Ah, I just put my finger on more of what bothers me about your slow-rotator model.
The day side's temperature shouldn't get more than 20% hotter than the global average temperature, not accounting for atmosphere feedback effects. The rotation state enters the equations as a factor of 4 (from the surface area for a sphere) under a fourth-root. A slow rotator changes that to a 2, so you get a small increase in day-side temperature. But not nearly as much as you might expect thanks to that fourth-root.
Sorry for the delay in that. You made me think for a while to spot that.:-)
You're arguing from your gut. I'm telling you: research HAS been done. I believe it was by the Kasting group in Pennsylvania. Feel free to look it up. (The journal will be Icarus, I'm fairly sure.)
The simulations show that Earth in Venus's orbit is toast, regardless of spin rate. And at Mars's orbit it's frozen, or nearly so. (The models are a little shakey on that point, as I recall.) The atmospheric models DO account for greenhouse gases, so I trust them much more than your guesses. In fact, they dial up the gasses to maximum possibly effect to test the limits of the habitable zone.
And note that CO2 is generally a wimpy greenhouse gas and isn't very effective. Also, Earth's globally averaged temperature isn't 98 F, although I suspect you knew that. It's actually not far above freezing. (Your post has a vague implication that you think that it is that high, so I wanted to be clear on that.)
And I concede your idea about spin, but it will only matter in a narrow boundary at the edge of the habitable zone. Where Venus is, water will always be unstable, even for a fast rotator. So Venus was screwed no matter what. Models show that it goes to hell pretty fast, too, regardless of the length of the day. Farther out, things get more interesting because there will be feedbacks. (Heat on the day side will tend to redistribute itself to the night side, reducing the greenhouse effect on the day side. So it isn't clear what will happen. I don't know if anyone has modelled slow rotators at different orbital distances.)
Finally, yes, the heat from the interior is there. It amounts to about 1 part in a million compared to the solar flux, so it is irrelevent.
Energy=cost, pretty much. Fuel is fuel, not matter how quickly or slowly you use it. And for TNOs you have to HAUL it out there to use it. Which costs... fuel.
"Closer orbits are faster. p=mv." Apologies, I was not specific. *Angular* momentum. I had rather thought you knew that, though, since linear momentum is totally irrelevent here as is abundantly obvious. Apparently not. And while I didn't particlarly mean to patronize you, it's becoming clear that you don't have a very good grasp of orbital mechanics.
And the context was never asteroids. Kindly go back and check. Hell, read the title of this story. Don't waste my time if you can't be troubled to at least do the easiest fact-checking availible.
Surface temperature is set by the energy balace between incoming solar radiation and outgoing radiation. Internal heat is not a significant player on any solid worlds, as far as I can think of. (This balance is not just set by solar proximity, of course. Albedo is a key player and so is the atmosphere, if it exists. The latter is why Venus is hotter than Mercury.)
The interior temperature is basically unaffected by solar proximity, but is set by internal heat sources. (Accretional heat from formation, heat from differentiation, radiogenic heat, and tidal heat from select bodies.)
The reasons Mars's internal heat has allowed water to freeze is because the loss of atmosphere. Enough greenhouse gases and Mars might be able to support liquid water at the surface. (It's looking more and more like it did, so that might is quickly becoming an "is".) But when the interal heat goes away, there is no more outgasing to resuply the atmosphere and no more magnetic field to protect from solar wind sputtering. So goodbye greenhouse.
The article is accurate for the most part. (Venus had tectonics and I'm sure Jonathan Luinine knows that. But I also know that he would know that it appears to lack *plate* tectonics, which I'll wager is what he told reporters.)
Wrong on both counts, it would seem. Rather complex models of atmospheres have been done to explore what happens when you change the distance to the star. Earth at Mars's distance is (according to the models) uninhabitable or at best juuuuust barely so. Earth at Venus's distance quickly becomes much too hot. (Which is the sensible answer, isn't it? Venus is just about Earth's size, but is obviously planet hell. It would be rather surprising if Earth could be habitable there, then.)
