Because Latin sounds more impressive than everyday English. It's the same reason that the Romans of Caesar's day spoke Greek when they wanted to sound especially impressive. (Hence the line in Shakespeare's "Julius Caesar", "But for mine own part, it was Greek to me," in reference to Cicero's speech earlier.)
Better question: why do you ask and why do you single out NASA? The US motto ("e pluribus unum") is in Latin, as are countless other mottos, slogans, and inscriptions around this country. And if you look, the Latin is translated into English on this NASA patch.
In any event, it wasn't exactly a vital safety message, it's just a slogan. If you haven't studied Latin, you're not really missing something important.
The idea that the atmosphere/ionosphere can be used to set up counter-currents to exclude the solar wind from the planet (or at least shield it a lot) isn't really revolutionary. It's possible that the Earth-magnetospheres people aren't talking to the planetary folks enough, but the latter have been thinking about this for years. When you wonder how the solar wind behaves when it encounters, say, Venus, you're in this regime. It's also the basic category that includes those ever-sexy critters, comets.
I don't know that anyone has done a similar calculation for the Earth and if so if this new model is significantly different. But the basic idea has been out there. We covered it in my magnetospheres class 4 years ago and it was in the textbook well before that.
I'm going to assume you mean deflected towards the Earth, although not necessarily hitting us.
I don't think that gravity is a significant player, here. The solar wind hits Earth at around 150 km/second. That's quite a bit in excess of Earth's escape speed, 11 km/sec. As a rule, something travelling a lot faster than the local escape speed isn't affected by gravity much.
As a side note, while I was never much good in the field, I can't recall anyone taking gravity into account much in magnetospheres work. (Based on having been in the field for a couple of years.)
It doesn't seem to have been insulation as foam inside a TV camera. While that is indeed sheltered somewhat, it'd be useful to know how dense and thick the foam was. A small peice of light foam isn't going to block a lot of radiation. I've certainly never heard anyone argue that it would do so, although some do claim that the bacteria contaiminated the sample after it arrived back on Earth.
Either way, while I don't think it proves that the little buggers can survive in space, it's reason to consider the possibility.
Well, how possible this is depends on, among other things, your interpretion of ALH84001.
And we know that organisms can survive in open space: the found some still-viable critters on one of the Ranger spacecraft when an Apollo mission brought some bits back from the Moon.
They make perfect sense when they apply to different *conclusions* drawn from the evidence. That some meteorites found on Earth originated on Mars now seems pretty much certain (as certain as things can really get in science, anyway). That cross-seeding of organisms occurred is nowhere near as definate.
I didn't say shielding doesn't occur. Of course it does. Materials can definately alter the paths of field lines that would otherwise pass through them. (Superconductors, for example, actually expel fields, up to a point.)
I said that the presence of iron doesn't magically reach out and grab field lines, dragging them through the metal, when they were originally running high above the Earth's surface. That's what this article was implying iron in Earth's crust was doing. Unless you know of a way of doing that.
Well, we frequently have to replace out Timmys in out labs, but we let the kids have blowtorches.
In this case, the thermal gradient is the cause of the charge seperation, just like is believed to happen in the Earth. There might be loads of cats and amber rods, but that's not well-supported in the seismology data.
"Yeah? Which part of the Moon did you have in mind? Poles? Maria? Farside?"
Um, the whole thing... the cratering rate appears to have been fairly constant over the past 3-4 billion or so years. Thanks to the fact that the Moon has areas of different ages, we can figure out the cratering rate. (You date those surfaces with those nifty rocks that the Apollo astronauts brought back.)
Thanks for asking, though. I suggest reading "THe New Solar System" next time *before* you assume that we're making stuff up.
"Did you? Why? Serious question. I'm interested in seen how straight an answer you'll give."
Because when crackpots like yourself are the only ones talking, people start to believe you. Sad, but true.
Serious question: why does my replying bother you?
Actually, if you pay closer attention, the third paper only says that they COULD be seeing a rapid shift. Not that they are. The authors themselves are pretty hesitant to claim what you're jumping on so readily.
