Usually, and that means in the past year, when you look at the false color MDI image from SOHO, you can look at the corresponding magnetogram and see some sort of disturbance going on, even it it is not visible as a sunspot, sunspeck, or plage area.
Not today.
Left: SOHO MDI “visible” image Right: SOHO Magnetogram
Click for larger image
Wherefore art though, cycle 24?
In contrast, September 28th, 2001
Leif Svalgaard (06:51:09) :
Now, before progress can be made, the above facts or deductions (M1-M12) must be agreed upon. So, anybody disagreeing with any of them?
P.S. you are supposed to disagree with precisely one of them.
Leif Svalgaard:
The friction slows down the Earth (M8) which changes the spin angular momentum of the Earth (M9). Because angular momentum is conserved (M10), the Moon must gain angular momentum about the same axis (M11), not about any other axis (M12), therefore its distance must increase (explaining M1).
M11 bothers me. That looks like ‘spin-orbit coupling’, which I thought you had disposed of. Why should there be any gain in the Moon’s angular momentum (around the centre of the Earth or Earth-Moon centre of mass) just because the Earth loses a bit of spin angular momentum? Or if it’s true or Earth and Moon, it should be true of Sun and planets as well.
M5 bothers me a bit too.
That heat is radiated away from the Earth-Moon system (M4), therefore the system loses the rotational energy that was converted into heat (M5)
Why should something spin faster when it’s hot, slower when it’s cold? Never mind the tiny frictional forces of tides, what about the radiant energy of the Sun as it falls on planets? They heat up a bit when they get nearer the Sun, and cool down when they move away. Do they spin faster and slower as a consequence?
idlex (08:07:57) :
Do you remember the careful parenthesis of : “except for the tiny effect of the tides”
The tides ARE a spin orbit effect. Just the energy available through gravitation is not enough to explain what the barycenter lovers want to explain.
You helped prove that kinematically this is true too. The energetic argument was true anyway, does not need complicated calculations.
M11 bothers me too. The lost radiation energy is taken from the rotation loss.
If it’s compensated for you have increased the energy of the universe.
idlex (08:07:57) :
M11 bothers me. That looks like ’spin-orbit coupling’, which I thought you had disposed of. Why should there be any gain in the Moon’s angular momentum (around the centre of the Earth or Earth-Moon centre of mass) just because the Earth loses a bit of spin angular momentum? Or if it’s true or Earth and Moon, it should be true of Sun and planets as well.
Because of M8, the Earth is slowed down hence loses AM around its axis. Because of M10, the Moon must gain (M11). And it will be true of the Sun and the planets too, of course: The planets cause tides on the Sun, that slows down the Sun, therefore the planets move away from the Sun, just the same as for the Earth and the Moon. Because the tides on the Sun are so minute, the slowdown is VERY small [beyond the last decimal point of your calculation], so there is a coupling [the friction]. If there was no friction, the tides would not slow down the Earth.
M5 bothers me a bit too.
Why should something spin faster when it’s hot, slower when it’s cold? Never mind the tiny frictional forces of tides, what about the radiant energy of the Sun as it falls on planets?
It is not the heat that does it. It is the friction. When you step on your car brake, the friction between the brakepads and the wheel slows down rotation of the wheel. Friction makes the brakes hot [try to feel it, or just rub your hands together vigorously] and that heat is lost to space, and cannot be recovered, so the Sun has lost rotational energy that cannot be regained. This is why the tides cause a one-way change in rotation.
lgl (08:55:15) :
M11 bothers me too. The lost radiation energy is taken from the rotation loss. If it’s compensated for you have increased the energy of the universe.
You are confusing energy and angular momentum [as in most of your posts on this – and the realization of this confusion may the Aha-moment you need], and the energy is not compensated for. If you agree with M1, M3, M4, M5, M7, and M8, then consider that the AM is the product of distance, mass, and speed. The distance goes up 4 cm/yr [M1, agree?], the mass does not change [agree?], and the speed goes down a little bit [but less than the distance goes up, in fact with the square root of the distance AM = r * m * v, and v = 2pi*r/T, where T ~ r^(3/2) Kepler’s third law, agree?], so the AM goes up due to the Moon receding which is M11 [now agree?].
lgl (08:55:15) :
M11 bothers me too. The lost radiation energy is taken from the rotation loss. If it’s compensated for you have increased the energy of the universe.
Instead of thinking in terms of angular momentum [which seems to cause endless confusion], one can also approach the problem from purely interaction between gravity and friction:
http://www.astronomy.ohio-state.edu/~pogge/Ast161/Unit4/tides.html
The net result is the same: friction robs the Earth of rotation and makes the Moon recede. This is a one-way street [no cycles can result from it] and THAT is the important insight.