Venus's spin has nothing to do with the high temperature. Actually, it ought to make one side of the planet hotter than the other, but it doesn't. (That's that dense atmosphere at work.) The average temperature is unaffected by spin rate, though, since temperature is basically a question of energy balance. (Input=output)
Also, Earth's interior energy does not heat the surface. (Although it does allow for a magnetic field.) At least not noticably. The incoming solar flux averages about 1300 W/m^2 on the day side of the Earth while the outgoing flux due to internal heat is about 0.001 W/m^2. Guess which sets the surface temperature.
You're right that size and composition are important, but your details are disturbingly inaccurate.
Actually, quite wrong. It takes about 10 times as much energy to haul something from Pluto's orbit to Mars's orbit as it does to haul it off of the Earth. Moving something from the Kuiper Belt to the Moon would be even more costly since Earth is nearer the Sun. Even with gravity assists to lose momentum (not gain it; you're going *in*, here), it's unlikely that it would be cheaper, especially since I can arrange for gravity assists leaving from the Earth as well as leaving from the outer solar system.
This is why space probes have been travelling into Earth orbit for two decades longer than to the outer solar system and why humans have never gone to the latter location. It costs way more.
Check your data before you post.
That aside, you miss the point. We can't haul that kind of water anywhere in the solar system, period. That capability isn't even on the horizon right now. Speculating about mining Trans-Neptunian objects, let along moving them in bulk, for terraforming is complete science-fiction right now and will be fore the foreseeable future.
Except that you'd have to extract the water from the methane and ammonia first. Not to mention the enormous difficulty in hauling that much water across the entire solar system. It's something we're utterly incapable of now and will be for the foreseeable future, so it's not really worth counting on.
Well, unless we find a vastly more efficent and cheap way to get objects into Earth orbit and then beyond, then no. It's simply a lot cheaper to mine things on Earth. Maybe if/when we start to run out of certain materials, it might make sense. But even then we would go to the asteroids, not comets. Asteroids are both closer *and* richer in metals. Comets are mostly ices, after all.
So I'd saying having any expectations of mining these objects is sort of a stretch right now.
" Re:We can't even agree on global warming (Score:2) by lgw (121541) Alter Relationship on Tuesday September 06, @09:15AM (#13489975) (Last Journal: Tuesday June 28, @11:57AM) All of the circulation in the mantle comes from (we think) convection currents. This is not a frictionless system spinning in isolation, it's a system where the spin is powered and damped. The torque you're looking for comes from the thermal energy being carried away, and is constantly being applied, much like the "torque" that causes eddy currents in a river comes from the flow of the river and the friction of the banks.
How do you suppose the Earth's magnetic field reverses if the circular convection currents creating the field aren't reversing direction (or, more realistically, changing in some more complex way, as the circulation pattern is no doubt as complex as the atmosphere's)."
You post *that* and then you go wondering what I'm replying to? You either aren't posting clearly as you think you are or you simply don't get the physics one bit.
If you're thinking that the Earth's convection cells contain significant angular momentum, they don't. They rotate too slowly, for one thing. (Plus, as far as I know, they average out to zero net angular momentum. But come to think of it, I've never heard anyone claim anything either way on that.)
Since plate tectonics has persisted on geological timescales, I'm not sure why you think that the convection cells are unstable as a collective. Furthermore, since Earth's magnetic field has changed direction many times with no evidence of change in Earth's rotation to correspond to it and since the Sun's magnetic field does the same thing every 11 years (with no discernable change in the Sun's rotation), I have to ask you why you think there's any reason to worry.
Also, note that the move the WHOLE crust you need a WHOLE spher convection cell. Which is contradory. Every cell needs an opposite cell. Look at the velocity fields and you'll see why.
And can the name-dropping. I'm not even convinced you went to Caltech, since you spell it differently than every alum and professor I know, not to mention the school itself. Even if you did, I'm not impressed: it just means that you learned a lot less than you think you did. Name-dropping counts for nothing in a scientific argument.
Anyway, I laid out my challenge: if you don't believe me, ask your old professor. Or ask any geophysicist. You don't have to believe me, after all. Either way, this has become pointless and I'm stopping.
I'm going to guess you aren't a physicist. You're showing a rather significant misunderstanding of rotational dynamics.
Earth's spin is NOT powered and it is NOT significantly damped. And it CANNOT be damped by Earth itself. There's no way, it's a closed system. Thermal energy cannot carry away angular momentum. At least not in anywhere NEAR the quantities you're discussing. (Photons do carry momentum, but in miniscule amounts.)
