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Archive for the ‘Meteorology’ Category

Earth Rings perhaps

Recently, Judith Curry, a well-respected climatologist, stepped down from her position at Georgia Tech because of the politicization of climate science. It is a problem! And after many years of politicization, we are now in the situation where so many positions of influence are held as political plums, that it is easy (and true) to say that there is a consensus on anthropogenic global warming. Fire everyone who does not agree, and you have consensus.

What if Earth had a ring?

Today, I would like to mention a very interesting possible driver of climate: suppose Earth had a ring.

If we had a ring, it would cause shading on the Earth. Furthermore, as Earth traveled around the sun, the shade of the ring would fall on the northern hemisphere for one half-year and on the southern hemisphere for the other half-year. Indeed, it would fall on the northern half during our winter, and on the southern half during “their” winter. The effect would be to intensify winter. So who would notice that? Bears?

Where would the ring come from

But a ring is made of stuff – dust essentially – and that stuff would eventually fall down. Even a very fine dust would eventually fall to Earth, and after that, there would be no ring. So a ring has to be fed more dust, and there is only one way to do that efficiently: get the Moon to contribute dust on a moderately regular basis. This requires that the Moon be geologically active – it must have active volcanoes.

There is a big argument about that, but if it has volcanoes, it can supply a ring. In fact, if it has volcanoes, we must certainly have a ring, because some of what explodes upward on the Moon will not fall down. It will orbit the Moon, then be captured by the Earth and orbit Earth in an Earth-Moon orbit, then collapse into a Moon-tilted Earth orbit, then fall into an equatorial orbit, and finally fall down.

If lunar volcanoes, then Earth-ring; if Earth-ring, then lunar volcanoes.

Surely we would see it!

How could we not see an Earth ring? We see the rings of Saturn from millions and millions of miles away. Over a billion, actually.

Two reasons not to see an Earth ring:

First: Because Earth is rounder than Saturn (Saturn is more oblate), our ring would be more diffuse, more fluffy. It would be harder to see. Ask your local physicist about that.

Second: The rings would be relatively close to the Earth, and would be visible, if at all, only near the horizon. When we do astronomy, we look up very high. We don’t look near the horizon because there is a lot of interference there – city lights for one, and haze of various kinds for another. If we want to see something close to the eastern or western horizon, we choose a different time of night, when our target star is up high. If we want to see something close to the northern or southern horizon, we move north or south.

How might on see it?

There is, of course a third reason not to see it: we are not looking. If we were looking, and if we knew exactly what we were looking for, we might see it.

Somebody might go to Jamaica, for example, where the southern horizon does not have any cities. She might get a time-lapse camera and just photograph the sky all night. If there were a ring, she would see the stars against that light familiar haze that makes astronomers not do near-horizon investigations, but she would tell herself it was the ring dust, illumined by the Sun long after dark, because it is so high – one or a few ten thousands of miles or so.

She would expect that in the middle of the night, the shadow of the earth would fall on the ring and this “light haze” would disappear for a few hours. Since there would be no cities turning off their lights to deepen the darkness, she would have evidence of the ring. This has been done, and the darkness did seem to appear. The camera was cheap, and the darkness not spectacular, but it seemed to be there.

And you don’t have to go to Jamaica. Any place in the middle latitudes that has no cities for a long way south will work… In high latitudes, the rings would be too low on the horizon.

So what?

I mean, does this have consequences?

Well, don’t you see, the rings would – or might — be a significant climate driver. We do know that the ice ages were primarily a result of colder winters. Colder winters do cause late summers, which may then be cooler, but the problem is a winter problem. That is how rings would affect climate: colder winters first of all. However, because rings could be a climate driver, their study is not a way to get tenure or good appointments; the only climate driver permitted to be discussed is human activity.

Nevertheless, whatever is, is, and whatever isn’t, isn’t.  If the Moon is active, there must be rings. Go find them.

