How public is public? How do you define "purpose"? If I plan to tell a friend that a second friend totally committed a murder last night, I'm clear from having to testify? Taken to the extreme, that definition only leaves out people who acquired information with the purpose (found through mind reading?) of keeping it to themselves.
There's a difference between saying that you only get the protection if you're somehow accredited (whether it be by the government or by a separate, professional body) and saying you can or cannot publish stories at all. (As with free speech, you can publish what you want, but you may face consequences for publishing things, like libelous or classified material.)
In the end, this would be a new protection that the constitution doesn't appear to already grant journalists, so it's hard to see that not extending it to everyone is necessarily unconstitutional.
The problem is that if they interview someone for a story, they can be forced to reveal their source. That may have negative repercussions for the sources or their ability to get sources. That does have a rather chilling effect on journalism. (A similar effect is at play for social scientists, incidentally.)
There are already similar laws protecting patient-doctor confidences and client-lawyer confidences. (Also, I have vague feeling, clergy-parishoner?) However, there's a notable difference between these cases and the journalists: it's fairly simple to ascertain who is a lawyer and acting as someone's lawyer. The ABA keeps a pretty good gateway to that privileged. There is no equivalent way to tell who is really a journalist and who is a random citizen with a blog. That's where this gets tricky and generally bogs down.
Here, consider this: the Moon suffered about half as many impacts per area as the Earth throughout its history. It has no recycling and no oceans to lose what hits the surface. There are basically no metals on the lunar surface. If asteroids were bringing the metals in, the Moon would have more metals per square km than Earth.
Continental crust has been erupted multiple times. Over time, more material has been through the subduction/eruption cycle and so we've gotten more such crust. So yes, on the average, continental material has grown over time.
I may not be an expert in geology, but I'll trust my graduate professors in the area.
This lends significant credibility to the previous authors argument that heavy elements came primarily from asteroids.
Please read more carefully. Most of the Earth is oceans. This was even more true in the past. So any asteroid strikes are far more likely to have hit oceans than land. And then be cycled into the mantle... where according to the original poster, they'll lose their metals.
Perhaps you didn't stop to consider that a significant portion of asteroids are basically lumps of iron?
Nope, oddly I didn't fail to consider that. In fact, I explicitly said it. Please read more carefully before trying to be rude.
That's just the thing, I haven't seen any convincing evidence that catastrophic global warming is very likely, or indeed, at all possible to happen. All of those catastrophic climate forecasts are based on models which do not account for cloud cover for example, which makes their predictive value highly suspect. They have failed to predict the last 10 years of stable temperature for one. As far as hurricanes are concerned, those have struck many coasts so there is plenty of empirical evidence for the possibility. Catastrophic global warming, on the other hand, would be unprecedented.
Depends what you mean by "catastrophic", really. Drier weather in inhabited areas causing water to run low? Hurricanes? Floods? Ocean level rises?
And where did you get the idea that the models don't use cloud cover? The ones I've stepped through in grad classes definitely do. The modeling is crude, to be sure, but it's in there. If it's not precise enough for you, say so, but how precise do you demand it be then?
harmful emissions by portraying CO2 as a harmful pollutant
It is a pollutant. We're churning it out and it has a negative effect. It doesn't have to directly harm humans to be a pollutant. Look at fertilizer run-off. You're bending the definition of the word to suit your desire.
In short, higher CO2 concentrations enhance plant growth and only extremely high levels of CO2 are directly harmful to humans or animals
Ocean acidification. It's happening, it's killing animals right now. So your absolute statement isn't accurate. You might not have encountered harmful outcomes of CO2 rises, but they exist. There was a nice piece in The American Scientist a month or few ago about it, in fact.
In short, I think you're confusing lack of media coverage with lack of problems. (And turning that into absolute statements of fact rather than tentative statements of limited knowledge.) That's very dangerous.
No, it's not. It's valid to suggest that there may exist within the non-drinking population a group that has a lot of stress, in part because of strict moral rules like not drinking. But that's not what you said. You made sweeping generalizations about non-drinkers that were insulting and now you're trying to justify it.