Your example of river currents show what I am talking about: the torque comes from outside the river. (And, if you include the river bank, the net torque and the net change in angular momentum is zero.)
Now, as it happens, you do *not* have to change the Earth's convection patterns to reverse the field. Which is good, because there is no way in hell Earth's pathetic magnetic field can brake and redirect all of rocky material. The field *can* undergo reconnection, however. That can lead to a chance in the field without altering the mantle convection.
Look, it's pretty clear to me that you don't understand the physics here. So please go ask one of your physics professors about it. Or grab a textbook. Honest, you can't change the spin state of the Earth (or Earth's core, even) without a LOT of torque. And there's no way that the magnetic fields can provide that. Magnetic fields are puny and weak in this regime.
Yes, there is a reason to think that the net anuglar momentum will be unchanged. Angular momentum is conserved unless an outside torque acts on the objects. Very few torques powerful enough to alter the Earth's spin act on Earth. The Moon and the Sun are about it, but they act over extremely long periods.
So if you're positing that a change in Earth's magnetic field will cause or will herald a change in the core's spin, you are *inherently* positing some torque. Since you are tying all of this back to the field, you seem to be assuming that the torque is due to the magnetic field.
The field has to be generated in the outer core if it is a dynamo, which we think it is. The inner core is solid so it can't produce a dynamo. And the reversals certainly do not imply a change in angular momentum. In fact, you should be shocked if they did: the outer core has a beefy moment of inertia, so to change the spin state significantly would take very serious torques. And there's a question of where to get those torques. Magnetic fields aren't strong enough to do that over a reasonable time scale.
"Given that it's pretty important to surviving solar radiation to begin with, and is merely a symptom of something even more mysterious happening in the core, it could be quite dangerous."
Or, it could be the usual pole reversal Earth undergoes every now and then. (Similar to what the Sun undergoes every 11 years or so.) We've survived it before, so why are you getting frightened? The radiation won't be that bad, really. We *do* still have an atmosphere, after all. Few particles will make it through that to the surface.
Solar activity could affect Earth's climate because the ultraviolet output of the Sun increases during the more active stages of the solar cycle. But correlations there are very dubious in the eyes of most researchers.
Also, as a point of minor correction, note that the Earth's crust floats on the mantle. The mantle and core are not spinning at the same rate. I find it difficult to imagine how the core will change rotation rates due to a chaning magnetic field. I don't believe that there is nearly enough angular momentum in the Earth's magnetic field to significantly affect the core.
Wrong. For moment of intertia (which is what we're about here, not torque: we're not changing the angular momentum), it's the mass *and* the radius. Radius comes in to the formula squared. But mass comes in linearly. So while radius is important, you can't go neglecting mass distribution at all. And with the overwelming majority of Earth's mass being in the core and mantle (and most of the mass of the crust being rock...), the oceans expanding a few meters isn't going to really siginificantly alter Earth's moment of intertia. The result may be *measureable*, but it's nothing significant.
Except that you're ignoring the fact that the Earth's spin IS slowing because the Moon IS moving away from us. The latter has been measured. Conservation of angular momentum *requires* Earth to slow down in response.
(In fact, frictional dissipation due to convection doesn't do anything to spin since there is no torque.)
The expansion of the oceans due to global warming will raise sea level a few meters. Tens of meters, tops.
Compared to Earth's radius (6378 km), that's chump change. Particularly when you consider that the interior of the Earth isn't going to warm up and will therefore not adjust at all, and that's where the overwelming majority of Earth's mass is.
Also, note that adding a leap hour every 500 years isn't the same as saying that Earth's spin period will increase by 1 hour in that time. (I get the impression that that is how you're reading this. Apologies if not.) It's saying that the Earth's spin includes and extra 3600 seconds in 16 billion, or 1 parting in 4.5 million. That's not a serious increase at all.
Except that the crust isn't heavier than the stuff in the middle. Earth has already mostly differentiated by desnity. (Iron IS the dense stuff.) The crust is basically the lowest density rocky bits, the scum on the top if you will.
So if the crust broke off and fell inward (for reasons unclear), it would force a denser bit UP and actually slow our rotation.
