No, I wasn't talking about calculating the current time. I'm talking about calculating the number of seconds between now and some time in the future. That's what you can't do, and I can't think of any reason why you'd ever need to do that.
I can. Imagine agreeing to do something at a certain future time, and then setting up a piece of hardware to do it. If you use a timescale with leap seconds, like UTC, then that device may have to be reprogrammed to deal with leap seconds an arbitrary number of times before that event occurs. If not for leap seconds, your hardware could be a simple down counter programmed with the difference between the agreed-upon future time and the current time.
Here's another example based on satellite tracking. Standard practice when describing a satellite orbit is to give a set of six orbital elements and an epoch time when they are valid. (The orbital elements can be Keplerian elements, or position and velocity state vectors, it doesn't matter). For practical reasons, the epoch time is often an externally specified parameter to the orbital element generator. And that time might well be in the future (since satellite orbits, at least over the short term, are pretty predictable). NORAD epoch times are UTC, and that creates a trap if you're not careful about leap seconds.
A related example comes from astronomy. When giving the coordinates of a celestial object, you must account for the precession of the earth's axis by also giving the epoch at which the coordinates are valid. Two epochs were often used in the latter half of the 20th century: B1950.0 and J2000.0. Although the latter date has now passed, J2000.0-based coordinates were in widespread use well before that date. Obviously that epoch date could not move around arbitrarily as a result of leap seconds, so it's based on "terrestrial time", another standard time scale related to TAI that doesn't follow leap seconds.
That's impossible to do precisely anyway due to relativity, and as the time between the two events increases the precision goes down more and more.
Well...yes. But the error caused by an incorrectly handled (or unhandled) leap second is likely to be far greater than any relativistic error in any real-world engineering application I'm likely to encounter. Besides, it's common in relativistic applications to just pick a frame of reference and make it your standard of measurement. UTC is that way, btw. It's defined at the geoid (approximately mean sea level) and relativistic corrections have to be made to atomic clocks at altitudes other than sea level.
What's difficult about it? I don't understand this point at all. There is a very clear and unambiguous way to date any event, regardless of whether or not it occurs near or during a leap second. "1998-12-31T23:59:59.00Z, 1998-12-31T23:59:60.00Z, 1999-01-01T00:00:00.00Z, 1999-01-01T00:00:01.00Z". You must be talking about UNIX time.
Yes, I was talking about UNIX time, sorry I wasn't more clear. You are absolutely right that UTC is not intended to be encoded as an integer. Unfortunately, that's what UNIX tries to do, and that's why there are problems dating events around leap seconds on UNIX. What actually happens is that a 1-second discontinuity ripples throughout the NTP hierarchy and clocks eventually settle on the "new" UTC after a fairly significant period of uncertainty. Or at least that's the way it used to work with NTP; I haven't followed the more recent versions. In any case, that's nonsense; a fundamental timescale should never have to "jump" in this way.
So I think we completely agree on the main point: UNIX's internal representation of time is fundamentally broken. It ought to be based on a count of seconds from some epoch on a timescale that does not use leap seconds, and conversion to or from UTC should be done only when needed for human consumption or input.
One could even argue that UNIX already does this, and it's the conversion routines that are broken. As you
It actually does matter a lot in some applications. Take satellite tracking. A low earth orbit satellite moves about 7 km in one second. If you're off by one second because of confusion about a leap second, you've made a position error of 7 km. That's a lot.
There are many perfectly valid arguments against leap seconds. The difficulty in calculating the exact number of seconds between two events, the fact that calculations involving future times can give different results after leap seconds are declared, the difficulty of dating events that occur near or during leap seconds, all are serious drawbacks.
But these are not good arguments for removing leap seconds from UTC! Why do that when you can choose from two perfectly good standard time scales that don't have leap seconds? Those are the GPS (Global Positioning System) time scale and the TAI (International Atomic Time) timescale. They differ by a fixed offset: TAI is 19 seconds ahead of GPS and will remain so despite any future leap seconds added to UTC. (Strictly speaking the offset between TAI and GPS typically varies by some tens or hundreds of nanoseconds around 19 seconds, but the GPS system operators try to drive that error to zero, and they publish those offsets. The big advantage of GPS time, of course, is its ready availability from inexpensive receivers.)
CDMA digital cellular is one system that chose the GPS timescale to avoid the nasty discontinuities associated with UTC leap seconds. GPS times are still easily converted to UTC (or local time) for human consumption.
It would have been really nice had the UNIX designers chosen the TAI timescale instead of UTC as the internal representation of time. (GPS didn't exist back in the 1970s when UNIX was developed). Library routines could easily convert between TAI and UTC as needed for input and display, using configuration files updated every time a new leap second is declared, but you'd get a much cleaner internal representation of time. You wouldn't have the present situation where every timestamp for a past event is effectively moved one second every time there's a leap second.
I wonder if it's too late to make such a change...
Perhaps you've already forgotten the invasion in 2003 that did involve quite a few American bombs falling on Iraq, even though the damage and death toll far exceeded that of 9/11 in the United States. That's understandable; Westerners, especially Americans tend to have very short attention spans, and they always discount the value of humans in non-Western countries.
You may honestly think the American presence in Iraq is a benign thing, and we're doing the right thing by training a native police force and army. But the insurgents (and the apparent large numbers of civilians that sympathize with and support them) think differently. To them, we're just like the Germans in France, and they're the Resistance, fighting the occupation and its collaborators in any way they can, even if it unfortunately kills some innocent civilians in the process. Now you and I may disagree with this view, but that's irrelevant; what they think is what drives their actions.
In any society you will always find a small number of sociopaths, but most people in Arab countries aren't born to become terrorist radicals. They're conditioned that way by their environment and upbringing, and by what they see other countries doing to them. And for decades, we've done the best we can to create that environment all throughout the Islamic world. One of the most frightening things I saw after 9/11 was footage of a fundamentalist Islamic school in Pakistan teaching 5-year-old kids to chant "death to America!" And these schools are all over the place. In another 15 years, they will become the next wave of terrorists we'll have to deal with unless we're ready to take the next logical step and begin a full-scale genocidal campaign. Even George Bush probably wouldn't do that.
I'm sure you honestly think that we did Iraq a favor by ridding them of Saddam Hussein, but as I said, Americans have a talent for self-delusion. Few in the Middle East really believe the US was motivated, as we so often claim, by a pure, altruistic desire to rid the world of a terrible tyrant. They tend to judge us by our actions, not our words. They see us ignoring many other brutal tyrants, especially in Africa, where no oilfields are at stake. Worse, they saw us prop up many tyrants during the Cold War whenever that enhanced our position against the Soviets. And as for our so-called War on Terrorism, they also see us sponsoring terrorism on a large scale whenever it suits our purposes, such as our support for the Nicaraguan Contras, or the Mujahaideen in Afghanistan during the Russian occupation. (That group, as is now well known, included Usama bin Laden).
