The thing is, the detention report doesn't indicate any form of mouthing off beyond arguing back. If the student were being rude, belligerent, or otherwise unruly, I'd expect to see that documented in the teacher's report -- if only as a cover-your-ass move. If responding to an order you find unreasonable or unfair with a counter-argument is mouthing-off, we've got some serious problems that need addressing here.
Why is it obvious? Your example, the Moon, is dead wrong. Our Moon is moving away from the Earth, not towards it. (Granted, in about 5 billion years, after the Earth is likely to be gone anyway, it will reverse direction because of the effects of solar tides on the Earth. But the the collision, if the Earth survives that long, is therefore ~15 billion years off, three times the age of the solar system.) The ring material isn't even subject to those forces since they aren't large enough individually to raise bulges and are collectively evenly distributed longitudinally, so no such leading or trailing bulge will appear. (Even if they did, around half -- or more -- of the ring material would be outside of co-rotation and evolve outwards, not inwards.)
Are you unfamiliar with the fact that Cassini is measuring the dust in the Saturnian system? Check the instrument listing, look for "CDA" (Cassini Dust Analyzer). Not that this is the first time that this has been done.
Why would the orbits decay? Are you worried that the Moon will be hitting us soon?
Re:Shouldn't this have been the default assumption
on
Saturn's Rings Are Ancient
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· Score: 2, Informative
There are many things in the solar system that are younger than 4.55 Gyr; a lot of asteroids, for example, are the results of more recent breakups. You have impact craters and other geologic features on practically all bodies. Honestly, assuming that anything you look at is primordial is a pretty daft assumption unless you can make *some* argument as to why it should be.
As for Saturn's rings, a modicum of research would tell you that there are both dynamical reasons to think that rings are younger (models say that they should grind down to dust relatively fast) as well as observational evidence: the amount of meteoric dust that they've accumulated is smaller than should be there if they were as old as the planet itself. In fact, had you read the article, you would have learned that.
Mostly, they've found transient clumps of material in the rings which suggests that some of the ring particles might break up and re-clump periodically. This means that ages derived from looking at meteoritic contamination are off since the volume that the meteoroid dust must be spread in is larger than thought.
Honestly, it's data that doesn't refute and weakly supports the older age, I think. Interesting, but then he's been saying this for years.
I agree. And it isn't news, either: Larry Esposito has been saying this (and sending out press-releases) for years to this effect. He's just found another small bit of evidence that supports -- or at least doesn't refute -- his idea.
Sure, there are a lot of analytic models out there even today. Also, you can construct a physical model to study many phenomena (e.g., river formation in a lab).
Not that I relish being negative, but I don't recommend getting too excited. I've seen way, way too many of these kinds press-releases -- especially about Mars and especially-especially about evidence of life there -- to get excited yet. Even if they find any evidence of life, it will almost certainly quickly be disputed by other groups and then counter-disputed by the original group and the whole thing will turn into a non-score tie. It also seems like the Martian astrobiology folks have a rather lower threshold for "exciting evidence" of life than many of the rest of us. (Maybe that's a selection effect and maybe that's just common to all scientists, each in his or her own field.)
On the other hand, the responsiblity for the murder is solely on th eman who committed the murder. That's neither true legally nor, in my view, morally. While I agree that the existence of the list in no way absolves the murderer of his responsibly for his actions, the man's responsibility does not preclude the possibility that there are others who are also morally (and perhaps legally) also at least partially responsible. Guilt is flexible, it can stretch to cover many parties if the situation warrants it.
(This is not to say that I've made up my mind about this specific case.)
Ah, I see the source of the confusion. My first sentence was not meant to suggest a definitive knowledge, I figured the fact that it was a theory was to be understood and wasn't the point in any case.
I did no such thing, please re-read my message more carefully. I was simply pointing out the differences in the theories; there are major reasons why this new work is different from the models of lunar formation which is what necessitated this research in the first place.
See above, but basically, no. Iapetus's ridge is a lot small, relatively speaking, and probably tectonic in nature. These bulges seriously alter the shapes of the ring-moons and are do to emplacement of material as it hits the moon.
Speaking as a ring scientist, I don't actually know of any other real contending theories for the origin of the rings. This isn't to say that we have the story all figured out, but as far as I've ever heard, people seem pretty comfortable with the break-up model. (For one thing, it's stochastic and therefore would reasonably explain why only Saturn has a really massive ring system.)