The Moon's tides are about twice as strong as the Sun's. (Which is why spring and neap tides occur in the first place.) It's a bit surprising that they're that close, but the Moon's proximity almost balances the Sun's killer mass. (And recall that tidal forces fall off like 1/r^3, so distance is more important here than for gravitational force where the Sun kicks the Moon's non-existent ass.)
What this means is that in around 45 billion years Earth will have a spin period of around 47 days and will be locked in a 1:1 spin:orbit resonance with the Moon (just like Pluto and Charon are now). Then something very cool happens: the Moon starts approaching Earth again and the Earth's spin continues to slow as it tries to match period with the Earth's orbital period.
Of course, we'll probably be long gone by then, what the Sun's red giant stage and all. But still, pretty cool.
(For more on these and other fascinating topics in solary system dynamics, check out Murray and Dermott's book.)
It's not that simple at all. A perfect fluid wouldn't cause any friction at all, after all. And in fact, much of the friction in the ocean is caused by the choke points where the land channels the water into narrow passages. (At Capes Horn and Good Hope, for example.) This is why the dissipation rate of the Earth has changed considerably over geological history as continents moved about. (Thus explaining why the young Earth folks' simple calculation can appear to result in the Moon being in contact with Earth less than 4.5 billion years ago.)
It's not the universities that are responsible for the textbook prices. It's the publishing companies. They push authors to release new editions every 2 years, now, so that they can sell brand spankin' new copies (at $100 a pop) rather than lost money on the used copies. Of course, this means a lot of work for authors and little new content. (In some cases, it means that the quality goes *down*, in fact.)
Wouldn't that be like taking a hygrometer to the bottom of the ocean? You don't need it to tell you what's out there, and it seems like you'd just break the equipment with the overload.
Um, check your facts. Bin Laden has NEVER been keen on claiming responsibility for his actions. He's found that it works better for PR not to.
Yes, it's true that he didn't coin the name that we use for his group. But that doesn't make the organization less real, does it?
And given that Al Quaeda was key in the installation fo the Taliban regime (and bin Laden a shaper of their policies), I have a hard time swallowing your claims. For that matter, we have the USS Cole and bomed embassies in Africa to suggest that he wasn't a nobody, even before 9/11. Clinton wanted to go after him at the end of his presidency, which I find sort of amazing if bin Laden was nobody.
Can you back your claims up with facts?
(Incidentally, I'm basing my facts on "Inside Al Qaeda", by Rohan Gunaratna. Maybe he's lying to me, but he sure went through a lot of trouble to make up quotes, dates, places, and names. Right now, he has my confidence more than you do, either way.)
How can Al Qaeada be a list of allies against the Soviets when it wasn't formed until after the Soviets left Afganistan?
The group was originally comprised of a lot of the people who fought beside bin Laden against the Soviets, but the makeup of the organization is hardly exclusive to that crowd. A few minutes of research would reveal that to you.
Al Quaeda is real. It's a rarity amoung terrorist organizations in terms of its international striking power and the threat may be over-blown in many respects, but it's a real group with a real agenda and it's a real threat.
I'm one of the first people to step up and say that the "war on terror" (sorry, what is it today? struggle against violenet extremism?) is mainly an excuse for certain politicians to do what they wanted to do anyway (and not do much to make Americans safer). But denying the existance of a real organization that does pose a real theat does no good to anyone, except perhaps aforementioned politicians who can now dismiss critics as wackos and uninformed yokels.
Having have read some of Zubrin's stuff, I agree, he's an optimist. Not wrong, but he definitely takes the sunnier side of the statistics. Qualifications or not, when you want a result really badly you are almost assured of not making an objective analysis. Zubrin really wants people to go to Mars, so whether he's consciously aware of it or not, he tends to assume the best for his ideas.
And before you take his qualifications as the end-all of the discussion, bear in mind that there are quite of equally-qualified people who are far, far more pessimistic. (Why do you think NASA is worried.) Heck, I've heard from people with *better* qualifications (a PhD in nuclear engineering isn't the best qualification to judge the biological effects of radiation, sorry to say) who think that the radiation sheilding is a show-stopper at the moment.
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Ah, I just put my finger on more of what bothers me about your slow-rotator model.