Where do rings go

So if the rings are composed of Moon dust, where do they go? After all, if the Ice Age was caused by the rings, where did they go? The dust fell down, okay, but what makes the dust fall one year (or one decade or century or millennium) and not another?

Well, if the dust is very small (and the YORP effect guarantees that it will end up small if it doesn’t start small) if it is very small, then solar storms, which release floods of high-energy charged particles, can cause a sudden downfall of dust from one sector of the ring. The immediate effect might be a local storm, possibly quite a large one. Unexpected storms are not so unusual. During a phase of very active sun, lots of sunspots that is, the ring would erode very considerably. But during quiet sun, the ring could get thicker.

We do know that the Maunder minimum was a time of very few sunspots, seventy years with no spots visible, and the Jesuits were watching closely. The Maunder Minimum is the middle of the Little Ice Age. So there is a correlation; there might be causation.

There might be.

Quiet sun might cause thickening rings, colder winters. And we have a very quiet sun these days, these years. You can’t wake up the sun by parking your car.

Has anyone really seen a ring

The ancient astronomy sites such as Newgrange in Ireland have lots of astronomical markers, and then lots of mysterious loops that have no astronomical significance at all. Were the rings visible in those days? We really do not know, but Lucy Hancock offers this visualization of the rings.

One more question

If there is a ring, or a set of rings, even a mushy one, and if the ring is thickening, could it affect the visuals of an eclipse? We in the United States have a very spectacular eclipse coming up in August. We are hoping for millions of people to see the wonderful corona of the sun; it is said to be the most beautiful, most awesome of sights.

If — If — If there were a ring, and if the path of the ring crossed the path of the view of the eclipse, (and if there were no clouds) then if the corona diminished at a certain point for no good reason… That would be very sad for the viewers, but very interesting for the ring seekers.

We could calculate where the ring, if there is one, might intersect the path of the view of the eclipse, but nobody has done that yet. It is not a priority. Return to top…

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While working on a degree in psychology, and suffering considerable chagrin at the emphasis on statistical behaviorism, I have found other material that is objective, scientific, and fascinating without the outrageous vulnerabilities or the political and ethical dubiums of experimenting on people’s subjectivity.

Jaak Panksepp is a researcher in psychology. His strongest interest is in finding a solution for depression, and you can listen to his TED talk, which offers an extremely powerful key to a central issue in psychology, the concept of emotion.

He has discovered seven specific “circuits” in the brain, corresponding to seven emotional paths. These emotions cross species not only through all the mammals, but crossing into birds and reptiles. They are brain functions, and his work is interesting because the definition of emotion in psychology is completely unsettled and this contributes to the chaos of behavioral research. Tying the definition of emotion to something objective would therefore be an achievement of the first order.

Perhaps the best traditional definition of emotion is “energy in motion.” Emotion is what motivates us to act, and without emotion we would, ignorant and indifferent, subside into the dust. In fact, people whose lives are emotionally blunted in various ways are at risk of losing those lives, one way or another: to suicide at one end, or to one of the various diseases of indifference.

But much as I like this definition, it is mushy. So let us proceed to Panksepp, who makes it stand up straight. Let me list his seven and explain something of how I perceive them.

1: Seeking is the first: curiosity: the impulse to explore and find the next piece. When you are thinking of emotions in terms of love and hate, seeking is an unexpected intruder, but it does activate us and motivate us, so that is enough. We readily accept desire as an emotion, and seeking is a form of desire. In Panksepp’s system, as you will see, various kinds of desire are separated, and this is based on things that happen in the brain: trains are distinguished, circuits, pathways of response that are so specific they can be activated by electrodes.

2: Play is an emotion; the impulse to play is another specific circuit, and while its path lies near others because the brain is only so large, play has its distinct path. Obviously play, and the desire for play, is a motivator. The significance of its being a circuit is that if you are on another circuit, say, depression (below), activating the play circuit can pull you off. We have all experienced this, of course, giving toys to sad children. Play can also sidetrack your studies… For all the delight we take in learning, play is a different circuit.

