Right - because there's not currently much to do with raw iron in orbit. And why would there be, when it costs $12,000/kg?
But, if lunar iron can be delivered at $10-$100/kg, then it starts being valuable for building orbital structures and interplanetary ships.
And there's no particular reason that it would be particularly expensive to get lunar resources to orbit, or to Earth for that matter. After all, you don't need any rockets or rocket fuel - without an atmosphere you can use a rail gun, sling, or various other moon-mounted launch systems to get stuff into Earth orbit, or launch a bit faster and send it all the way to Earth - you just need to add a heat shield and parachutes, or some other landing system, for the final approach.
It's getting to that point that's going to be expensive, without a whole lot of immediate payoff. But those who lead the way will have an immense first-mover advantage as things accelerate from there. The Americas were colonized by European powers in order to profit Europe, but even before we won our independence, most of the wealth produced in America was staying here, and the canny businessmen who invested here made money hand over fist.
Space probably isn't going to have quite the same appeal for a long time, and may never have much to appeal to the common man (other than a place to escape from whatever insanity is taking place on Earth). But for a certain brand of skilled and ambitious dreamer it offers unlimited wealth and room for expansion. A chance to build businesses and societies from the ground up, in an environment that can sustain the fantasy of unlimited growth for centuries or millenia to come, while Earth is already beginning to collapse under the strain.
And Earth benefits, at a minimum, from unlimited mineral resources without an environmental mining cost, and the technology for building mostly-closed ecosystems, extremely efficient recycling, and all the other such things are are far, far more valuable to sustainable space colonies than planet-side living, but will be extremely valuable as we struggle to adapt to an ecosystem collapsing under the weight of our demands.
No, they're all about physics and engineering. When we first went to the moon we did the calculations on slide rules, and could only send large quantities of data as physical documents.
Electric cars were invented long before gasoline cars - but were abandoned once the internal combustion engine was invented, because we didn't have the battery technology to begin compete with gasoline.
We can't fly across the Atlantic at supersonic speeds because there's not enough of a business case to build and maintain supersonic aircraft just for trans-ocean flights, and nobody wants the noise pollution from using them for continental flights
We haven't gone back to the moon in any serious way, because the moon has nothing to offer until we're ready to move into space in a substantial way - which we haven't had the technology to do in a cost-appealing way. But we have been mapping it's resources in detail from orbit, against the day that we're ready. And we now have reusable rockets that are dropping the price of getting into space dramatically, with further dramatic improvements in cost and capacity looking likely within the next few years. The enabling technology is finally reaching the point where establishing real infrastructure in space is economically viable.
We're probably not quite there yet, but it's looking inevitable that we will get there within the next few decades, and so ambitious engineers are working hard to be ready, and ambitious businessmen are beginning to invest in being able to establish a first-mover advantage when the time is right. Much as the first European colonies in America weren't particularly profitable at first, but soon became very lucrative for early investors.
I don't believe we've even begun to exhaustively characterize all possible Lagrangian orbits, though I could be wrong about that.
But for starters, every single orbit that passed near you (as seen from "above"), substantially out-of-plane. You'd need a camera with a near 180* field of view along at least 1 axis, perpendicular to the ecliptic, to be able to spot all possible orbits, while still being able to spot an asteroid from hundreds of thousands of miles away, since those halos can be large. And you'd be haunted by those high angles suffering from the same poor illumination crescent that you get from Earth. You'd be much closer, so it's a reduced issue, but it still increases the maximum size of an unspottable object significantly.
You could no doubt make something work, it just seems much simpler to take a more typical telescope and put it a little closer to the sun, so that at least the vast majority of orbits would lie entirely within the viewing volume it sweeps out, and you'd have maximally-effective lighting conditions.
A 1% speed change... yeah, I guess after a year thing will have spread out enough it wouldn't be an issue. I'm sure it might re-coallesce eventually, but as you said, we should hopefully have better solutions at hand - if we haven't already mined the fragments to nothingness.