And, as you note, most geophysicists don't think that those rocks are suggesting what you're accepting as fact. The problem with real science is that the data aren't always as clear cut as in the labs you do in classes.
Interestingly, this is the first time you've posted anything with substance. You're right, there is evidence there for a rapid reverse. Not *good* evidence, but evidence.
In any event, you're either jerking my chain or you're a raving lunatic. Either way, there's little point in continuing this.
"OK... so if Mercury spins 3x faster, it should have roughly 3x, or 3^2x the field depending on how your dynamo works?"
Well, it isn't linear, for one thing. Why do you assume that it is? Do you know anything about dynamo theory? (The non-linearity is what makes it such a thorny field in the first place, after all.)
"One of the few forces which explain nearly all of the features of Valles Marineris is lightning"
I'm not sure that this even deserves a reply. This is just too bizarre. Valles Marineris is way to big to be carved by lightening.
On the other hand, while you causually dismiss erosion and tectonics, you probably should step up to the plate and explain the Grand Canyon on Earth (erosion-caused) and the Himilays (tectonics). And while you're at it, you can use your lightening "theory" to explain the Tharsis Bulge on Mars.
"How you'd set about reconciling a dynamo theory with the lesser gas giants is beyond me."
What's to explain? The usual suspecion is that they have oceans in their mantle with ions dissolved in them. This would do the trick nicely, just like it does on the icy satellites of Jupiter.
Why you're worried about the tilts, I'm not sure. No on said that magnetic fields have to be perfectly aligned with the spin axes. Your failure to recognize that is just that: your failure.
In other words, you have nothing that you can put forth to show what you're talking about. You're resorting to accusing scientists of censoring your results, when in fact we'd be all *over* something revolutationary and new. History is full of examples of this: GR was generally quickly accepted. So was quantum mechanics (the best and brightest young physicists flocked to it in the early part of the 20th century). The Giant Impact model of the Moon's formation took hold quite quickly, too. Sure, we don't just drop an old position. But scientists will listen to new data and theories and if there's anything there at all, usually you'll find a number of them quickly jumping into the new field. (That's how you make a name for youself, after all.)
Basically, your post has all the hallmarks of a crackpot's rantings, I'm sorry to say.
"None the less, I tend to like simpler solutions than a chaotic tri-poled earth magnetic field, or whatever currently is the explanation."
Yes, but surely you like an explanation that is *accurate* even more than you like one that is simple. I mean, I can think of simpler explanations for the striping quite easily. (Like, "There is no striping. These are not the droids you're looking for...") But they probably wouldn't reconcile with the various data very well.:-)
(Also, magnetic fields fall off as least like 1/r^3. The lowest order moment is a dipole, remember. At least until someone finds a magnetic monople, anyway.)
To get at the article you linked:
First of all, it suggests that the planets' fields are all oriented the same way with respect to their spins. Not true. See my post, above. Jupiter's field is oppositely oriented to that of Earth, for example.
It goes on to "point out" that Uranus's field is aligned with it's odd spin vector. Surprisingly little research with Google would have shown that to be very wrong. Uranus's spin and magnetic field axes are about 60 degrees apart. That's no where near alignment.
He (I'll assume that the author is male) procedes to blame large amounts of cobalt and iron in Earth's crust for the slightly off spin axis magnetic field axis. Large amounts? The overwelming majority of Earth's iron is in the core or mantle, not the crust. What is in the crust is fairly evenly distributed. It's hard to imagine that the symmetry is broken that much, isn't it? (Sorry I don't have the raw numbers for the distributation, but I doubt that anyone has worked it out.) But if the iron in the core wants to direct the field along the spin axis, how is the miniscule amount of iron in the crust going to "redirect" that field significantly over global scales? (Sure, you've got a bigger lever-arm at the crust than the core. But only by a factor of a few. We're being told that that offsets the massively higher concentration of iron in the core.) Also, why is Earth's field offset as well as titled? (No lever-arm helps you with that one.)