3: Care, originally in the sense of maternal care, is another specific circuit. While it is common to both sexes and all ages, the key is the place of maternity in life and motivation. This is important, because care is a completely distinct circuit from another circuit that is often called love.

4: Lust is the name Panksepp gives to the circuit involved in sexual feelings and emotions. This is significant in case you had some inclination to think that tenderness naturally slides into sexual feelings or that sexual expression is the deepest kind of loving care. Not at all. It is a different circuit. A woman who senses that a guy has shifted gears from tenderness to lust is noticing something real and specific.

5: Fear is always recognized as the emotional response to danger. But notice that, since the circuits are specific, a certain level of fear can be controlled by stepping onto another circuit. The person who takes an interest in bugs and spiders may thus overcome his entomological fear. In general, the deliberate activation of one of the other circuits has the potential to interrupt fear and even bring freedom from its mental lock-up.

6: Panic is different from fear. Its key is the young mammal’s loss of its mother, and its extension is depression. It’s really very different from fear. Put it this way: fear of abandonment is different from fear of tigers. That’s easy! Notice, however, that play and curiosity are natural antidotes to depression (or panic) because they move you onto a different circuit, and apparently you don’t wander around on two circuits at once. Panksepp’s research has borne some fruit in noticing that one of the chemical adjuncts of the play circuit can be used to interrupt depression. It’s in trials now, and it seems to be effective and without side effects. Meantime, try a joke book.

7: Anger, of course – everyone recognizes this as an energy activator. Apropos, however, one more note: anger, fear, and panic are catabolic. That is, while they have important functions in moving us forward in certain kinds of situations, they hinder digestion and break down the body in various ways. They are not possible as a way of life; ultimately they need to be countered. There are (at least) three ways to counter them: curiosity, play, and tenderness. Sex is also used, but that brings other vulnerabilities.

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There’s a harrible (okay horrible!) new movie in process of creation. I won’t advertize it more than to say that, and maybe it will never see the light of day, but in case it does, this is my response.

Copernicus Desecrated

Welcome to Sungenis world
Where gravity’s dead and Earth unwhirled
And all the realm of discovery furled.
 
Venus may orbit the mighty Sun,
But we suppose it does so just for fun
While Mars just meanders a blood-stained run.
 
And the stars whirl round us, faster than light
Yet leave no trail of their terrible flight —
For which give thanks; ‘twould sear the sight.
 
…Velvet black is the sky of our night
Rich with the dance of galactic might
Pure and deep, as of infinite height.
 
Not to mention the Hadley cell
That swept ol’ Chris on the ocean swell
Whence the Gulf Stream returned his ships as well.
 
Some may long for world less stunning
A paste-up world, inept at running,
Each motion, the whim of Deity cunning.
 
But give me my ration of Logos Land
Alive in itself, and alight from the Hand
Of a Lord so humble, he lets us stand
 
On our own two feet.
Praise him for bitter; praise for sweet.
Love Him who gives us minds to meet.

Reflections

The importance of gravity is at stake when the motion of the earth is denied. Gravity is what makes the earth circle the sun and what makes all the other planets do the same and what makes the Moon circle the earth. (Ellipse the earth if you will. :)
If Earth does not orbit the Sun, but is stationary in the universe, then it is not subject to gravity which is what makes everything else follow their orbits, which is what makes spoons fall and apples fall (notes from Galileo and Newton respectively) and also makes the moons of Jupiter circle their planet.
Yes, Einstein may have said that observation would not force you to choose one model over another, earth-centered or not, but the quest for an orderly universe (Wisdom 11:20) would. And that is the foundation of the scientific revolution which these blokes would like to upend in favor of an unbelievably brash and careless critique, a real desecration of Copernicus, and a ridiculous defense of the Italian inquisition’s censure of Galileo.
A universe where gravity is occasional! Pathetic!
And all the stars of the universe whirl round us every 24 hours… Spare me! But if it were so, the slightest offset, such as a photograph from a space vehicle, would find a sky with streaks instead of points of light.