The sample of those who were studied included individuals between ages 55 and 65 who had had any kind of outpatient care in the previous three years. The 1,824 participants were followed for 20 years. One drawback of the sample: a disproportionate number, 63%, were men. Just over 69% of the never-drinkers died during the 20 years, 60% of the heavy drinkers died and only 41% of moderate drinkers died.
What's missing is information on the uncertainty. The difference between 60% and 69% mortality isn't that much in a study this small. If you divide up the participants equally into three categories, I can easily see the two values being not statistically significantly different. (It's harder to imagine the 41% isn't significantly lower, though.)
You do know that many non-drinkers have no intrinsic problem with drinking, but abstain for a variety of personal reasons, right? To me, alcohol takes foul and triggers migraines, so I avoid it. (I have no actual problem with anyone else drinking, usual cavaets about moderation, driving, etc. in effect.) I have friends who come from families of alcoholics and who therefore avoid alcohol for pretty obvious reasons. Frankly, you're been pretty insulting to all of us with your generalizations.
(For that matter, anyone who can only relax by drinking probably has as many problems as anyone who can't unwind long enough to drink. Just saying.)
Not without a burn, no. And even without, you've got the 11 km/sec escape speed. You can build a craft that aerobrakes, but that requires aiming. (And I'm not sure how effective that will be with a cargo container that is filled with metal. That's a lot of momentum and not a lot of area.)
You're more receptive to new evidence than most people denying global warming I've encountered. You do seem to be an honest skeptic, but you also have got to be able to see that there are many people who fight the science tooth and nail without regard to the merits of the case.
And no, it's not really an ad hominem attack to label them "deniers". Just because a negative word fits doesn't make it a logical fallacy any more than calling a convicted felon a "felon" is an ad hominem.
Also, a few points on your bullets:
Therefore I cannot believe in catastrophic warming, since there is no proof for it.
Of course there isn't. There's never proof, this is science. Eventually, it may happen. But it'll be a little late. This is rather like saying you don't believe the hurricane will strike your coast because there's no proof. Sure, but if the forecasts show a high probability, you may still want to act.
Please do not call CO2 a pollutant or a health risk since it is not one. A vast majority of the real pollutants that fossil energy generation generates are currently filtered out in the western world and the air quality has improved a lot since the industrial revolution because of that. Therefore I classify arguments based on "poisoning the planet" to be silly and alarmist.
Are you arguing that because we're filtering other pollutants, CO2 can't be a pollutant? That makes no sense at all.
As far as whether anything can or should be done about the current warming cycle, in my view the best thing that could be done is to wait and see what happens in the next decade or so.
This is not an unreasonable position in that you're not denying the science. Policy isn't science and people really need to stop confusing the two. It's possible to accept AGW without feeling that we should act or agree on what action to take.
My main problem is that the 'solutions' to AGW are almost universally bad. Either ridiculously overpriced, overintrusive, undereffective, unfair... and most often some mixture of all of these.
You've stumbled on something important, there:
The solutions to AGW have nothing to do with the science saying AGW is happening. Solutions aren't really a part of science, that's politics (plus input from engineering, philosophy/ethics, and science). It may well be that even though we're almost certainly warming the planet up, we should do nothing. But that's a separate issue from the science saying it's happening. That gets lost in a lot of these argument.
Yeah, it's hard to imagine the economics going the other way. I mean, if we developed cheap, clean ways to launch and return spacecraft, maybe. But I'm not seeing how that would happen, right now. (I'd love it to, of course, so we should certainly try.)
That... doesn't help. I wasn't talking about parking it into Earth orbit, although that wouldn't hurt. I was talking about matching EARTH'S orbit. If you don't, your impact speed is the relative speed before you start falling and the escape speed of the Earth. (They actually add in quadrature. Why is left as an exercise to the reader, but it hinges on conservation of energy.) So even for the mid-asteroid belt, you'd be getting impact speeds of around 15 km/sec. At those speeds, hitting the water would be like hitting a rock.