>So as to maximize the momentum change of the remaining mass. Fair enough. Except - maximizing the momentum change isn't actually your goal. Minimizing the risk to Earth is. Unless it's a *very* last-minute operation, you've got momentum to spare to deflect the asteroid onto a safe path. The risk, is that you fail to deflect a dangerously large fragment, which is then shielded from further efforts by a cloud of debris.
Except, you're not going to find things *at* L4/L5, you're going to find things "orbitting" them on all sorts of strange paths, and not necessarily just neatly planar ones.
1) because you don't want to see what's at *one* specific place - you want to see what's at *all* the specific places something might be
2) because if you're sitting at the L5 point, asteroids "orbiting" around that point could be passing you in any direction in 3D space - you'd want an omni-directional camera to avoid missing anything, and you'd still end up having a lot of things passing you closer closer to the sun so you couldn't see them. Much easier to sit with the sun at your back, and be relatively certain that everything of interest is going to pass in front of your uni-directional camera.
Except projectile orbital motion always brings you back to where you began. Every single one of those fragments will return to the detonation point at the end of every orbit. And the orbital period will not have been appreciably altered by a few m/s change, so they'll all be doing so at roughly the same time.
It's similar to the problem of trying to launch something into orbit using some sort of "cannon" on the planet's surface - it can't be done, because after one orbit the object will pass back through the point where the cannon was located, and impact with the surface. You can launch to escape velocity, or you can fire some secondary rockets to circularize your orbit, raising your perigee to avoid intersecting the planet. But on a purely ballistic orbital trajectory, it's a guaranteed impact within one orbit. Same thing trying to use air-breathing engines to reach orbit - so long as you can only apply thrust while inside the atmosphere, your orbit will always bring you back into the atmosphere.
Besides, once you're committing to not blowing it up symmetrically, why try to blow it up at all? The thing about a detonation, is that the center of mass always continues on the exact same trajectory it was on, so you're trying very hard to avoid leaving any major fragments traveling along along the original orbital path.
If instead you detonate off to the side, the jet of vaporized surface material (and reflected blast energy) act as a rocket engine, pushing the asteroid off course. And without fragments, you don't have to worry about how they get distributed.
As for there being fewer objects as they get larger - absolutely. But there's still an estimated 10,000 such objects larger than 10km in the asteroid belt alone, and we haven't spotted most of them.
And then there's the outer system objects. The real dark horse of the problem. Something trans-Neptunian, or from the Oort cloud, would be going screamingly fast by the time it got close in enough to have any chance of seeing it. Even with a broadly distributed asteroid-spotting system, we might only have months between it first becoming visible, and impact.
You are right - I should have said the sun needs to be on the same side of the object as us, not necessarily behind us. Venus and Mercury orbit separately from Earth, so they're often at the opposite side of the sun from us, and with the sun between us, they're illuminated.
Most near -Earth asteroids never get far enough from Earth for that to work though. They wander within about +/- 60 degrees of Earth in roughly the same orbit, and while they get better lit in terms of percentage of surface area the further they are from us, the inverse-square law means they don't really get much brighter as seen from Earth.
As for my "relative close up view", picture this: If we're trying to, from Earth, see something at the L5 point, 60 degrees away in our orbit, we're trying to see something from 1 AU away, with only a sliver of visible crescent
If instead we put that orbital telescope in a slightly smaller orbit around the sun than us, say at 0.9AU, and then have it look directly outward at our orbit, it will never be more than 0.1AU away from whatever it's photographing. And, in the time it takes it's faster orbit to lap us, going all the way around the sun from our perspective, it will get that 0.1AU close-up of the entire orbit of Earth. Including the L3 point that's forever invisible from Earth, on the exact opposite side of the sun, 2 AU away.
Not at all. If the terms of use do in fact transfer copyright ownership to them, then the first site you uploaded to would own the pictures, and you would be committing copyright infringement and fraud by uploading those images to the other sites without permission from the copyright holder (the first site).
Basically, as soon as you transfer the copyright to someone else, it's just as illegal for you to upload a copy of a photo you took, as it is to upload a pirated Hollywood movie.
>Fortunately, there's also this 1360 W/m^2 light flux near 1 AU making things significantly easier for us. Which is only useful if we are between the asteroid and the sun. That's my point. My shining a flashlight towards you doesn't help you see anything between us, except in silhouette. And there's no background in space for a silhouette to be visible against.
