, the surface chemistry is wrong, the colors are wrong and the gravitational dynamics are giving us fits trying to model them. It is not that unreasonable to question that the Newtonian equivalance principle - so completely consistant on the surface of the earth - is not sustainable elsewhere.

[stutefish]

Jerry, can you provide a link to your original predictions?

ETA: Also--and perhaps more importantly--can you provide links to support your claims regarding what is observed, and what was expected?

Thanks!

[djellison]

We keep seeing heavy metals in places we do not expect them:

Please cite references that show we do not 'expect' heavy metals in these places, and references showing that we do find them.

[quote] On and in comets; and on some of the moons of Saturn.

Moons of Saturn; according to Newtonian principles, must be very low in density - made up primarily of water-ice and such. In the formation of such a moon, it is rational (using other Newtonian rules) to assume most of the heavy metals settled into cores.

Please cite references for this.

Cassini fly-bys of Titan seem to indicate the moon is virtually undifferentiated.

Wrong.

http://www.astrobio.net/pressrelease...moods-of-titan

The work shows the moon’s interior is partly or possibly even fully differentiated. This means that the core is denser than outer parts of the moon, although less dense than expected. This may be because the core still contains a large amount of ice or because the rocks have reacted with water to form low-density minerals.

There are similar problems with the IR signatures of the outer planets: They are too warm.

How warm 'should' they be. Why do currently accepted theories to explain this not work for you.

The temperatures are wrong, the surface chemistry is wrong, the colors are wrong and the gravitational dynamics are giving us fits trying to model them.

Again - what 'should' these be - in what way are they different - and why are any current scientific theories to explain this not valid in your opinion.

And somewhat tangentially but in your world of physics clearly somewhat related - have you given up on your anomalistic theory regarding Huygens EDL yet?

Near: Just as engineers had a devil of a time figuring out how near Hayabusa was to Itokawa; Near is going to find navigation very close to asteroids highly problematic. Expect results as terse as the first atmospheric braking exercises in the Martian orbiters - a lot of trial-and-error.

I will assume you mean Dawn....not NEAR? Navigation around low mass bodies is always challenging - period. Please cite the "devil of a time figuring out how near Hayabusa was to Itokawa" and how that is a result of some missinterpretation of physical properties or laws of physics rather that a simple engineering challenge with an unwell spacecraft.

Also - What about NEAR. What would you have expected that spacecraft's challenges to be orbiting Eros - and how did it actually play out.

Please explain what was 'wrong' with Aerobraking at Mars with MGS and MODY.

[John Mendenhall]

It is not that unreasonable to question that the Newtonian equivalance principle - so completely consistant on the surface of the earth - is not sustainable elsewhere.

Nice call on the impact, Jerry.

On the one above, could you clarify what you mean. Equal and opposite reaction?

Thanks, John M.

[Reality Check]

Starting with Deep Impact: This prediction is spot on, although it would have helped if I would have quantified with numbers - the Deep impact site was barely discernable, a modest 100 meter diameter crater with no only a few meters of discernable depth - about what an impact of an object on the moon would have created.

No numbers means that this was not a prediction, basically just a guess. You need to start with telling us the size and depth of the crater that Deep Impact would have made on the Moon.

[djellison]

The size of the crater on Tempel 1 is consistent with a surface material fine enough to produce the huge, fine cloud of ejecta we saw with Deep Impact. I'm really not sure what's 'wrong' with this or why it speaks to some fault within Newtonian physics.

Elaborate, please, Jerry.

[captain swoop]

If Newtonian Mechanics is so wrong how did they hit the comet?

[Jerry]

The size of the crater on Tempel 1 is consistent with a surface material fine enough to produce the huge, fine cloud of ejecta we saw with Deep Impact.

I'm really not sure what's 'wrong' with this or why it speaks to some fault within Newtonian physics.

Elaborate, please, Jerry.

When Deep Impact struck Tempel 1; most of the ejecta was iron-rich silicates with a very low percentage of water. After the Deep Impact event, mission scientists estimated the mean density of Tempel 1 to be about 2gm/cc; much too light for a body made of layered sand with little water. Mission scientists speculated that Tempel 1 is a highly porous body with a great amount of void volume, and this honeycomb structure allows the comet to be composed of iron silicates and still have a low density. This is why they thought the Deep Impact probe penetrated deep into the comet, and they generally expected a massive impact crater.