Unless you want to hit the ground at more than 11 km/sec, you want to use rockets to slow the speed to at least match Earth's orbit and then drop it down kind of gently. You don't have to soft land it, but slamming it into the Indian Ocean at that speed probably won't be conducive to finding your ores.
I didn't say it all was. It doesn't need to be. The point is, if you take the rare asteroid strike and couple it with the theory of near-perfect differentiation advocated by the GP, you wouldn't get a lot of metals left over here.
here is plenty of surface that is more than billion years old,
Sort of true. Yeah, there's a good amount of land mass older than 1 billion years, but as you get older, it gets pretty rare pretty fast. And since we're adding that layer of complexity: as you go back in time, land becomes rarer, making it harder to collect metals on land masses (and not be recycled into the mantle).
here is plenty of surface that is more than billion years old,
Sort of true. There is definitely a good amount of land mass older than 1 billion years, but as you get older, it gets a lot rarer. And since we're adding that layer of complexity to the argument, the amount of land has been growing with time, so as you go further back in time, you get less land area for asteroids to land on, so it's still crazy hard to get a lot of metals built up in that way.
Again, I disagree. You're fixated on "truth" which has no real bearing on things. The deniers aren't termed that because they have a dissenting view, they're deniers because they refuse to change their view no matter how much evidence they see. They raise the bar and demand still more evidence when they've had their "concerns" addressed and ignore the contrary facts when their own theories meet those facts. That's denialism, which is very different from standing up to the standard view. (I know many scientists who hold views that one widely supported theory or another is wrong, but most of them seem perfectly ready to switch sides if strong evidence arises to point that way.)
If there is a cogent alternative interpretation to the climate data, I for one am happy to hear it. So far, what few even vaguely reasonable alternate models there were have been pretty soundly shot down by newer data. At this point, people aren't presenting alternate theories as much as outright attacks on the researchers responsible.
Not sure if you're serious (always hard to tell), but outside of Hollywood, no. I apologize if my offhand reference to Earth's bulk composition (which was a comparison to the asteroids' lower average metal content since I imagine a lot of people assume it's like the average Earth composition) was confusing. I probably should have been clearer.
You seem to be confusing the earth's crust with the earth's core, with statements like "In fact, Earth is more metal per mass than the average asteroid."
Nope, I'm quite explicitly talking about the bulk Earth compared to the bulk asteroids, which are (overall) less metallic than Earth. That's all I'm saying. So your next paragraph is moot.
Don't forget, mining the crust has a certain cost, to the environment.
Absolutely. There's also an impact around building rockets to loft mining gear and lower metals in large quantities. I have no idea which is worse (or is necessarily worse, more precisely), but I doubt it's that one-sided.
Finally, not all metals are common in the Earth's crust.
Sure, but we're still a pretty long ways from exhausting our supplies to the point where it's cheaper to (again) lower the materials to ther Earth. 'cause you know what else is limited? Cheap sources of energy needed to make fuel for rockets. And my bet is that it'll be cheaper and easier to recycle the metals than to go the space route.
As for calcium, that was off the top of my head; according to your link, it's fairly common, but aside from that, I've never heard of it being particularly valuable
I never said it was. I was saying you were quoting wrong facts and that your theory about asteroid delivery wasn't accurate. (Which you seem to have dropped. Since that was my main point in posting, I don't really feel like arguing the merits of mining asteroids since I think we can disagree on that in the ample uncertainty that currently exists.)
In fact, everything that we currently mine (copper, iron, zinc, platinum, gold, etc.) came from asteroid impacts.
Only in the sense that Earth is basically built of asteroids in the first place. But in that limit, you're just advocating mining on Earth again, the nearest and most habitable such body.
all those elements moved to the core, leaving only things like calcium and silicon and carbon in the Earth's crust when it cooled. All the useful elements came from asteroid impacts after that.
Good lord, no. Certainly elements did tend to head to the core preferentially. Such siderophilic (iron-loving) elements are fairly rare in the Earth's upper layers. Others are still fairly common. Or at least common enough. Even iron, which lead the charge to the core during differentiation, is awfully common in the crust.
