"Not nearly representative enough?" What does that mean, exactly? Would you suggest that we abandon the representative ideal altogether and go for pure democracy? I won't bother to explain what's wrong with that idea. Read some Plato for insight, if you're so inclined.
If we're on the same page about the democracy thing, then it's really just a matter of degrees. When I go to the polls-- next month, in fact-- I will vote for my chosen representative. Why I vote for him is entirely up to me; maybe I agree with his position, maybe I respect his character, maybe I just like the way he parts his hair. Whatever my reason, I choose.
At the end of that day, one of the candidates will have more votes than the other or others. That guy goes to the legislature.
Therefore, our system as it stands now is directly representative of the majority. That's how our government is designed to work, and it works well.
Your suggestion that we "get rid of winner take all" is confusing to me, because it seems to contradict the idea that the government represents the majority. You can't say, "the government shall be composed of representatives elected by the majority, and these four legally recognized minorities, to whom we shall throw a bone every two years." That's not fair, and it's not practical. The only reasonable system of representative government is the idea of representation of the majority.
Worked for whom? Why, for the people for whom the system is intended to work, of course. That set started with white male property owners and has grown larger over time. Today that set includes any recognized citizen (by birth or naturalization) over the age of 18 of any race, gender, or national origin.
And I disagree with your assertion that the American system of government doesn't work for "the poor or the recent migrants." Our country offers as many opportunities to poor people as any country in the world, and more than most. My girlfriend's father, for example, immigrated to this country in 1975. In Vietnam, he had been a lawyer and a politician. After he immigrated, he took a job as a janitor while he attended night school to learn English and to become an accountant. Today he makes an upper-middle-class living working for city government and as a real estate agent. His wife works a part-time job as a secretary because she wants to; they don't need the money. They've put two kids through college, medical school (my girlfriend), and law school (her brother). Our government worked just fine for them, as it continues to now.
And as for the rest of your comment... where did you get your education? You start by saying the idea of executive veto is "rediculous," but you don't say why. Then you say that the founding fathers "only had monarchies to examine," which is demonstrably false. The founding fathers were, to a man, classically educated men. They were students of history, and all intimately familiar with the democratic and republican ideals of government. Saying they "only had monarchies to examine" is so wrong it's practically laughable.
Finally...
I never cease to be amazed at the self-congratulatory arrogance of the common American citizen.
Get used to it, friend. Our country, while certainly flawed in many ways and of course with an imperfect history, is nonetheless the finest nation the world has ever seen.
Your post was, of course, utter bullshit. The bit about "there is so little difference [between the parties] as to be insulting," particularly so. If you let your political opinions get sufficiently out of whack with the mainstream, then I suppose it's possible that Republicans and Democrats might look pretty much the same to you. Both parties advocate various degrees of laisse faire capitalism, for example. This is not inherently a bad thing.
Our system of government is not designed to be the best of all possible systems. It's designed to be just good enough. That's why it's stood unchallenged for over 225 years.
And your little remark about "the illusion of democracy?" The United States of America is not now, and never has been, a democracy. Pure democracy is a system fraught with more flaws than you can shake a pointed stick at. After all, the saying goes that a dictatorship is a country where you have to do what one stupid asshole says, and a democracy is a country where you have to do what one million stupid assholes say.
So the USA is not a democracy. It's a representative republic. Is this the perfect system? I doubt it. But is it the best one we've-- as a species, I mean-- come up with so far? Yes, definitely. Name one government that has worked as long or as well as the United States'.
only the copyright holder (the U.S. government) could re-release it
First, traditionally works commissioned by the government have been placed in the public domain. There is no copyright holder on those works. Does that mean that nobody could re-release them?
But still, this gets right back to the "why bother" question. You said that code released under two licenses-- that's what you mean by "dual-licensing," right?-- can be applied to both proprietary uses and GPL-based projects, but that's unnecessary. Software released into the public domain can be used for proprietary uses and for GPL-licensed uses. So can software released under the BSD license.
You also said, "The government would have to be convinced of the benefits of GPL'd open source." Seems to me there aren't any.
Your post was interesting until it dissolved into science fiction. Sometimes it's disappointing to see that people, especially educated, well-read people, have trouble distinguishing between the two.