Another interesting error is the (apparent) assertion in the tidal breaking section that Earth will eventually spin 1/28 as fast to match the Moon's orbital period. That's half true, we will match the Moon's orbital period in about 5 billion years. (Just in time to be destroyed by the Sun's red giant phase. Yay!) But a simple knowledge of conservation of angular momentum tells you that we won't be spinning once every 28 days. It's more like a 89 day period, if you work it out. (Funny how he can use conservation of energy to apparently bolster his case when he wants to, but doesn't know what conservation of angular momentum is. While both are adhered to, with the latter it is much harder to "fake" a violation.)
Next up... mass extinctions. He claims that palentologists have determined that they (the extinctions, not the palentologists) occur every 32 million years. Hm. About five mass extinctions in the history of the Earth (the last 65 million years ago) are known (http://www.bagheera.com/inthewild/spot_massextinc tions.htm) spanning back 440 million years or so. That's 380 million years and 4 intervals between them. Quick math check... I get that that's one every 95 million years. (Is that what you get, too?) For proving that exctinction events aren't caused by impacts, that's pretty weak. (Based on the cratering record on the Moon, mainly, the calculated interval between mass exinction causing impacts is about 100 million years. Roughly speaking.)
Next bit of funniness. He claims that "Therefore a reversal in ion polarity would indeed reverse the Earth's magnetic field;" and then goes on to try to show that this is silly. Which is a strawman, since I don't know anyone who asserts that the ions will reverse polarity. How do you get ions to reverse polarity?? Unlike in chemistry, ions in astronomical contexts are essentially
Appart from the general off-topic nature of that rambling post, it shows a poor understanding of the data, unless someone has utterly failed to clue me in on some breaking developments in astronomy. (Possible, but my collegues like talking about their work too much for me to think that that's likely.)
You'd better show me a paper that suggest that gravitational redshift doesn't happen, because I have yet to hear of it. And since that'd be Nobel-quality work, showing that GR breaks down (where it should hold up), I'd be surprised if the research happened. In fact, I attended an entire comps on GPS. While GR was certainly discussed, since they need to take it into account for GPS to work, no corrections to that theory were mentioned. Seems sort of odd that the speaker would talk about GR without mentioning that it broke down.
And I have yet to see a steady-state model that matches the data very well at all. The whole "cosmic microwave background" thing is hard to get around. Since I just attended a lecture by a well-known cosmologist and he didn't say a word about the Big Bang being "broken", I will have to once again ask you to back up your rather grandiose assertions.
As for planetary magentic fields:
There are lots of ways that Mercury can have a fluid core, still. The most commonly argued one is to have more sulfur mixed in. This should lower the freezing point sufficiently to keep it molten still. It's also worth noting that Mercury has an unusually large core for its size. This might play in to things.
Mars lacks a global field (today) because it has almost certainly cooled off too far. (If we assume the same composition as the Earth, anyway.) This is supported by the lack of ongoing volcanism or tectonics, which also require a molten interior to proceed. However, in the past Mars *did* have a global field. This is quite consistent with the theory, since it would have been warmer inside.
As far as I know, no one has ever suggested that Venus's retrograde spin is the cause of the lack of a magnetic field. That's fairly silly, since the field doesn't know which "way" the planet is spinning anyway. (Magnetic field on other planets are can be found oriented both ways with respect to their planets' spins and we know that Earth's field has changed direction.) However, the astute person would have noticed that Venus does spin very, very slowly. This would generally lead to a small or non-existant field, since planet spin is thought to be tied in to the dynamo process. (There's a strong correlation between field strength and planet's angular momentum, for example.) Of course, Mercury only spins 3 times faster, but that's still something.
I'd also love to see your proported research showing field changes if 90 minutes or less. How in the heck do you DATE to that accuracy? You can't, unless you pretty much just watched it cool. (In which case, why didn't every compass on Earth notice the switch?)
No one is saying that we totally understand cosmology or magnetic dynamoes. But to suggest that we're "whistling in the dark" is to down-play the wonderful and careful work of far too many people to let you get away with saying that here. We might not have the details all down, but I'd say that we're doing alright on the theories.