In fact, silicon (the second most abundant element in the crust) is only about ten times more common than iron, which is about as abundant as calcium (which you cite as being abundant). Aluminum is more abundant than calcium and is in fact only a few times less abundant than silicon. (Oxygen, incidentally, is the most common element in the crust, beating silicon out by a factor of a few.) In fact, most metals we're particularly attached to are about one-in-ten-thousandth as common as silicon. If you factor in the fact that they're usually found in clumps, that's a very cheerful thought.
By the way, if your theory of asteroid delivery were true, I'm pretty sure we wouldn't have very much metals to work with. The Earth's crust is tectonically recycled every several hundred million years (any given chunk has been subducted and recycled several times, more or less; we estimated this my first year of grad school, but I forget the numbers exactly), so you could only rely on the metals delivered in the past few hundred million years. Asteroid impacts are getting rarer all the time, especially big ones.
Also, recall that a given asteroid is as likely as much rock as metal. In fact, Earth is more metal per mass than the average asteroid. (A lot of our silicates ended up in the Moon instead.) However, some asteroids are definitely mostly metallic and for mining purposes, that's a mad bonus. (For metals raining down from heaven, however, you have to factor in the fraction of the asteroids that isn't metal.)
Also, you're not factoring in the costs of bringing metals back to the Earth (if that's your goal). It's far more expensive to do that than to mine them here and will be for the foreseeable future. Of course, if your goal is to use them in space anyway, then it might be better to mine them there. (On the other hand, then you have to build the refining and construction infrastructure in space, which has a lot of challenges of its own.)
No, to deny merely means to refuse to accept the claim regardless of what evidence has been put forward. The word makes not assumptions as to whether the claim is true or untrue. It's possible to disagree with AGW without being a denier, but such a person would be open to the possibility of it being accurate.
These people are certainly deniers. Their counter-claims have little validity (most have none and many are outright fabrications) and most of their arguments lately have been ad hominem attacks on the researchers. So far, I have yet to see one of them acknowledge the strength of the data or admit to having made a mistake when they were shown to be wrong. They're deniers, pure and simple.
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How public is public? How do you define "purpose"? If I plan to tell a friend that a second friend totally committed a murder last night, I'm clear from having to testify? Taken to the extreme, that definition only leaves out people who acquired information with the purpose (found through mind reading?) of keeping it to themselves.
There's a difference between saying that you only get the protection if you're somehow accredited (whether it be by the government or by a separate, professional body) and saying you can or cannot publish stories at all. (As with free speech, you can publish what you want, but you may face consequences for publishing things, like libelous or classified material.)
In the end, this would be a new protection that the constitution doesn't appear to already grant journalists, so it's hard to see that not extending it to everyone is necessarily unconstitutional.
The problem is that if they interview someone for a story, they can be forced to reveal their source. That may have negative repercussions for the sources or their ability to get sources. That does have a rather chilling effect on journalism. (A similar effect is at play for social scientists, incidentally.)
There are already similar laws protecting patient-doctor confidences and client-lawyer confidences. (Also, I have vague feeling, clergy-parishoner?) However, there's a notable difference between these cases and the journalists: it's fairly simple to ascertain who is a lawyer and acting as someone's lawyer. The ABA keeps a pretty good gateway to that privileged. There is no equivalent way to tell who is really a journalist and who is a random citizen with a blog. That's where this gets tricky and generally bogs down.
Here, consider this: the Moon suffered about half as many impacts per area as the Earth throughout its history. It has no recycling and no oceans to lose what hits the surface. There are basically no metals on the lunar surface. If asteroids were bringing the metals in, the Moon would have more metals per square km than Earth.
Does that help?
Continental crust has been erupted multiple times. Over time, more material has been through the subduction/eruption cycle and so we've gotten more such crust. So yes, on the average, continental material has grown over time.
I may not be an expert in geology, but I'll trust my graduate professors in the area.
This lends significant credibility to the previous authors argument that heavy elements came primarily from asteroids.
Please read more carefully. Most of the Earth is oceans. This was even more true in the past. So any asteroid strikes are far more likely to have hit oceans than land. And then be cycled into the mantle... where according to the original poster, they'll lose their metals.
