See speck run

Geoff Sharp (16:17:00) :
So have you ever seen an attempt to measure the overall solar rotation velocity?
Provided that you can agree to distinguish correctly between rotation and flows, the data exists for that, as helioseismology provides up with the Doppler data needed for this. Since there a [almost] discontinuous changes in the profile it may not may much sense to compute an average, much as it does not make much sense to say that the average temperature on the Moon be computed by averaging the night time temperature and the day time temperature, giving an average result like -10C and then basing your heating/cooling need on that average.

Geoff Sharp (22:10:07) :
You know the data I am looking for, but I dont expect you to arm the opposition.
Of course, I would if I could. That is just basic scientific decency [although according to Paul Vaughan, I not a decent scientist 🙂 ]. But it will be a hard, frustrating slug to search for something that violates physical laws, but then the reward would be commensurate with the misery.

Geoff Sharp (02:26:56) :
I am just looking for solar rotation data similar to earths LOD measurements. Neither of these violate any physical laws, on the contrary I would have thought.
You stated that your are doing this in a “search for a trade off”. It is the trade off that is the violation. I don’t think you care about what the solar LOD is if it would show no ‘trade off’.

Geoff Sharp (07:14:32) :
I take offense at what you think I care about
Fair enough.

Geoff Sharp (15:33:43) :
Lets assume the Sun slows its rotation because of friction at the Tachocline…would we not see an increase in the semi-major axis of its satellite?
To clarify: if the friction is internal to the Sun [i.e. not caused by planetary tides] then there would be no change in the orbit of the satellite, but the two layers rubbing against one another at the tachocline because there is shear there, would equalize their rotation rates, one would slow down, the other would speed up to maintain constancy of angular momentum. So, the shear and the friction will over time disappear.
Only if it is the satellite that is causing the friction, never if the friction is due to, say, tides raised by another planet, e.g. Jupiter
There are two additional problems:
1) the energy available to slow the Sun down by friction is minuscule because the tides are so small and would not be concentrated just at the tachocline if due to planets far away.
2) the friction is always one-way, so you never get a speed-up of the Sun [to make a cycle].

Geoff Sharp (18:09:44) :
The area that is not clear to me is: why is it only the satellite that is causing the friction, experiencing the orbit trade off. Your saying the increase in semi-major axis is a result of friction and conservation of angular momentum and not conservation alone?
For something to change its speed [a change in speed is acceleration] a force must be applied [Newton’s second law: Force = Mass x Acceleration (F=M a), or a = F/M. No force, no change. The friction provides that force: no friction, no force, no change.
Now, consider a planet [satellite] in orbit, call it A. There is a gravitational force [general relativity aside – Newton is good enough for this] between the Sun [S] and A. Let A raise a tide on the Sun giving rise to another force [at right angle to the gravitational force between S and A] slowing S down and increasing the distance of A. Consider another planet B and let it be much smaller than A [or much farther away]. Its tidal force working at right angles to the gravitational force between S and B will be much smaller than that of A and cause a much smaller friction and thus a much smaller slowdown of S and therefore a much smaller increase of distance to B. In the limit that B is VERY small [a small artificial satellite], the effect on B will be negligible.
The salient point is that the system comprised of S and A is independent from the system comprised of S and B. This may be the sticking point for you. If the above consideration is correct then we can consider the case where Moon did not raise a tide [e.g. if the Moon were much farther away]. The Sun still raises a tide [half of the Moon’s present tide] and there is still friction due to the solar tidal bulge, and that friction will cause the Earth to rotate slower and the Sun to recede [very little] to preserve angular momentum in the Sun-Earth system, but will not cause the Moon to recede any further, because the Moon is no longer tidally coupled to the Earth [remember we considered the case [far in the future] where the Moon had receded to the point of its tides being negligible].
The treatment above was a little bit sloppy, because the mechanism is slightly more complex. The Earth rotates much faster than the Moon revolves so the tidal bulge is actually carried forward [in the sense of Earth’s rotation] and it is the gravitational force on the bulge that slows the Earth. The friction serves only to make the bulge move forward. On the Earth, this is a trivial detail and can be glossed over in a simple explanation. But there is another system where the precise mechanism becomes crucial, and that is Mars and its two satellites Deimos and Phobos. Deimos is the furthest away and its orbital period is longer than Mars’ day, so everything works just as in the Moon-Earth system. The interesting part is that Phobos is so close to Mars that its orbital period is shorter than mars’ day. This means that the bulge will not [as on Earth and Deimos] be carried forward by the faster rotation, but will lag behind, so the Phobos is not moving away from Mars [as Deimos and the Moon from the Earth], but is moving closer to Mars. So in the Martian system, the two satellites behave independently: one moves away and the other moves closer. So, the movement of one does not influence the movement of the other. And that is the crucial point.
You can get a feel for the math behind this by following these lectures:
http://iapetus.phy.umist.ac.uk/Teaching/SolarSystem/Lecture1.pdf
change ‘Lecture1’ to ‘Lecture2’ to get the next one, and so on. Tides are discussed in number 7 and on.

Geoff Sharp (04:17:53) :
I take it you mean the semi-major axis will increase, can you expand on your reasoning here or provide a link that describes the process. The Sun receding is the real meat on the bones in my opinion.
The process is the same as for the Moon. As far is the process is concerned, you can consider the Sun to be a satellite around the Earth. There is not much meat on that bone as the effect is unmeasurably small because the Sun’s mass is so huge. The important point is that [just as with Deimos and Phobos] the tidal effects of the Sun and the Moon are independent. So tides on the Sun raised by Jupiter will not have any effect on the orbit of another planet. Note also that if your satellite is close to the Sun [orbital period less than 27 days] the effect [as for Phobos] goes the other way. Anyway, one more time: tides on the Sun raised by one planet will not have any effect on the orbit of another planet.