What we have observed on Temple I, is what appears to be sedimentary layers, and yes, the impact result is entirely consistent with fine, nearly dry sand. It is the density of these surface materials that create a problem for Newtonian dynamics. A mean density of two, is too low.

Cassini fly-bys of Titan seem to indicate the moon is virtually undifferentiated.

Wrong.

http://www.astrobio.net/pressrelease...moods-of-titan

The work shows the moon’s interior is partly or possibly even fully differentiated. This means that the core is denser than outer parts of the moon, although less dense than expected. This may be because the core still contains a large amount of ice or because the rocks have reacted with water to form low-density minerals.

The 'virtually undifferentiated' and 'partially differentiated' are almost synomonous. What the gravity field demonstrates is that it is impossible to use Newtonian physics and fully differentiate Titan. A moon the size of Titan should be differentiated - We see evidence of layering on bodies the size of small asteroids and comets. It is silly to talk about water in the core of a body as large as Titan. If there is as much iron in Titan as we are finding on the surface and in the skin layers of comets, Titan should have a healthy iron and possibly nickel core.

[R.A.F.]

If there is as much iron in Titan as we are finding on the surface and in the skin layers of comets...

Cite please.

[djellison]

When Deep Impact struck Tempel 1; most of the ejecta was iron-rich silicates with a very low percentage of water. After the Deep Impact event, mission scientists estimated the mean density of Tempel 1 to be about 2gm/cc; much too light for a body made of layered sand with little water (1). Mission scientists speculated that Tempel 1 is a highly porous body with a great amount of void volume, and this honeycomb structure allows the comet to be composed of iron silicates and still have a low density. This is why they thought the Deep Impact probe penetrated deep into the comet, and they generally expected a massive impact crater.

What we have observed on Temple I, is what appears to be sedimentary layers, and yes, the impact result is entirely consistent with fine, nearly dry sand. It is the density of these surface materials that create a problem for Newtonian dynamics. A mean density of two, is too low.(2)

The 'virtually undifferentiated' and 'partially differentiated' are almost synomonous. What the gravity field demonstrates is that it is impossible to use Newtonian physics and fully differentiate Titan(3). A moon the size of Titan should be differentiated(4) - We see evidence of layering on bodies the size of small asteroids and comets. It is silly to talk about water in the core of a body as large as Titan.(5) If there is as much iron in Titan as we are finding on the surface and in the skin layers of comets, Titan should have a healthy iron and possibly nickel core(6).

I have put numbers on 6 different claims. Please cite sources for these claims. It is OK to say 'no source, just my opinion'

Moreover - I asked 8 different questions earlier in this thread that you are yet to answer. This is ATM - you are obliged to do so, even if your answer is 'I don't know'

[Jeff Root]

If Titan has little differentiation, could it be due to forming
relatively slowly and remaining cold the whole time?

-- Jeff, in Minneapolis

[tusenfem]

I have put numbers on 6 different claims. Please cite sources for these claims. It is OK to say 'no source, just my opinion'

Moreover - I asked 8 different questions earlier in this thread that you are yet to answer. This is ATM - you are obliged to do so, even if your answer is 'I don't know'

Let's make this official: Jerry you will answer all the questions that are put to you in this thread. Not just the handwaving arguments without any support, but as thorough answers as you can give them backed up with actual citations to results and measurements.

Example: You give a number for the moment of inertia of Titan (~0.34), and then explain about what this number means (see e.g. this paper from which I took the number) what value has a fully differentiated object (e.g. Ganymede 0.31), what value has a totally non differentiated object (that would be 0.4), etc. etc.

You have some work to do.

[djellison]

I'd also like to ask Jerry what single piece of science data he thinks best highlights his proposed flaw in Newtonian physics. It seems there's quite a lot of scattergunning going on - blasting any and every planetary target with some alleged discrepancy. What do you consider to be the single most convincing piece of evidence for your opinion Jerry?

[Jerry]

I have put numbers on 6 different claims. Please cite sources for these claims. It is OK to say 'no source, just my opinion'

Moreover - I asked 8 different questions earlier in this thread that you are yet to answer. This is ATM - you are obliged to do so, even if your answer is 'I don't know'

Somewhat obliged. I posted a list of predictions and the results. One of the results was wrong; and that kinda killed the reasoning behind the prediction; falsifying the theory; because it only takes one false - I need to modify the theory, or deep six it - at the moment it is not defensible!