No, the Moon formed in a notably different way: no dense seed was required to form it. In the rings, tidal forces keep things from building into moons. Our Moon almost certainly formed outside of Earth's Roche limit where it was able to coalesce without significant hindrance.
In short, no, we don't think that this mechanism explains Iapetus. Best guess there is that you have some tectonic effect due to its thermal history. There are some recent papers out there on the topic, although I'm very familiar with the details.
They're not packed very tightly, in as much as the densities are around half that of liquid water.
They're not compressed. They are probably sintered together thanks to repeated exposures to sunlight and then dipping into the planet's shadow, although the details of that we did not work out.
Probably. The problem is that the rings can't accrete into moons because of tidal forces. (They do form temporary aggregates, but those tear apart again in roughly one orbital period.) So the presence of moons in this region is a bit of a mystery. One possibility was that they were large shards of whatever body broke up and formed the rings. What we found in our research is that there are indeed seed-cores in the middles of the moons, but that the moons then accreted a lot more material into a mantle, lowering their densities to almost absurdly small values and reshaping them. The moons you have now are a hybrid of progenitor material and ring particles.
Since the data came from Cassini ISS and since we're the authors on the paper, I feel no qualms about suggesting visiting http://ciclops.org/view_event.php?id=73
In as much as it was previously thought that the moons *couldn't* grow in the ring-region (what with tides), I'm a little curious as to how come you think their grown is obvious.
"single rocket scientist, physicist, engineer, and even computer programmer"
Uh, speaking as an astrophysicists, I find this rather hyperbolic. Most of us born in the post-Apollo years are impressed, but not exactly over-awed by what happened a decade or more before we were born and has had little chance of happening again in our lifetimes. Honestly, I've never really found any part of the manned program to have motivated my career choice and I know few in my generation who have stated the reverse. A lot of us *have* been drawn in by robotic missions, though.
While I agree with the overall point (excitement in the field entices students and future scientists/engineers), you're getting carried away assigning more credit to the manned space program than I think it's due. It's one part of the overall, but it's not alone.
(I also question your dollar values, but that will be very difficult to quantify either way.)
Slashdot Mirror
The thing is, the detention report doesn't indicate any form of mouthing off beyond arguing back. If the student were being rude, belligerent, or otherwise unruly, I'd expect to see that documented in the teacher's report -- if only as a cover-your-ass move. If responding to an order you find unreasonable or unfair with a counter-argument is mouthing-off, we've got some serious problems that need addressing here.
Why is it obvious? Your example, the Moon, is dead wrong. Our Moon is moving away from the Earth, not towards it. (Granted, in about 5 billion years, after the Earth is likely to be gone anyway, it will reverse direction because of the effects of solar tides on the Earth. But the the collision, if the Earth survives that long, is therefore ~15 billion years off, three times the age of the solar system.) The ring material isn't even subject to those forces since they aren't large enough individually to raise bulges and are collectively evenly distributed longitudinally, so no such leading or trailing bulge will appear. (Even if they did, around half -- or more -- of the ring material would be outside of co-rotation and evolve outwards, not inwards.)
Are you unfamiliar with the fact that Cassini is measuring the dust in the Saturnian system? Check the instrument listing, look for "CDA" (Cassini Dust Analyzer). Not that this is the first time that this has been done.
Why would the orbits decay? Are you worried that the Moon will be hitting us soon?
There are many things in the solar system that are younger than 4.55 Gyr; a lot of asteroids, for example, are the results of more recent breakups. You have impact craters and other geologic features on practically all bodies. Honestly, assuming that anything you look at is primordial is a pretty daft assumption unless you can make *some* argument as to why it should be.
As for Saturn's rings, a modicum of research would tell you that there are both dynamical reasons to think that rings are younger (models say that they should grind down to dust relatively fast) as well as observational evidence: the amount of meteoric dust that they've accumulated is smaller than should be there if they were as old as the planet itself. In fact, had you read the article, you would have learned that.
Mostly, they've found transient clumps of material in the rings which suggests that some of the ring particles might break up and re-clump periodically. This means that ages derived from looking at meteoritic contamination are off since the volume that the meteoroid dust must be spread in is larger than thought.