Re:A thick atmosphere in low gravity?
on
Titanic Saturn
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· Score: 1
Heh. Given that Niven is accurate most of the time (as far as the then-current state of understanding was at the time of writing), it's not hard to be tricked by him:-)
Re:A thick atmosphere in low gravity?
on
Titanic Saturn
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· Score: 4, Informative
I don't know who told you that, but that's totally wrong. There's no way a significant fraction of the atmosphere would ever be re-accreted by the planet from a torus, first of all. (Io has a very distinct torus and its atmosphere is all by non-existant.)
Second of all, we have yet to observe any Titan-torus, last I heard. (About two weeks ago, a comment made from one of the Cassini principle investigators.) If there's so much gas there, why can't we see it?
Finally, the reason Titan can hold a thick atmosphere is, as some already stated, because it's so bloody cold. You can do the simple atmospheric calculations and show that at the tempertures of Titan, it can hold that atmosphere pretty nicely.
A good place to look for details is _The New Solar System_, Beatty, Petersen, and Chaikin, editors.
That doesn't illustrate how quickly things are changing, the postponing only occured a few days ago. It just represents unfortuante timing for the release of the article.
However, there is at least one glaring (to me) error: Cassini. Cassini doesn't arrive until July, so postpone your orbital insertion parties from June (which is what the article claims). And don't hold your breath on Huygens's launch into Titan: that doesn't occur until, I believe, the fourth orbit. (This is a change of plan from the original orbital plan. When they discovered the failure to account for the Doppler shift in the probe transmitter, they adjusted the first several orbits to make everything work out. However, the change of plan occured about two years ago, so it's a bit odd that the author of the article didn't find this out.)
Actually, probably the team that proposed the mission in the first place. That's usually where they come from these days. Mercury is a Discovery-class mission, which means that it was proposed out of house, rather than created and designed within NASA. I don't recongize the ECHO acronymn, but NOAA isn't part of NASA at all (it comes in under the Dept. of Commerce, I believe) and SOHO is jointly run with the European space agency, not a pure NASA endevor.
Coming up with forced acronymns and impressively useless code-names for things isn't only a NASA activity, of course.
The links already posted answer the question, but the short, simple answer is "angular momentum". Specifically, the need to dump a lot of it (and, equivelently, a lot of energy). The energy changed needed to get to Mercury is actually greater than that needed to reach Pluto. This means that it's better to use the inner planets (Earth, Venus, and/or Mercury) in gravitational slingshots (but backwards of how we usually use them) to save fuel. In theory, if you jacked up NASA's budget, you could go straight there once a synodic (not sideral: it doesn't matter how often Mercury orbits, but how long it takes to get back to the same relative arrange with Earth) period. But NASA, alas, has a finite budget for this sort of thing, so slow and cheap is the way to go.
What's wrong with the standard "galactic tides" model for populating the Oort cloud? Jupiter flings the stuff into highly eccentric orbits. With such long period orbits and large aphelia, the comets are much more readily affected by stellar perturbations and, even more, the over-all galactic potential. This raises their perihelia and also tends to more or less randomize their inclinations. (This may not be as true of the Inner Oort Cloud, of which Sedna is a candidate for membership. The models I've seen show a flared and rather fat disk rather than a nearly random spherical cloud.)
Of course, I completely agree that this is what makes Sedna most interesting: we may have finally spotted an Oort Cloud Comet in situ. Until now, we've always been stuck with active comets, whose orbits are generally perturbed by the inner planets before we see them (we can try to model that out) and -- worse -- have generally started to heat up and sublimate their outer layers. Sedn
I'm not sure that we're really improved. Less than 4 years ago, the kinda-sorta-alignment on 5 May 2000 generated a lot of doomsday nonsense. This one may have just slipped in under the radar, so to speak. (Maybe all of the doomsday folks are still chagrined that we're all still alive depsite their predictions that we'd die when the 12th planet swung by last May?)