:-)
The day side's temperature shouldn't get more than 20% hotter than the global average temperature, not accounting for atmosphere feedback effects. The rotation state enters the equations as a factor of 4 (from the surface area for a sphere) under a fourth-root. A slow rotator changes that to a 2, so you get a small increase in day-side temperature. But not nearly as much as you might expect thanks to that fourth-root.
Sorry for the delay in that. You made me think for a while to spot that.
You're arguing from your gut. I'm telling you: research HAS been done. I believe it was by the Kasting group in Pennsylvania. Feel free to look it up. (The journal will be Icarus, I'm fairly sure.)
The simulations show that Earth in Venus's orbit is toast, regardless of spin rate. And at Mars's orbit it's frozen, or nearly so. (The models are a little shakey on that point, as I recall.) The atmospheric models DO account for greenhouse gases, so I trust them much more than your guesses. In fact, they dial up the gasses to maximum possibly effect to test the limits of the habitable zone.
And note that CO2 is generally a wimpy greenhouse gas and isn't very effective. Also, Earth's globally averaged temperature isn't 98 F, although I suspect you knew that. It's actually not far above freezing. (Your post has a vague implication that you think that it is that high, so I wanted to be clear on that.)
And I concede your idea about spin, but it will only matter in a narrow boundary at the edge of the habitable zone. Where Venus is, water will always be unstable, even for a fast rotator. So Venus was screwed no matter what. Models show that it goes to hell pretty fast, too, regardless of the length of the day. Farther out, things get more interesting because there will be feedbacks. (Heat on the day side will tend to redistribute itself to the night side, reducing the greenhouse effect on the day side. So it isn't clear what will happen. I don't know if anyone has modelled slow rotators at different orbital distances.)
Finally, yes, the heat from the interior is there. It amounts to about 1 part in a million compared to the solar flux, so it is irrelevent.
Energy=cost, pretty much. Fuel is fuel, not matter how quickly or slowly you use it. And for TNOs you have to HAUL it out there to use it. Which costs... fuel.
"Closer orbits are faster. p=mv."
Apologies, I was not specific. *Angular* momentum. I had rather thought you knew that, though, since linear momentum is totally irrelevent here as is abundantly obvious. Apparently not. And while I didn't particlarly mean to patronize you, it's becoming clear that you don't have a very good grasp of orbital mechanics.
And the context was never asteroids. Kindly go back and check. Hell, read the title of this story. Don't waste my time if you can't be troubled to at least do the easiest fact-checking availible.
That depends on what you mean by "heat".
Surface temperature is set by the energy balace between incoming solar radiation and outgoing radiation. Internal heat is not a significant player on any solid worlds, as far as I can think of. (This balance is not just set by solar proximity, of course. Albedo is a key player and so is the atmosphere, if it exists. The latter is why Venus is hotter than Mercury.)
The interior temperature is basically unaffected by solar proximity, but is set by internal heat sources. (Accretional heat from formation, heat from differentiation, radiogenic heat, and tidal heat from select bodies.)
The reasons Mars's internal heat has allowed water to freeze is because the loss of atmosphere. Enough greenhouse gases and Mars might be able to support liquid water at the surface. (It's looking more and more like it did, so that might is quickly becoming an "is".) But when the interal heat goes away, there is no more outgasing to resuply the atmosphere and no more magnetic field to protect from solar wind sputtering. So goodbye greenhouse.
The article is accurate for the most part. (Venus had tectonics and I'm sure Jonathan Luinine knows that. But I also know that he would know that it appears to lack *plate* tectonics, which I'll wager is what he told reporters.)
Wrong on both counts, it would seem. Rather complex models of atmospheres have been done to explore what happens when you change the distance to the star. Earth at Mars's distance is (according to the models) uninhabitable or at best juuuuust barely so. Earth at Venus's distance quickly becomes much too hot. (Which is the sensible answer, isn't it? Venus is just about Earth's size, but is obviously planet hell. It would be rather surprising if Earth could be habitable there, then.)