But I don't think the mainstream theory is defensible, either: We just slammed a copper bullet the size of a major appliance into a comet and hardly made a dent in it. What happens to a moon made out of Ice when a comet that doesn't flinch when it is hit by a canon crashes into it? Hyperion looks like I would expect an icy body to look like: deep craters with major deep plumes. Mimas and Janus don't - the crater floors are shallow and include clear impact nipples. I don't think they are made out of Ice any more than the moon is - just coated with Ice to a fairly shallow layer.

Again, it is the density implied by the topography and surface features of Tempel 1; coupled with the sandy ejecta that challenge the theory that these outer solar system travelers are low density bodies.

[djellison]

We just slammed a copper bullet the size of a major appliance into a comet and hardly made a dent in it.

So? Also - I don't tend to call 7 years ago as 'just'. Moreover - we made quite a significant dent in it.

What dent would you have expected?
Why?
What composition AND bull material property would you have expected Tempel 1 to have?
What, after the impact, do you believe is different about these than the precitions?
How do you correlate data such as this ( http://deepimpact.umd.edu/gallery/spectrometer2.html ) with your theory?
How do you correlate your theory versus peer reviewed data such as this ( http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2214.pdf ) ?

What happens to a moon made out of Ice when a comet that doesn't flinch when it is hit by a canon crashes into it?

What does this have to do with the comet?
Why do you say 'doesn't flinch' when something the size of a washing machine made a 100 meter wide crater. Clearly - it flinched, and fliched in a large way.

Hyperion looks like I would expect an icy body to look like: deep craters with major deep plumes.

Why do you 'expect' icy bodies to look like that

Mimas and Janus don't - the crater floors are shallow and include clear impact nipples. I don't think they are made out of Ice any more than the moon is - just coated with Ice to a fairly shallow layer.

'the moon' - do you mean 'our' moon? Why, exactly, don't you think Mimas are Janus are not icy? What's your evidence for this?

Again, it is the density implied by the topography and surface features of Tempel 1; coupled with the sandy ejecta that challenge the theory that these outer solar system travelers are low density bodies.

How, exactly?

I think you've now got more than 20 questions to answer in this thread. Do you intend to do so or am I just wasting my time here?

[Reality Check]

Again, it is the density implied by the topography and surface features of Tempel 1; coupled with the sandy ejecta that challenge the theory that these outer solar system travelers are low density bodies.

Doubly wrong:
No one estimated the density from the topography and surface features of Tempel 1.
The "sandy ejecta" allowed the density of Tempel 1 to be measured and it is low (~0.62 g/cm^3).
Deep Impact: Excavating Comet Tempel 1

Deep Impact collided with comet Tempel 1, excavating a crater controlled by gravity. The comet's outer layer is composed of 1- to 100-micrometer fine particles with negligible strength (<65 pascals). Local gravitational field and average nucleus density (600 kilograms per cubic meter) are estimated from ejecta fallback.

and more measured densities of comets:
D. T. Britt; G. J. Consol-magno SJ; W. J. Merline (2006). "Small Body Density and Porosity: New Data, New Insights (PDF)

[Jerry]

Why do you say 'doesn't flinch' when something the size of a washing machine made a 100 meter wide crater. Clearly - it flinched, and fliched in a large way.

This is the same size, same depth and same shape of crater this thing would have made impacting the moon or the earth - regoth we are very familiar with. If Temple 1 is the hollow beast it has to be to have a bulk density of ~2, the crater should be more pronounced. Or, if Temple 1 was a dirty snowball, the probe should have released tons of steam and penetrated very deeply. It did not. It hit dirt.

It appears from the close images, that Tempel 1 likely has sedimentary layers - not what one expects to see in a non-friable solid full of voids. This comet is not the out-solar-system comet model that held for many decades. The dirty ice ball theory is false. The question then arises: What happens when comets and other similar debries impact moons that are mostly ice? They should blast deep, deep craters with flat, melted floors.

Why do you 'expect' icy bodies to look like that?

-Truly Icy bodies are stuck with the physical properties of water, which reacts very differently to an impact than sand. It is the difference between refractory minerals and volatiles: You wouldn't make a crater with the same relative physical shape slamming a copper slug into a mountain as you would slamming it into an anchored iceburg, or into an ocean.