Slashdot Mirror
Because Latin sounds more impressive than everyday English. It's the same reason that the Romans of Caesar's day spoke Greek when they wanted to sound especially impressive. (Hence the line in Shakespeare's "Julius Caesar", "But for mine own part, it was Greek to me," in reference to Cicero's speech earlier.)
Better question: why do you ask and why do you single out NASA? The US motto ("e pluribus unum") is in Latin, as are countless other mottos, slogans, and inscriptions around this country. And if you look, the Latin is translated into English on this NASA patch.
In any event, it wasn't exactly a vital safety message, it's just a slogan. If you haven't studied Latin, you're not really missing something important.
The idea that the atmosphere/ionosphere can be used to set up counter-currents to exclude the solar wind from the planet (or at least shield it a lot) isn't really revolutionary. It's possible that the Earth-magnetospheres people aren't talking to the planetary folks enough, but the latter have been thinking about this for years. When you wonder how the solar wind behaves when it encounters, say, Venus, you're in this regime. It's also the basic category that includes those ever-sexy critters, comets.
I don't know that anyone has done a similar calculation for the Earth and if so if this new model is significantly different. But the basic idea has been out there. We covered it in my magnetospheres class 4 years ago and it was in the textbook well before that.
I'm going to assume you mean deflected towards the Earth, although not necessarily hitting us.
I don't think that gravity is a significant player, here. The solar wind hits Earth at around 150 km/second. That's quite a bit in excess of Earth's escape speed, 11 km/sec. As a rule, something travelling a lot faster than the local escape speed isn't affected by gravity much.
As a side note, while I was never much good in the field, I can't recall anyone taking gravity into account much in magnetospheres work. (Based on having been in the field for a couple of years.)
It doesn't seem to have been insulation as foam inside a TV camera. While that is indeed sheltered somewhat, it'd be useful to know how dense and thick the foam was. A small peice of light foam isn't going to block a lot of radiation. I've certainly never heard anyone argue that it would do so, although some do claim that the bacteria contaiminated the sample after it arrived back on Earth.
Either way, while I don't think it proves that the little buggers can survive in space, it's reason to consider the possibility.
Well, how possible this is depends on, among other things, your interpretion of ALH84001.
And we know that organisms can survive in open space: the found some still-viable critters on one of the Ranger spacecraft when an Apollo mission brought some bits back from the Moon.
They make perfect sense when they apply to different *conclusions* drawn from the evidence. That some meteorites found on Earth originated on Mars now seems pretty much certain (as certain as things can really get in science, anyway). That cross-seeding of organisms occurred is nowhere near as definate.
As far as I can recall, we only have meteorites from the Moon and Mars. Worse, a Venus sample return mission seems unlikely for the near future...
I didn't say shielding doesn't occur. Of course it does. Materials can definately alter the paths of field lines that would otherwise pass through them. (Superconductors, for example, actually expel fields, up to a point.)
I said that the presence of iron doesn't magically reach out and grab field lines, dragging them through the metal, when they were originally running high above the Earth's surface. That's what this article was implying iron in Earth's crust was doing. Unless you know of a way of doing that.
Well, we frequently have to replace out Timmys in out labs, but we let the kids have blowtorches.
In this case, the thermal gradient is the cause of the charge seperation, just like is believed to happen in the Earth. There might be loads of cats and amber rods, but that's not well-supported in the seismology data.
"Yeah? Which part of the Moon did you have in mind? Poles? Maria? Farside?"
Um, the whole thing... the cratering rate appears to have been fairly constant over the past 3-4 billion or so years. Thanks to the fact that the Moon has areas of different ages, we can figure out the cratering rate. (You date those surfaces with those nifty rocks that the Apollo astronauts brought back.)
Thanks for asking, though. I suggest reading "THe New Solar System" next time *before* you assume that we're making stuff up.
"Did you? Why? Serious question. I'm interested in seen how straight an answer you'll give."
Because when crackpots like yourself are the only ones talking, people start to believe you. Sad, but true.
Serious question: why does my replying bother you?
Actually, if you pay closer attention, the third paper only says that they COULD be seeing a rapid shift. Not that they are. The authors themselves are pretty hesitant to claim what you're jumping on so readily.