Worse, we're not actually looking. Current astronomy amounts to a few hundred people looking through drinking straws at the sky - the vast majority of the sky never gets looked at for long enough to spot any particular asteroid, even if it's perfectly visible in theory.
Plus, near-Earth asteroids are the most persistent threat - and they spend their entire orbital path quite near Earth's orbit, mostly locked into a 1:1 orbital resonance with Earth. Which means they're basically invisible from Earth, except when we happen to be inside their orbit near their closest approach. Any other time, they're lit from the wrong direction to be visible. And Lagrangian orbits tend to be chaotic strange-attractor type paths when viewed from the non-reference point of the planet they're locked in resonance with - there's no guarantee that they'd get anywhere close to Earth, and thus become visible, before they're on a path for collision. And a relatively minor collision or gravitational deflection at the wrong time could deflect an asteroid from a previously stable orbit onto an Earth-colliding path.
It's not that they're hard to see - they're just hard to see *from here*. One of the proposals (several, probably), is to put asteroid spotting space-telescope(s) in a solar orbit inside our own, looking outward, so that they'll circle the sun independently from us, and every time they lap us around the sun, they will have had a chance to photograph the entire near-Earth asteroid belt in full sunlight. That, and some good software to spot the asteroids amongst the camera noise, and we could actually be fairly confident we spotted everything big (at least that's not extremely dark-colored). That strategy also has the benefit that the telescope stays very close (relatively) to what it's photographing, making it much easier to spot smaller still-dangerous asteroids.
Perhaps, but I think you're underestimating how much energy is needed to move mountains. I'll run some numbers to confirm:
Lets take a modestly large asteroid, say 10km across, the lower extreme of the 10-80km size estimate for the dinosaur killer. There's an estimate 10,000 asteroids that size or larger. Maybe make it a bit bigger to make it an even 1000cubic kilometers, and we'll say it's a nice low-density icy asteroid, at around 1kg/L. So the whole thing masses about 10^15 kg
Then we'll hit it with a Tsar Bomba, the largest nuke ever developed,at 60 megatons, or 2.5x10^17J. Assuming we're able to convert 100% of that energy into accelerating asteroid fragments, we're talking 250J/kg = 250(m/s)^2 = 16m/s.
So I guess you're right - plenty of energy to accelerate the entire asteroid *way* past self-escape velocity. We could blow it into a million smithereens, never to re-coallesce. Well, except that all the smithereens are still in basically the same orbit, 16m/s isn't enough to make more than a tiny difference to that. And eventually their repeated close passes, collisions, and mututal gravitation will cause at least some of them to re-coallesce again. But that could take a very long time.
That's if we're lucky. The real question is could we make it break up in a way that we could be sure doesn't leave any major fragments on a collision course with Earth? And that could be a trick, as demolition of completely unknown rock formations can be more than a little chaotic. And the debris cloud could make a second attempt all but impossible. Becasue the real problem is that it's impossible to distribute the acceleration uniformly if it breaks up, and you'll have lots of debris that got barely any kick at all, and will float in lazy chaotic orbits around the remaining center of mass.
It means that the copyright owners have to pay the artists more rather than keeping the profit for themselves.
"Copyright owner" is generally trotted out to make it sound like the publisher, that usually owns the copyright, is actually the artist(s) that originally created the work.
If size was the issue, you'd see them for just as long coming as going. The problem is light. An unlit object in space is completely black in the visible spectrum. And black also happens to be the exact shade of empty space. The result being that anything coming at you from the general direction of the sun, and thus only being lit on its far side, is completely invisible.
You start getting a slight visible crescent as the angle between the asteroid and the sun expands, but we know the Earth probably has companion asteroid fields around its L4 and L5 points, we've spotted at least one when it wandered very close to us, but at 60 degrees from the sun the main field remains invisible from Earth.
They're starting too, which is why you're pissed off.
Every time people call you out for saying sexist or racist things - that's the check not being in the mail any more.