Perhaps you didn't stop to consider that a significant portion of asteroids are basically lumps of iron?
Nope, oddly I didn't fail to consider that. In fact, I explicitly said it. Please read more carefully before trying to be rude.
That's just the thing, I haven't seen any convincing evidence that catastrophic global warming is very likely, or indeed, at all possible to happen. All of those catastrophic climate forecasts are based on models which do not account for cloud cover for example, which makes their predictive value highly suspect. They have failed to predict the last 10 years of stable temperature for one. As far as hurricanes are concerned, those have struck many coasts so there is plenty of empirical evidence for the possibility. Catastrophic global warming, on the other hand, would be unprecedented.
Depends what you mean by "catastrophic", really. Drier weather in inhabited areas causing water to run low? Hurricanes? Floods? Ocean level rises?
And where did you get the idea that the models don't use cloud cover? The ones I've stepped through in grad classes definitely do. The modeling is crude, to be sure, but it's in there. If it's not precise enough for you, say so, but how precise do you demand it be then?
harmful emissions by portraying CO2 as a harmful pollutant
It is a pollutant. We're churning it out and it has a negative effect. It doesn't have to directly harm humans to be a pollutant. Look at fertilizer run-off. You're bending the definition of the word to suit your desire.
In short, higher CO2 concentrations enhance plant growth and only extremely high levels of CO2 are directly harmful to humans or animals
Ocean acidification. It's happening, it's killing animals right now. So your absolute statement isn't accurate. You might not have encountered harmful outcomes of CO2 rises, but they exist. There was a nice piece in The American Scientist a month or few ago about it, in fact.
In short, I think you're confusing lack of media coverage with lack of problems. (And turning that into absolute statements of fact rather than tentative statements of limited knowledge.) That's very dangerous.
No, it's not. It's valid to suggest that there may exist within the non-drinking population a group that has a lot of stress, in part because of strict moral rules like not drinking. But that's not what you said. You made sweeping generalizations about non-drinkers that were insulting and now you're trying to justify it.
The sample of those who were studied included individuals between ages 55 and 65 who had had any kind of outpatient care in the previous three years. The 1,824 participants were followed for 20 years. One drawback of the sample: a disproportionate number, 63%, were men. Just over 69% of the never-drinkers died during the 20 years, 60% of the heavy drinkers died and only 41% of moderate drinkers died.
What's missing is information on the uncertainty. The difference between 60% and 69% mortality isn't that much in a study this small. If you divide up the participants equally into three categories, I can easily see the two values being not statistically significantly different. (It's harder to imagine the 41% isn't significantly lower, though.)
The article says that they define heavy drinking as more than three drinks a day.
Does that help?
You do know that many non-drinkers have no intrinsic problem with drinking, but abstain for a variety of personal reasons, right? To me, alcohol takes foul and triggers migraines, so I avoid it. (I have no actual problem with anyone else drinking, usual cavaets about moderation, driving, etc. in effect.) I have friends who come from families of alcoholics and who therefore avoid alcohol for pretty obvious reasons. Frankly, you're been pretty insulting to all of us with your generalizations.
(For that matter, anyone who can only relax by drinking probably has as many problems as anyone who can't unwind long enough to drink. Just saying.)
Not without a burn, no. And even without, you've got the 11 km/sec escape speed. You can build a craft that aerobrakes, but that requires aiming. (And I'm not sure how effective that will be with a cargo container that is filled with metal. That's a lot of momentum and not a lot of area.)
You're more receptive to new evidence than most people denying global warming I've encountered. You do seem to be an honest skeptic, but you also have got to be able to see that there are many people who fight the science tooth and nail without regard to the merits of the case.
And no, it's not really an ad hominem attack to label them "deniers". Just because a negative word fits doesn't make it a logical fallacy any more than calling a convicted felon a "felon" is an ad hominem.
Also, a few points on your bullets:
Therefore I cannot believe in catastrophic warming, since there is no proof for it.
Of course there isn't. There's never proof, this is science. Eventually, it may happen. But it'll be a little late. This is rather like saying you don't believe the hurricane will strike your coast because there's no proof. Sure, but if the forecasts show a high probability, you may still want to act.