The bit about water, though... if it turns out that there is water on the moon-- this is still unconfirmed-- and that it's of sufficient quantity to be useful, then you've got a good point. Of course, if the water we think we've seen is nothing more than a hoar-frost, then it's back to the drawing board again.
I should look up the figures, but I'm too lazy. People often talk about cracking water into oxygen and hydrogen with electrolysis. I wonder how dense LH2 and LO2 are compared to liquid water? How silly would it be to ship LH2 and LO2 to orbit, then render it into pure water through combustion?
So let me see if I get your scenario: the government sponsors some work, and the product of that work is some code. That code is released to the public under the GPL. Somebody else takes that code, without changing it, and releases it under a more liberal license. You're saying this would be allowed, because the second release of the code is not derivative of the first, GPL'd, release.
That's clearly not true, though. The second release would obviously be derived from the first release in that case.
If what you're saying, on the other hand, is that the government itself could choose to re-release the software under a more liberal license, that's certainly true. But it begs the question of why, then, anyone would go to the trouble of releasing under the GPL at all. Just go with the most liberal license-- which would be no license at all, of course, but simply assignment to the public domain.
The GPL is not ambiguous on this issue. One software has been released under the GPL, that software or any work derived from that software may not be released under any more liberal license than the GPL. That is, in fact, the whole point of the GPL. Which is why it's totally inappropriate for government-sponsored work.
Except that the verbiage of the GPL says that the license must be applied to all derivative works. In your example, a re-release of version 1.0 under a more liberal license than the GPL would not be permitted, because the re-released code would be considered a derivative work.
If you read the GPL carefully, you'll find that once you're in it, it's not possible to get out of it again.
It's a long way from bauxite to aluminum sheeting. In order for the moon to be a useful source of raw materials for spacecraft, we'd have to do an unbelievable amount of work: smelting, refining, fabricating, and so on. It probably wouldn't be cost-effective. We can do all that stuff on Earth so much cheaper and more easily that it offsets the added cost of lifting materials to orbit.
You're right, but think practically instead of theoretically for a minute. Let's say you want to launch a thousand-ton spaceship to Mars. (Pulled that figure out of my ear, just for discussion purposes. For perspective, that's about the mass of two fully-loaded 747s. That's unrealistic, but it gives us a figure to start with.) Launching such a spaceship in one big piece probably wouldn't be practical; for comparison's sake, the Apollo command capsule and moon lander, together, weighed about 50 tons, and it took the 3,100 ton Saturn V to fling it toward the moon. So launching a 1,000 ton spaceship to Mars from the Earth's surface would be a challenge, to say the least.
Instead, you'd loft the pieces of the Mars spaceship to some stable point in space and assemble it there, then fire it off toward parts elsewhere. The obvious thing to do would be to build the spaceship in low Earth orbit, just like we're building the space station now. But that's not especially helpful, because it takes very nearly the same amount of energy to lift a spaceship out of low Earth orbit as it takes to lift it all the way from the surface of the Earth. So you're still talking about some monster rocket engines.
A better idea would be to assemble the spaceship pieces at L1. You still have to expend a lot of energy to get all the pieces up there, but you don't have to do it all at once. And when it comes to actually setting off for Mars, you can use a slingshot maneuver around the Earth to get some monster delta v without having to burn rocket engines for it.
So getting stuff to L1 still requires a lot of energy, but we can expend that energy in little parcels rather than all at once. And getting from L1 to points elsewhere in the solar system is a lot easier than getting there from Earth or Earth orbit.
I can't speak about the Earth-Sun L4 and L5 points, but the Earth-Jupiter L4 and L5 points are sufficiently stable-- that is, their regions of stability are sufficiently large-- that they've become home to over 1,500 asteroids. They're called Trojan asteroids: 588 Achilles, 624 Hektor, and 911 Agamemnon, and so on. You can find the whole list here if you're interested.
There are, if memory serves me right, 6 asteroids in a Trojan relationship with Mars, too.
This also means thet the "points" are actually regions.
Well... no, not exactly. The libration points are just that: points. While it's true that nothing is a point-mass, bodies act like point masses because the net sum of all the gravitational forces between all the atoms in both objects add up to be exactly the same as if the bodies were both dimensionless objects of equal mass. This is true in all cases except when you're actually inside a body.
