Yes. I fully understand that things like the moon can’t really spontaneously disappear; I’m just asking what would happen to a system like the Earth’s tides if a significant component of the force driving it were to abruptly cease acting.
Yes, but any consequence of that event might also have a staggeringly low probability. So my answer is still: “anything.”
**Third, even a modest axial tilt would have an effect on the climate by altering the duration and intensity of the seasons, and additional nutational modes resulting from the sudden disappearance of the Moon would certainly contribute to this, but again such variations would be minor (fractions of a degree) over periods of centuries or larger. **
“Minor”? I differ to beg with you sir, and I refer you to this cite:http://findarticles.com/p/articles/mi_m1511/is_n1_v15/ai_14908885
I quote:
*STRIPPED OF ITS ROMANCE AND POETRY, THE MOON IS AN INERT, OVER-SIZE ROCK DEVOID OF AIR, WATER, AND LIFE. YET WE MAY OWE OUR VERY EXISTENCE TO IT. THAT IS THE SURPRISING IMPLICATIONS OF COMPUTER SIMULATIONS REPORTED LAST FEBRUARY BY ASTONOMER JACQUES LASKAR AND HIS COLLEAGUES AT THE BUREAU OF LOGITUDES IN PARIS. OUR UNSUALLY LARGE MOON, THEY SAY, EXERTS A stabilizing influence on Earth’s spin axis that has prevented the planet from wobbling like an out-of-control top–and has thereby saved it from wild climate fluctuations that would have been hostile to life. “We are in an exceptional state,” says Laskar. “We owe our stability only to the presence of the moon.” Romantics and poets are entitled to feel vindicated.
The tilt of Earth’s spin axis, called the obliquity, is what give us seasons. If Earth were spinning like a perfectly upright top, perpendicular to the plane of its orbit around the sun (an obliquity of zero), we would hardly experience seasons at all because every point on the planet would receive a constant amount of sunlight all year long. But if Earth were rolling on its side (an obliquity of 90 degrees), each pole would swing between extreme heat and total darkness every year. Because Earth’s spin axis is only slightly tilted, by about 23.5 degrees, the planter enjoys moderate seasonal variations.
And it has done so for eons, says Laskar, thanks to the moon. He and his colleagues used a computer model to calculate what the long-term behavior of Earth’s spin axis would be if the moon weren’t around. Because Earth spins, the planet bulges at the equator. The sun and planets exert a gravitational pull on this bulge, causing Earth’s axis to rock slowly. As the planets move in their orbits–and as they deform one another’s orbits through their gravitational interactions–the overall strenght of the various forces acting on Earth’s bulge fluctuates erratically. Laskar and his colleagues found that this would cause the spin axis to oscillate in an inherently unpredictable, chaotic way: a small disturbance in the obliquity today would yield a very large change a million years from now. “We found that without the moon the obliquity of Earth is unstable and can go anywhere from 0 to 84 degrees,” says Laskar.*
So… it doesn’t seem “minor”, does it? Fractions of a degree? more like 0-84 degrees sir.
Dean.
The potential energy involved in moving a chunk of the world’s oceans a few centimeters is huge.
Any way you slice it, it’s a lot of energy being released in a very short amount of time. I predict lots of tsunamis.
Oh, Laskar. You might try citing some of his actual papers rather than a pop-sci article; here (warning: PDF) for instance, or here is an abstract from Nature. If you look at his references, however, you’ll see that most of them refer to his own publications. That’s because Laskar is pretty much out there on his own without any consensus or support among astronomers and planetologists. Take a look at the first paper I cited; his only explanation for the mechanism causing planets to spin around is this single statement: “The chaotic motion of the solar system is mainly due to the interactions of the secular resonances in the precessing motion of the inner planets,…”
So, until someone presents a more comprehensive hypothesis to explain the alleged wild gyrations of an Earth sans the Moon based on some hand-waving about chaotic motion due to secular references, I’ll stick with what we currently know about planetary dynamics.