Honestly, it's data that doesn't refute and weakly supports the older age, I think. Interesting, but then he's been saying this for years.
I agree. And it isn't news, either: Larry Esposito has been saying this (and sending out press-releases) for years to this effect. He's just found another small bit of evidence that supports -- or at least doesn't refute -- his idea.
Sure, there are a lot of analytic models out there even today. Also, you can construct a physical model to study many phenomena (e.g., river formation in a lab).
Not that I relish being negative, but I don't recommend getting too excited. I've seen way, way too many of these kinds press-releases -- especially about Mars and especially-especially about evidence of life there -- to get excited yet. Even if they find any evidence of life, it will almost certainly quickly be disputed by other groups and then counter-disputed by the original group and the whole thing will turn into a non-score tie. It also seems like the Martian astrobiology folks have a rather lower threshold for "exciting evidence" of life than many of the rest of us. (Maybe that's a selection effect and maybe that's just common to all scientists, each in his or her own field.)
(This is not to say that I've made up my mind about this specific case.)
Because he did the research and, more importantly, put the movie together.
Honestly, Sebastien's English is so much better than my French, I would never complain.
Ah, I see the source of the confusion. My first sentence was not meant to suggest a definitive knowledge, I figured the fact that it was a theory was to be understood and wasn't the point in any case.
I did no such thing, please re-read my message more carefully. I was simply pointing out the differences in the theories; there are major reasons why this new work is different from the models of lunar formation which is what necessitated this research in the first place.
See above, but basically, no. Iapetus's ridge is a lot small, relatively speaking, and probably tectonic in nature. These bulges seriously alter the shapes of the ring-moons and are do to emplacement of material as it hits the moon.
Yep, the point of these papers isn't composition, it's process.
Speaking as a ring scientist, I don't actually know of any other real contending theories for the origin of the rings. This isn't to say that we have the story all figured out, but as far as I've ever heard, people seem pretty comfortable with the break-up model. (For one thing, it's stochastic and therefore would reasonably explain why only Saturn has a really massive ring system.)
Yes? How is that relevant to my reply?
No, the Moon formed in a notably different way: no dense seed was required to form it. In the rings, tidal forces keep things from building into moons. Our Moon almost certainly formed outside of Earth's Roche limit where it was able to coalesce without significant hindrance.
Gravitational forces are way too weak. On the surfaces of these guys, the escape speed is (literally) zero thanks to tidal and centrifugal forces.
They aren't compressed at all. That's why the densities are so incredibly low.
In short, no, we don't think that this mechanism explains Iapetus. Best guess there is that you have some tectonic effect due to its thermal history. There are some recent papers out there on the topic, although I'm very familiar with the details.
They're not packed very tightly, in as much as the densities are around half that of liquid water.
They're not compressed. They are probably sintered together thanks to repeated exposures to sunlight and then dipping into the planet's shadow, although the details of that we did not work out.
Probably. The problem is that the rings can't accrete into moons because of tidal forces. (They do form temporary aggregates, but those tear apart again in roughly one orbital period.) So the presence of moons in this region is a bit of a mystery. One possibility was that they were large shards of whatever body broke up and formed the rings. What we found in our research is that there are indeed seed-cores in the middles of the moons, but that the moons then accreted a lot more material into a mantle, lowering their densities to almost absurdly small values and reshaping them. The moons you have now are a hybrid of progenitor material and ring particles.
Since the data came from Cassini ISS and since we're the authors on the paper, I feel no qualms about suggesting visiting http://ciclops.org/view_event.php?id=73
In as much as it was previously thought that the moons *couldn't* grow in the ring-region (what with tides), I'm a little curious as to how come you think their grown is obvious.
"single rocket scientist, physicist, engineer, and even computer programmer"
Uh, speaking as an astrophysicists, I find this rather hyperbolic. Most of us born in the post-Apollo years are impressed, but not exactly over-awed by what happened a decade or more before we were born and has had little chance of happening again in our lifetimes. Honestly, I've never really found any part of the manned program to have motivated my career choice and I know few in my generation who have stated the reverse. A lot of us *have* been drawn in by robotic missions, though.
While I agree with the overall point (excitement in the field entices students and future scientists/engineers), you're getting carried away assigning more credit to the manned space program than I think it's due. It's one part of the overall, but it's not alone.
(I also question your dollar values, but that will be very difficult to quantify either way.)