Velvet sky

A note about the “velvet” sky. Anyone who has a printer in the modern world knows the difference between flat black, which is what we have with black ink, and that specially rich black from a color printer. Similarly, the night sky is that rich black — it is not flat. You see that when you look. Why?

Well, perhaps we really do see, one photon at a time, all those galaxies that are in the Hubble photos, but, not having a 16-hour exposure, we get only enough photons to make the darkness not flat. Imperceptibly sparkling.

Another thing that is interesting in the sky is that, because the stars lack parallax, seeing them feels like seeing infinity. No matter how long we look, we do not sense the convergence of our lines of sight (from two eyes) and this gives a deepening impression of infinity, the longer we look. Over time, the stars even cross the sky, but still no parallax. Awesome!

The Trades

Another important effect, and therefore evidence, of the earth’s turning, is the several bands of atmospheric motion — the Hadley, Ferrel, and Polar cells which drive much of our weather and are a consequence of our spinning. So is the Gulf Stream, by the way. The Hadley cell drives the trade winds that brought Columbus here, and the Gulf Stream and northern Ferrel cell returned him, all three being direct consequences of the turning of the Earth.

Jupiter also has weather bands similar to our own, but more because it’s bigger.

Logos the Beloved

The Lord has made a world where he may be known partly through his works, which are reasonable and hence worth study. He is the Logos, the Word from our Father whose mind is the source of Rationality and who gave us minds so that we could know him and praise him for his mighty works.

And he is the Beloved.

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Zodiacal light

Under very good observing conditions, there are some interesting lights in the night sky.

The first is the zodiacal light, so named because it is a faint lane of light across the sky in the area of the zodiac, the ring of 12 constellations through which the Sun seems to move, — that is, if you think of the Sun circling Earth, as people imagined through all the years when the constellations were getting their names.

But not only the Sun; let me say more.

Where are the planets?

The planets, including Earth, orbit the Sun as if they were sitting on a disk that spins round with the Sun at the center. That is, they don’t orbit every which way in three dimensions, but sedately, one orbit beyond the next so that the solar system is flat as a pancake – even flatter. It’s not really two-dimensional, of course, but it’s pretty flat, and if Earth spun on an axis that was vertical with respect to the solar system, the planets would always pass directly overhead.

Because the Earth is tilted on its axis, however, the passing of the planets changes over the space of the year. Thus, if we look out into the system from Earth, on the equinox, (either March 21 or September 21, any planet crossing the sky will be visible about as far down from the zenith as the latitude of the observer.

Thus: if you are on the equator, the planets will pass right over your head; if you are at latitude 23°, they will be high in the sky, about 67° above the horizon. (90 – 23 = 67)  In Venice (Italy), or Minneapolis (Minnesota), at latitude 45°, planets will be halfway between the zenith and the horizon. From the poles, the planets will be right at the horizon and not actually visible.

At all other times of the year, there has to be a correction for the tilt of the Earth. In our northern winter, Earth’s axis northern is much closer to the disk of the solar system, and the planets are quite high in the sky. At the same time, for southerners, planets are low in the sky. In our summer, it is the opposite: planets are to be found closer to the horizon in Europe Asia, and America, but higher in the sky for Australia and for most of South America and Africa.