So, you see it's a dangerous mistake to assume that others disagree with or dislike us because they're stupid or evil.
That's an interesting point you make about Hitler's support. Obviously the man, as evil as he was, couldn't have killed 57 million people (the WW2 casualty count) all by himself. He needed a lot of help, and yes, he got it by tapping deep into the German psyche (and by being a terrific orator). And it's entirely possible that neither Hitler nor bin Laden have ever killed anyone with their own hands.
You are quite right that we did not deserve 9/11 any more than the world deserved Hitler in the 1930s. I never said we did. But that's not the issue. It's simply a question of forseeable reactions to our own policies and actions which, for some reason, apologists for the Administration never concede even when there is plenty of warning.
Step back about a decade before 1933, the year Hitler came to power. Hitler was already a whackjob, but what was the nature of the relationship between Germany and the Western Powers? Read the terms of the Versailles Treaty, how it was perceived in Germany, the actions taken by the Western Powers to enforce it, particularly the occupation of the Ruhr in early 1923, and the effects those actions had on German public opinion and politics.
Hitler had two rapid spikes in popularity. The first began in 1922 when hyperinflation -- a direct result of punitive western demands for war reparations -- made German currency worthless. Hitler's "Beer Hall Putsch" was in November 1923. After it collapsed, Hitler was jailed and the Nazi party banned, the government managed to restore economic prosperity. The small Nazi hard core went into hiding, licked their wounds and waited. Hitler wrote Mein Kampf -- his warning to the world. Then when the world economy collapsed in 1929, and Germany's with it, Hitler's star began to rise again. The rest you know.
So what lesson I draw from this history? Simple. You need a two-pronged approach in dealing with your enemies. You need to go after those who've attacked you; I really don't disagree with that. But in so doing, you must be extremely selective and careful. You must take the time to learn as much as you can about your enemy: who he is and what he thinks.
And it's just as important to understand who your enemy isn't. You must avoid, at almost any cost, collectively punishing an entire population or culture for the actions of a few of its members, especially when they are not even governmental leaders (elected or otherwise). Otherwise you'll just turn them all into a renewable source of new enemies to replace those you kill or capture.
Strictly speaking, of course, you needn't be so picky if you plan to wipe them all out anyway. That was the basis of Nazi war policy, but it still didn't work for them. But I presume that even George W. Bush hasn't made genocide a basis of US policy, so it remains important to be selective. That's the basic mistake that Bush has made, and that's why this war will never end until that mistake is corrected.
Oh, as far as Camp Gitmo goes, I take it you wouldn't really want to be there even if Dick says the food is really good. And I think Amnesty International's description of it as the "gulag of our times" was right on the button; any differences between them are matters of scale, not of kind. I think that's why their report struck such a nerve.
Funny that you should mention fear, as it has been the Bush Administration's primary means to ensure domestic compliance. This is hardly new; fearmongering about "them" has been the favored tactic of despots throughout history for a simple reason: it works. So, you see I am thinking about the good of the country, and I have never been as worried about its direction and future as I have been in the past few years.
I concede the point: (nonexistent) WMDs were really the prime pretext for the current war on Iraq. But it clearly wasn't our only pretext; 9/11 was definitely in there too. Richard Clarke wrote about how, within hours and days of 9/11, Bush wanted to pin it on Iraq whether or not they were actually involved. He has apparently succeeded, as we still have a substantial fraction of the US public (most of whom watch Fox News...) believing that Iraq was somehow involved in 9/11 despite the complete lack of evidence, and despite the clear absurdity of a collaboration between a radical Islamic fundamentalist and an almost totally secular Arab dictator who had nothing to gain and everything to lose. Remember that Osama's #1 enemy is not the US, it's the Saudi monarchy who he considers not religious enough, and thoroughly corrupt -- much like Saddam.
I think you're unreasonably hard on the UN Security Council. Despite what the Administration and certain members of Congress would have you believe, I don't think any of those members cared much for Saddam Hussein. It was just a question of whether another war would, on balance, help or hurt the situation when the sanctions and weapons inspectors, as imperfect as they were, were having the desired effect. France, for example, made it very clear that they thought our belligerent approach would likely backfire. Subsequent events, of course, have proven them quite correct. Our reaction to the French position, of course, perfectly illustrated Bush's simplistic "you're with us or with the terrorists" mentality.
Comparisons to World War II are not apt because in that war we were part of a collective defense answering clear aggression by the other side. There was simply no compelling reason for the US to attack Iraq in 2003; the fact that Bush felt the need to create and breathlessly hype a bogus WMD threat shows that even he understood that.
It would be much better to compare WW II to the first Gulf War, as that was also a collective response to an equally naked aggression (even if such aggressions happen all the time without a response from us when the countries involved have no oil).
The fact that we had many more countries supporting us in the first Gulf War than in the second underscores my point. While it's true that WWII and the first Gulf War differ in that the Allies occupied Germany and Japan but not Iraq, there was a good reason for this difference: Germany and Japan were serious threats to other countries almost until each one surrendered, while Iraq's threat to others was neutralized without the need for occupation. The events following Bush Jr.'s war show just how wise it was for Bush Sr. to stop when he did.
Anyway, if by now you can't see that our response to 9/11 has done us far more harm than good, I don't know what more to say -- except to watch the new crop of bin Ladens that we are so effectively cultivating.
While my comparison between UBL and the DC snipers certainly isn't perfect, I hardly think it absurd. You say that the snipers had no sympathizers while UBL has many. That's exactly my point! Why do you think UBL has so many sympathizers willing to protect the man from the biggest and best funded manhunt in history? Why do you think that Al Qaeda seems to have no problem recruiting new lieutenants and foot soldiers to take the place of those who've been killed or captured, or alternatively inspiring independent groups to emulate them? Do you seriously believe it's just because they hate the supposedly free way we Americans live within the borders of our own country? Or might all that just possibly have something to do with our continuing actions in their countries since 9/11?
I remain open on the question of whether it's a civil war (with the coalition on one side, as you say) or simply a bunch of people who see themselves as the latest equivalent of the French Resistance. (I suspect those in the Resistance would bristle at the notion that they were in a French civil war with the Vichy government on the other side.)
I do wish it were possible to get the kind of news reporting that would actually shed some light on this issue. After years of fighting, and despite having the largest and most expensive intelligence service in the world, even the US government still seems totally in the dark about the size, scope and motivations of the Iraqi insurgency, and their degree of support among the civilian population. Otherwise you wouldn't see such ridiculous farces as last month's statement by Dick Cheney that the "insurgency was in its last throes", followed by backpedaling (after a general publicly said otherwise) in which he "clarified" his remarks by saying that "last throes" could last as long as 12 years... (Jon Stewart had a lot of fun with that one.)
