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Comment: Re:No they don't (Score 1) 117

by Immerman (#49371335) Attached to: Chinese Scientists Plan Solar Power Station In Space

Why would you have sunlight shining directly on your orbital panels? That would be stupid, you would be much better off putting them on Earth. What you want to do is put up massive mylar parabolic reflectors, possibly many km across and stabilized by photon pressure and/or gyroscopic effects, that concentrate sunlight onto extremely high-power photovoltaics. Orbital reflectors can cost practically nothing to deploy and maintain, unlike their Earth-side counterparts which must be built strong enough to survive gravity, weather, and life, and will consume land area that could be put to other use or allowed to lie fallow for ecosystem restoration. (especially important for island nations)

And microwave lasers (aka masers - a technology that predates lasers considerably) actually make incredible sense for beaming the power back to Earth, since the atmosphere is extremely transparent to microwaves. Of course even a tightly focused maser will spread out after 36,000km, so you'll need massive receiving antennas on Earth covering many square kilometers, especially if you want to avoid cooking everything in the airspace alive, but power density could easily be many times the palty 1kW/m^2 of sunlight, and microwave mirrors and antennas are a much more rugged, simple, and efficient technology than optical mirrors and photovoltaics.

Plus, if you're willing to put up with the bureaucracy, you can probably get your military interested in testing its potential as an orbital death ray, dramatically improving the funding available for at least the early facilities.

Comment: Re:I'd put a 'may' there (Score 1) 41

by Immerman (#49360839) Attached to: Taxpayer Subsidies To ULA To End

Considering how quickly SpaceX is leapfrogging the ULA, I'm inclined to suspect that a more open bidding process will end up saving the government a fair amount of money in the long run. It does seem that the ULA has been mostly sitting on their laurels sucking at the government teat for a long while now. Why should they improve efficiency when it will only reduce profits?
My own objection is that saving the government money is a *very* different thing than saving the taxpayer money. What's your bet, will we all get a 0.01% reduction in taxes, or will the government just find some other pork-barrel project to spend it on? Not that that's necessarily a bad thing - I'd much rather get more for my tax dollars than less, but lets not pretend it's going to actually save taxpayers money.

Comment: Re:Chemists and Biologists (Score 1) 485

by Immerman (#49337589) Attached to: No, It's Not Always Quicker To Do Things In Memory

Sure, except that had they used buffered string concatenation, so that the implementation was actually remotely comparable to the buffered disk access, they would have gotten radically different results.

As it is, they've only actually showed that doing things in basically the slowest possible way in memory can be slower than writing to the disk cache (also entirely in memory, they never initiated an actual write to disk at all, only queued it)

Comment: Re:Check their work or check the summary? (Score 1) 485

by Immerman (#49337527) Attached to: No, It's Not Always Quicker To Do Things In Memory

Sure, if you expose enough of the implementation details it becomes obvious when you're doing something stupid

  for (int i=0; i numIter; i++) {
                    char * newString = malloc ( strlen(concatString) + strlen(addstring) + 1);
                    memcpy (...);
                    memcpy(...) ;
                    free(concatString);
                  concatString = newString;
}

Suggests strongly a number of different potential optimization routes, though most would require either multiple traversals of the source material, or a growable buffer which would greatly increase the code complexity (or does C offer such a thing these days? I've been on ++ for a long while now)

You've got to admit though, that's a lot uglier to work with for most incidental string-manipulation where performance is largely irrelevant.

Comment: Don't over-optimize (Score 1) 485

by Immerman (#49337443) Attached to: No, It's Not Always Quicker To Do Things In Memory

Correction: Dumb concatenation is for situations where clarity and convenience are more important than performance. That is to say, most of your code. If you're using a buffered string building system to perform a simple concatenation of file name components before opening the file to begin the real work, then you're creating maintenance headaches for an irrelevant performance boost. In an inner loop dedicated to string manipulation though...