If you put a body exactly at the L4 point (say, the Earth-Jupiter L4 point) and nudge it slightly out of position, it will fall back toward the L4 point and oscillate there. If you nudge it too far, though, the body will fall away from the L4 point and go into an orbit around the Sun. This defines the notion of a "region of stability" around the L4 point. The same is true of L5. That's why asteroids tend to collect there; they're all oscillating around the L4 and L5 points in the Earth-Jupiter system.
But that's not the same thing as saying that L4 and L5 are regions rather than points. The situation is more complex than that.
No, it takes more energy. Earth's gravity well is said to be about 6,400 kilometers deep. That is, escaping the Earth's gravity requires the same amount of energy as climbing out of a well 6,400 kilometers deep. (This isn't meant to be a literal expression of distance; it's just a generalization. See Clarke's The Exploration of Space for a good explanation, I think.)
So climbing out of Earth's gravity well requires a lot of energy; can you imagine pulling a spacecraft out of a 6,400 kilometer deep hole? That's a lot of pulling. Of course, the radius of the moon isn't anywhere near far enough to be truly free of Earth's gravity, but talking about it in terms of absolutes gives us a good idea of the energy involved.
If I had about two more cups of coffee in me, I'd do some back-of-the-napkin calculations to estimate the energy required, in joules per kilogram, to loft an object-- starting with U = GMm/r-- but I'm not that motivated.
So even if you make it 5/6 of the way to the moon, you can't just coast up the rest of the way. You still have to expend energy-- a lot of it, proportional to the mass of your spaceship-- to lift yourself that last 40,000 miles or so. Of course, we would do this by expending all the energy in one big impulse at low Earth orbit, putting the spaceship into an elliptical orbit with apogee at the L4 or L5 point, then another impulse at apogee to put the spaceship into stable orbit. The difference in energy between a trip to L1 and a trip to L4 or L5 would be evident by the delta v needed-- and, consequently, the size of the impulse required-- to create the initial transfer orbit. It'd be a nontrivial difference.
As noted elsewhere, the SOHO is at the Earth-Sun L1 point, inside the orbit of the Earth. We've been talking about the Earth-moon L1 point, between the Earth and the moon. Different things.
As for your other question, a libration (or Lagrange, or Lagrangian, or whatever) point is just that: a point. L1 is the dimensionless point in space where the gravitational forces pulling toward Earth and toward the moon exactly equal one another. If the center of mass (also a dimensionless point) of a body is parked exactly on the libration point, then the body will experience no net gravitational pull in either direction, because the forces will be balanced.
Of course, keeping the center of mass of a body parked on the L1 point is not a trivial thing. Even the pressure of light from the sun will be enough to nudge it slightly out of position, and once out of position, the body will tend to fall further out of position due to gravity of either the Earth or the moon. So the real question is this: how gentle or steep is the gravity gradient surrounding the L1 point? In other words, how much does the force of gravity change over time as one moves in and out of the L1 point?
Remember that gravity is an inverse-square relation. The force varies with the square of the distance between two objects. So when the two objects are close together, the force varies a lot over a small distance. But when the objects are farther apart, the force varies less over the same distance. When bodies are far, the gravitational gradient (distance rate change of force) between them is said to be shallow or smooth, and when they're close together it's said to be steep.
All that adds up to is this: it's easier to keep a body at the Earth-Sun L1 point than at the Earth-moon L1 point because the gravitational gradient is steeper in the Earth-moon system than in the Earth-Sun system.
Now, the L4 and L5 points are different. L4 and L5 are local attractors; you could put an object in orbit around L4 or L5 itself, and it would tend toward stability. So it's easier to put multiple objects at L4 and L5 than it is to put them at L1, L2, or L3.
Only problem with using a liquid as a shield is that when the station is in darkness it'll be frozen....
It's pretty trivial, both in terms of effort and in terms of mass, to build insulated water tanks that keep water liquid over a vast range of temperatures. It'd be easier to keep the water liquid all the time than to pump energy into it to thaw it when needed.