'the moon' - do you mean 'our' moon? Why, exactly, don't you think Mimas are Janus are not icy? What's your evidence for this?

When a crater is blasted into an icy surface by a sandy object, there should not be central coning, the ice should melt and flatten - turning the crater floor into a hockey rink - like the craters of Europa (and some of the craters of Luna). But the craters of Mima and Janus have textbook inner solar-system regoth - central cones that are consistent with the impacting material and the target having great compression strength and very high melting points - refractory elements, not ice.

Add this to the fact that every comet we have visited is teaming with silicates and iron, and it is difficult to see how such bodies impacting icy bodies would yield such terrestrial craters. Sure, there are layers of Ice on Janus and Mima, but I argue - because of the nature of the craters, the ice is a relatively thin condensate, deposited after the craters formed.

I think you've now got more than 20 questions to answer in this thread. Do you intend to do so or am I just wasting my time here?

I can't get to all the questions - even though they all deserve answers.

[Jerry]

Doubly wrong:
No one estimated the density from the topography and surface features of Tempel 1.
The "sandy ejecta" allowed the density of Tempel 1 to be measured and it is low (~0.62 g/cm^3).

If you can come up with a material with a density of 0.62 that can absorb all of the energy of a 50 mm round with less than 5mm of penetration, you just solved half the problems with putting anything we want into space. That is what Temple 1 did, and I don't think that is possible. Temple I is made of sandy refractory materials that are much to dense to for the body to have a bulk density of 0.6g/cc. Something is wrong.

[djellison]

the ice should melt and flatten

And boom - you're totally and utterly wrong. Ice doesn't 'melt' in the vacuum of space - it sublimates away if warmed.

You will never ever see 'melted' ice forming flat bottomed craters on any of these bodies that have no atmosphere. Not at Tempel 1, not at Janus, not at Mima ( I assume you mean Mimas ) - please show me craters that have frozen melted water at their floor on Europa ( because I can guarantee you - it's not happened there either)

Flat bottomed craters on the Moon are the result of lava inflow. Water doesn't 'melt' in the vacuum of space.

Surely you knew this?

[tusenfem]

Jerry, again this is just waffle with no support whatsoever, except your opinions of "what should be."
Did you actually read my warning?
Infraction for not following the rules of ATM and moderator comments.

[Jerry]

Let's make this official: Jerry you will answer all the questions that are put to you in this thread. Not just the handwaving arguments without any support, but as thorough answers as you can give them backed up with actual citations to results and measurements.

Example: You give a number for the moment of inertia of Titan (~0.34), and then explain about what this number means (see e.g. this paper from which I took the number) what value has a fully differentiated object (e.g. Ganymede 0.31), what value has a totally non differentiated object (that would be 0.4), etc. etc.

You have some work to do.

This is a good example.

We determine the moment-of-inertia of rocket motors by suspending them from the fulcrum on each axis from a single cable, and then give them a push on the axis arm, recording how much energy it takes to accelerate the motor. It is a tricky operation; but it yields a good estimate of how the mass is distributed within the motor - so good, that we can even estimate where large voids may exist within the propellant grain. (I don’t actually perform the tests, but I did write software that identifies and localizes the voids.)

We can’t suspend moons from a cable, so obtaining estimates of the moment-of-inertia and other internal metrics is complicated - especially so for Titan: We coast Cassini close to the moon while carefully monitoring the Doppler signal from the Earth, using radar, we carefully measuring the tug of Titan as Cassini approaches and then recedes from the moon. A spike towards Titan as Cassini crosses the limb indicates how centralized the mass of the moon is: The sharper the spike, the more differentiated the moon.

(The actual process is much more difficult - each pass returns different values and the angle of approach and recession come into play, as does the relative position of Saturn, the Sun, and other moons; along with corrections for every conceivable drift factor, resets for each thruster action, changes in the antenna position relative to the earth - these are amazing, far from the back of the envelope calculations.)

Matter assembled into moons and planets varies greatly in density and physical properties. When a body has sufficient gravitational mass, it will condense into a sphere and the heavy elements will congregate into the middle. The degree of differentiation depends upon the friability, compressability, particle size, volatility, tensile strength, melting point, freezing point - virtually all of the physical and chemical properties of the materials making up the body.