And, as you note, most geophysicists don't think that those rocks are suggesting what you're accepting as fact. The problem with real science is that the data aren't always as clear cut as in the labs you do in classes.
Interestingly, this is the first time you've posted anything with substance. You're right, there is evidence there for a rapid reverse. Not *good* evidence, but evidence.
In any event, you're either jerking my chain or you're a raving lunatic. Either way, there's little point in continuing this.
"OK... so if Mercury spins 3x faster, it should have roughly 3x, or 3^2x the field depending on how your dynamo works?"
Well, it isn't linear, for one thing. Why do you assume that it is? Do you know anything about dynamo theory? (The non-linearity is what makes it such a thorny field in the first place, after all.)
"One of the few forces which explain nearly all of the features of Valles Marineris is lightning"
I'm not sure that this even deserves a reply. This is just too bizarre. Valles Marineris is way to big to be carved by lightening.
On the other hand, while you causually dismiss erosion and tectonics, you probably should step up to the plate and explain the Grand Canyon on Earth (erosion-caused) and the Himilays (tectonics). And while you're at it, you can use your lightening "theory" to explain the Tharsis Bulge on Mars.
"How you'd set about reconciling a dynamo theory with the lesser gas giants is beyond me."
What's to explain? The usual suspecion is that they have oceans in their mantle with ions dissolved in them. This would do the trick nicely, just like it does on the icy satellites of Jupiter.
Why you're worried about the tilts, I'm not sure. No on said that magnetic fields have to be perfectly aligned with the spin axes. Your failure to recognize that is just that: your failure.
In other words, you have nothing that you can put forth to show what you're talking about. You're resorting to accusing scientists of censoring your results, when in fact we'd be all *over* something revolutationary and new. History is full of examples of this: GR was generally quickly accepted. So was quantum mechanics (the best and brightest young physicists flocked to it in the early part of the 20th century). The Giant Impact model of the Moon's formation took hold quite quickly, too. Sure, we don't just drop an old position. But scientists will listen to new data and theories and if there's anything there at all, usually you'll find a number of them quickly jumping into the new field. (That's how you make a name for youself, after all.)
Basically, your post has all the hallmarks of a crackpot's rantings, I'm sorry to say.
Same place sperm have been racing to for millions of years: an ovum.
"None the less, I tend to like simpler solutions than a chaotic tri-poled earth magnetic field, or whatever currently is the explanation."
:-)
Yes, but surely you like an explanation that is *accurate* even more than you like one that is simple. I mean, I can think of simpler explanations for the striping quite easily. (Like, "There is no striping. These are not the droids you're looking for...") But they probably wouldn't reconcile with the various data very well.
(Also, magnetic fields fall off as least like 1/r^3. The lowest order moment is a dipole, remember. At least until someone finds a magnetic monople, anyway.)
To get at the article you linked:
First of all, it suggests that the planets' fields are all oriented the same way with respect to their spins. Not true. See my post, above. Jupiter's field is oppositely oriented to that of Earth, for example.
It goes on to "point out" that Uranus's field is aligned with it's odd spin vector. Surprisingly little research with Google would have shown that to be very wrong. Uranus's spin and magnetic field axes are about 60 degrees apart. That's no where near alignment.
He (I'll assume that the author is male) procedes to blame large amounts of cobalt and iron in Earth's crust for the slightly off spin axis magnetic field axis. Large amounts? The overwelming majority of Earth's iron is in the core or mantle, not the crust. What is in the crust is fairly evenly distributed. It's hard to imagine that the symmetry is broken that much, isn't it? (Sorry I don't have the raw numbers for the distributation, but I doubt that anyone has worked it out.) But if the iron in the core wants to direct the field along the spin axis, how is the miniscule amount of iron in the crust going to "redirect" that field significantly over global scales? (Sure, you've got a bigger lever-arm at the crust than the core. But only by a factor of a few. We're being told that that offsets the massively higher concentration of iron in the core.) Also, why is Earth's field offset as well as titled? (No lever-arm helps you with that one.)