Every time you go looking for an apartment and don't have the vacancies mysteriously disappear - that's the check in the mail. Every time you've gotten a job rather than a better-qualified minority guy - that's the check in the mail. Every time you negotiate a higher salary or assert yourself in a meeting without being considered a pushy bitch - that's the check in the mail.
Those are all common problems women and minorities deal with on a regular basis - the fact that you never see them is because you're in the privileged class. Most racism, sexism, etc. is largely invisible to those not effected, precisely because it's only done to other people, so unless you're actually in the room and paying attention when it happens to someone else, you'll never see it.
It is. But right now, as a white, CIS male, we are in the historic majority, and almost everything about society caters to us as being "a normal person", so that everybody else has to adapt to function in a society designed for people like us.
That necessarily means that as society embraces diversity, it *must* turn partially away from us, in order to embrace all the other kinds of "normal" that actually exist. And in order to continue to function effectively, we are going to have to learn to adapt to the unfolding, less discriminatory new "normal".
And of course, as that happens it's going to feel like we're being discriminated against, because people are becoming less tolerant of us. That's not discrimination though (mostly, there's always exceptions) - that's just loss of privilege. We're just starting to have to face the same difficulties of adapting to a society designed for an alien "normal" that everyone else has always had to deal with.
Of course then you bring in one of the articles' findings - if the cone is too small, the asteroid will re-coallesce. And one of the big problems with shattering as a goal is that you don't significantly change the path of the center of mass - so Earth will still be right in the bullseye.
That's why the asteroid-spotting plans typically call for an array of a low-magnification, wide field of view telescopes. I believe one of the major plans calls for dozens of telescopes that re-image the entire night sky (well, at least within several degrees of the ecliptic), many times per year (possibly even weekly?), so that computer analysis could rapidly identify and track each asteroid and compute its orbit. It wouldn't be perfect, but it would get most of the big stuff we really need to be worried about.
I'm trying to figure out what you might mean, given the fact that asteroids are typically invisible to radio telescopes, and the amount of radio power you'd need to broadcast to illuminate even a tiny sliver of the night sky brightly enough to spot an asteroid from half a billion km away would be mind-boggling.
And no need for magical detection - we just need some decent array of IR telescopes capable of seeing back-lit asteroids, that can cover enough of the sky to map out the orbits of everything of appreciable size. We've already had a few such projects get scrapped due to lack of funding - all the magic we'd need is for someone with money to take the threat seriously.
> if you're not at the center of mass, your rocket fuel will be spent to make the rock spin. That should be "in line with" rather than "at", but in that case yes, some of it will. But unless you're more than 45 degrees from vertical, most of it will go towards deflection.
There's always a direct line between you and the center of mass, and it's easy to find it: just dangle a sensitive plumb-bob to find exactly which direction gravity is pulling in. Your rocket will need adjustable legs so that it can land vertically - but so long as it's vertical, the thrust will act through a point very close to the center of mass. It may be off a bit if the asteroid is significantly non-spherical, but that will become very rapidly apparent as you begin to apply thrust, and you can modify your thrust vector to compensate. (a.k.a. tilt the rocket on its landing feet)
As for the rest - you're grossly overestimating the influence of the asteroid's gravity. An asteroid over 7km across will have about 1/10,000th the surface gravity of Earth. A fully fueled Falcon 9 Block 5 549 tonnes at takeoff. On the asteroid, it would weigh the same as 55kg (121lb) on Earth. If you could get a good grip, you could lift it all by yourself.
All other forces would be dwarfed by the thrust of the rocket. So long as the rocket exhaust can be vectored, as most can these days, you won't have any problems with falling over.
The surface might collapse, that is a valid risk, but that could be mitigated by scanning the surface with ground-penetrating radar before landing. Or bombing a prospective landing site with small impactors before committing. Or even just installing a slightly more powerful landing rocket, so that you can immediately cut the main engines and re-launch if the ground starts to give way as you throttle up. It isn't going to take much rocket to provide 6N of thrust to launch.
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But first, you need to stake your claim. And then defend it against claim-jumpers.
Right - because there's not currently much to do with raw iron in orbit. And why would there be, when it costs $12,000/kg?
But, if lunar iron can be delivered at $10-$100/kg, then it starts being valuable for building orbital structures and interplanetary ships.