Geoff Sharp (07:59:27) :
I asked the question because there seemed to be 2 schools of thought on the earth/moon system. The one outlined in your referenced lecture notes does not attribute the outward movement of the moon to angular momentum but suggests the forward bulge accelerates the moon which moves it out (which seems opposite to Kepler’s law).
There is only one school of thought. The ‘angular momentum’ is not a mechanism per se, but a constraint on what can happen [whatever process works must keep the AM the same]. Only a force can change anything. And that the Moon moves out when accelerated is what is supposed to happen. Think of the space station having to fire its engines now and then to attain a higher orbit, whenever atmospheric drag has lowered it. If you want to even higher, e.g. to the Moon, you have to let the engine burn a lot longer.
The Martian example: tidal effects work no matter what shape the bodies have and they don’t have to be fluid or gases. The effect is so large because the moons are so close. If you move our Moon in to 1/10th the distance, the tidal effects go up thousand fold as they depend on the cube of the distance [which is why even mighty Jupiter raises such a minuscule tide on the Sun].
I am not sure if your Martian example is applicable as there are many differences, the only bulge involved would be a very thin atmosphere and the shape of Mars itself. The moons themselves are not spheres and are very small but still we see a fairly big movement in the orbit reduction of Phobos of around 20 meters per century…the numbers dont look right?
I also have an interesting thought experiment re bulges. If we go on the bulge theory (I dont think its generally accepted) eventually over time the earth’s rotation would slow to match the lunar period which would only leave the Sun as a tidal mechanism. The earth would slow further putting the moon in a faster orbit than the rotation of earth which would generate a bulge behind the moon thus dragging the earth into a faster rotation and equalizing again. So maybe there is a possibility of tides increasing rotation?
If we go on the bulge theory (I dont think its generally accepted)
the only one there is and accepted by all, except pseudo-scientist peddling stuff on the Internet 🙂
eventually over time the earth’s rotation would slow to match the lunar period which would only leave the Sun as a tidal mechanism. The earth would slow further putting the moon in a faster orbit
Once the Sun is the only tidal mechanism, any further slowing of the Earth will have no effect on the Moon. I think I may have failed completely in getting that across; perhaps one more time: tides raised by one body will not have any effect on the orbit of another body.
So maybe there is a possibility of tides increasing rotation?
I think I said that several times. If the orbital revolution is faster than rotation, it goes the other way [Phobos], but in the solar system all planets have periods greater than 27 days. Interesting enough, in the early solar system when the planets were forming, friction between a planet and the solar system protoplanet disk caused the planet to loose energy and migrate closer to the Sun. Some exoplanets are very close to their suns, not because they formed there [it is too hot], but because they moved there by tidal forces. Tides are very important in the universe and are well-understood. The crucial point is that one must calculate what their sizes are to establish how important they are for any particular case, and for the present solar system, the tides raised by the planets are just too small to have any effect.

Leif Svalgaard (09:12:12) :
“eventually over time the earth’s rotation would slow to match the lunar period which would only leave the Sun as a tidal mechanism. The earth would slow further putting the moon in a faster orbit…”
Once the Sun is the only tidal mechanism, any further slowing of the Earth will have no effect on the Moon.
Perhaps a clarification: as long as the Sun is the only tidal mechanism this holds, but if you slow down the Earth further, the Earth’s rotation and the lunar period would no longer match and lunar tidal effects would pick up again. One has to be VERY precise in these things.

Geoff Sharp (17:02:34) :
The reason I said not generally accepted is I dont think the science is settled on this one. The bodies responsible for collecting LOD measurements seem to be very non committal on the causes of slowing process mentioning external tides and other internal processes.
As far as external tides are concerned the science was settled 100 years ago. There are internal changes to the Earth’s moment of inertia due to movements of magma inside the Earth, and to friction at the interface between the core and both the mantle and the inner core. All of this are just details that becomes observable as our ability to measure these things increase. They do not reflect uncertainty in the physical underpinning of these phenomena. It is like, because we can’t predict the weather a year from today does not mean that the physical laws are incomplete or unknown.
But my main point is that you could get a two way result because of friction, the earth could increase and decrease its rotation because of tidal effects.
Don’t cling to this one because for all current planets at this time friction in the Sun is a one-way process. And it is not your point, I explained to you.
Your earlier point re AM is more a background process that must be conserved
It doesn’t matter in which direction the vectors point. Our physical understanding of this is solid and three hundred years old. If you postulate other [unknown] physical laws to be operating, anything goes, of course, but that was the hard slug I was referring to. but there must be other forces at playwell, none we know of.
It all boils down to this: there are only three mechanisms within known physical laws that can transfer angular momentum:
1) tides with friction
2) magnetic torques due to stretching of file lines
3) the Poynting-Robertson effect caused by absorption [from one direction] and re-emission [in all directions] of light.
All of these are much too small at the present time to have any measurable effect on the Sun [for 1 and 2] or planets [3].
If one wants to stick to the correlations being caused by angular momentum transfer, one must postulate that in spite of these shortcomings it somehow works anyway. This is an acceptable position as long as it is not coupled with a claim that these things are science-based.