As for who's responsible for the bombings, it seems beyond the ability of many conservative Americans to even entertain the notion that the people we call "insurgents" might actually see themselves as "freedom fighters" defending their country against an evil (to them) occupation, and that they honestly think they're doing the right thing by blowing up as many Americans and Iraqi "collaborators" as they can even if that unfortunately takes out many innocent Iraqis as well.
(I emphasize that I'm not saying that I agree with their image of themselves. But it sure seems to me that anyone who deliberately sacrifices his life in a suicide bombing was probably at least somewhat sincere about his cause, whether we think it's a good one or not. What you or I think doesn't matter. They're motivated by what they think.)
The Brits clearly share our difficulties in being honest to oneself. Just as it seems beyond the ability of many Americans to entertain the notion that we just might have provoked the ongoing Iraqi insurgency, it seems beyond the ability of many Brits to entertain the notion that the recent attacks in London just might be in retaliation for their support of the US in Iraq.
Accepting what seem to me to be obvious, objective facts hardly means that you support what the bombers did. Nor does it even mean that you must oppose your own government's policy (though I obviously do). It simply means having the integrity to concede that your government's military actions overseas can provoke reactions, and that any honest accounting of the costs of going to war must take those consequences into account.
But let's say, just for the sake of argument, that our enemies are not sentient beings motivated by notions of morality and self-sacrifice, as misguided as those notions may seem to us. Let's assume they're just like mindless staphylococci bacteria just doing what's in their malign little natures: hurting innocent humans whenever they get the chance. And suppose, by your actions, you knowingly do something that gives them that chance. Then who's to blame? The bacteria? I suppose it might make you feel good at some level to rail in fury at the evil bacteria, but it won't do you much good. Clearly the blame is yours for setting up the conditions for it to happen.
In every war, every belligerent's propaganda always heaps the complete moral blame for every casualty on every side on the other side(s) regardless of proximate cause. Unfortunately, that propaganda is frequently all too effective.
Yes, I have watched Fox, though I admit I can't watch it for very long before I get physically sick and have to switch it off. Bill O'Reilly's "interview" of Jeremy Glick comes to mind.
Who is blowing up civilians in Iraq? I admit the answer depends strongly on the year in question. In 2003, we did an awful lot of it. In 2004 and 2005, the Iraqi "insurgents" were doing it -- but they weren't doing it before we arrived, now were they? I would like to see some firm figures (such data is hard to come by with an Administration with an amazing fetish for secrecy) but I wouldn't be at all surprised if our totals are still well ahead of their totals.
I suspect that if you could talk to the insurgents, they'd claim (just as we do) that they only go after "legitimate targets", and they "sincerely regret" any collateral damage. To them, the legitimate targets are the US and coalition forces, plus any Iraqis they consider collaborators with their occupiers. But whether you're trying to blow up an Iraqi police station deemed full of "collaborators" or a house in a residential area that you think might harbor Saddam Hussein, it's often hard to kill only your desired target. That's an unpleasant truth about warfare.
As for photos and reports of abuse of prisoners in US prison camps, many of those prisoners have been there for years. For a while there was a fresh new batch of abuse photos every day. More recently the supply of photos seems to have dried up, but no one seriously believes that's because the abuses have stopped; our soldiers simply learned not to use their cameras. But if you think it has all ended, then why did the reporters who went down to Gitmo for a tour all say it was a total farce? Why weren't they allowed to see anything or talk to any prisoners? The supply of new revelations seems to depend mainly on how lucky the ACLU and similar groups have been with their FOIA requests. It's kind of amazing that they get anything at all with the, uh, fox guarding the henhouse.
Regarding "abstract values like our Bill of Rights", perhaps you can't detect sarcasm very well. I wish I could remember who said it, but expecting to bomb Iraq into a democracy is a bit like expecting to bomb a redwood forest into lawn furniture. Then again, I thought it was the conservatives in this country who think that physical security trumps civil rights and freedoms; after everything that has happened in the past few years, the Iraqis just might be forgiven for agreeing.
See the movie "Control Room"; it just might change your view of Al Jazeera. One of the producers candidly concedes that every news media tailors its output to suit its intended audience, including both Al Jazeera and Fox News. But the tailoring consists not of manufacturing the news so much as choosing what and what not to report, and how to spin it. Perhaps it would be good if each side took the time to see what the other side sees on the tube every day. Americans would get a somewhat more realistic (and certainly bloodier and all-around less pleasant) picture of what life has been like in Iraq since 2003, and Arabs would understand that Americans are arguably the most self-absorbed and self-deluded people on the planet, and that's why Bush is still in power.
So you're making the old "they hate our freedoms" argument, eh?
If so, then why hasn't al Qaeda attacked Sweden?
bin Laden said exactly this in one of his recent tapes, not that most Americans heard it. (I guess they don't want to risk being accused of treason or something. Or maybe they just never heard the expression "know your enemy".)
Now of course I wouldn't necessarily give any more credence to what bin Laden has to say than I do to George W Bush, except that bin Laden's actions have been far more consistent with his statements than Bush's actions have been with his.
But let's say that bin Laden is lying, and they really do hate our freedoms. In that case, I have to admit that he has succeeded in spectacular fashion in destroying them. Of course, he didn't do it himself. Bush and the Republican Congress did it for him.
It's easy to look back with hindsight and say that we should have done more after the first WTC attack. But I think the US did as much as it realistically could given the prevailing political climate and the information that it had at the time. We did capture and prosecute everyone we could identify as being involved and who we could get our hands on. That attack didn't even do as much damage as the Oklahoma City bombing, and I think you'd have to agree that the government reactions to both attacks was appropriate and effective. We caught the bad guys, and we didn't alienate the whole world in the process.
Indeed, I think the evidence is plain that our response to the second attack (9/11) has done us far more harm than good. That response, of course, included using 9/11 as a phony pretext to attack Iraq.
It should be now be abundantly clear that effectively fighting an enemy like Al Qaeda depends not on conventional military power but on having the sympathy and support of the rest of the world. If we had cultivated that support after 9/11 instead of utterly squandering it, we would have captured bin Laden long ago because somebody would have told us where he was. But we have so totally alienated the Arab and Islamic world that a very large fraction of it sees absolutely no reason to help us. You might think they're wrong, but what you and I think doesn't matter. Even worse, the abysmal image of the US across the Arab and Islamic world is rapidly breeding a whole new generation of bin Ladens and al Qaeda cells, so it may not even matter anymore if we do catch him.
Remember the DC Snipers? Within hours of identifying them and their vehicle, an alert civilian spotted the car and called the police. Without a supportive and helpful populace, they might not have been caught for a long time. Why shouldn't the same principle apply in fighting Al Qaeda?
How many suicide bombings occurred in Iraq on a daily basis before 2003? Why do you think their number suddenly increased later that year? Coincidence?