You can get a planisphere, or star wheel and check this for yourself. It is fairly easy to make one, and also easy to buy one. The complication of making one is that they have a slightly different construction for different latitudes.

star wheel

With or without a star wheel, we learn that the zodiac is the band of twelve constellations above our tropics, and the zodiacal light is a faint band of illumination in this area. It is believed (by almost everybody) that this dust might have been dropped by comets on their way close in to the sun; or it may be infalling dust from broken-up asteroids, or perhaps it is leftover from the beginning of the solar system. These would all be reasonable dust sources. Any such combination of sources could make a kind of pancake of dust orbiting the Sun, and that pancake could be visible from earth as a pale streak across the night sky. Wikipedia has an image by Y Beletsky, working from the Southern Astronomical Observatory in Paranal, in northern Chili.

Zodiacal light

Zodiacal light observed from the southern hemisphere, Paranal, Chili, November 19, 2009

I presume that the bright star at the top of the image is Venus. And in case you are wondering whether it is dawn, it is not; I believe it is near sunset. The zodiacal light does give a false impression of dawn — remember the zodiac is the set of constellations where the Sun travels.

And here is another image, close to sunrise, with both Venus and Jupiter caught in its glow.

Astrophoto: Zodiacal Light with Venus and Jupiter

Picture by Felipe Gallego, taken in northern Spain

But could the zodiacal light really be a dust ring around Earth instead of a dust ring around the Sun? It would look like a streak either way; it would be in the zodiac either way. If it were around the Earth, we might conclude that the Phoebe ring is visible and it has been seen: it has simply been misidentified.

This is not an easy question, and I cannot answer it, but I can offer a reason to examine it further.

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What could we learn from the rings?

There is now a weather forecast based on a simulation of the relationship between the Earth, the Sun, and the hypothesized Earth rings. The simulation is complex and hard to watch; that’s why I saved it until I could lay out some background. Today I would like to explain what it might contribute to a weather forecast, but let me begin by reiterating that this is a hypothesis, not a prophecy. There are many influences on weather; this is a hypothesis that Earth rings could be one of them, and such rings would be more important during years of quiet sun; in fact, the better I understand them, the more important they seem so: disclaimer finished.

Of course, the rings won’t change the mountains near you; they won’t stop “lake effect” snow; they won’t make the Earth revolve backwards around the Sun or shift the equator or stop the jet stream (though they might guide the Hadley cells…) But after all the things we can’t change have been taken into account, there’s still a lot of weather that still takes us completely by surprise and seems to have no cause at all. Some of it fits into the ring model. It’s worth looking to see how much.

Here are a few things to help you watch the simulation.

Where am I?

First of all, notice the position of our northern hemisphere. The simulation begins in January, and you are lobserving Earth and its rings from the Sun. Jan 1 is very close to the winter solstice, and the South Pole is in full view; the North Pole is in back.

Second, notice that there are two sets of rings, two discs, one equatorial, and the other tilted slightly across the equator. The tilted set slips from side to side each month. That’s because it’s the Phoebe ring, and its center is actually the gravitational center of the Earth-Moon system, rather than the center of the Earth. As the Moon goes around the Earth each month, the uptilt of the disc follows it and so does the center of rotation. Watch how the Phoebe rings slip from left to right and back again because this will help you distinguish them from the equatorial rings.

Third, because the Earth is tilted 23° with respect to the sun, and because your point of view in this video is as if you stood on the Sun, the tilt of the equatorial ring system also shifts, making the rings very confusing sometimes. Majestic, but confusing!

Key: the equatorial disc of rings shifts its angle but not its center; it tilts, but it does not slip from side to side.

The equatorial ring:

  1. In January, you are looking at the rings from the south, so they cast their shadows north.
  2. In spring, you have one day (March 20) of looking at those rings edge-on. This is always a possible storm time, but noticing the heaviness of the Phoebe ring suggested that it would also be cold, and that this cold would persist for a while. See below. Notice also that the North Pole is coming into view.
  3. In summer, the equatorial ring shadow is cast south as you look at the disk from the north. An equatorial ring system would make the winters colder but would not affect the summers. Here is the North Pole in full view.
  4. On September 22, there is another day of edge-on for the equatorial rings, and then they begin again to cast their shadows north again; if the equatorial rings are heavy, they will make the winter colder, but they will never affect the summer.
  5. Because both sets of rings are sometimes tilted, their motions can be very confusing. Note that the equatorial rings are the ones that do not slide from left to right.
  6. As winter progresses, the equatorial disk gradually spreads out across the background of the Earth, until it is fully opened around Dec 22; then it begins to fold back again.