Applying estimates of the Newtonian mass of Titan, the over-all density of the moon indicates that it is very light and made up of mostly low density molecules and minerals - Water, ammonia salts and such. Iron, aluminum and sulfur are so plentiful That Titan certainly contains these elements and minerals of these elements as well. Iron minerals are much heavier, and should condense into the center of a body composed largely of water - we find very little iron included into the ice on polar Earth and Mars. If Titan is mostly water, most of the heavy stuff should be at the bottom.

Concluding a body the size of Titan to be only partially differentiated is a major surprise finding of the Cassini mission. Looking back at how this determination is made - slight accelerations in the Cassini space ship due to gravitational tugs of Titan are only valid if Newton’s equivalence principle is correct: Even a minor change in the value of ‘Big G’ that follows the inverse square law will throw off every estimate of every mass that is not made on the surface of the earth. The error would be subtle, because the mass of every object in the universe is based upon the universal assumption Big G is constant. We don’t know that to be a fact.

Using a constant value of Big G yields a density for Temple 1 of as low as 0.6. I am of the opinion that this is a silly estimate for a body we know has a composition of dense silicates, pyrites and other refractory element. How do you build a body with a bulk density of 0.6 when the materials making up the body have a density of about 4g/cc? Temple 1 looks sedimentary, so the void volume should be low. The math is simple: Rocks are heavy. Too Heavy. Newtonian estimates of the bulk density can’t be right.

None of our outer solar system sailing provides us with affirming information about the value of Big G. We always assume it is constant, and determine masses and mass distributions accordingly. According to these determinations, Pluto must have very low density - virtually no iron and other heavy elements. We already know the colors of Pluto and her moons, and they are not consistent with water-ice scenarios. When New Horizons visits - how will you explain the mineral-rich surface of this planet? How do you explain the mineral rich surface of Phoebe? According to our Newtonian estimates, Phoebe has a bulk density of only 1.6g/cc. Something is wrong, and I think it is a fundamental assumption that has not been properly tested.

[djellison]

Applying estimates of the Newtonian mass of Titan, the over-all density of the moon indicates that it is very light and made up of mostly low density molecules and minerals - Water, ammonia salts and such.

It's very similar to Callisto and Ganymede. Ganymede - 1.94. Callisto - 1.83. Titan - 1.88.

Iron, aluminum and sulfur are so plentiful That Titan certainly contains these elements and minerals of these elements as well. Iron minerals are much heavier, and should condense into the center of a body composed largely of water - we find very little iron included into the ice on polar Earth and Mars. If Titan is mostly water, most of the heavy stuff should be at the bottom.

You are assuming that Titan has a certain quantity of heavy elements in it.
On what basis are you making that assumption? What quantity of these elements are you assuming to be there?

Using a constant value of Big G yields a density for Temple 1 of as low as 0.6. I am of the opinion that this is a silly estimate for a body we know has a composition of dense silicates, pyrites and other refractory element. How do you build a body with a bulk density of 0.6 when the materials making up the body have a density of about 4g/cc?

If Tempel ( not Temple) 1 was a solid lump of material of 4g/cc - then you would have a point. The nature of the impact tells us it's exceptionally porous. Indeed -the dynamics of the impact tell us that the bulk physical properties - at least at the surface - represent something like a snow bank. Snow is fluffy. It's density is about 0.08g/cc - 8% the density of pure water. Even if we assume that every single mineral on Tempel 1 is, when solid, 4g/cc - then it need only be 15% solid, 85% gap, to match the 0.6g/cc total density. This is in keeping with the material property we saw - something fluffy like snow.

I would challenge you to explain the impact and ejecta with a 4g/cc solid material. It doesn't work.

Temple 1 looks sedimentary, so the void volume should be low.

Why? Porous materials can and do form layers.

None of our outer solar system sailing provides us with affirming information about the value of Big G. We always assume it is constant, and determine masses and mass distributions accordingly.

Guess what....that value is one that helps us deliver spacecraft to astonishingly accurate. Mars Odyssey, for example, was delivered with an accuracy of about 730 meters, after a flight of around half a billion km.

According to these determinations, Pluto must have very low density - virtually no iron and other heavy elements.

From wiki : While Pluto's internal composition is unknown, Hubble Space Telescope observations suggest that the planet's density lies between 1.8 and 2.1 gm/cm3 which indicates that the planet is probably a mixture of 50 to 70 percent rock with the remainder being water and other ices much like Nepture's moon Triton.

What's wrong with that?