The French Resistance killed (and caused to be killed) many civilians while fighting the Germans through what were, by any objective description, terrorist activities. (The Germans even called them terrorists, and Hitler of course painted them as a mortal threat to the survival of the German nation). Yet to us they're now selfless heroes. The US has long engaged in its own large scale, stage-sponsored terrorism; remember the Nicaraguan Contras? They also killed lots of civilians. But to us they were "freedom fighters". I guess that makes it okay.
I cannot defend the tactics of the Iraqi "insurgents" any more than I can defend the tactics of Palestinian suicide bombers. But what I think doesn't matter. What matters is that the Iraqis and the Palestinians see them as selfless heroes, and individual Iraqis and Palestinians will keep blowing themselves up along with as many of their occupiers as they can as long as they consider it necessary.
The whole point is that violence breeds violence. Wars have always consisted of long strings of attack and retaliation, with each side justifying its actions on the basis of what the other side has already done to them. The Iraqis and the Palestinians fight with suicide bombs because they perceive them as the only effective weapon they have against a vastly stronger conventional army.
Remember the saying "Know your enemy". But these days, Americans seem to think that's somehow unpatriotic. Maybe, deep down, they're a little afraid that if they took the time to understand why all those Arabs are blowing themselves up, we just might find that they're doing it for reasons quite different from what our "leaders" are telling us.
Again, I hardly agree with what they're doing. Nor do I want to see Americans or Iraqi civilians die. I'm simply stating obvious facts that, for some reason, seem to really anger many flag-wavers around here whenever they're pointed out.
"Uh yeah, I'd really trust a channel that spews whatever crap is coming out of terrorists."
Your ignorance, not to mention your gullibility, is showing. Stop watching Fox News for a couple of hours and watch the documentary "Control Room". Then tell me if you still have the same opinion of Al Jazeera.
"Limped-dick response to the first WTC bombing?" What are you talking about? The people responsible were caught fairly quickly through good police work, with a major break coming when one of the idiots tried to get his deposit back on the rental truck that was used. Don't you remember that?
I guess you must not consider our response to 9/11 to be limped-dick. That must explain why we still haven't caught bin Laden.
Turn on the TV? Which channel? Fox News, our very own version of Pravda, with red, white and blue text banners and pundits foaming at the mouth about how it's treason to disagree with our Leader in time of war, a war which conveniently will never end? If that's all you watch, I can see why your view of the world is so screwed up.
Check out Al Jazeera, if you can find it. Then you might see a sampling of what's really going on over there: shot after shot of dead civilians, including many kids. Many more shots of civilians, barely alive, lying in squalid hospital beds, the remains of their arms and legs wrapped in bandages after being blown off by bombs. Innocent civilians being harassed and humiliated at roadblocks, or worse if they panic and fail to comply with a shouted command they can't understand because it's in English.
You'll see footage of heavily armed US troops kicking in doors of houses, pointing their weapons at civilians, shouting (again in English!) at women and childen cowering in the corners and crying. You'll see picture after picture of abuse of prisoners in US prison camps and hear about people, most of them completely innocent even by admission of the US commanders, who disappear into them for years without charges, without lawyers and without any chance to defend themselves.
Every other day there seems to be yet another suicide bombing in Iraq that kills as many people as the one in London two weeks ago. That attack is still getting saturation coverage on the US networks, but the bombings in Iraq rate, at most, a brief mention each.
Arab culture is quite different from ours, and we can't assume they share our more abstract values like our Bill of Rights (that is, if we actually practiced them ourselves). But they belong to the very same species as we, so it does seem somewhat reasonable to believe that they, no more than we, like being killed or maimed or abused or imprisoned, or having that happen to our friends and families.
Still can't figure out why they hate us? Or are you going to tell me that all that footage is faked somehow?
The only significant bottleneck in most people's broadband service is the uplink out of your house, and you have control over that.
I have Speakeasy DSL (768 up, 6000 down) with their own VoIP (actually Level3). My router is a Soekris Engineering net4801 running Linux. The standard Linux tc (traffic control) QoS stuff works absolutely wonderfully once you tune it correctly. I can load up my link with Bit Torrent traffic, pick up the phone and make a call, and it always sounds fine.
I actually created four traffic classes. VoIP is the highest, so it gets unconditional priority over everything else. Bit Torrent is the lowest, and the middle two are for interactive and bulk computer data. Within each class, stochastic fairness makes sure that no one flow gets it all.
I don't know what kind of QoS Speakeasy implements in their downstream direction (they refused to tell me when I asked) but it seems adequate. Because my downstream pipe is so much faster than my uplink, downlink QoS is not nearly as critical as upstream QoS.
I presume you never buy PPV movies. If you do, the box reports them over the phone line so you can get billed. I know that if you unplug the phone with unreported PPV movies, the box will get increasingly insistent about phoning home, and it will limit how many PPV purchases you can make.
You're not the first to realize this. Back during one of the JPL missions that used gravity assist, someone (a science reporter, I think) jokingly created a environmental "organization" he called SAME (Save the Angular Momentum of the Earth). I think it was the Galileo mission, as that was the first big-time mission to use the earth in a gravity assist maneuver.
It certainly seems obvious, but receiver sensing doesn't really work. You can't rely on the absence of a signal at the transmitter to ensure that you won't interfere with someone if you transmit, and conversely you aren't guaranteed to interfere with a signal you can hear. This is the problem with plain CSMA on radio channels.
A better approach is to have each receiver (not transmitter) indicate where and when it is listening so that other transmitters can avoid interfering with it. Busy Tone Multiple Access (BTMA), proposed way back in the 1970s, is probably the earliest such scheme. The MACA (Multiple Access with Collision Avoidance) scheme I invented for amateur packet radio circa 1990 that found its way (with enhancements by others) into 802.11 is basically time-division BTMA on a single channel.
A few years after I proposed MACA, I also suggested a more general purpose dynamic frequency coordination scheme for the amateur service based on packet radio. It was inspired by the backlash to the proposals to broaden the use of spread spectrum on the ham bands. You'd have a coordination channel on which receivers would broadcast the frequencies and times that they were listening so that nearby transmitters could avoid interfering with them. You could get fancy and have each transmitter send a test transmission to see if a receiver is bothered by it, and if not then that transmitter would not have to defer to that receiver.
Naturally this never went anywhere because the vast majority of hams are not really interested in any kind of technical innovation. They didn't want to have to do anything new just to continue using the frequencies they've always used, which they tend to treat as their own personal property. The spread spectrum proposal was eviscerated, and I let the idea drop. I wouldn't be surprised if the xG guys are now trying to patent my ideas. Wouldn't be the first time companies have tried to claim innovations placed into the public domain by hams as their own.
Why does beauty or complexity have to indicate the presence of a divine creator? Quite a lot of complexity has shown to arise naturally without intervention being necessary, provided a source of energy.