As per the moderator request, I will just post this short thank you to Anthony for hosting this very interesting debate, where I learned something I doubted before: There is no spin orbit coupling between the Sun and the planets. The reasons have been stated in this thread, and our computer simulations confirm that orbital AM is completely balanced between the Sun and the planets.
I have just completed a run where the sum of AM is computed for the Sun and planets between 1940 and 2076, on 24373 different dates. The orbital AM sum is constant at 3.12621258E+43 (SI units) on all these dates.
Thanks to Leif for the patience, and to everyone else for their contributions. Now it is time to really figure out why SC24 looks to be so weak.
Thanks Leif,
but this is not my problem (admitting my last comment was not very smart) My problem is that you and others have repeatedly confirmed the spin-orbit coupling. I haven’t seen the proof that the Sun can’t gain some energy from the planets through gravitation, giving it some ‘extra’ potential energy, miniscule in the big picture, which is later lost again so that the average is 0.
lgl (10:48:35) :
My problem is that you and others have repeatedly confirmed the spin-orbit coupling. I haven’t seen the proof that the Sun can’t gain some energy from the planets through gravitation, giving it some ‘extra’ potential energy, miniscule in the big picture, which is later lost again so that the average is 0.
The issue is one of energy or magnitude [of the coupling]. There has NEVER been an issue that the coupling does not exist. The ONLY issue is how big it is, and it is VERY VERY small compared to the movements and turmoil that take place on the messy Sun. If one wants to claim that those minuscule effects cause the cycle, one has to overcome the energy problem [and the onus is one the claimants]. And in addition, as I have stressed so often [but to no avail] that the coupling goes always in one direction [slowing down the Sun] and therefore is not cyclic while solar activity is.
Being sort of planet-arist I tried to follow your discussion, frequently got lost, but still appreciate all contributions. Thanks.
BTW, just managed, indirectly, to get from Dr.S an estimate of SC24 timing (it is 2014 but don’t tell anyone).
Anthony how about it for a new thread?
Should be SC24 Max
Leif,
All that is perfectly understood. My point is how can you know there is not something in addition, some kind of energy transfer back and forth?
Then you are of course rightfully asking me what, and ask me to explain the mechanism, something I of course can not do. One thing to remember however is that if you are searching for something and find nothing, that does not mean that what you are searching does not exist. It is very often because you used the wrong method in you search.
Leif,
Yes, I understand the friction bit. I confused myself over the heat, which is just something that gets lost. So M5 doesn’t bother me any more. But back to M11.
Leif Svalgaard:
The friction slows down the Earth (M8) which changes the spin angular momentum of the Earth (M9). Because angular momentum is conserved (M10), the Moon must gain angular momentum about the same axis (M11), not about any other axis (M12), therefore its distance must increase (explaining M1).
What you’re doing here is to add the spin angular momentum of the Earth to the orbital angular momentum of the Moon around the centre of the Earth. As I see it, you’re adding one sort of angular momentum to another different sort. When we worked out the orbital angular momentum of the solar system, we didn’t add in their spin angular momentum as well.
But I can maybe see why. Perhaps you’re finding the angular momentum of mass in general about a particular axis. And at the centre of the Earth, there’s the whole mass of the Earth turning round it, and the Moon further away (and also the sun and the other planets, because they’ll contribute as well?)
But when we worked out the orbital angular momentum of the Sun and planets around the SSB, we didn’t add in the spin angular momentum of the planets, because the sun and planets weren’t spinning at the barycentre, and so planetary spin momentum contributed nothing to orbital spin momentum?
I think my difficulty here is that I don’t think about things using angular momentum, or barycentres, or even ellipses. My simulation model doesn’t use them, although it can be called upon to calculate them. So when I think about things, at the moment it’s all just masses in motion. And furthermore there’s nothing spinning in my simulation. So I can’t use my simulation to look at solar or planetary spin (although I’m thinking of building spinning dodecahedra instead of point masses). Same with tides. My model doesn’t simulate tides either (but I think my idea of ball bearings rolling over the surface of planetary spheres is probably a “tidal” model of a sort).
It’s rather as if with my simulation model I’ve built myself a fast motorway through mountainous country, and it works very well at doing that. But as soon as I get off that motorway, all I’ve got is the physics that I happen to know anyway, and that is like so many dirt tracks, and it becomes hard going then.
P.S. I can instantly understand how the tidal bulge of the Earth’s oceans can tug the Moon forwards slightly, so go slightly faster, and so reced from the Earth.
http://www.astronomy.ohio-state.edu/~pogge/Ast161/Unit4/notes.html#braking
But I’m now puzzled why the tidal bulge leads the Moon by 10 degrees. They say it’s due to friction, but intuitively it feels like the bulge ought to trail by 10 degrees.
idlex (15:05:56)
“But I’m now puzzled why the tidal bulge leads the Moon by 10 degrees. They say it’s due to friction, but intuitively it feels like the bulge ought to trail by 10 degrees.”
