Not sure if the article addressed this, but another point is that you'd have to assemble the fissionable material very carefully since you need to get it super-critical, but not have any of it blow too early, before you have enough. It's the classic bomb-making problem, only without anyone to supervise it.
Pangea post-dates the Earth's accretion by (literally) billions of years. It has nothing to do with the accretion process in any way you can map sensibly. Right after accretion, there were no continents at all since the continents are composed of re-processed rock. It takes billions of years to build up all this larger-generation material until the effects of plate tectonics.
I don't think anyone is suggesting that the Moon formed from a thin layer of crust skimmed from the earth's surface.
That's exactly my point: the Moon is more than a surface scar, it would require a deep, deep gouge. That said, see my comment to the original post about timescales.
As noted, the site is Slashdotted so I can't read it straight up. That said, this doesn't make sense to me. A large explosion on the Earth's surface wouldn't launch material into Earth orbit unless it were launched at a very precise angle (probably nearly horizontal). The authors (based on previous comments) complain that the Giant Impact hypothesis requires a finely-tuned impact angle, but what about their model? I'd expect an explosion to blow material almost radially outward. To posit that you'd get the finely-tuned launch angle from their model seems much more of a stretch than that an impact should strike a glancing blow (especially when we don't know how many similarly-sized impactors hit with the wrong conditions and were simply absorbed).
Also, note that you need to loft a lot more material than just the Moon's mass to make the Moon. it's not an efficient process, a lot (most?) of the material rains back down on the Earth. It has to, it starts out in an orbit that intersects the Earth after all.
For the first point, it's not all that unlikely. (I don't know of any simulations that show that the impact would destroy the Earth, but you do need a specific range of impact angles to blow material off into orbit.) Remember, there were numerous collisions in that epoch, even between fairly large objects.
As to the second point, I call BS. The moon isn't made of the original material of the impactor. If the authors say it is, they're showing that they don't understand the theory that they're deriding. The Moon is made (principally) of the Earth's mantle. That's why the giant impact theory is so appealing, it explains the compositional similarities.
(That said, I seem to recall simulation work from about a decade ago that indicated that ALL the terrestrial planets had more or less the same composition since the planetesimals would be well-mixed in this region.)
Everyone who has replied so far makes fair points, but misses the biggest point: the Moon is over 4 billion years old. There are virtually no rocks on the Earth's surface that even approach its age. That means that the ENTIRE Earth's surface has been replaced and reshaped in the interim. Things haven't just "shifted considerably", we've got a totally different surface. Any scar from that period is long, long since erased. And hole as deep as the Moon has long since filled in since the Earth is still very much a fluid over these timescales.
That's what George Darwin said, but no. There's not enough evacuated volume there. Think about it: the Pacific is huge, but not very deep on planetary scales. Volume-wise, you're off by orders of magnitude. (I don't believe Darwin knew the depth of the ocean, so he's off the hook.)
No, the article is about whether vaccines trigger chronic conditions like asthma. Adverse reactions to vaccines have long been known, are very rare, and manifest very soon after the vaccine (and can be dealt with accordingly). You get warned of this every time you get a vaccine and they also instruct you what to do if you *do* have an adverse reaction.
What they're trying to answer is "How did our planets form?" It's hard to imagine any findings on Europa (even life) that would significantly out-weigh an answer to this question, although some would probably rival it in importance. But given that this mission can almost certainly address the questions it's being sent up to answer and given that the technological hurdles of studying Europa properly are so high, this is a much more sensible mission to send at the moment, in my view.
Er, not to deflate the coolness of this mission (and it is a damn cool mission), but Juno was selected in 2005. All that this is saying is that it hasn't been derailed, although their wording obscures this. See the mission website.
Once again, NASA's press office shows that it's keen on issuing a hyped release about any old thing.
On the flip side, robotic exploration of the solar system (Mars rovers, Cassini orbiter, Pluto flyby, etc.) runs around $2 billion/year. It's likely that were ISS not hoovering up money, at least some of that $50-$100 billion would have gone to the robotic exploration (especially since cost overruns in one place tend to tie up funds from other places). Even a small fraction of that money could have greatly enhanced our exploration. So while I agree that ISS is cheap compared to the DoD, it's still a ton of money that could have (depending on how you value things) probably done more elsewhere.
The flip side of using a lot of marble and good stone in building is that a lot of Roman buildings were cannibalized for their stone. The Colesseum has been stripped, for one. (The best example I can think of is Piazza dell'Anfiteatro in Lucca, Italy, where the entire original amphitheater is totally gone, but the fossilzed shape remains in the piazza.)
As a result, most of what we still have is from places that were buried (a la Pompeii), were converted to other uses (the Pantheon is now a church, for example), or places that were abandoned (Ephesus, for instance).
Yet contrary to that article, NASA's NEO site claims it's work is well underway and will be completed in a decade. (No mention of needing an ultra-expensive new mission, in fact.) Putting a telescope around Venus sound ridiculously expensive and wasteful. (And rather like yet another reporter at New Scientist was trying to hype a non-story, if you ask me.)