The SOHO satellite isn't interacting with other objects, though. Any manned-- or even occasionally manned-- space station will have to dock with visiting spacecraft and whatnot, which will involve significant transfers of momentum. Keeping an L1 space station on station will be a harder job than simply keeping the SOHO on station.
Not impossible, but hard.
The danger, of course, is that an L1 space station could drift so far from the actual L1 point in space that it requires more delta v to move it back than the structure can withstand. That'd be a worst-case kind of disaster, though.
I thought Lagrange points collected a lot of dust, which would be bad for optics.
L4 and L5 are gravitationally stable points, so there may be collections of dust there. (In the Jupiter-Sun L4 and L5 points, there are collections of asteroids.)
But L1, L2, and L3 are all gravitationally unstable. A body at one of those three points will tend to fall away from the point rather than staying in it.
L4 and L5 are like being at the bottom of a depression: whichever way you go, gravity tends to pull you back toward the middle. L1, L2, and L3 are more like being at the top of a hill. If you're right at the very center, you're fine. But if you're even slightly off-center, gravity will pull you down the hill.
In theory, L1 ought to be the cleanest point between the Earth and the moon. Nothing can stay in orbit at L1 without active station-keeping.
Gee, Doc, have you done any payload arithmetic lately? Lofting lead is possibly the dumbest idea ever-- no offense intended.
In terms of pounds of mass per gray-- meaning the amount of radiation that can be absorbed in a given unit of mass-- water is a better radiation shield than lead. Dual-purpose, too.
Useful in what sense? There's nothing on the moon that we need or want, at least not with current technologies at hand. If you put some kind of space station in a gravitationally unstable point, like L1, then you can use it to launch trips to points elsewhere very inexpensively. (Assuming the cost of maintaining the orbit of the L1 station turns out to be manageable.) Once you're at L1, you've basically spent all the energy you need to spend to get out of the Earth-moon system. Refueling or restaging at L1 for longer trips to Mars and elsewhere makes a lot of sense.
Science fiction from the late 1900's aside, moon bases just don't make that much sense right now.
a space station at a LaGrange point (in this case L1) wouldn't have to use thrusters to maintain a stable orbit and would never leave it's stable orbit around the earth
That's not true. L1, L2, and L3 are all gravitationally unstable points. A space station at L1, if nudged out of position even slightly, will tend to spiral inward toward Earth or outward toward the moon. The L4 and L5 points are the only stable Lagrangian points in a two-body system.
Why not just build on the moon? Why stop at 5/6 the way to the moon?
Because the whole point of staging at L1 is that it allows low-energy transfers to other points in the solar system. Launching a trip to Mars, for example, from L1 would require much less energy than from either the surface of the Earth, or low Earth orbit, or the surface of the moon.
Of course, this ignores the biggest problem with the L1 point: it's unstable. A body placed at L1 will tend to either fall inward toward the Earth or outward toward the moon at the slightest push. Any space station at L1 will have to correct its position regularly, probably using simple chemical rockets. These rockets will have to be refueled periodically and so on, making for a nontrivial amount of effort to keep an L1 space station in position.
The L4 and L5 points, on the other hand, are gravitationally stable. If a body at L4 or L5 starts to drift out of position-- due to a collision or outgassing or whatever-- the Earth-moon system will tend to pull it back to the point of stability again. But since L4 and L5 are farther from Earth than L1 is, it takes more time and energy to get there from LEO.
I really wasn't planning on responding at all to this thread, because this sort of argument usually just ends up making me mad. But in all the comments I've read so far, this is the only one that gets it right.
Code released under a nonrestrictive license like the BSD one can later be re-released by another party under the GPL. There's no rule against this whatsoever.
Code released under the GPL, however, can never be re-released under another license. Ever.
It's clear that the right course of action is for the government to make code available under the least restrictive terms possible. If somebody wants to then take one or another program and "GPL-ize" is, they're free to do so.
This will, of course, not satisfy RMS. But anybody who's familiar with my past comments on this subject already knows how I feel about that.
Slashdot Mirror
It should be noted that "web log" is actually pronounced "wee-blog." Thus was the term "blog" coined.
The Isle of Man is not a sovereign nation. Never has been. So the Tynwald doesn't count as a national government.
If somebody had suggested San Marino, they might have at least had a point. But the Isle of Man? Hardly.