Strictly speaking, it's not so much a source of energy that you need, but something whose entropy can increase to compensate for the decrease of entropy in the self-organizing complex system. In the case of the evolution of life on earth, that thing is the sun. Its increase in entropy far exceeds the decrease of entropy on earth represented by living things.
We humans tend to define "energy" not as energy per se, but usable energy that can be used to decrease the entropy of some subsystem. We're surrounded by enormous amounts of energy in the form of ambient heat, e.g., in the oceans, but we can't use it without some sort of cold heatsink because of the second law of thermodynamics.
Sounds like you could learn some orbital mechanics too. A delta V of 10 km/sec is still a delta V of 10 km/sec whether you do it quickly with a large engine or slowly with a small engine.
Yes, an ion drive can produce considerably more delta-V than a chemical rocket with the same propellant mass, but 10 km/sec is still a lot of delta V even for an ion rocket. According to the article you cited, Deep Space 1's ion engine produced a total delta-V of only about 3 km/sec over its entire firing time of about a year and a half. Ion engines have *very* small thrusts and require a great deal of power, so missions take much planning and much time to execute.
Let me guess: you picked up the term "slingshot effect" from watching Star Trek IV, no? And you've been looking for your chance to use it until now, right?
The proper term is "gravity assist maneuver", and a moving, massive body like a planet is required. Unlike Star Trek, the sun cannot be used for maneuvers within the solar system as it does not move relative to the solar system. Planning these things is extremely complex, and flying them can also take many years. Because of Mercury's very high orbital velocity, the Messenger probe to orbit that planet will require one Earth flyby, two Venus flybys and three Mercury flybys before it can finally approach Mercury with a small enough relative velocity to be able to enter orbit with the available fuel. The whole thing will take 6 1/2 years, while just crashing a probe into Mercury (or flying by it, as was done by Mariner 10 in the 1970s) could be done in a matter of months.
Slashdot Mirror
I can. Imagine agreeing to do something at a certain future time, and then setting up a piece of hardware to do it. If you use a timescale with leap seconds, like UTC, then that device may have to be reprogrammed to deal with leap seconds an arbitrary number of times before that event occurs. If not for leap seconds, your hardware could be a simple down counter programmed with the difference between the agreed-upon future time and the current time.
Here's another example based on satellite tracking. Standard practice when describing a satellite orbit is to give a set of six orbital elements and an epoch time when they are valid. (The orbital elements can be Keplerian elements, or position and velocity state vectors, it doesn't matter). For practical reasons, the epoch time is often an externally specified parameter to the orbital element generator. And that time might well be in the future (since satellite orbits, at least over the short term, are pretty predictable). NORAD epoch times are UTC, and that creates a trap if you're not careful about leap seconds.
A related example comes from astronomy. When giving the coordinates of a celestial object, you must account for the precession of the earth's axis by also giving the epoch at which the coordinates are valid. Two epochs were often used in the latter half of the 20th century: B1950.0 and J2000.0. Although the latter date has now passed, J2000.0-based coordinates were in widespread use well before that date. Obviously that epoch date could not move around arbitrarily as a result of leap seconds, so it's based on "terrestrial time", another standard time scale related to TAI that doesn't follow leap seconds.
That's impossible to do precisely anyway due to relativity, and as the time between the two events increases the precision goes down more and more.
Well...yes. But the error caused by an incorrectly handled (or unhandled) leap second is likely to be far greater than any relativistic error in any real-world engineering application I'm likely to encounter. Besides, it's common in relativistic applications to just pick a frame of reference and make it your standard of measurement. UTC is that way, btw. It's defined at the geoid (approximately mean sea level) and relativistic corrections have to be made to atomic clocks at altitudes other than sea level.
What's difficult about it? I don't understand this point at all. There is a very clear and unambiguous way to date any event, regardless of whether or not it occurs near or during a leap second. "1998-12-31T23:59:59.00Z, 1998-12-31T23:59:60.00Z, 1999-01-01T00:00:00.00Z, 1999-01-01T00:00:01.00Z". You must be talking about UNIX time.
Yes, I was talking about UNIX time, sorry I wasn't more clear. You are absolutely right that UTC is not intended to be encoded as an integer. Unfortunately, that's what UNIX tries to do, and that's why there are problems dating events around leap seconds on UNIX. What actually happens is that a 1-second discontinuity ripples throughout the NTP hierarchy and clocks eventually settle on the "new" UTC after a fairly significant period of uncertainty. Or at least that's the way it used to work with NTP; I haven't followed the more recent versions. In any case, that's nonsense; a fundamental timescale should never have to "jump" in this way.
So I think we completely agree on the main point: UNIX's internal representation of time is fundamentally broken. It ought to be based on a count of seconds from some epoch on a timescale that does not use leap seconds, and conversion to or from UTC should be done only when needed for human consumption or input.
One could even argue that UNIX already does this, and it's the conversion routines that are broken. As you
There are many perfectly valid arguments against leap seconds. The difficulty in calculating the exact number of seconds between two events, the fact that calculations involving future times can give different results after leap seconds are declared, the difficulty of dating events that occur near or during leap seconds, all are serious drawbacks.
But these are not good arguments for removing leap seconds from UTC! Why do that when you can choose from two perfectly good standard time scales that don't have leap seconds? Those are the GPS (Global Positioning System) time scale and the TAI (International Atomic Time) timescale. They differ by a fixed offset: TAI is 19 seconds ahead of GPS and will remain so despite any future leap seconds added to UTC. (Strictly speaking the offset between TAI and GPS typically varies by some tens or hundreds of nanoseconds around 19 seconds, but the GPS system operators try to drive that error to zero, and they publish those offsets. The big advantage of GPS time, of course, is its ready availability from inexpensive receivers.)
CDMA digital cellular is one system that chose the GPS timescale to avoid the nasty discontinuities associated with UTC leap seconds. GPS times are still easily converted to UTC (or local time) for human consumption.
It would have been really nice had the UNIX designers chosen the TAI timescale instead of UTC as the internal representation of time. (GPS didn't exist back in the 1970s when UNIX was developed). Library routines could easily convert between TAI and UTC as needed for input and display, using configuration files updated every time a new leap second is declared, but you'd get a much cleaner internal representation of time. You wouldn't have the present situation where every timestamp for a past event is effectively moved one second every time there's a leap second.
I wonder if it's too late to make such a change...
You may honestly think the American presence in Iraq is a benign thing, and we're doing the right thing by training a native police force and army. But the insurgents (and the apparent large numbers of civilians that sympathize with and support them) think differently. To them, we're just like the Germans in France, and they're the Resistance, fighting the occupation and its collaborators in any way they can, even if it unfortunately kills some innocent civilians in the process. Now you and I may disagree with this view, but that's irrelevant; what they think is what drives their actions.