Venus's spin has nothing to do with the high temperature. Actually, it ought to make one side of the planet hotter than the other, but it doesn't. (That's that dense atmosphere at work.) The average temperature is unaffected by spin rate, though, since temperature is basically a question of energy balance. (Input=output)
Also, Earth's interior energy does not heat the surface. (Although it does allow for a magnetic field.) At least not noticably. The incoming solar flux averages about 1300 W/m^2 on the day side of the Earth while the outgoing flux due to internal heat is about 0.001 W/m^2. Guess which sets the surface temperature.
You're right that size and composition are important, but your details are disturbingly inaccurate.
Actually, quite wrong. It takes about 10 times as much energy to haul something from Pluto's orbit to Mars's orbit as it does to haul it off of the Earth. Moving something from the Kuiper Belt to the Moon would be even more costly since Earth is nearer the Sun. Even with gravity assists to lose momentum (not gain it; you're going *in*, here), it's unlikely that it would be cheaper, especially since I can arrange for gravity assists leaving from the Earth as well as leaving from the outer solar system.
This is why space probes have been travelling into Earth orbit for two decades longer than to the outer solar system and why humans have never gone to the latter location. It costs way more.
Check your data before you post.
That aside, you miss the point. We can't haul that kind of water anywhere in the solar system, period. That capability isn't even on the horizon right now. Speculating about mining Trans-Neptunian objects, let along moving them in bulk, for terraforming is complete science-fiction right now and will be fore the foreseeable future.
Except that you'd have to extract the water from the methane and ammonia first. Not to mention the enormous difficulty in hauling that much water across the entire solar system. It's something we're utterly incapable of now and will be for the foreseeable future, so it's not really worth counting on.
Well, unless we find a vastly more efficent and cheap way to get objects into Earth orbit and then beyond, then no. It's simply a lot cheaper to mine things on Earth. Maybe if/when we start to run out of certain materials, it might make sense. But even then we would go to the asteroids, not comets. Asteroids are both closer *and* richer in metals. Comets are mostly ices, after all.
So I'd saying having any expectations of mining these objects is sort of a stretch right now.
" Re:We can't even agree on global warming (Score:2)
by lgw (121541) Alter Relationship on Tuesday September 06, @09:15AM (#13489975)
(Last Journal: Tuesday June 28, @11:57AM)
All of the circulation in the mantle comes from (we think) convection currents. This is not a frictionless system spinning in isolation, it's a system where the spin is powered and damped. The torque you're looking for comes from the thermal energy being carried away, and is constantly being applied, much like the "torque" that causes eddy currents in a river comes from the flow of the river and the friction of the banks.
How do you suppose the Earth's magnetic field reverses if the circular convection currents creating the field aren't reversing direction (or, more realistically, changing in some more complex way, as the circulation pattern is no doubt as complex as the atmosphere's)."
You post *that* and then you go wondering what I'm replying to? You either aren't posting clearly as you think you are or you simply don't get the physics one bit.
If you're thinking that the Earth's convection cells contain significant angular momentum, they don't. They rotate too slowly, for one thing. (Plus, as far as I know, they average out to zero net angular momentum. But come to think of it, I've never heard anyone claim anything either way on that.)
Since plate tectonics has persisted on geological timescales, I'm not sure why you think that the convection cells are unstable as a collective. Furthermore, since Earth's magnetic field has changed direction many times with no evidence of change in Earth's rotation to correspond to it and since the Sun's magnetic field does the same thing every 11 years (with no discernable change in the Sun's rotation), I have to ask you why you think there's any reason to worry.
Also, note that the move the WHOLE crust you need a WHOLE spher convection cell. Which is contradory. Every cell needs an opposite cell. Look at the velocity fields and you'll see why.
And can the name-dropping. I'm not even convinced you went to Caltech, since you spell it differently than every alum and professor I know, not to mention the school itself. Even if you did, I'm not impressed: it just means that you learned a lot less than you think you did. Name-dropping counts for nothing in a scientific argument.
Anyway, I laid out my challenge: if you don't believe me, ask your old professor. Or ask any geophysicist. You don't have to believe me, after all. Either way, this has become pointless and I'm stopping.
I'm going to guess you aren't a physicist. You're showing a rather significant misunderstanding of rotational dynamics.
Earth's spin is NOT powered and it is NOT significantly damped. And it CANNOT be damped by Earth itself. There's no way, it's a closed system. Thermal energy cannot carry away angular momentum. At least not in anywhere NEAR the quantities you're discussing. (Photons do carry momentum, but in miniscule amounts.)