"Not nearly representative enough?" What does that mean, exactly? Would you suggest that we abandon the representative ideal altogether and go for pure democracy? I won't bother to explain what's wrong with that idea. Read some Plato for insight, if you're so inclined.
If we're on the same page about the democracy thing, then it's really just a matter of degrees. When I go to the polls-- next month, in fact-- I will vote for my chosen representative. Why I vote for him is entirely up to me; maybe I agree with his position, maybe I respect his character, maybe I just like the way he parts his hair. Whatever my reason, I choose.
At the end of that day, one of the candidates will have more votes than the other or others. That guy goes to the legislature.
Therefore, our system as it stands now is directly representative of the majority. That's how our government is designed to work, and it works well.
Your suggestion that we "get rid of winner take all" is confusing to me, because it seems to contradict the idea that the government represents the majority. You can't say, "the government shall be composed of representatives elected by the majority, and these four legally recognized minorities, to whom we shall throw a bone every two years." That's not fair, and it's not practical. The only reasonable system of representative government is the idea of representation of the majority.
Worked for whom? Why, for the people for whom the system is intended to work, of course. That set started with white male property owners and has grown larger over time. Today that set includes any recognized citizen (by birth or naturalization) over the age of 18 of any race, gender, or national origin.
And I disagree with your assertion that the American system of government doesn't work for "the poor or the recent migrants." Our country offers as many opportunities to poor people as any country in the world, and more than most. My girlfriend's father, for example, immigrated to this country in 1975. In Vietnam, he had been a lawyer and a politician. After he immigrated, he took a job as a janitor while he attended night school to learn English and to become an accountant. Today he makes an upper-middle-class living working for city government and as a real estate agent. His wife works a part-time job as a secretary because she wants to; they don't need the money. They've put two kids through college, medical school (my girlfriend), and law school (her brother). Our government worked just fine for them, as it continues to now.
And as for the rest of your comment... where did you get your education? You start by saying the idea of executive veto is "rediculous," but you don't say why. Then you say that the founding fathers "only had monarchies to examine," which is demonstrably false. The founding fathers were, to a man, classically educated men. They were students of history, and all intimately familiar with the democratic and republican ideals of government. Saying they "only had monarchies to examine" is so wrong it's practically laughable.
Finally...
I never cease to be amazed at the self-congratulatory arrogance of the common American citizen.
Get used to it, friend. Our country, while certainly flawed in many ways and of course with an imperfect history, is nonetheless the finest nation the world has ever seen.
Your post was, of course, utter bullshit. The bit about "there is so little difference [between the parties] as to be insulting," particularly so. If you let your political opinions get sufficiently out of whack with the mainstream, then I suppose it's possible that Republicans and Democrats might look pretty much the same to you. Both parties advocate various degrees of laisse faire capitalism, for example. This is not inherently a bad thing.
Our system of government is not designed to be the best of all possible systems. It's designed to be just good enough. That's why it's stood unchallenged for over 225 years.
And your little remark about "the illusion of democracy?" The United States of America is not now, and never has been, a democracy. Pure democracy is a system fraught with more flaws than you can shake a pointed stick at. After all, the saying goes that a dictatorship is a country where you have to do what one stupid asshole says, and a democracy is a country where you have to do what one million stupid assholes say.
So the USA is not a democracy. It's a representative republic. Is this the perfect system? I doubt it. But is it the best one we've-- as a species, I mean-- come up with so far? Yes, definitely. Name one government that has worked as long or as well as the United States'.
only the copyright holder (the U.S. government) could re-release it
First, traditionally works commissioned by the government have been placed in the public domain. There is no copyright holder on those works. Does that mean that nobody could re-release them?
But still, this gets right back to the "why bother" question. You said that code released under two licenses-- that's what you mean by "dual-licensing," right?-- can be applied to both proprietary uses and GPL-based projects, but that's unnecessary. Software released into the public domain can be used for proprietary uses and for GPL-licensed uses. So can software released under the BSD license.
You also said, "The government would have to be convinced of the benefits of GPL'd open source." Seems to me there aren't any.
Your post was interesting until it dissolved into science fiction. Sometimes it's disappointing to see that people, especially educated, well-read people, have trouble distinguishing between the two.