In any society you will always find a small number of sociopaths, but most people in Arab countries aren't born to become terrorist radicals. They're conditioned that way by their environment and upbringing, and by what they see other countries doing to them. And for decades, we've done the best we can to create that environment all throughout the Islamic world. One of the most frightening things I saw after 9/11 was footage of a fundamentalist Islamic school in Pakistan teaching 5-year-old kids to chant "death to America!" And these schools are all over the place. In another 15 years, they will become the next wave of terrorists we'll have to deal with unless we're ready to take the next logical step and begin a full-scale genocidal campaign. Even George Bush probably wouldn't do that.
I'm sure you honestly think that we did Iraq a favor by ridding them of Saddam Hussein, but as I said, Americans have a talent for self-delusion. Few in the Middle East really believe the US was motivated, as we so often claim, by a pure, altruistic desire to rid the world of a terrible tyrant. They tend to judge us by our actions, not our words. They see us ignoring many other brutal tyrants, especially in Africa, where no oilfields are at stake. Worse, they saw us prop up many tyrants during the Cold War whenever that enhanced our position against the Soviets. And as for our so-called War on Terrorism, they also see us sponsoring terrorism on a large scale whenever it suits our purposes, such as our support for the Nicaraguan Contras, or the Mujahaideen in Afghanistan during the Russian occupation. (That group, as is now well known, included Usama bin Laden).
So, you see it's a dangerous mistake to assume that others disagree with or dislike us because they're stupid or evil.
For those who think Al Jazeera is a terrorist front, that must explain the long and (to me) well-written opinion piece they're carrying entitled "Al Qaeda: wrong answers to real problems" at http://english.aljazeera.net/NR/exeres/25D45C98-47 1B-4A36-8253-F2120BEA180F.htm
You are quite right that we did not deserve 9/11 any more than the world deserved Hitler in the 1930s. I never said we did. But that's not the issue. It's simply a question of forseeable reactions to our own policies and actions which, for some reason, apologists for the Administration never concede even when there is plenty of warning.
Step back about a decade before 1933, the year Hitler came to power. Hitler was already a whackjob, but what was the nature of the relationship between Germany and the Western Powers? Read the terms of the Versailles Treaty, how it was perceived in Germany, the actions taken by the Western Powers to enforce it, particularly the occupation of the Ruhr in early 1923, and the effects those actions had on German public opinion and politics.
Hitler had two rapid spikes in popularity. The first began in 1922 when hyperinflation -- a direct result of punitive western demands for war reparations -- made German currency worthless. Hitler's "Beer Hall Putsch" was in November 1923. After it collapsed, Hitler was jailed and the Nazi party banned, the government managed to restore economic prosperity. The small Nazi hard core went into hiding, licked their wounds and waited. Hitler wrote Mein Kampf -- his warning to the world. Then when the world economy collapsed in 1929, and Germany's with it, Hitler's star began to rise again. The rest you know.
So what lesson I draw from this history? Simple. You need a two-pronged approach in dealing with your enemies. You need to go after those who've attacked you; I really don't disagree with that. But in so doing, you must be extremely selective and careful. You must take the time to learn as much as you can about your enemy: who he is and what he thinks.
And it's just as important to understand who your enemy isn't. You must avoid, at almost any cost, collectively punishing an entire population or culture for the actions of a few of its members, especially when they are not even governmental leaders (elected or otherwise). Otherwise you'll just turn them all into a renewable source of new enemies to replace those you kill or capture.
Strictly speaking, of course, you needn't be so picky if you plan to wipe them all out anyway. That was the basis of Nazi war policy, but it still didn't work for them. But I presume that even George W. Bush hasn't made genocide a basis of US policy, so it remains important to be selective. That's the basic mistake that Bush has made, and that's why this war will never end until that mistake is corrected.
Oh, as far as Camp Gitmo goes, I take it you wouldn't really want to be there even if Dick says the food is really good. And I think Amnesty International's description of it as the "gulag of our times" was right on the button; any differences between them are matters of scale, not of kind. I think that's why their report struck such a nerve.
Funny that you should mention fear, as it has been the Bush Administration's primary means to ensure domestic compliance. This is hardly new; fearmongering about "them" has been the favored tactic of despots throughout history for a simple reason: it works. So, you see I am thinking about the good of the country, and I have never been as worried about its direction and future as I have been in the past few years.
I think you're unreasonably hard on the UN Security Council. Despite what the Administration and certain members of Congress would have you believe, I don't think any of those members cared much for Saddam Hussein. It was just a question of whether another war would, on balance, help or hurt the situation when the sanctions and weapons inspectors, as imperfect as they were, were having the desired effect. France, for example, made it very clear that they thought our belligerent approach would likely backfire. Subsequent events, of course, have proven them quite correct. Our reaction to the French position, of course, perfectly illustrated Bush's simplistic "you're with us or with the terrorists" mentality.
Comparisons to World War II are not apt because in that war we were part of a collective defense answering clear aggression by the other side. There was simply no compelling reason for the US to attack Iraq in 2003; the fact that Bush felt the need to create and breathlessly hype a bogus WMD threat shows that even he understood that.
It would be much better to compare WW II to the first Gulf War, as that was also a collective response to an equally naked aggression (even if such aggressions happen all the time without a response from us when the countries involved have no oil).
The fact that we had many more countries supporting us in the first Gulf War than in the second underscores my point. While it's true that WWII and the first Gulf War differ in that the Allies occupied Germany and Japan but not Iraq, there was a good reason for this difference: Germany and Japan were serious threats to other countries almost until each one surrendered, while Iraq's threat to others was neutralized without the need for occupation. The events following Bush Jr.'s war show just how wise it was for Bush Sr. to stop when he did.
Anyway, if by now you can't see that our response to 9/11 has done us far more harm than good, I don't know what more to say -- except to watch the new crop of bin Ladens that we are so effectively cultivating.
While my comparison between UBL and the DC snipers certainly isn't perfect, I hardly think it absurd. You say that the snipers had no sympathizers while UBL has many. That's exactly my point! Why do you think UBL has so many sympathizers willing to protect the man from the biggest and best funded manhunt in history? Why do you think that Al Qaeda seems to have no problem recruiting new lieutenants and foot soldiers to take the place of those who've been killed or captured, or alternatively inspiring independent groups to emulate them? Do you seriously believe it's just because they hate the supposedly free way we Americans live within the borders of our own country? Or might all that just possibly have something to do with our continuing actions in their countries since 9/11?
I do wish it were possible to get the kind of news reporting that would actually shed some light on this issue. After years of fighting, and despite having the largest and most expensive intelligence service in the world, even the US government still seems totally in the dark about the size, scope and motivations of the Iraqi insurgency, and their degree of support among the civilian population. Otherwise you wouldn't see such ridiculous farces as last month's statement by Dick Cheney that the "insurgency was in its last throes", followed by backpedaling (after a general publicly said otherwise) in which he "clarified" his remarks by saying that "last throes" could last as long as 12 years... (Jon Stewart had a lot of fun with that one.)