The Phoebe ring

  1. As the simulation begins, the Phoebe ring is casting its shadow north along with the equatorial ring.
  2. As you approach May 7, the Phoebe ring is folding up. Its increasingly heavy and localized shadow might be expected to cause storms, which would eventually move southwards with its maximum shadow. This is the reason for the forecast of a rough April, which is certainly being fulfilled in South Dakota. (The ring forecast was made January 1.)
  3. May 7, the Phoebe ring is edge-on to the Sun, and everything north of the tropics is out of its shadow.
  4. After that, its shadow falls south, which mostly affects the southern hemisphere but also the equator, at least for a while. In any case, it leaves the North Temperate zone clear. All summer, you see the Phoebe ring sliding from right to left, from left to right, but always with its shadow southward. That’s why the ring forecast is for a relatively mild and warm summer. For us. For the US, and also for Europe and the northern hemisphere generally. At the same time, it could mean a colder winter for the southern hemisphere, which faces both rings from May to September.
  5. On October 30-31, the Phoebe disc of rings is edge-on. Again, this deep shadow could cause storms, and at the same time, the equatorial rings have been spreading chill northwards all month. From then on, the northern hemisphere has both sets of shadows, with the Phoebe rings swinging majestically from side to side, but continuing to supply a north-falling shadow. It is hard to say exactly how the two discs will interact, especially since we don’t know their detailed structure – we don’t know which rings are heaviest and how far out.

But it looks cold. And if you watch the simulation at the youTube site, there is a longer and more detailed forecast underneath. It’s from Lucy Hancock, the architect of this whole

There is also a forecast for next March being harsh like this April, but I don’t have the simulation for that. That’s when the Phoebe ring-shadow falls north again, not on the same date as this year, but earlier.

All of this is based on the work of Lucy Hancock, who has her own blog on earthrings.

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You may remember that in 2008 and 2009, there was a lot of talk about the quiet sun. There were days and days without sunspots. People who knew a little history remembered that there was a “Little ice age” in Europe centered on the Maunder Minimum, the 70 years when there were no sunspots at all. Well, maybe with our better instruments they would have seen some sunspots, but basically, there were no visible spots for at least 70 years, from 1645-1715.

Because it was so cold at that time, people wonder whether sunspots make for warm weather; and conversely, whether a lack of sunspots could make for cold weather. Perhaps I should call it cold climate because the effect is not instant – we don’t get hot weather the day of a sunspot, and it was actually cold not just for 70 years, but for about 500 years, until the mid-19th century.

So take a look at the sunspot history of the 19th and 20th century. Faithfully, every eleven years, there are lots of sunspots, and then fewer in the years between. A sunspot maximum, a sunspot minimum, regular as a clock.

Sunspot cycles from 1750 to 2000. Notice how regular they are. Notice the low spot in the mid-19th century; notice the high spot in the late 1950’s.

Now, 2008, or maybe mid-2007, was supposed to be the minimum for the current sunspot cycle, so it was okay to be short of sunspots those years. But this minimum was a little too minimal for comfort. There were 200 days in a row with no sunspots. And 2008 stretched into 2009 with the spots still very sparse. Now we are at 2013, which should be the solar maximum, and we have some sunspots every day, but not very many and not very bright.

Here is the sunspot cycle through 2012.

Some people are hoping that the real max will come later; maybe the little bump we see  halfway through 2011 was a fake max or the first part of a twin max.

Maybe.

Maybe not.