And there's no particular reason that it would be particularly expensive to get lunar resources to orbit, or to Earth for that matter. After all, you don't need any rockets or rocket fuel - without an atmosphere you can use a rail gun, sling, or various other moon-mounted launch systems to get stuff into Earth orbit, or launch a bit faster and send it all the way to Earth - you just need to add a heat shield and parachutes, or some other landing system, for the final approach.
It's getting to that point that's going to be expensive, without a whole lot of immediate payoff. But those who lead the way will have an immense first-mover advantage as things accelerate from there. The Americas were colonized by European powers in order to profit Europe, but even before we won our independence, most of the wealth produced in America was staying here, and the canny businessmen who invested here made money hand over fist.
Space probably isn't going to have quite the same appeal for a long time, and may never have much to appeal to the common man (other than a place to escape from whatever insanity is taking place on Earth). But for a certain brand of skilled and ambitious dreamer it offers unlimited wealth and room for expansion. A chance to build businesses and societies from the ground up, in an environment that can sustain the fantasy of unlimited growth for centuries or millenia to come, while Earth is already beginning to collapse under the strain.
And Earth benefits, at a minimum, from unlimited mineral resources without an environmental mining cost, and the technology for building mostly-closed ecosystems, extremely efficient recycling, and all the other such things are are far, far more valuable to sustainable space colonies than planet-side living, but will be extremely valuable as we struggle to adapt to an ecosystem collapsing under the weight of our demands.
No, they're all about physics and engineering. When we first went to the moon we did the calculations on slide rules, and could only send large quantities of data as physical documents.
Electric cars were invented long before gasoline cars - but were abandoned once the internal combustion engine was invented, because we didn't have the battery technology to begin compete with gasoline.
We can't fly across the Atlantic at supersonic speeds because there's not enough of a business case to build and maintain supersonic aircraft just for trans-ocean flights, and nobody wants the noise pollution from using them for continental flights
We haven't gone back to the moon in any serious way, because the moon has nothing to offer until we're ready to move into space in a substantial way - which we haven't had the technology to do in a cost-appealing way. But we have been mapping it's resources in detail from orbit, against the day that we're ready. And we now have reusable rockets that are dropping the price of getting into space dramatically, with further dramatic improvements in cost and capacity looking likely within the next few years. The enabling technology is finally reaching the point where establishing real infrastructure in space is economically viable.
We're probably not quite there yet, but it's looking inevitable that we will get there within the next few decades, and so ambitious engineers are working hard to be ready, and ambitious businessmen are beginning to invest in being able to establish a first-mover advantage when the time is right. Much as the first European colonies in America weren't particularly profitable at first, but soon became very lucrative for early investors.
Sort of - if posting to Facebook actually contributed something of value to the world.
I don't believe we've even begun to exhaustively characterize all possible Lagrangian orbits, though I could be wrong about that.
But for starters, every single orbit that passed near you (as seen from "above"), substantially out-of-plane. You'd need a camera with a near 180* field of view along at least 1 axis, perpendicular to the ecliptic, to be able to spot all possible orbits, while still being able to spot an asteroid from hundreds of thousands of miles away, since those halos can be large. And you'd be haunted by those high angles suffering from the same poor illumination crescent that you get from Earth. You'd be much closer, so it's a reduced issue, but it still increases the maximum size of an unspottable object significantly.
You could no doubt make something work, it just seems much simpler to take a more typical telescope and put it a little closer to the sun, so that at least the vast majority of orbits would lie entirely within the viewing volume it sweeps out, and you'd have maximally-effective lighting conditions.
A 1% speed change... yeah, I guess after a year thing will have spread out enough it wouldn't be an issue. I'm sure it might re-coallesce eventually, but as you said, we should hopefully have better solutions at hand - if we haven't already mined the fragments to nothingness.
>So as to maximize the momentum change of the remaining mass.
Fair enough. Except - maximizing the momentum change isn't actually your goal. Minimizing the risk to Earth is. Unless it's a *very* last-minute operation, you've got momentum to spare to deflect the asteroid onto a safe path. The risk, is that you fail to deflect a dangerously large fragment, which is then shielded from further efforts by a cloud of debris.