We already know the colors of Pluto and her moons, and they are not consistent with water-ice scenarios. When New Horizons visits - how will you explain the mineral-rich surface of this planet?

from
http://www.sciencemag.org/content/261/5122/745
(0.026,0.005, and 0.969 for CH4, CO, and N2,respectively)

The surface of Pluto, as a molar fraction, is 97% N2 - which in frozen form is <1g/cc.

What 'colors' are you seing that preclude an icy body, exactly?

Something is wrong, and I think it is a fundamental assumption that has not been properly tested.

The assumption you're making is that the detection of any mineral on the surface of a body dictates that the entire body must be a solid version of that mineral.

That's a wrong assumption.

Sand is about 1.5g/cc

The Earth is about 5.5g/cc

What you're doing is looking at the Sahara desert, looking at the 5.5g/cc figure and saying 'Sorry - physics is wrong'.

[tusenfem]

Concluding a body the size of Titan to be only partially differentiated is a major surprise finding of the Cassini mission. Looking back at how this determination is made - slight accelerations in the Cassini space ship due to gravitational tugs of Titan are only valid if Newton’s equivalence principle is correct: Even a minor change in the value of ‘Big G’ that follows the inverse square law will throw off every estimate of every mass that is not made on the surface of the earth. The error would be subtle, because the mass of every object in the universe is based upon the universal assumption Big G is constant. We don’t know that to be a fact.

This stance does not really make sense, because using exactly the same technique at Ganymede we find that the moon is fully differentiated, with extra evidence the internal magnetic field. So now you have to come up with a reason why it does work for Ganymede and does not work for Titan.

[tusenfem]

We can’t suspend moons from a cable, so obtaining estimates of the moment-of-inertia and other internal metrics is complicated - especially so for Titan: We coast Cassini close to the moon while carefully monitoring the Doppler signal from the Earth, using radar, we carefully measuring the tug of Titan as Cassini approaches and then recedes from the moon. A spike towards Titan as Cassini crosses the limb indicates how centralized the mass of the moon is: The sharper the spike, the more differentiated the moon.

I have no idea what "a spike towards Titan as Cassini crosses the limb" means. Let's take a look at the actual data, where the acceleration of the Cassini spacecraft is shown in Fig. 1. I see a gradual pattern which I would expect for a spacecraft flying by a gravitating object. I would love to be pointed out this so called "spike."

[slang]

I have no idea what "a spike towards Titan as Cassini crosses the limb" means. Let's take a look at the actual data, where the acceleration of the Cassini spacecraft is shown in Fig. 1. I see a gradual pattern which I would expect for a spacecraft flying by a gravitating object. I would love to be pointed out this so called "spike."

fixed your link so it actually is a link.

[Jerry]

If Newtonian Mechanics is so wrong how did they hit the comet?

The same way the Americans threw the shot put and hit the earth a centrury and a half ago. It didn't matter that the shot they were using was heavier than the European shot. It doesn't matter what the mass of a comet is - we determine masses indirectly via the equvalence principle. If the principle is wrong, so is the mass.

[Jerry]

I have no idea what "a spike towards Titan as Cassini crosses the limb" means. Let's take a look at the actual data, where the acceleration of the Cassini spacecraft is shown in Fig. 1. I see a gradual pattern which I would expect for a spacecraft flying by a gravitating object. I would love to be pointed out this so called "spike."

Whether it is a 'spike' or 'gradual pattern' depends upon the compression in the time scale. It is actually the second and higher order derivatives that yeild moment of inertia and gravitational field information.

[Jerry]

This stance does not really make sense, because using exactly the same technique at Ganymede we find that the moon is fully differentiated, with extra evidence the internal magnetic field. So now you have to come up with a reason why it does work for Ganymede and does not work for Titan.

This is a very good point. Ganymede is quite a bit larger, closer to the sun, and close to a larger planet, but i must agree with you! Once again, I need to come up with a rational modification, rationalization or discard the premise.

[tusenfem]

Whether it is a 'spike' or 'gradual pattern' depends upon the compression in the time scale. It is actually the second and higher order derivatives that yeild moment of inertia and gravitational field information.

No that is baloney (to quote my favourite adversary MM), a spike is a spike and a gradual pattern is a gradual pattern, it does not depend on the compression of the time scale. A spike usually has only 1 or 2 data points in it. Look at the number of points in the plots in Figure 1. You are just making up claims to try to get your right.