The red line that marks the prediction is looking more hopeful than plausible. This doesn’t look like much of a max, and the signs that we should already be seeing for the onset of the next solar cycle are seriously subdued.

While some people are still talking about global warming, others are saying that, yes, maybe there was some warming in the late 20th century, which was also a time of nice sun cycles you’ll notice, but there hasn’t been a speck of warming for 15 years, and if history is any indication, we could be in Big Trouble, not with warm, but with cold.

So are we still talking about Earth rings?

We are still talking about Earth Rings.

Two things can make dust fall out of the ring. One is that there is some natural decay in any orbit. Eventually, gravity is going to win all the way and the dust is going to fall. Even the Moon itself is subject to this: it will come home; don’t worry, not soon.

But another influence on space dust would be interaction with the solar wind. The solar wind is the stream of particles that flows out of solar storms. The particles in the solar wind are small, not even atoms, but they are fast and charged, and if there is a ring, they are bound to disturb its particles, and that will thin it out, blast by blast. An unstable orbit is more likely to dump its contents. The YORP effect.

With a quiet sun, however, rings could be expected to grow heavy and dense.

That is the reason for certain parts of the ring forecast. It is based on the position of the rings, which is a very simple calculation based on physics, not on observation: if there is a disc of rings, we can say exactly where it must be.

Second, the forecast is based on the hypothesis that the rings are thickening. If there are rings, they would be expected to thicken during solar quietude. This means more shading and a colder effect on the Earth.

The ring forecast calls for a warm, still summer (likely to involve re-initiation of global warmism), then the onset of autumn as usual, maybe a bit on the harsh side.

Tomorrow, we will look at a simulation to explain and extend the ring forecast.

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No, I didn’t spell it wrong, and it’s not slang.

The YORP effect is named after four scientists who worked out the way that photons can cause small space objects to spin. Now, small can mean a lot of things. If we are talking about asteroids, we are talking about objects of a few miles or a few tens of miles in diameter. Since many asteroids are clumps of rocks, rather than a single rock, a spin could overbalance the light hold of gravity and cause them to break up. In fact, there are many double asteroids, and the YORP effect seems to be the reason.

By the way, the four scientists are Yarkovsky, O’Keefe, Radzievskii, and Paddack. I knew you wanted to know.

And just for the record, there is one asteroid, 1862 Apollo, which gains about 4 minutes a year in its rotations. Whopping spin! If the earth slowed like that, we’d squeeze another month into the calendar every 10,000 years. If it sped up like that, we’d lose a month and be standing still by now.

But YORP isn’t just a matter of speeding up or breaking up asteroids. We have been talking about dust in Earth rings. Individual grains of dust can also have a spin. The spin comes about because the photons hit the dust grains and push them around. Furthermore, they heat the grains unevenly because they are grains, not spheres, and then the grains give off the heat again, with the same kind of thrust we have on a rocket when it’s burned gases go out the back. It’s a very small thrust, but remember that grains of dust in space are also small, and are not floating in the sort of atmosphere that could quickly damp a tiny thrust. They’re out there in a vacuum, and whatever motion begins goes on and on. If photons hit them repeatedly – when photons hit them, all day every day, they can begin to spin and then spin up a little more and a little more. Then when they bump each other, as they are bound to do, they are going to get all ground up.

Thus, the YORP effect makes the ring material get dustier over time. We’ll come back to the dust.

Phoebe ring

I have been trying to find out the reason for the name Phoebe for the second set of rings, the ones whose orbit is tilted towards the Moon. Wiki informs us that Saturn has a moon named Phoebe, and just inside the orbit of Phoebe is a ring that is clearly composed of dust from Phoebe. It is clear for several reasons, but the simplest is that Phoebe orbits Saturn in the opposite direction of most of its other moons, and the dust in this nearby ring orbits in the same unusual direction.

So the hypothesized Moon-oriented ring is called the Phoebe ring.

And I figured out how to embed the YouTube I linked before.

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