Your example of river currents show what I am talking about: the torque comes from outside the river. (And, if you include the river bank, the net torque and the net change in angular momentum is zero.)
Now, as it happens, you do *not* have to change the Earth's convection patterns to reverse the field. Which is good, because there is no way in hell Earth's pathetic magnetic field can brake and redirect all of rocky material. The field *can* undergo reconnection, however. That can lead to a chance in the field without altering the mantle convection.
Look, it's pretty clear to me that you don't understand the physics here. So please go ask one of your physics professors about it. Or grab a textbook. Honest, you can't change the spin state of the Earth (or Earth's core, even) without a LOT of torque. And there's no way that the magnetic fields can provide that. Magnetic fields are puny and weak in this regime.
Yes, there is a reason to think that the net anuglar momentum will be unchanged. Angular momentum is conserved unless an outside torque acts on the objects. Very few torques powerful enough to alter the Earth's spin act on Earth. The Moon and the Sun are about it, but they act over extremely long periods.
So if you're positing that a change in Earth's magnetic field will cause or will herald a change in the core's spin, you are *inherently* positing some torque. Since you are tying all of this back to the field, you seem to be assuming that the torque is due to the magnetic field.
The field has to be generated in the outer core if it is a dynamo, which we think it is. The inner core is solid so it can't produce a dynamo. And the reversals certainly do not imply a change in angular momentum. In fact, you should be shocked if they did: the outer core has a beefy moment of inertia, so to change the spin state significantly would take very serious torques. And there's a question of where to get those torques. Magnetic fields aren't strong enough to do that over a reasonable time scale.
"Given that it's pretty important to surviving solar radiation to begin with, and is merely a symptom of something even more mysterious happening in the core, it could be quite dangerous."
Or, it could be the usual pole reversal Earth undergoes every now and then. (Similar to what the Sun undergoes every 11 years or so.) We've survived it before, so why are you getting frightened? The radiation won't be that bad, really. We *do* still have an atmosphere, after all. Few particles will make it through that to the surface.
Solar activity could affect Earth's climate because the ultraviolet output of the Sun increases during the more active stages of the solar cycle. But correlations there are very dubious in the eyes of most researchers.
Also, as a point of minor correction, note that the Earth's crust floats on the mantle. The mantle and core are not spinning at the same rate. I find it difficult to imagine how the core will change rotation rates due to a chaning magnetic field. I don't believe that there is nearly enough angular momentum in the Earth's magnetic field to significantly affect the core.
Have any sources for this?
Wrong. For moment of intertia (which is what we're about here, not torque: we're not changing the angular momentum), it's the mass *and* the radius. Radius comes in to the formula squared. But mass comes in linearly. So while radius is important, you can't go neglecting mass distribution at all. And with the overwelming majority of Earth's mass being in the core and mantle (and most of the mass of the crust being rock...), the oceans expanding a few meters isn't going to really siginificantly alter Earth's moment of intertia. The result may be *measureable*, but it's nothing significant.
Frictional dissipition isn't a source of heat? Whaaa?
Check out Io and Europa and then reconsider that statement.
Except that you're ignoring the fact that the Earth's spin IS slowing because the Moon IS moving away from us. The latter has been measured. Conservation of angular momentum *requires* Earth to slow down in response.
(In fact, frictional dissipation due to convection doesn't do anything to spin since there is no torque.)
The expansion of the oceans due to global warming will raise sea level a few meters. Tens of meters, tops.
Compared to Earth's radius (6378 km), that's chump change. Particularly when you consider that the interior of the Earth isn't going to warm up and will therefore not adjust at all, and that's where the overwelming majority of Earth's mass is.
Also, note that adding a leap hour every 500 years isn't the same as saying that Earth's spin period will increase by 1 hour in that time. (I get the impression that that is how you're reading this. Apologies if not.) It's saying that the Earth's spin includes and extra 3600 seconds in 16 billion, or 1 parting in 4.5 million. That's not a serious increase at all.
Except that the crust isn't heavier than the stuff in the middle. Earth has already mostly differentiated by desnity. (Iron IS the dense stuff.) The crust is basically the lowest density rocky bits, the scum on the top if you will.