As for who's responsible for the bombings, it seems beyond the ability of many conservative Americans to even entertain the notion that the people we call "insurgents" might actually see themselves as "freedom fighters" defending their country against an evil (to them) occupation, and that they honestly think they're doing the right thing by blowing up as many Americans and Iraqi "collaborators" as they can even if that unfortunately takes out many innocent Iraqis as well.
(I emphasize that I'm not saying that I agree with their image of themselves. But it sure seems to me that anyone who deliberately sacrifices his life in a suicide bombing was probably at least somewhat sincere about his cause, whether we think it's a good one or not. What you or I think doesn't matter. They're motivated by what they think.)
The Brits clearly share our difficulties in being honest to oneself. Just as it seems beyond the ability of many Americans to entertain the notion that we just might have provoked the ongoing Iraqi insurgency, it seems beyond the ability of many Brits to entertain the notion that the recent attacks in London just might be in retaliation for their support of the US in Iraq.
Accepting what seem to me to be obvious, objective facts hardly means that you support what the bombers did. Nor does it even mean that you must oppose your own government's policy (though I obviously do). It simply means having the integrity to concede that your government's military actions overseas can provoke reactions, and that any honest accounting of the costs of going to war must take those consequences into account.
But let's say, just for the sake of argument, that our enemies are not sentient beings motivated by notions of morality and self-sacrifice, as misguided as those notions may seem to us. Let's assume they're just like mindless staphylococci bacteria just doing what's in their malign little natures: hurting innocent humans whenever they get the chance. And suppose, by your actions, you knowingly do something that gives them that chance. Then who's to blame? The bacteria? I suppose it might make you feel good at some level to rail in fury at the evil bacteria, but it won't do you much good. Clearly the blame is yours for setting up the conditions for it to happen.
In every war, every belligerent's propaganda always heaps the complete moral blame for every casualty on every side on the other side(s) regardless of proximate cause. Unfortunately, that propaganda is frequently all too effective.
Okay, where's your bridge? I'm sure you won't mind if I run a title check. Routine procedure, you understand.
Yes, I have watched Fox, though I admit I can't watch it for very long before I get physically sick and have to switch it off. Bill O'Reilly's "interview" of Jeremy Glick comes to mind.
I suspect that if you could talk to the insurgents, they'd claim (just as we do) that they only go after "legitimate targets", and they "sincerely regret" any collateral damage. To them, the legitimate targets are the US and coalition forces, plus any Iraqis they consider collaborators with their occupiers. But whether you're trying to blow up an Iraqi police station deemed full of "collaborators" or a house in a residential area that you think might harbor Saddam Hussein, it's often hard to kill only your desired target. That's an unpleasant truth about warfare.
As for photos and reports of abuse of prisoners in US prison camps, many of those prisoners have been there for years. For a while there was a fresh new batch of abuse photos every day. More recently the supply of photos seems to have dried up, but no one seriously believes that's because the abuses have stopped; our soldiers simply learned not to use their cameras. But if you think it has all ended, then why did the reporters who went down to Gitmo for a tour all say it was a total farce? Why weren't they allowed to see anything or talk to any prisoners? The supply of new revelations seems to depend mainly on how lucky the ACLU and similar groups have been with their FOIA requests. It's kind of amazing that they get anything at all with the, uh, fox guarding the henhouse.
Regarding "abstract values like our Bill of Rights", perhaps you can't detect sarcasm very well. I wish I could remember who said it, but expecting to bomb Iraq into a democracy is a bit like expecting to bomb a redwood forest into lawn furniture. Then again, I thought it was the conservatives in this country who think that physical security trumps civil rights and freedoms; after everything that has happened in the past few years, the Iraqis just might be forgiven for agreeing.
See the movie "Control Room"; it just might change your view of Al Jazeera. One of the producers candidly concedes that every news media tailors its output to suit its intended audience, including both Al Jazeera and Fox News. But the tailoring consists not of manufacturing the news so much as choosing what and what not to report, and how to spin it. Perhaps it would be good if each side took the time to see what the other side sees on the tube every day. Americans would get a somewhat more realistic (and certainly bloodier and all-around less pleasant) picture of what life has been like in Iraq since 2003, and Arabs would understand that Americans are arguably the most self-absorbed and self-deluded people on the planet, and that's why Bush is still in power.
If so, then why hasn't al Qaeda attacked Sweden?
bin Laden said exactly this in one of his recent tapes, not that most Americans heard it. (I guess they don't want to risk being accused of treason or something. Or maybe they just never heard the expression "know your enemy".)
Now of course I wouldn't necessarily give any more credence to what bin Laden has to say than I do to George W Bush, except that bin Laden's actions have been far more consistent with his statements than Bush's actions have been with his.
But let's say that bin Laden is lying, and they really do hate our freedoms. In that case, I have to admit that he has succeeded in spectacular fashion in destroying them. Of course, he didn't do it himself. Bush and the Republican Congress did it for him.
If so, I think Al Jazeera would spend even less time reporting the US side.
I agree; bin Laden is being assisted by a lot of people. Now why do you think that is?
Indeed, I think the evidence is plain that our response to the second attack (9/11) has done us far more harm than good. That response, of course, included using 9/11 as a phony pretext to attack Iraq.
It should be now be abundantly clear that effectively fighting an enemy like Al Qaeda depends not on conventional military power but on having the sympathy and support of the rest of the world. If we had cultivated that support after 9/11 instead of utterly squandering it, we would have captured bin Laden long ago because somebody would have told us where he was. But we have so totally alienated the Arab and Islamic world that a very large fraction of it sees absolutely no reason to help us. You might think they're wrong, but what you and I think doesn't matter. Even worse, the abysmal image of the US across the Arab and Islamic world is rapidly breeding a whole new generation of bin Ladens and al Qaeda cells, so it may not even matter anymore if we do catch him.
Remember the DC Snipers? Within hours of identifying them and their vehicle, an alert civilian spotted the car and called the police. Without a supportive and helpful populace, they might not have been caught for a long time. Why shouldn't the same principle apply in fighting Al Qaeda?
Watch the documentary "Control Room", then decide if you think they're as biased as Fox News.
The French Resistance killed (and caused to be killed) many civilians while fighting the Germans through what were, by any objective description, terrorist activities. (The Germans even called them terrorists, and Hitler of course painted them as a mortal threat to the survival of the German nation). Yet to us they're now selfless heroes. The US has long engaged in its own large scale, stage-sponsored terrorism; remember the Nicaraguan Contras? They also killed lots of civilians. But to us they were "freedom fighters". I guess that makes it okay.
I cannot defend the tactics of the Iraqi "insurgents" any more than I can defend the tactics of Palestinian suicide bombers. But what I think doesn't matter. What matters is that the Iraqis and the Palestinians see them as selfless heroes, and individual Iraqis and Palestinians will keep blowing themselves up along with as many of their occupiers as they can as long as they consider it necessary.