Please do not call CO2 a pollutant or a health risk since it is not one. A vast majority of the real pollutants that fossil energy generation generates are currently filtered out in the western world and the air quality has improved a lot since the industrial revolution because of that. Therefore I classify arguments based on "poisoning the planet" to be silly and alarmist.
Are you arguing that because we're filtering other pollutants, CO2 can't be a pollutant? That makes no sense at all.
As far as whether anything can or should be done about the current warming cycle, in my view the best thing that could be done is to wait and see what happens in the next decade or so.
This is not an unreasonable position in that you're not denying the science. Policy isn't science and people really need to stop confusing the two. It's possible to accept AGW without feeling that we should act or agree on what action to take.
My main problem is that the 'solutions' to AGW are almost universally bad. Either ridiculously overpriced, overintrusive, undereffective, unfair... and most often some mixture of all of these.
You've stumbled on something important, there:
The solutions to AGW have nothing to do with the science saying AGW is happening. Solutions aren't really a part of science, that's politics (plus input from engineering, philosophy/ethics, and science). It may well be that even though we're almost certainly warming the planet up, we should do nothing. But that's a separate issue from the science saying it's happening. That gets lost in a lot of these argument.
Yeah, it's hard to imagine the economics going the other way. I mean, if we developed cheap, clean ways to launch and return spacecraft, maybe. But I'm not seeing how that would happen, right now. (I'd love it to, of course, so we should certainly try.)
That... doesn't help. I wasn't talking about parking it into Earth orbit, although that wouldn't hurt. I was talking about matching EARTH'S orbit. If you don't, your impact speed is the relative speed before you start falling and the escape speed of the Earth. (They actually add in quadrature. Why is left as an exercise to the reader, but it hinges on conservation of energy.) So even for the mid-asteroid belt, you'd be getting impact speeds of around 15 km/sec. At those speeds, hitting the water would be like hitting a rock.
Unless you want to hit the ground at more than 11 km/sec, you want to use rockets to slow the speed to at least match Earth's orbit and then drop it down kind of gently. You don't have to soft land it, but slamming it into the Indian Ocean at that speed probably won't be conducive to finding your ores.
I didn't say it all was. It doesn't need to be. The point is, if you take the rare asteroid strike and couple it with the theory of near-perfect differentiation advocated by the GP, you wouldn't get a lot of metals left over here.
here is plenty of surface that is more than billion years old,
Sort of true. Yeah, there's a good amount of land mass older than 1 billion years, but as you get older, it gets pretty rare pretty fast. And since we're adding that layer of complexity: as you go back in time, land becomes rarer, making it harder to collect metals on land masses (and not be recycled into the mantle).
here is plenty of surface that is more than billion years old,
Sort of true. There is definitely a good amount of land mass older than 1 billion years, but as you get older, it gets a lot rarer. And since we're adding that layer of complexity to the argument, the amount of land has been growing with time, so as you go further back in time, you get less land area for asteroids to land on, so it's still crazy hard to get a lot of metals built up in that way.
Again, I disagree. You're fixated on "truth" which has no real bearing on things. The deniers aren't termed that because they have a dissenting view, they're deniers because they refuse to change their view no matter how much evidence they see. They raise the bar and demand still more evidence when they've had their "concerns" addressed and ignore the contrary facts when their own theories meet those facts. That's denialism, which is very different from standing up to the standard view. (I know many scientists who hold views that one widely supported theory or another is wrong, but most of them seem perfectly ready to switch sides if strong evidence arises to point that way.)
If there is a cogent alternative interpretation to the climate data, I for one am happy to hear it. So far, what few even vaguely reasonable alternate models there were have been pretty soundly shot down by newer data. At this point, people aren't presenting alternate theories as much as outright attacks on the researchers responsible.
Not sure if you're serious (always hard to tell), but outside of Hollywood, no. I apologize if my offhand reference to Earth's bulk composition (which was a comparison to the asteroids' lower average metal content since I imagine a lot of people assume it's like the average Earth composition) was confusing. I probably should have been clearer.