Another interesting error is the (apparent) assertion in the tidal breaking section that Earth will eventually spin 1/28 as fast to match the Moon's orbital period. That's half true, we will match the Moon's orbital period in about 5 billion years. (Just in time to be destroyed by the Sun's red giant phase. Yay!) But a simple knowledge of conservation of angular momentum tells you that we won't be spinning once every 28 days. It's more like a 89 day period, if you work it out. (Funny how he can use conservation of energy to apparently bolster his case when he wants to, but doesn't know what conservation of angular momentum is. While both are adhered to, with the latter it is much harder to "fake" a violation.)
Next up... mass extinctions. He claims that palentologists have determined that they (the extinctions, not the palentologists) occur every 32 million years. Hm. About five mass extinctions in the history of the Earth (the last 65 million years ago) are known (http://www.bagheera.com/inthewild/spot_massextinc tions.htm) spanning back 440 million years or so. That's 380 million years and 4 intervals between them. Quick math check... I get that that's one every 95 million years. (Is that what you get, too?) For proving that exctinction events aren't caused by impacts, that's pretty weak. (Based on the cratering record on the Moon, mainly, the calculated interval between mass exinction causing impacts is about 100 million years. Roughly speaking.)
Next bit of funniness. He claims that "Therefore a reversal in ion polarity would indeed reverse the Earth's magnetic field;" and then goes on to try to show that this is silly. Which is a strawman, since I don't know anyone who asserts that the ions will reverse polarity. How do you get ions to reverse polarity?? Unlike in chemistry, ions in astronomical contexts are essentially
Appart from the general off-topic nature of that rambling post, it shows a poor understanding of the data, unless someone has utterly failed to clue me in on some breaking developments in astronomy. (Possible, but my collegues like talking about their work too much for me to think that that's likely.)
You'd better show me a paper that suggest that gravitational redshift doesn't happen, because I have yet to hear of it. And since that'd be Nobel-quality work, showing that GR breaks down (where it should hold up), I'd be surprised if the research happened. In fact, I attended an entire comps on GPS. While GR was certainly discussed, since they need to take it into account for GPS to work, no corrections to that theory were mentioned. Seems sort of odd that the speaker would talk about GR without mentioning that it broke down.
And I have yet to see a steady-state model that matches the data very well at all. The whole "cosmic microwave background" thing is hard to get around. Since I just attended a lecture by a well-known cosmologist and he didn't say a word about the Big Bang being "broken", I will have to once again ask you to back up your rather grandiose assertions.
As for planetary magentic fields:
There are lots of ways that Mercury can have a fluid core, still. The most commonly argued one is to have more sulfur mixed in. This should lower the freezing point sufficiently to keep it molten still. It's also worth noting that Mercury has an unusually large core for its size. This might play in to things.
Mars lacks a global field (today) because it has almost certainly cooled off too far. (If we assume the same composition as the Earth, anyway.) This is supported by the lack of ongoing volcanism or tectonics, which also require a molten interior to proceed. However, in the past Mars *did* have a global field. This is quite consistent with the theory, since it would have been warmer inside.
As far as I know, no one has ever suggested that Venus's retrograde spin is the cause of the lack of a magnetic field. That's fairly silly, since the field doesn't know which "way" the planet is spinning anyway. (Magnetic field on other planets are can be found oriented both ways with respect to their planets' spins and we know that Earth's field has changed direction.) However, the astute person would have noticed that Venus does spin very, very slowly. This would generally lead to a small or non-existant field, since planet spin is thought to be tied in to the dynamo process. (There's a strong correlation between field strength and planet's angular momentum, for example.) Of course, Mercury only spins 3 times faster, but that's still something.
I'd also love to see your proported research showing field changes if 90 minutes or less. How in the heck do you DATE to that accuracy? You can't, unless you pretty much just watched it cool. (In which case, why didn't every compass on Earth notice the switch?)
No one is saying that we totally understand cosmology or magnetic dynamoes. But to suggest that we're "whistling in the dark" is to down-play the wonderful and careful work of far too many people to let you get away with saying that here. We might not have the details all down, but I'd say that we're doing alright on the theories.