Earth rotation angular velocity > Moon orbit angular velocity
(why Moon & tides fall behind a little every day)
I see it now. The Earth is spinning under the oceans, and the friction between the two is advancing the oceans, as well as retarding the Earth.
I would like to thank Anthony and the other moderators for putting up with our theoretical discussions. Its obvious by the amount of discussion that there is a lot of interest in this topic and it will not diminish while there are big questions still unanswered.
For me the biggest result was the confirmation that a change in Sun/planet distance (outside of normal aphelion/perihelion changes) will result in a change of solar rotation rate. This is seen to occur every orbit with Jup/Sun but I have not deduced why…yet. There is new data and continued discussion at:
http://solarcycle24com.proboards.com/index.cgi?action=display&board=general&thread=488&page=1
Geoff Sharp (17:11:02) :
For me the biggest result was the confirmation that a change in Sun/planet distance (outside of normal aphelion/perihelion changes) will result in a change of solar rotation rate.
Huh? where did you get that one from? The chain of causality goes the other way. Planetary tides can slow down the Sun, resulting in receding planets [always one way; tides do never speed up the Sun always slow down].
lgl (12:22:34) :
My point is how can you know there is not something in addition, some kind of energy transfer back and forth?
Because we think that we know how the Universe works at the energies and distances we are talking about. And we usually do not invent new causes unless we have to and even then only with the greatest reluctance. We don’t usually postulate additional forces or laws all the time in order to explain something we think we have observed. Very rarely we have to, but that only happens a few times each century and is not likely to be the case here. But feel free to assume that we have something here ‘that will change the face of solar physics’ as long as you also add that it is based on unknown laws [or the ultimate in CYA strategy: ‘unknowable laws’]
“Planetary tides can slow down the Sun, resulting in receding planets [always one way; tides do never speed up the Sun always slow down].”
Explain that one please….especially the part in the brackets….
Thanks.
savethesharks (20:28:08) :
“Planetary tides can slow down the Sun, resulting in receding planets [always one way; tides do never speed up the Sun always slow down].”
Explain that one please….especially the part in the brackets….
I have already [many times], but here it is again: Planets raise a tidal bulge on the Sun [under the planet and on the opposite side of the Sun as well]. The Sun rotates through this bulge which causes friction with the bulk of the Sun. Friction results in heat which is lost to the system by radiation and friction also slows down the Sun [much as stepping on your car brake causes the brakepads to slow down the wheels by friction making them hot in the process, and not causing the wheels to spin faster]. So the tides brake the Sun all the time and irreversibly because of the lost heat]. I think I’ll begin to count the number of times I’ve explained this. Let the count start at ten. [!@ur momisugly#$% is a search string for me to find to ease the counting process in the future]
Leif Svalgaard (19:55:19)
“Planetary tides can slow down the Sun, resulting in receding planets [always one way; tides do never speed up the Sun always slow down].”
savethesharks (20:28:08)
“Explain that one please….especially the part in the brackets…. Thanks.”
In brief: works like brakes on a car.
(See Leif Svalgaard (08:59:52) — & idlex (16:27:45), which is an analogy where the amplitudes are ‘significant’ — see “VERY VERY small compared to the movements and turmoil that take place on the messy Sun” at Leif Svalgaard (11:20:31) for comparison.)
Well in the future just don’t answer if you don’t want to. ;~).
If it has been stated and it makes logical sense then the onus is on the uninformed (me LOL).
Hey but thanks for your efforts…they are much appreciated.
Chris
Norfolk, VA
savethesharks (21:14:21) :
Well in the future just don’t answer if you don’t want to. ;~).
If it has been stated and it makes logical sense then the onus is on the uninformed (me LOL).
I ALWAYS answer [lest I miss a question in the flurry]. But allow me to point out that I have already. In a courtroom cross examination lawyers have an acknowledge phrase: “asked and answered” to prevent endlessly repetitive questions.
Responding to Loose ends:
– – – – – – –
lgl (02:43:51) :
“Paul, […] Why the peak at 5.35 ?”
I have a suspicion, but I would want more information from the person who created the graphical summary before commenting.
– – – – – – –
tallbloke (02:01:09)
“You saying the gun was firing blanks? ;-)”
Lots of smoke!
[You tell the truth (‘smoking gun’).]
– – – – – – –
I appreciate the elegant simplicity with which anna v (05:56:25) was able to break the AM issue down.
– – – – – – –
Thank you charles, others – & ‘Watts Up?’ more generally.