Except, you're not going to find things *at* L4/L5, you're going to find things "orbitting" them on all sorts of strange paths, and not necessarily just neatly planar ones.
1) because you don't want to see what's at *one* specific place - you want to see what's at *all* the specific places something might be
2) because if you're sitting at the L5 point, asteroids "orbiting" around that point could be passing you in any direction in 3D space - you'd want an omni-directional camera to avoid missing anything, and you'd still end up having a lot of things passing you closer closer to the sun so you couldn't see them. Much easier to sit with the sun at your back, and be relatively certain that everything of interest is going to pass in front of your uni-directional camera.
Except projectile orbital motion always brings you back to where you began. Every single one of those fragments will return to the detonation point at the end of every orbit. And the orbital period will not have been appreciably altered by a few m/s change, so they'll all be doing so at roughly the same time.
It's similar to the problem of trying to launch something into orbit using some sort of "cannon" on the planet's surface - it can't be done, because after one orbit the object will pass back through the point where the cannon was located, and impact with the surface. You can launch to escape velocity, or you can fire some secondary rockets to circularize your orbit, raising your perigee to avoid intersecting the planet. But on a purely ballistic orbital trajectory, it's a guaranteed impact within one orbit. Same thing trying to use air-breathing engines to reach orbit - so long as you can only apply thrust while inside the atmosphere, your orbit will always bring you back into the atmosphere.
Besides, once you're committing to not blowing it up symmetrically, why try to blow it up at all? The thing about a detonation, is that the center of mass always continues on the exact same trajectory it was on, so you're trying very hard to avoid leaving any major fragments traveling along along the original orbital path.
If instead you detonate off to the side, the jet of vaporized surface material (and reflected blast energy) act as a rocket engine, pushing the asteroid off course. And without fragments, you don't have to worry about how they get distributed.
As for there being fewer objects as they get larger - absolutely. But there's still an estimated 10,000 such objects larger than 10km in the asteroid belt alone, and we haven't spotted most of them.
And then there's the outer system objects. The real dark horse of the problem. Something trans-Neptunian, or from the Oort cloud, would be going screamingly fast by the time it got close in enough to have any chance of seeing it. Even with a broadly distributed asteroid-spotting system, we might only have months between it first becoming visible, and impact.
You are right - I should have said the sun needs to be on the same side of the object as us, not necessarily behind us. Venus and Mercury orbit separately from Earth, so they're often at the opposite side of the sun from us, and with the sun between us, they're illuminated.
Most near -Earth asteroids never get far enough from Earth for that to work though. They wander within about +/- 60 degrees of Earth in roughly the same orbit, and while they get better lit in terms of percentage of surface area the further they are from us, the inverse-square law means they don't really get much brighter as seen from Earth.
As for my "relative close up view", picture this: If we're trying to, from Earth, see something at the L5 point, 60 degrees away in our orbit, we're trying to see something from 1 AU away, with only a sliver of visible crescent
If instead we put that orbital telescope in a slightly smaller orbit around the sun than us, say at 0.9AU, and then have it look directly outward at our orbit, it will never be more than 0.1AU away from whatever it's photographing. And, in the time it takes it's faster orbit to lap us, going all the way around the sun from our perspective, it will get that 0.1AU close-up of the entire orbit of Earth. Including the L3 point that's forever invisible from Earth, on the exact opposite side of the sun, 2 AU away.
Not at all. If the terms of use do in fact transfer copyright ownership to them, then the first site you uploaded to would own the pictures, and you would be committing copyright infringement and fraud by uploading those images to the other sites without permission from the copyright holder (the first site).
Basically, as soon as you transfer the copyright to someone else, it's just as illegal for you to upload a copy of a photo you took, as it is to upload a pirated Hollywood movie.
>Fortunately, there's also this 1360 W/m^2 light flux near 1 AU making things significantly easier for us.
Which is only useful if we are between the asteroid and the sun. That's my point. My shining a flashlight towards you doesn't help you see anything between us, except in silhouette. And there's no background in space for a silhouette to be visible against.