The bit about water, though... if it turns out that there is water on the moon-- this is still unconfirmed-- and that it's of sufficient quantity to be useful, then you've got a good point. Of course, if the water we think we've seen is nothing more than a hoar-frost, then it's back to the drawing board again.
I should look up the figures, but I'm too lazy. People often talk about cracking water into oxygen and hydrogen with electrolysis. I wonder how dense LH2 and LO2 are compared to liquid water? How silly would it be to ship LH2 and LO2 to orbit, then render it into pure water through combustion?
Now that's just silly....
So let me see if I get your scenario: the government sponsors some work, and the product of that work is some code. That code is released to the public under the GPL. Somebody else takes that code, without changing it, and releases it under a more liberal license. You're saying this would be allowed, because the second release of the code is not derivative of the first, GPL'd, release.
That's clearly not true, though. The second release would obviously be derived from the first release in that case.
If what you're saying, on the other hand, is that the government itself could choose to re-release the software under a more liberal license, that's certainly true. But it begs the question of why, then, anyone would go to the trouble of releasing under the GPL at all. Just go with the most liberal license-- which would be no license at all, of course, but simply assignment to the public domain.
The GPL is not ambiguous on this issue. One software has been released under the GPL, that software or any work derived from that software may not be released under any more liberal license than the GPL. That is, in fact, the whole point of the GPL. Which is why it's totally inappropriate for government-sponsored work.
Confucious say, man who post then argue with moderator like train with no wheels: very quickly, get nowhere.
That code is virtually identical, except for some intricacies of syntax, to PHP or JSP.
All embedded scripting code looks pretty much the same. Mason is no more or less readable than any of the others.
Except that the verbiage of the GPL says that the license must be applied to all derivative works. In your example, a re-release of version 1.0 under a more liberal license than the GPL would not be permitted, because the re-released code would be considered a derivative work.
If you read the GPL carefully, you'll find that once you're in it, it's not possible to get out of it again.
It's a long way from bauxite to aluminum sheeting. In order for the moon to be a useful source of raw materials for spacecraft, we'd have to do an unbelievable amount of work: smelting, refining, fabricating, and so on. It probably wouldn't be cost-effective. We can do all that stuff on Earth so much cheaper and more easily that it offsets the added cost of lifting materials to orbit.
You're right, but think practically instead of theoretically for a minute. Let's say you want to launch a thousand-ton spaceship to Mars. (Pulled that figure out of my ear, just for discussion purposes. For perspective, that's about the mass of two fully-loaded 747s. That's unrealistic, but it gives us a figure to start with.) Launching such a spaceship in one big piece probably wouldn't be practical; for comparison's sake, the Apollo command capsule and moon lander, together, weighed about 50 tons, and it took the 3,100 ton Saturn V to fling it toward the moon. So launching a 1,000 ton spaceship to Mars from the Earth's surface would be a challenge, to say the least.
Instead, you'd loft the pieces of the Mars spaceship to some stable point in space and assemble it there, then fire it off toward parts elsewhere. The obvious thing to do would be to build the spaceship in low Earth orbit, just like we're building the space station now. But that's not especially helpful, because it takes very nearly the same amount of energy to lift a spaceship out of low Earth orbit as it takes to lift it all the way from the surface of the Earth. So you're still talking about some monster rocket engines.
A better idea would be to assemble the spaceship pieces at L1. You still have to expend a lot of energy to get all the pieces up there, but you don't have to do it all at once. And when it comes to actually setting off for Mars, you can use a slingshot maneuver around the Earth to get some monster delta v without having to burn rocket engines for it.
So getting stuff to L1 still requires a lot of energy, but we can expend that energy in little parcels rather than all at once. And getting from L1 to points elsewhere in the solar system is a lot easier than getting there from Earth or Earth orbit.
I can't speak about the Earth-Sun L4 and L5 points, but the Earth-Jupiter L4 and L5 points are sufficiently stable-- that is, their regions of stability are sufficiently large-- that they've become home to over 1,500 asteroids. They're called Trojan asteroids: 588 Achilles, 624 Hektor, and 911 Agamemnon, and so on. You can find the whole list here if you're interested.