The major problem with the Galilean moons, however, is that they liquid is 1 km or more below the surface. That means that anything you see on the surface is an indirect measure of the liquid underneath. They're interesting bodies, but they are harder to study in many respects.
"We need a Titan-dedicated orbiter because after four years of Cassini, we still haven't mapped more than 25 percent of Titan's surface," says Coustenis. "When you see the diversity the moon has, you realize it needs full-coverage mapping. And we can have a polar orbiter, whereas Cassini only passes by Titan on the ecliptic."
Er, what? We've mapped the entire surface, although not all at great resolution. And I'm not remotely clear what she means about the orbit. I know she can't mean that Cassini only passes Titan on equatorial (not ecliptic!) orbits, because that's clearly not the case. Look at the radar swaths taken over the poles, for example.
Asteroid belt objects are unlikely to hit the Earth during the course of the human race's existence. They're in fairly stable, roughly circular orbits that don't cross Earth's orbit. You're more worried about NON-Belt asteroids and, perhaps more so, comets.
In any case, it isn't a zero-sum game: funding Titan research doesn't mean that asteroids don't get studied.
Meanwhile, we *do* have projects to catalog all such asteroids *and* a mission to the asteroid belt in play right now. So what's your complaint?
(As a grad student, I saw *way* too many students come through the state university who were there because their parents wanted them there and/or because it was expected and didn't really care about the outcome. So it does happen and it's depressing to watch.)
I'm not sure I accept "have to". OK, it's probably true at least some of the time, but I think a lot of people get so obsessed with charting a career path that they lose sight of the education itself. I know a lot of people I went to high school with were obsessed with planning careers that far out and ignored options because of it. I suppose it all boils down to goals: if you're out to have a fast career and make good money, your options are a lot more limited than if you want to study your passion and see where it leads later.
It's one thing to go to college because you're genuinely interested in the subject you've chosen
seem contradictory. The latter seems to agree with what I said above, the former says I was unequivocally wrong. So which is it: is an education for an education's sake OK or not? (I agree that going because just because it's expected or because you "want a four-year vacation" is wrong, so let's not even argue about that. It's not something anyone would disagree with.)
I know a lot of people who haven't had a job plan for after college, studied what really, truly interested them while in college, and gone on to very happy (even successful) careers. It isn't for everyone, to be sure, but if you really love something, follow it where it leads and don't stress too much about planning out how it'll pay off. (But don't bank on it paying well, either, I guess.)
Slashdot Mirror
Not sure if the article addressed this, but another point is that you'd have to assemble the fissionable material very carefully since you need to get it super-critical, but not have any of it blow too early, before you have enough. It's the classic bomb-making problem, only without anyone to supervise it.
Ah. But even then, you have to consider that over 4.5 billion years, that crust will have been recycled and erased.
Pangea post-dates the Earth's accretion by (literally) billions of years. It has nothing to do with the accretion process in any way you can map sensibly. Right after accretion, there were no continents at all since the continents are composed of re-processed rock. It takes billions of years to build up all this larger-generation material until the effects of plate tectonics.
I don't think anyone is suggesting that the Moon formed from a thin layer of crust skimmed from the earth's surface.
That's exactly my point: the Moon is more than a surface scar, it would require a deep, deep gouge. That said, see my comment to the original post about timescales.
As noted, the site is Slashdotted so I can't read it straight up. That said, this doesn't make sense to me. A large explosion on the Earth's surface wouldn't launch material into Earth orbit unless it were launched at a very precise angle (probably nearly horizontal). The authors (based on previous comments) complain that the Giant Impact hypothesis requires a finely-tuned impact angle, but what about their model? I'd expect an explosion to blow material almost radially outward. To posit that you'd get the finely-tuned launch angle from their model seems much more of a stretch than that an impact should strike a glancing blow (especially when we don't know how many similarly-sized impactors hit with the wrong conditions and were simply absorbed).
Also, note that you need to loft a lot more material than just the Moon's mass to make the Moon. it's not an efficient process, a lot (most?) of the material rains back down on the Earth. It has to, it starts out in an orbit that intersects the Earth after all.
For the first point, it's not all that unlikely. (I don't know of any simulations that show that the impact would destroy the Earth, but you do need a specific range of impact angles to blow material off into orbit.) Remember, there were numerous collisions in that epoch, even between fairly large objects.
As to the second point, I call BS. The moon isn't made of the original material of the impactor. If the authors say it is, they're showing that they don't understand the theory that they're deriding. The Moon is made (principally) of the Earth's mantle. That's why the giant impact theory is so appealing, it explains the compositional similarities.
(That said, I seem to recall simulation work from about a decade ago that indicated that ALL the terrestrial planets had more or less the same composition since the planetesimals would be well-mixed in this region.)
Everyone who has replied so far makes fair points, but misses the biggest point: the Moon is over 4 billion years old. There are virtually no rocks on the Earth's surface that even approach its age. That means that the ENTIRE Earth's surface has been replaced and reshaped in the interim. Things haven't just "shifted considerably", we've got a totally different surface. Any scar from that period is long, long since erased. And hole as deep as the Moon has long since filled in since the Earth is still very much a fluid over these timescales.