One of the most important aspects of programming is knowing how to choose the right tool for the job - typically 80-90% of your codebase is executed so infrequently that even abysmal performance won't be noticeable to the user, and optimizing that code will actually be counter-productive due to the time and maintenance overhead it imposes. Moreover, most programmers (and especially the inexperienced) are quite poor at recognizing which parts of their code are actually performance critical. Recognizing that, it may often make sense to default to doing things the simple, slow, way and only worry about optimization after performance analysis has highlighted the bottlenecks. Personally I'll often write the expected hotspots with some basic "low-cost" optimizations (like StringBuilder) and an eye towards making future optimization simple (expected optimizations should never require an architecture overhaul, and maybe it's worth passing in certain data that will be necessary for future optimization of a heavily used function, just to avoid having to re-write a million function calls if/when it comes time to optimize it), but primarily focus on correctness. Then, after everything is working correctly, and performance analysis has shown me which bits of code are actually causing issues (including the bits I never would have suspected), then I go back and break out the heavy guns. I've gotten burned too many times over-optimizing the wrong things and generating headaches down the road to make a habit out of it anymore. Unless it's something fun to implement of course...

Comment: Re:WTF? (Score 1) 79

by Immerman (#49336879) Attached to: Judicial Committee Approves FBI Plan To Expand Hacking Powers

Ah, one of those statements with a convoluted historical meaning that departs from the literal one. Gotcha.

Can't say I disagree much with your major points, so then why do you object to my voting third party and preferring those candidate who espouse policy I actually agree with? Sounds to me like you think that's exactly what I *should* be doing.

As for your foxes and chickens, I quite agree. However, there are occasionally times when the chickens can squawk loud enough that the foxes will actually pass some laws to limit themselves rather than risk losing control of the situation. Threats of assembling a constitutional congress being one example that has motivated several concessions. Or, at the extreme end, there are moments when well-armed chickens can impose new laws upon the foxes (the Magna Carta springs to mind). To fail to, at our leisure, consider the form such imposed rules might take does a great disservice to mankind when one of those rare opportunities arises, and we have few well-considered options to suggest.

Comment: Re:He's an Angel (Score 1) 569

Assuming he's guilty, and that there were warning signs of such destructive behavior (and there usually are) "He would never swat" suggests willful blindness, not unconditional love. Admittedly perhaps she's just trying to cover his ass, but I've seen far more examples of people employing willful blindness to force their perception of a person into a form they can love, than actual unconditional love.

Comment: Re:WTF? (Score 1) 79

by Immerman (#49320505) Attached to: Judicial Committee Approves FBI Plan To Expand Hacking Powers

When has justice ever had anything to do with the law?

When did I say it did?

When you said "an unjust law is no law at all". By that logic most of the laws in the history of the world were "no law at all" - but tell that to the many people who suffered or died for breaking them. What exactly do you think a law is?

I won't contest that the system we have in the US exalts capitalism at the near-total expense of democracy - but I believe that's a result of the system we chose to create, rather than an inherent and intractable contradiction. Reclassify politicians accepting *any* form of financial or other reciprocation as treason and we'd be well on our way to allowing the two systems to coexist - no more campaign contributions, no more revolving doors. Or we could, say, replace the House of Representatives with some form of direct (or quasi-direct) democracy - give people the ability to vote directly on issues rather than just representatives who can proceed to ignore our wishes. Sure, the population could be lead by the nose by moneyed interests, at least up to a point, but if you can get the majority to believe your bullshit then democracy has spoken.

As for voting third party - I don't see how that really changes anything so long as the system remains as it is. So long as one of the two major parties still wins the office, the Kochs have gotten their money's worth - they don't actually care whether the winning candidate got 90% of the vote, or eked in with a 34% "mandate", just so long as it's their man in office. If we could muster enough support to get a seriously competitive third party, then sure, they might have to spend 50% more to assure that they have all three potential winners in their pocket - but we're talking about the Koch brothers and their ilk, they could spend 10x that without hardly noticing, and they would still be getting an incredible return on investment.

Sure, I vote a nearly straight third party ticket, preferring those whose policies I actually agree with when available

Which, does nothing to change the influence of lobbyists or force parties to actually listen to voters when setting the agenda. If you keep picking from the offered cards hoping for a game that you control you're just hoping for the triumph of optimism over experience.

So then oh wise master, what exactly are you trying to suggest? Should I write in another candidate, do you think that would change something? Abstaining certainly won't, that just sends the message that hey, there's one more sucker we can ignore completely.