Heh. Given that Niven is accurate most of the time (as far as the then-current state of understanding was at the time of writing), it's not hard to be tricked by him :-)
I don't know who told you that, but that's totally wrong. There's no way a significant fraction of the atmosphere would ever be re-accreted by the planet from a torus, first of all. (Io has a very distinct torus and its atmosphere is all by non-existant.)
Second of all, we have yet to observe any Titan-torus, last I heard. (About two weeks ago, a comment made from one of the Cassini principle investigators.) If there's so much gas there, why can't we see it?
Finally, the reason Titan can hold a thick atmosphere is, as some already stated, because it's so bloody cold. You can do the simple atmospheric calculations and show that at the tempertures of Titan, it can hold that atmosphere pretty nicely.
A good place to look for details is _The New Solar System_, Beatty, Petersen, and Chaikin, editors.
Well, 1.5 bars, so only 50% more atmospheric pressure than Earth.
And I wouldn't want to hold my breath to December, even of this year. I can barely make it one length of the pool underwater...
That doesn't illustrate how quickly things are changing, the postponing only occured a few days ago. It just represents unfortuante timing for the release of the article.
However, there is at least one glaring (to me) error: Cassini. Cassini doesn't arrive until July, so postpone your orbital insertion parties from June (which is what the article claims). And don't hold your breath on Huygens's launch into Titan: that doesn't occur until, I believe, the fourth orbit. (This is a change of plan from the original orbital plan. When they discovered the failure to account for the Doppler shift in the probe transmitter, they adjusted the first several orbits to make everything work out. However, the change of plan occured about two years ago, so it's a bit odd that the author of the article didn't find this out.)
Yeah, but given that it isn't even supposed to arrive until something like 2020, it's not suprising that it wasn't mentioned.
Actually, probably the team that proposed the mission in the first place. That's usually where they come from these days. Mercury is a Discovery-class mission, which means that it was proposed out of house, rather than created and designed within NASA.
I don't recongize the ECHO acronymn, but NOAA isn't part of NASA at all (it comes in under the Dept. of Commerce, I believe) and SOHO is jointly run with the European space agency, not a pure NASA endevor.
Coming up with forced acronymns and impressively useless code-names for things isn't only a NASA activity, of course.
The links already posted answer the question, but the short, simple answer is "angular momentum". Specifically, the need to dump a lot of it (and, equivelently, a lot of energy). The energy changed needed to get to Mercury is actually greater than that needed to reach Pluto. This means that it's better to use the inner planets (Earth, Venus, and/or Mercury) in gravitational slingshots (but backwards of how we usually use them) to save fuel. In theory, if you jacked up NASA's budget, you could go straight there once a synodic (not sideral: it doesn't matter how often Mercury orbits, but how long it takes to get back to the same relative arrange with Earth) period. But NASA, alas, has a finite budget for this sort of thing, so slow and cheap is the way to go.
What's wrong with the standard "galactic tides" model for populating the Oort cloud? Jupiter flings the stuff into highly eccentric orbits. With such long period orbits and large aphelia, the comets are much more readily affected by stellar perturbations and, even more, the over-all galactic potential. This raises their perihelia and also tends to more or less randomize their inclinations. (This may not be as true of the Inner Oort Cloud, of which Sedna is a candidate for membership. The models I've seen show a flared and rather fat disk rather than a nearly random spherical cloud.)
Of course, I completely agree that this is what makes Sedna most interesting: we may have finally spotted an Oort Cloud Comet in situ. Until now, we've always been stuck with active comets, whose orbits are generally perturbed by the inner planets before we see them (we can try to model that out) and -- worse -- have generally started to heat up and sublimate their outer layers. Sedn
I'm not sure that we're really improved. Less than 4 years ago, the kinda-sorta-alignment on 5 May 2000 generated a lot of doomsday nonsense. This one may have just slipped in under the radar, so to speak. (Maybe all of the doomsday folks are still chagrined that we're all still alive depsite their predictions that we'd die when the 12th planet swung by last May?)