Worse, we're not actually looking. Current astronomy amounts to a few hundred people looking through drinking straws at the sky - the vast majority of the sky never gets looked at for long enough to spot any particular asteroid, even if it's perfectly visible in theory.
Plus, near-Earth asteroids are the most persistent threat - and they spend their entire orbital path quite near Earth's orbit, mostly locked into a 1:1 orbital resonance with Earth. Which means they're basically invisible from Earth, except when we happen to be inside their orbit near their closest approach. Any other time, they're lit from the wrong direction to be visible. And Lagrangian orbits tend to be chaotic strange-attractor type paths when viewed from the non-reference point of the planet they're locked in resonance with - there's no guarantee that they'd get anywhere close to Earth, and thus become visible, before they're on a path for collision. And a relatively minor collision or gravitational deflection at the wrong time could deflect an asteroid from a previously stable orbit onto an Earth-colliding path.
It's not that they're hard to see - they're just hard to see *from here*. One of the proposals (several, probably), is to put asteroid spotting space-telescope(s) in a solar orbit inside our own, looking outward, so that they'll circle the sun independently from us, and every time they lap us around the sun, they will have had a chance to photograph the entire near-Earth asteroid belt in full sunlight. That, and some good software to spot the asteroids amongst the camera noise, and we could actually be fairly confident we spotted everything big (at least that's not extremely dark-colored). That strategy also has the benefit that the telescope stays very close (relatively) to what it's photographing, making it much easier to spot smaller still-dangerous asteroids.
Perhaps, but I think you're underestimating how much energy is needed to move mountains. I'll run some numbers to confirm:
Lets take a modestly large asteroid, say 10km across, the lower extreme of the 10-80km size estimate for the dinosaur killer. There's an estimate 10,000 asteroids that size or larger. Maybe make it a bit bigger to make it an even 1000cubic kilometers, and we'll say it's a nice low-density icy asteroid, at around 1kg/L. So the whole thing masses about 10^15 kg
Then we'll hit it with a Tsar Bomba, the largest nuke ever developed,at 60 megatons, or 2.5x10^17J. Assuming we're able to convert 100% of that energy into accelerating asteroid fragments, we're talking 250J/kg = 250(m/s)^2 = 16m/s.
So I guess you're right - plenty of energy to accelerate the entire asteroid *way* past self-escape velocity. We could blow it into a million smithereens, never to re-coallesce. Well, except that all the smithereens are still in basically the same orbit, 16m/s isn't enough to make more than a tiny difference to that. And eventually their repeated close passes, collisions, and mututal gravitation will cause at least some of them to re-coallesce again. But that could take a very long time.
That's if we're lucky. The real question is could we make it break up in a way that we could be sure doesn't leave any major fragments on a collision course with Earth? And that could be a trick, as demolition of completely unknown rock formations can be more than a little chaotic. And the debris cloud could make a second attempt all but impossible. Becasue the real problem is that it's impossible to distribute the acceleration uniformly if it breaks up, and you'll have lots of debris that got barely any kick at all, and will float in lazy chaotic orbits around the remaining center of mass.
Don't believe me - try it for yourself. Start *really* paying attention to how people around you get treated. Especially when assholes are involved.
It means that the copyright owners have to pay the artists more rather than keeping the profit for themselves.
"Copyright owner" is generally trotted out to make it sound like the publisher, that usually owns the copyright, is actually the artist(s) that originally created the work.
You know, you're right! I apparently replied to the wrong comment, and then completely failed to notice.
If size was the issue, you'd see them for just as long coming as going. The problem is light. An unlit object in space is completely black in the visible spectrum. And black also happens to be the exact shade of empty space. The result being that anything coming at you from the general direction of the sun, and thus only being lit on its far side, is completely invisible.
You start getting a slight visible crescent as the angle between the asteroid and the sun expands, but we know the Earth probably has companion asteroid fields around its L4 and L5 points, we've spotted at least one when it wandered very close to us, but at 60 degrees from the sun the main field remains invisible from Earth.
They're starting too, which is why you're pissed off.
Every time people call you out for saying sexist or racist things - that's the check not being in the mail any more.