Stranger
Thinking through my fingers for a moment…
At this moment, the moon is affecting the shape of the earth, pulling the near side more than the far side, distorting its shape. The most noticeable effect of this is the tides, but in fact, the moon distorts the shape of the whole planet. The rotation of the earth also means that the bulge is not colinear with the moon. The moon slows the near part of the bulge down, causing the moon to speed up and get farther away.
So suddenly the moon is not there. The gravitational effects of the moon vanish, and the forces keeping the earth bulged out in this fashion are gone. That means to me that the earth should react elastically, with the extremities moving toward the center, and the earth bulging outward perpendicularly to the direction of the now former bulge. Then this reactionary bulge would dissipate, causing the earth to bulge in its former direction again, and so on back and forth, following the principles of damped simple harmonic motion. Of course the energy could spread longitudinally as well, causing the poles to bob up and down. Tides would be extremely different for this transition period, and after that, much smaller and only around noon and midnight. I see the possibility for massive wave events, and also for sever earthquakes, as this rubbery period could have effects on the stress built up along major fault lines.
The length of the day on Earth will cease to increase. As far as the mutual center of gravity, it depends on what happens when you spin a sphere or spheroid about an axis that is parallel but not collinear with the axis through its center, and then “let it go”. I can’t remember from college physics what happens according to the laws of angular momentum.
The survival of the ecosystem depends on the adaptability of organisms to the newly seemingly chaotic tides for a period and then the longer term smaller solar tides, as well as the absence of moonlight as a trigger for certain behavior. How far that reaches would depend on how the reaction of these organisms affects the entire biosystem of the planet.
So my expert opinion is that if the moon were to wink out of existence, it might suck.
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Is it not possible that dark matter would simply fill the (heh) void left by La Bella Luna ? In a recent perusing of Discover Magazine - the Tom Swift Adventures of the scientific world ( which is all I can handle)- I learned much about dark matter. I now envision the huge empty void of outer space as no longer emtpy. It is teeming with uncountable bits of stuff, each one taking up space in space but serving no immediately discernable useful purpose. A bit like the telephone service for US Airways, but I digress.
With all of that dark matter around, I’d think there would not be a void for more than a milifraction of a second before the void were filled forever. It is worth wondering what would happen to the fabric of space for that milifraction of a second, though…
Cartooniverse
Really? Could you pass on what you learned? There are a bunch of cosmologists and particle physicists who would love to know much about dark matter.
But seriously, about the only thing we really do know about dark matter is its (approximate) density. And when you average it over intergalactic scales, it’s significantly more dense than the ordinary matter we’re familiar with. But that’s just because the familiar sort of matter is much clumpier than dark matter. Around here, which is one of the places where the “normal” matter clumped, the local density is much greater than that of the dark matter. And any dark matter which would fill the void left by the Moon, is probably already occupying that space anyway: Whatever it is, it apparently interacts with other matter only very weakly, and could probably just pass right through the Moon as though it doesn’t exist.
–Huffily-- Well, I never !! Why don’t you buy your own damned subscriptions if you and your little friends are that curious ?
It was tough to get it, and I know the article was aimed at Feebs Like Myself. I couldn’t tell if dark matter occupies the same physical space as the clumpier matter ( to use your phrase ) we’re all familiar with here on Terra Firma, or if it is passing through clumpy matter all the time and we just don’t know it. The difference being that it is always on the move and not considered “in” a location at all.
It seemed to say the latter. that dark matter is so miniscule that it would be squashed by a nearby neutrino. Is this considered accurate? And if it is, is it fair to envision a universe filled with fast moving raindrops at all times that are so small that whatever else there might be in the universe does not alter the paths of said raindrops, which move through space, “filling” it but not affecting it in any way?
If so, then of course I am wrong. The moon would not be “replaced” in space by dark matter since dark matter already takes up the space along WITH the clumpy matter that makes up the moon as we see it.
Am I close? 
They would be referring there to the “hot” versus “cold” dark matter question. That one, too, has been more-or-less resolved: Most modern models require that the dark matter be “cold”, which is to say that the particles of it (whatever they are) travel at significantly less than the speed of light. Either way, though, it’s presumed to permeate all space, including that space which happens to already have moons or planets in it. And with that, I really have exhausted the topic of what’s known about dark matter.