So if the crust broke off and fell inward (for reasons unclear), it would force a denser bit UP and actually slow our rotation.
The Moon's tides are about twice as strong as the Sun's. (Which is why spring and neap tides occur in the first place.) It's a bit surprising that they're that close, but the Moon's proximity almost balances the Sun's killer mass. (And recall that tidal forces fall off like 1/r^3, so distance is more important here than for gravitational force where the Sun kicks the Moon's non-existent ass.)
What this means is that in around 45 billion years Earth will have a spin period of around 47 days and will be locked in a 1:1 spin:orbit resonance with the Moon (just like Pluto and Charon are now). Then something very cool happens: the Moon starts approaching Earth again and the Earth's spin continues to slow as it tries to match period with the Earth's orbital period.
Of course, we'll probably be long gone by then, what the Sun's red giant stage and all. But still, pretty cool.
(For more on these and other fascinating topics in solary system dynamics, check out Murray and Dermott's book.)
It's not that simple at all. A perfect fluid wouldn't cause any friction at all, after all. And in fact, much of the friction in the ocean is caused by the choke points where the land channels the water into narrow passages. (At Capes Horn and Good Hope, for example.) This is why the dissipation rate of the Earth has changed considerably over geological history as continents moved about. (Thus explaining why the young Earth folks' simple calculation can appear to result in the Moon being in contact with Earth less than 4.5 billion years ago.)
It's not the universities that are responsible for the textbook prices. It's the publishing companies. They push authors to release new editions every 2 years, now, so that they can sell brand spankin' new copies (at $100 a pop) rather than lost money on the used copies. Of course, this means a lot of work for authors and little new content. (In some cases, it means that the quality goes *down*, in fact.)
Wouldn't that be like taking a hygrometer to the bottom of the ocean? You don't need it to tell you what's out there, and it seems like you'd just break the equipment with the overload.
Um, check your facts. Bin Laden has NEVER been keen on claiming responsibility for his actions. He's found that it works better for PR not to.
Yes, it's true that he didn't coin the name that we use for his group. But that doesn't make the organization less real, does it?
And given that Al Quaeda was key in the installation fo the Taliban regime (and bin Laden a shaper of their policies), I have a hard time swallowing your claims. For that matter, we have the USS Cole and bomed embassies in Africa to suggest that he wasn't a nobody, even before 9/11. Clinton wanted to go after him at the end of his presidency, which I find sort of amazing if bin Laden was nobody.
Can you back your claims up with facts?
(Incidentally, I'm basing my facts on "Inside Al Qaeda", by Rohan Gunaratna. Maybe he's lying to me, but he sure went through a lot of trouble to make up quotes, dates, places, and names. Right now, he has my confidence more than you do, either way.)
How can Al Qaeada be a list of allies against the Soviets when it wasn't formed until after the Soviets left Afganistan?
The group was originally comprised of a lot of the people who fought beside bin Laden against the Soviets, but the makeup of the organization is hardly exclusive to that crowd. A few minutes of research would reveal that to you.
Al Quaeda is real. It's a rarity amoung terrorist organizations in terms of its international striking power and the threat may be over-blown in many respects, but it's a real group with a real agenda and it's a real threat.
I'm one of the first people to step up and say that the "war on terror" (sorry, what is it today? struggle against violenet extremism?) is mainly an excuse for certain politicians to do what they wanted to do anyway (and not do much to make Americans safer). But denying the existance of a real organization that does pose a real theat does no good to anyone, except perhaps aforementioned politicians who can now dismiss critics as wackos and uninformed yokels.
Having have read some of Zubrin's stuff, I agree, he's an optimist. Not wrong, but he definitely takes the sunnier side of the statistics. Qualifications or not, when you want a result really badly you are almost assured of not making an objective analysis. Zubrin really wants people to go to Mars, so whether he's consciously aware of it or not, he tends to assume the best for his ideas.
And before you take his qualifications as the end-all of the discussion, bear in mind that there are quite of equally-qualified people who are far, far more pessimistic. (Why do you think NASA is worried.) Heck, I've heard from people with *better* qualifications (a PhD in nuclear engineering isn't the best qualification to judge the biological effects of radiation, sorry to say) who think that the radiation sheilding is a show-stopper at the moment.