That's what George Darwin said, but no. There's not enough evacuated volume there. Think about it: the Pacific is huge, but not very deep on planetary scales. Volume-wise, you're off by orders of magnitude. (I don't believe Darwin knew the depth of the ocean, so he's off the hook.)
*Actually*, it's been both "Illudium Pu-36" and "Uranium Q-36". See http://en.wikipedia.org/wiki/Marvin_the_Martian
Yes, I know that off-hand. Yes, I should get out more.
No, the article is about whether vaccines trigger chronic conditions like asthma. Adverse reactions to vaccines have long been known, are very rare, and manifest very soon after the vaccine (and can be dealt with accordingly). You get warned of this every time you get a vaccine and they also instruct you what to do if you *do* have an adverse reaction.
See the difference?
What they're trying to answer is "How did our planets form?" It's hard to imagine any findings on Europa (even life) that would significantly out-weigh an answer to this question, although some would probably rival it in importance. But given that this mission can almost certainly address the questions it's being sent up to answer and given that the technological hurdles of studying Europa properly are so high, this is a much more sensible mission to send at the moment, in my view.
Er, not to deflate the coolness of this mission (and it is a damn cool mission), but Juno was selected in 2005. All that this is saying is that it hasn't been derailed, although their wording obscures this. See the mission website.
Once again, NASA's press office shows that it's keen on issuing a hyped release about any old thing.
Unless Google also claimed a write-off for the donation, in which case the IRS's interest is understandable.
On the flip side, robotic exploration of the solar system (Mars rovers, Cassini orbiter, Pluto flyby, etc.) runs around $2 billion/year. It's likely that were ISS not hoovering up money, at least some of that $50-$100 billion would have gone to the robotic exploration (especially since cost overruns in one place tend to tie up funds from other places). Even a small fraction of that money could have greatly enhanced our exploration. So while I agree that ISS is cheap compared to the DoD, it's still a ton of money that could have (depending on how you value things) probably done more elsewhere.
The flip side of using a lot of marble and good stone in building is that a lot of Roman buildings were cannibalized for their stone. The Colesseum has been stripped, for one. (The best example I can think of is Piazza dell'Anfiteatro in Lucca, Italy, where the entire original amphitheater is totally gone, but the fossilzed shape remains in the piazza.)
As a result, most of what we still have is from places that were buried (a la Pompeii), were converted to other uses (the Pantheon is now a church, for example), or places that were abandoned (Ephesus, for instance).
Cliff Ironjaw
Yet contrary to that article, NASA's NEO site claims it's work is well underway and will be completed in a decade. (No mention of needing an ultra-expensive new mission, in fact.) Putting a telescope around Venus sound ridiculously expensive and wasteful. (And rather like yet another reporter at New Scientist was trying to hype a non-story, if you ask me.)
The major problem with the Galilean moons, however, is that they liquid is 1 km or more below the surface. That means that anything you see on the surface is an indirect measure of the liquid underneath. They're interesting bodies, but they are harder to study in many respects.
Er, what? We've mapped the entire surface, although not all at great resolution. And I'm not remotely clear what she means about the orbit. I know she can't mean that Cassini only passes Titan on equatorial (not ecliptic!) orbits, because that's clearly not the case. Look at the radar swaths taken over the poles, for example.
I wonder if she was mis-quoted.
Asteroid belt objects are unlikely to hit the Earth during the course of the human race's existence. They're in fairly stable, roughly circular orbits that don't cross Earth's orbit. You're more worried about NON-Belt asteroids and, perhaps more so, comets.
In any case, it isn't a zero-sum game: funding Titan research doesn't mean that asteroids don't get studied.
Meanwhile, we *do* have projects to catalog all such asteroids *and* a mission to the asteroid belt in play right now. So what's your complaint?
I totally agree, then. :-)
(As a grad student, I saw *way* too many students come through the state university who were there because their parents wanted them there and/or because it was expected and didn't really care about the outcome. So it does happen and it's depressing to watch.)
I'm not sure I accept "have to". OK, it's probably true at least some of the time, but I think a lot of people get so obsessed with charting a career path that they lose sight of the education itself. I know a lot of people I went to high school with were obsessed with planning careers that far out and ignored options because of it. I suppose it all boils down to goals: if you're out to have a fast career and make good money, your options are a lot more limited than if you want to study your passion and see where it leads later.
Some people stay home and raise their children while a spouse works.
and
seem contradictory. The latter seems to agree with what I said above, the former says I was unequivocally wrong. So which is it: is an education for an education's sake OK or not? (I agree that going because just because it's expected or because you "want a four-year vacation" is wrong, so let's not even argue about that. It's not something anyone would disagree with.)
And there certainly are. Community colleges, for example, don't generally have fancy amenities for obvious reasons.
I know a lot of people who haven't had a job plan for after college, studied what really, truly interested them while in college, and gone on to very happy (even successful) careers. It isn't for everyone, to be sure, but if you really love something, follow it where it leads and don't stress too much about planning out how it'll pay off. (But don't bank on it paying well, either, I guess.)