You seem to be confusing the earth's crust with the earth's core, with statements like "In fact, Earth is more metal per mass than the average asteroid."
Nope, I'm quite explicitly talking about the bulk Earth compared to the bulk asteroids, which are (overall) less metallic than Earth. That's all I'm saying. So your next paragraph is moot.
Don't forget, mining the crust has a certain cost, to the environment.
Absolutely. There's also an impact around building rockets to loft mining gear and lower metals in large quantities. I have no idea which is worse (or is necessarily worse, more precisely), but I doubt it's that one-sided.
Finally, not all metals are common in the Earth's crust.
Sure, but we're still a pretty long ways from exhausting our supplies to the point where it's cheaper to (again) lower the materials to ther Earth. 'cause you know what else is limited? Cheap sources of energy needed to make fuel for rockets. And my bet is that it'll be cheaper and easier to recycle the metals than to go the space route.
As for calcium, that was off the top of my head; according to your link, it's fairly common, but aside from that, I've never heard of it being particularly valuable
I never said it was. I was saying you were quoting wrong facts and that your theory about asteroid delivery wasn't accurate. (Which you seem to have dropped. Since that was my main point in posting, I don't really feel like arguing the merits of mining asteroids since I think we can disagree on that in the ample uncertainty that currently exists.)
In fact, everything that we currently mine (copper, iron, zinc, platinum, gold, etc.) came from asteroid impacts.
Only in the sense that Earth is basically built of asteroids in the first place. But in that limit, you're just advocating mining on Earth again, the nearest and most habitable such body.
all those elements moved to the core, leaving only things like calcium and silicon and carbon in the Earth's crust when it cooled. All the useful elements came from asteroid impacts after that.
Good lord, no. Certainly elements did tend to head to the core preferentially. Such siderophilic (iron-loving) elements are fairly rare in the Earth's upper layers. Others are still fairly common. Or at least common enough. Even iron, which lead the charge to the core during differentiation, is awfully common in the crust.
In fact, silicon (the second most abundant element in the crust) is only about ten times more common than iron, which is about as abundant as calcium (which you cite as being abundant). Aluminum is more abundant than calcium and is in fact only a few times less abundant than silicon. (Oxygen, incidentally, is the most common element in the crust, beating silicon out by a factor of a few.) In fact, most metals we're particularly attached to are about one-in-ten-thousandth as common as silicon. If you factor in the fact that they're usually found in clumps, that's a very cheerful thought.
(For the record.)
By the way, if your theory of asteroid delivery were true, I'm pretty sure we wouldn't have very much metals to work with. The Earth's crust is tectonically recycled every several hundred million years (any given chunk has been subducted and recycled several times, more or less; we estimated this my first year of grad school, but I forget the numbers exactly), so you could only rely on the metals delivered in the past few hundred million years. Asteroid impacts are getting rarer all the time, especially big ones.
Also, recall that a given asteroid is as likely as much rock as metal. In fact, Earth is more metal per mass than the average asteroid. (A lot of our silicates ended up in the Moon instead.) However, some asteroids are definitely mostly metallic and for mining purposes, that's a mad bonus. (For metals raining down from heaven, however, you have to factor in the fraction of the asteroids that isn't metal.)
Also, you're not factoring in the costs of bringing metals back to the Earth (if that's your goal). It's far more expensive to do that than to mine them here and will be for the foreseeable future. Of course, if your goal is to use them in space anyway, then it might be better to mine them there. (On the other hand, then you have to build the refining and construction infrastructure in space, which has a lot of challenges of its own.)
No, to deny merely means to refuse to accept the claim regardless of what evidence has been put forward. The word makes not assumptions as to whether the claim is true or untrue. It's possible to disagree with AGW without being a denier, but such a person would be open to the possibility of it being accurate.
These people are certainly deniers. Their counter-claims have little validity (most have none and many are outright fabrications) and most of their arguments lately have been ad hominem attacks on the researchers. So far, I have yet to see one of them acknowledge the strength of the data or admit to having made a mistake when they were shown to be wrong. They're deniers, pure and simple.