Every time you go looking for an apartment and don't have the vacancies mysteriously disappear - that's the check in the mail.
Every time you've gotten a job rather than a better-qualified minority guy - that's the check in the mail.
Every time you negotiate a higher salary or assert yourself in a meeting without being considered a pushy bitch - that's the check in the mail.
Those are all common problems women and minorities deal with on a regular basis - the fact that you never see them is because you're in the privileged class. Most racism, sexism, etc. is largely invisible to those not effected, precisely because it's only done to other people, so unless you're actually in the room and paying attention when it happens to someone else, you'll never see it.
>Isn't diversity... EVERYONE?
It is. But right now, as a white, CIS male, we are in the historic majority, and almost everything about society caters to us as being "a normal person", so that everybody else has to adapt to function in a society designed for people like us.
That necessarily means that as society embraces diversity, it *must* turn partially away from us, in order to embrace all the other kinds of "normal" that actually exist. And in order to continue to function effectively, we are going to have to learn to adapt to the unfolding, less discriminatory new "normal".
And of course, as that happens it's going to feel like we're being discriminated against, because people are becoming less tolerant of us. That's not discrimination though (mostly, there's always exceptions) - that's just loss of privilege. We're just starting to have to face the same difficulties of adapting to a society designed for an alien "normal" that everyone else has always had to deal with.
Awesome. I'm far more confident of such a project getting adequately funded if someone thinks there's money to be made.
Of course then you bring in one of the articles' findings - if the cone is too small, the asteroid will re-coallesce. And one of the big problems with shattering as a goal is that you don't significantly change the path of the center of mass - so Earth will still be right in the bullseye.
That's why the asteroid-spotting plans typically call for an array of a low-magnification, wide field of view telescopes. I believe one of the major plans calls for dozens of telescopes that re-image the entire night sky (well, at least within several degrees of the ecliptic), many times per year (possibly even weekly?), so that computer analysis could rapidly identify and track each asteroid and compute its orbit. It wouldn't be perfect, but it would get most of the big stuff we really need to be worried about.
I'm trying to figure out what you might mean, given the fact that asteroids are typically invisible to radio telescopes, and the amount of radio power you'd need to broadcast to illuminate even a tiny sliver of the night sky brightly enough to spot an asteroid from half a billion km away would be mind-boggling.
Quite.
And no need for magical detection - we just need some decent array of IR telescopes capable of seeing back-lit asteroids, that can cover enough of the sky to map out the orbits of everything of appreciable size. We've already had a few such projects get scrapped due to lack of funding - all the magic we'd need is for someone with money to take the threat seriously.
> if you're not at the center of mass, your rocket fuel will be spent to make the rock spin.
That should be "in line with" rather than "at", but in that case yes, some of it will. But unless you're more than 45 degrees from vertical, most of it will go towards deflection.
There's always a direct line between you and the center of mass, and it's easy to find it: just dangle a sensitive plumb-bob to find exactly which direction gravity is pulling in. Your rocket will need adjustable legs so that it can land vertically - but so long as it's vertical, the thrust will act through a point very close to the center of mass. It may be off a bit if the asteroid is significantly non-spherical, but that will become very rapidly apparent as you begin to apply thrust, and you can modify your thrust vector to compensate. (a.k.a. tilt the rocket on its landing feet)
As for the rest - you're grossly overestimating the influence of the asteroid's gravity. An asteroid over 7km across will have about 1/10,000th the surface gravity of Earth. A fully fueled Falcon 9 Block 5 549 tonnes at takeoff. On the asteroid, it would weigh the same as 55kg (121lb) on Earth. If you could get a good grip, you could lift it all by yourself.
All other forces would be dwarfed by the thrust of the rocket. So long as the rocket exhaust can be vectored, as most can these days, you won't have any problems with falling over.
The surface might collapse, that is a valid risk, but that could be mitigated by scanning the surface with ground-penetrating radar before landing. Or bombing a prospective landing site with small impactors before committing. Or even just installing a slightly more powerful landing rocket, so that you can immediately cut the main engines and re-launch if the ground starts to give way as you throttle up. It isn't going to take much rocket to provide 6N of thrust to launch.