There are, if memory serves me right, 6 asteroids in a Trojan relationship with Mars, too.
This also means thet the "points" are actually regions.
Well... no, not exactly. The libration points are just that: points. While it's true that nothing is a point-mass, bodies act like point masses because the net sum of all the gravitational forces between all the atoms in both objects add up to be exactly the same as if the bodies were both dimensionless objects of equal mass. This is true in all cases except when you're actually inside a body.
If you put a body exactly at the L4 point (say, the Earth-Jupiter L4 point) and nudge it slightly out of position, it will fall back toward the L4 point and oscillate there. If you nudge it too far, though, the body will fall away from the L4 point and go into an orbit around the Sun. This defines the notion of a "region of stability" around the L4 point. The same is true of L5. That's why asteroids tend to collect there; they're all oscillating around the L4 and L5 points in the Earth-Jupiter system.
But that's not the same thing as saying that L4 and L5 are regions rather than points. The situation is more complex than that.
No, it takes more energy. Earth's gravity well is said to be about 6,400 kilometers deep. That is, escaping the Earth's gravity requires the same amount of energy as climbing out of a well 6,400 kilometers deep. (This isn't meant to be a literal expression of distance; it's just a generalization. See Clarke's The Exploration of Space for a good explanation, I think.)
So climbing out of Earth's gravity well requires a lot of energy; can you imagine pulling a spacecraft out of a 6,400 kilometer deep hole? That's a lot of pulling. Of course, the radius of the moon isn't anywhere near far enough to be truly free of Earth's gravity, but talking about it in terms of absolutes gives us a good idea of the energy involved.
If I had about two more cups of coffee in me, I'd do some back-of-the-napkin calculations to estimate the energy required, in joules per kilogram, to loft an object-- starting with U = GMm/r-- but I'm not that motivated.
So even if you make it 5/6 of the way to the moon, you can't just coast up the rest of the way. You still have to expend energy-- a lot of it, proportional to the mass of your spaceship-- to lift yourself that last 40,000 miles or so. Of course, we would do this by expending all the energy in one big impulse at low Earth orbit, putting the spaceship into an elliptical orbit with apogee at the L4 or L5 point, then another impulse at apogee to put the spaceship into stable orbit. The difference in energy between a trip to L1 and a trip to L4 or L5 would be evident by the delta v needed-- and, consequently, the size of the impulse required-- to create the initial transfer orbit. It'd be a nontrivial difference.
As noted elsewhere, the SOHO is at the Earth-Sun L1 point, inside the orbit of the Earth. We've been talking about the Earth-moon L1 point, between the Earth and the moon. Different things.
As for your other question, a libration (or Lagrange, or Lagrangian, or whatever) point is just that: a point. L1 is the dimensionless point in space where the gravitational forces pulling toward Earth and toward the moon exactly equal one another. If the center of mass (also a dimensionless point) of a body is parked exactly on the libration point, then the body will experience no net gravitational pull in either direction, because the forces will be balanced.
Of course, keeping the center of mass of a body parked on the L1 point is not a trivial thing. Even the pressure of light from the sun will be enough to nudge it slightly out of position, and once out of position, the body will tend to fall further out of position due to gravity of either the Earth or the moon. So the real question is this: how gentle or steep is the gravity gradient surrounding the L1 point? In other words, how much does the force of gravity change over time as one moves in and out of the L1 point?
Remember that gravity is an inverse-square relation. The force varies with the square of the distance between two objects. So when the two objects are close together, the force varies a lot over a small distance. But when the objects are farther apart, the force varies less over the same distance. When bodies are far, the gravitational gradient (distance rate change of force) between them is said to be shallow or smooth, and when they're close together it's said to be steep.
All that adds up to is this: it's easier to keep a body at the Earth-Sun L1 point than at the Earth-moon L1 point because the gravitational gradient is steeper in the Earth-moon system than in the Earth-Sun system.
Now, the L4 and L5 points are different. L4 and L5 are local attractors; you could put an object in orbit around L4 or L5 itself, and it would tend toward stability. So it's easier to put multiple objects at L4 and L5 than it is to put them at L1, L2, or L3.
Only problem with using a liquid as a shield is that when the station is in darkness it'll be frozen....