This is saying too much. First of all, dark matter doesn’t interact much with anything (except gravitationally, of course), and neutrinos don’t interact much with anything, either. So there would be no “squashing” going on, since “squashing”, whatever you mean by that, is presumably an interaction. Secondly, neutrinos themselves are one of the better candidates for the dark matter. Note, incidentally, that I’m not saying they’re a good candidate: There really aren’t any specific things which I’d call good candidates. It’s got to be something, but there are about twice as many possibilities as there are particle physicists. Third, if you’re talking about the mass of the dark matter particles compared to the mass of the neutrinos, we have very little notion of either. For neutrinos, all we know is that at least two of the three types of neutrino have a mass of at least 10[sup]-2[/sup] eV, at least one of them is over 5*10[sup]-2[/sup] eV, and all three of them are less than about 1 eV (the lightest one might be massless, for all we know). The dark matter particles, meanwhile, have mass estimates ranging from 10[sup]-6[/sup] - 10[sup]-4[/sup] eV or so, for axions, to even macroscopic masses (grams? Kilograms?), for quark nuggets or primordial black holes.
Thank you. That made sense, and taught me a lot more than the article did.
Well, Nature is peer-reviewed. Stranger, do you have a non-hand-waving reason to believe that the obliquity of the Earth wouldn’t be chaotic, or that Laskar’s results are suspect?
From the abstract from “The chaotic obliquity of Mars”, (bolding mine):
Here’s the fairly impressive publications page for Jack Wisdom, one of the authors, and a Professor of Planetary Science at MIT. The above paper is available as a PDF there, along with many others on related subjects. The obliquity of Mars varies from 11 to 49 degrees. While I couldn’t find direct confirmation of the Earth’s obliquity variation without the Moon present, that Mars’ obliquity varies so much is certainly qualitatively supportive of Laskar’s result. Also, among Wisdom’s papers is “Evolution of the Earth Moon system” where the author examines, well, the evolution of the Earth Moon system. I have to believe they would have looked at the Earth’s evolution without the Moon present, since they have all the tools needed to do so.
For anyone wondering what secular resonances are, from that article, “Secular spin orbit resonances occur where the period of precession of the spin axis of Mars is commensurate with one of the periods in the variation of the orbit of Mars.”
Just because a paper is peer reviewed doesn’t mean that the hypothesis it presents has been validated or even is held in consensus; indeed, if that were the case, we’d never publish any new theories or revelations at all. Peer review means that the work in the paper has at least met the minimum criteria for scientific dilligence, would be of interest and potential value to the intended audience of the journal, and isn’t clearly the work of a unhinged lunatic (though exceptions are made for Roger Penrose because his particular brand of lunacy is so beautiful and frequently ends up being brilliant as well).
Laskar’s claim is that resonances between the planets would cause chaotic wild gyrations that are otherwise outside of normal behavior of planetary objects described by classical linear mechanics. It’s an interesting claim, and there are some appearent high order commensurabilites between planets, but it’s not clear that these are either signficant or permanent. What I’ve read of his papers on the topic seems somewhat specious, in the “this could be, and thus it must be” line of reasoning. The strength of influences of the inner worlds on each other is tiny to the point of being insignificant, but Laskar offers up the notion that the rotational properties of the planets are readily perturbable, which is an extraordinary claim lacking corresponding evidence thereof.
So no, I can’t prove the negative of Laskar’s claims, nor can I state authoratively that the are wrong (or as the poster who originally brought the issue up said, “WRONG!”) Would the Earth, sans Moon, tend to nutate more dramatically? This is certainly possible. Would it change orientation to the point of “fluctuat[ing] more wildly…60-90 degrees,”? Unlikely. Where would the energy for these dramatic fluctuations (and corresponding changes in rotational momentum) come from? It’s one thing for Mars–a planet with 15% of the mass of the Earth and an apparently solid core–to shift orientation by a few tens of degrees, and quite another for Earth, with its dense spinning molten iron core, to shift around with abandon.
Stranger