Comment: Re:War on moons (Score 1) 111

by Immerman (#49316949) Attached to: Giant Lava Tubes Possible On the Moon

You are grossly underestimating the energies involved. Oh goody, Google located someone else who's already done the math (https://answers.yahoo.com/question/index?qid=20090102113458AADvZ2j)

Their conclusion was that to destroy the moon (i.e. completely neutralize the gravitational potential energy lost to the accretion of mass) would require 1.2445 x 10^(29) Joules, or the equivalent of 592.6 billion Tsar Bomba fusion bombs (the largest nuclear bomb ever detonated, at ~54 megatons of TNT, with a total destruction radius of 35 kilometers = 3848 square km). Now the surface of the Earth (land and sea combined) is only 510 million square kilometers, so we're talking the energy equivalent of 1,162 Tsar Bombas being detonated on every square kilometer of the planet. Or for an even more personal feel - if you live in a moderate-density urban area with 1/5 acre lots, that's one bomb capable of totally destroying Paris and the entire surrounding urban area (or New York City, three times over), dropped on *every* *single* *house*.

Somehow I think life on Earth would have a much easier time adapting to a little orbital bombardment and not having a moon anymore.

Comment: Re: Out of respect for Dice's agenda, let me ask.. (Score 0) 109

by Immerman (#49306493) Attached to: The Stolen Credit For What Makes Up the Sun

In fairness, she could possibly have delayed graduation another four years while gathering evidence to try to prove her hypothesis herself before publishing, but there was no guarantee she was right, and she was probably long past ready to graduate and get on with her life. I know I certainly was after only six years in college. Or she could have published prematurely and garnered the usual ridicule for making an outrageous claim without solid evidence, likely destroying her reputation and career before it even began - even after she was proven right the damage would likely have already been done. Even a man would be hard pressed to take that bet, and as a women in an almost exclusively male field she faced far greater risks of professional ostracization.

Instead she chose the safe path: didn't publish, graduated, and rode her credentials into what sounds like a very respectable career - an especially impressive accomplishment for a woman in a time and field that makes today's most mysogynistic CS departments look positively egalitarian. Her name may not have ended up in as many of the history books as she deserves, but she also didn't spend the time necessary to prove her hypothesis, and it sounds like her professor was (unusually?) honorable and gave her credit for it after he (aka, his future grad students) did the work of gathering sufficient evidence.

Comment: Re:War on moons (Score 1) 111

by Immerman (#49306277) Attached to: Giant Lava Tubes Possible On the Moon

Of course pieces of moon raining down on Earth would be devastating, my point is that it would be far *more* devastating if you simply unleashed the same amount of energy directly on the Earth instead.

As for the specific energy required to break up the moon - it would actually be even higher than that required to get a single rock off the surface. Everything on the surface has a certain gravitational potential energy which must be overcome to escape the gravity well, as you go deeper that energy requirement increases. The fact that you're moving other pieces away at the same time changes nothing - conservation of energy requires that that energy debt be paid in full to get the pieces to stay apart rather than falling back in on themselves, regardless of whether only a single rock is being launched, or the entire thing vaporized.

As for stuff being "pulled in to the Earth" - if it doesn't hit on the first pass, it's, for the most part, not going to hit. Neglecting the complicating factors of the rapidly dissipating gravitational well of the ex-moon, every frgment will, at the moment of ejection, be on an elliptical orbit around the center of the Earth. Some of those ellipses will intersect the Earth, in which case that fragment will collide on it's first pass, everything else will continue to orbit in that ellipse forever* - there's no resistance in space to slow things down so that the Earth can catch things on the next pass. And since the Earth is the primary, there's no "gravitational keyhole" games that can be played to fine-tune the orbit for future collisions, as can happen with asteroids orbitting the sun.

* of course that dissipating gravitational well *will* confound things - instead of one big well you have many small ones all in different, but intersecting orbits (every orbit will initially pass through the space previously occupied by the moon - conservation of momentum dictates that the center of mass of all the fragments remain unchanged after the explosion - just like a rocket ship: the center of mass of fuel+ship never moves). As those fragments gravitationally interact with each other they will tend to circularize and coalesce into a ring system, but in the process some fragments will lose too much angular momentum and fall to Earth, while others will get thrown out at velocities that will escape from the Earth altogether. But mostly anything that approaches the Earth will be on a near-miss trajectory, and will rapidly be deflected onto a safer trajectory after a few more orbits interacting with it's peers - just as comets and asteroids rarely hit the sun: as objects get closer their tangential velocity increases dramatically, making them far less responsive to the gravitational pull. The only way they can hit the Earth is if their orbit gets stretched into such a long, narrow ellipse that it intersects the Earth itself.

Money will say more in one moment than the most eloquent lover can in years.

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