It's pretty trivial, both in terms of effort and in terms of mass, to build insulated water tanks that keep water liquid over a vast range of temperatures. It'd be easier to keep the water liquid all the time than to pump energy into it to thaw it when needed.
The SOHO satellite isn't interacting with other objects, though. Any manned-- or even occasionally manned-- space station will have to dock with visiting spacecraft and whatnot, which will involve significant transfers of momentum. Keeping an L1 space station on station will be a harder job than simply keeping the SOHO on station.
Not impossible, but hard.
The danger, of course, is that an L1 space station could drift so far from the actual L1 point in space that it requires more delta v to move it back than the structure can withstand. That'd be a worst-case kind of disaster, though.
I thought Lagrange points collected a lot of dust, which would be bad for optics.
L4 and L5 are gravitationally stable points, so there may be collections of dust there. (In the Jupiter-Sun L4 and L5 points, there are collections of asteroids.)
But L1, L2, and L3 are all gravitationally unstable. A body at one of those three points will tend to fall away from the point rather than staying in it.
L4 and L5 are like being at the bottom of a depression: whichever way you go, gravity tends to pull you back toward the middle. L1, L2, and L3 are more like being at the top of a hill. If you're right at the very center, you're fine. But if you're even slightly off-center, gravity will pull you down the hill.
In theory, L1 ought to be the cleanest point between the Earth and the moon. Nothing can stay in orbit at L1 without active station-keeping.
Gee, Doc, have you done any payload arithmetic lately? Lofting lead is possibly the dumbest idea ever-- no offense intended.
In terms of pounds of mass per gray-- meaning the amount of radiation that can be absorbed in a given unit of mass-- water is a better radiation shield than lead. Dual-purpose, too.
Useful in what sense? There's nothing on the moon that we need or want, at least not with current technologies at hand. If you put some kind of space station in a gravitationally unstable point, like L1, then you can use it to launch trips to points elsewhere very inexpensively. (Assuming the cost of maintaining the orbit of the L1 station turns out to be manageable.) Once you're at L1, you've basically spent all the energy you need to spend to get out of the Earth-moon system. Refueling or restaging at L1 for longer trips to Mars and elsewhere makes a lot of sense.
Science fiction from the late 1900's aside, moon bases just don't make that much sense right now.
a space station at a LaGrange point (in this case L1) wouldn't have to use thrusters to maintain a stable orbit and would never leave it's stable orbit around the earth
That's not true. L1, L2, and L3 are all gravitationally unstable points. A space station at L1, if nudged out of position even slightly, will tend to spiral inward toward Earth or outward toward the moon. The L4 and L5 points are the only stable Lagrangian points in a two-body system.
Why not just build on the moon? Why stop at 5/6 the way to the moon?
Because the whole point of staging at L1 is that it allows low-energy transfers to other points in the solar system. Launching a trip to Mars, for example, from L1 would require much less energy than from either the surface of the Earth, or low Earth orbit, or the surface of the moon.
Of course, this ignores the biggest problem with the L1 point: it's unstable. A body placed at L1 will tend to either fall inward toward the Earth or outward toward the moon at the slightest push. Any space station at L1 will have to correct its position regularly, probably using simple chemical rockets. These rockets will have to be refueled periodically and so on, making for a nontrivial amount of effort to keep an L1 space station in position.
The L4 and L5 points, on the other hand, are gravitationally stable. If a body at L4 or L5 starts to drift out of position-- due to a collision or outgassing or whatever-- the Earth-moon system will tend to pull it back to the point of stability again. But since L4 and L5 are farther from Earth than L1 is, it takes more time and energy to get there from LEO.
I really wasn't planning on responding at all to this thread, because this sort of argument usually just ends up making me mad. But in all the comments I've read so far, this is the only one that gets it right.
Code released under a nonrestrictive license like the BSD one can later be re-released by another party under the GPL. There's no rule against this whatsoever.
Code released under the GPL, however, can never be re-released under another license. Ever.
It's clear that the right course of action is for the government to make code available under the least restrictive terms possible. If somebody wants to then take one or another program and "GPL-ize" is, they're free to do so.
This will, of course, not satisfy RMS. But anybody who's familiar with my past comments on this subject already knows how I feel about that.