The whole point is that violence breeds violence. Wars have always consisted of long strings of attack and retaliation, with each side justifying its actions on the basis of what the other side has already done to them. The Iraqis and the Palestinians fight with suicide bombs because they perceive them as the only effective weapon they have against a vastly stronger conventional army.
Remember the saying "Know your enemy". But these days, Americans seem to think that's somehow unpatriotic. Maybe, deep down, they're a little afraid that if they took the time to understand why all those Arabs are blowing themselves up, we just might find that they're doing it for reasons quite different from what our "leaders" are telling us.
Again, I hardly agree with what they're doing. Nor do I want to see Americans or Iraqi civilians die. I'm simply stating obvious facts that, for some reason, seem to really anger many flag-wavers around here whenever they're pointed out.
Your ignorance, not to mention your gullibility, is showing. Stop watching Fox News for a couple of hours and watch the documentary "Control Room". Then tell me if you still have the same opinion of Al Jazeera.
I guess you must not consider our response to 9/11 to be limped-dick. That must explain why we still haven't caught bin Laden.
Check out Al Jazeera, if you can find it. Then you might see a sampling of what's really going on over there: shot after shot of dead civilians, including many kids. Many more shots of civilians, barely alive, lying in squalid hospital beds, the remains of their arms and legs wrapped in bandages after being blown off by bombs. Innocent civilians being harassed and humiliated at roadblocks, or worse if they panic and fail to comply with a shouted command they can't understand because it's in English.
You'll see footage of heavily armed US troops kicking in doors of houses, pointing their weapons at civilians, shouting (again in English!) at women and childen cowering in the corners and crying. You'll see picture after picture of abuse of prisoners in US prison camps and hear about people, most of them completely innocent even by admission of the US commanders, who disappear into them for years without charges, without lawyers and without any chance to defend themselves.
Every other day there seems to be yet another suicide bombing in Iraq that kills as many people as the one in London two weeks ago. That attack is still getting saturation coverage on the US networks, but the bombings in Iraq rate, at most, a brief mention each.
Arab culture is quite different from ours, and we can't assume they share our more abstract values like our Bill of Rights (that is, if we actually practiced them ourselves). But they belong to the very same species as we, so it does seem somewhat reasonable to believe that they, no more than we, like being killed or maimed or abused or imprisoned, or having that happen to our friends and families.
Still can't figure out why they hate us? Or are you going to tell me that all that footage is faked somehow?
I have Speakeasy DSL (768 up, 6000 down) with their own VoIP (actually Level3). My router is a Soekris Engineering net4801 running Linux. The standard Linux tc (traffic control) QoS stuff works absolutely wonderfully once you tune it correctly. I can load up my link with Bit Torrent traffic, pick up the phone and make a call, and it always sounds fine.
I actually created four traffic classes. VoIP is the highest, so it gets unconditional priority over everything else. Bit Torrent is the lowest, and the middle two are for interactive and bulk computer data. Within each class, stochastic fairness makes sure that no one flow gets it all.
I don't know what kind of QoS Speakeasy implements in their downstream direction (they refused to tell me when I asked) but it seems adequate. Because my downstream pipe is so much faster than my uplink, downlink QoS is not nearly as critical as upstream QoS.
I presume you never buy PPV movies. If you do, the box reports them over the phone line so you can get billed. I know that if you unplug the phone with unreported PPV movies, the box will get increasingly insistent about phoning home, and it will limit how many PPV purchases you can make.
You're not the first to realize this. Back during one of the JPL missions that used gravity assist, someone (a science reporter, I think) jokingly created a environmental "organization" he called SAME (Save the Angular Momentum of the Earth). I think it was the Galileo mission, as that was the first big-time mission to use the earth in a gravity assist maneuver.
A better approach is to have each receiver (not transmitter) indicate where and when it is listening so that other transmitters can avoid interfering with it. Busy Tone Multiple Access (BTMA), proposed way back in the 1970s, is probably the earliest such scheme. The MACA (Multiple Access with Collision Avoidance) scheme I invented for amateur packet radio circa 1990 that found its way (with enhancements by others) into 802.11 is basically time-division BTMA on a single channel.
A few years after I proposed MACA, I also suggested a more general purpose dynamic frequency coordination scheme for the amateur service based on packet radio. It was inspired by the backlash to the proposals to broaden the use of spread spectrum on the ham bands. You'd have a coordination channel on which receivers would broadcast the frequencies and times that they were listening so that nearby transmitters could avoid interfering with them. You could get fancy and have each transmitter send a test transmission to see if a receiver is bothered by it, and if not then that transmitter would not have to defer to that receiver.
Naturally this never went anywhere because the vast majority of hams are not really interested in any kind of technical innovation. They didn't want to have to do anything new just to continue using the frequencies they've always used, which they tend to treat as their own personal property. The spread spectrum proposal was eviscerated, and I let the idea drop. I wouldn't be surprised if the xG guys are now trying to patent my ideas. Wouldn't be the first time companies have tried to claim innovations placed into the public domain by hams as their own.
Strictly speaking, it's not so much a source of energy that you need, but something whose entropy can increase to compensate for the decrease of entropy in the self-organizing complex system. In the case of the evolution of life on earth, that thing is the sun. Its increase in entropy far exceeds the decrease of entropy on earth represented by living things.
We humans tend to define "energy" not as energy per se, but usable energy that can be used to decrease the entropy of some subsystem. We're surrounded by enormous amounts of energy in the form of ambient heat, e.g., in the oceans, but we can't use it without some sort of cold heatsink because of the second law of thermodynamics.
Yes, an ion drive can produce considerably more delta-V than a chemical rocket with the same propellant mass, but 10 km/sec is still a lot of delta V even for an ion rocket. According to the article you cited, Deep Space 1's ion engine produced a total delta-V of only about 3 km/sec over its entire firing time of about a year and a half. Ion engines have *very* small thrusts and require a great deal of power, so missions take much planning and much time to execute.
Let me guess: you picked up the term "slingshot effect" from watching Star Trek IV, no? And you've been looking for your chance to use it until now, right?
The proper term is "gravity assist maneuver", and a moving, massive body like a planet is required. Unlike Star Trek, the sun cannot be used for maneuvers within the solar system as it does not move relative to the solar system. Planning these things is extremely complex, and flying them can also take many years. Because of Mercury's very high orbital velocity, the Messenger probe to orbit that planet will require one Earth flyby, two Venus flybys and three Mercury flybys before it can finally approach Mercury with a small enough relative velocity to be able to enter orbit with the available fuel. The whole thing will take 6 1/2 years, while just crashing a probe into Mercury (or flying by it, as was done by Mariner 10 in the 1970s) could be done in a matter of months.