"The future is here. It's just not evenly distributed." -- William Gibson
I've said before that predictions aren't something I ought to do very often, because I normally don't do them very well. And when we're talking about things like who's going to win an upcoming election, or which players will do well this season, that's a good rule of thumb. But today, I'm going to talk about technological trends. The future holds both wonders and horrors, and most of both are already with us in some form or another. Specifically, I'm going to be talking about the implications of a piece of modern technology that many of us already carry with us on a daily basis: smart phones.
This is part of what Gibson was talking about: the future is already here, it's just not uniformly distributed. The modern cellular telephone is still called a telephone, when in reality it's a palm-sized computer that has a telephone function. It can also send and receive text messages, e-mail, and function as a web browser. It can hold a small library of books, movies, and music. And it can function as a calculator, stopwatch, camera for both still and moving images. And a map. Never forget the map. We are raising a generation that has no clear idea of what it means to be involuntarily lost. In their mental universe, we've always been able to reach up into space and pull down our exact location.
However, that's just a drop in the bucket. The bottleneck, the thing that keeps these devices from being more pervasive than they already are, is the interface. There's a limit to what can be done with a few square inches of screen space.
We are about to transcend those limits. Researchers at the University of Wisconsin are designing an optical display that can fit within a contact lens. This means that future smartphones will be able to paint their displays directly upon your field of vision. The implications of this are immense.
You've heard of "virtual reality." This isn't it. This is something I've heard called "augmented reality." It's your world, with more information. That's both a good thing, and a bad thing. First, the good.
Right off, let's take a look at that turn-by-turn navigation feature that you hardly ever use while you're driving. Augmented Reality makes this far more useful. Instead of a tiny map that you cannot use safely while driving, you get a green line pasted on your field of view, telling you in no uncertain terms where you need to turn in order to get where it is you want to go. Merely asking, "How do I get home from here?" results in a path popping out in front of you, leading the way. And since you'll probably be able to use your fingers as a pointer, you can frame questions about anything you can point at. Asking "What is that?" can tell you anything from what species of bird that is, to what kind of airplane, to where that specific flight came from and where it's going. (Most UFO sightings will be disposed of within seconds.) You'll be able to see weather alerts, if you want to. It's already just about true that any of us with an internet connection can find the answer to just about any question whose answer is known, in the future that answer is available by voice query, and can be immediately displayed in front of your eyes, anytime, day or night.
But, it's not without disadvantages.
A horrifying new dimension of message spam opens up, when a hacker can hijack your visual display to force you to see anything they want you to see. Going by the contents of my spam bucket, most of this will be advertising for products you shouldn't mention in a family publication. Some of it will consist of more innocuous advertisements, say, a blurb about coffee when you walk past a Starbuck's. Others will be pranks played on you by ... friends. And we all have at least one friend like that, with a wildly inappropriate sense of humor. Worst of all, closing your eyes may not even block it out, depending on exactly how these things work. Personal data security will be of paramount importance, unless you like the idea of being bombarded with horrifying images on a fairly constant basis.
Further, an entirely new etiquette will have to be developed to account for this. We're already heading down that road, establishing when it is and isn't appropriate to use cell phones. However, things change when you no longer have to be looking at the device to interact with it. The guy who looks like he's politely paying attention may be doing nothing of the sort. He might be watching Casablanca. He might be playing Call of Duty. Unless you can tap the data stream, you have no way of knowing. I have no idea how we'll sort that out. But we'll have to figure it out once we get there.
And we will get there. The advantages so far outweigh the drawbacks that we won't be able to avoid it. There are parts I'm really looking forward to, and parts that I'm dreading, but on the whole it's a huge opportunity. Opportunity for what, we just don't know yet.
But it'll be fun to find out.
Friday, November 25, 2011
Friday, November 18, 2011
Video Del Fuego, Part XLIX
On November 4, 1979, a group of Iranian students (possibly with the backing of the revolutionary government, possibly not) took over the United States Embassy in Tehran. The Americans were held hostage for 444 days, until January 20, 1981. During their captivity, there were at least two plans made for a rescue. One is well known, the other less so.
The one that just about everyone's heard of is Operation Eagle Claw. Eagle Claw was a complex operation, involving eight RH-53 helicopters and four C-130 Hercules transport aircraft, three of which were carrying fuel for the return trip. It required close cooperation between elements from the Army, Navy, and Air Force. It also required a bit of luck with weather. The close cooperation worked tolerably well enough. The weather ... didn't. Eagle Claw ended in disaster when one of the helicopters collided with one of the tankers while they were preparing to abort the mission anyway, because they didn't have enough mechanically-fit helicopters to complete the mission.
But that wasn't the end of the matter. They had one more trick up their sleeve. One of the problems with Operation Eagle Claw was that it relied on too much coordination. They decided to simplify matters by using only one aircraft, staging the mission out of the continental United States, using multiple in-air re-fuelings on the way to Iran, and meeting up with a nearby aircraft carrier. The aircraft they chose was a C-130 Hercules, and they would land inside a soccer stadium close by the American Embassy.
"Now hold on a second," I hear you saying. "You can't actually do that." Well, not with a stock C-130, you can't. But this one? It's been modified. Ladies and gentlemen, behold Operation Credible Sport:
Yes, someone looked at a C-130 airframe and said, "You know what this thing needs? Rockets. A whole bunch of rockets." One set of rockets to soak up the high rate of descent. Another set of rockets to slow the beast down once you're on the deck. And a third set of rockets, to kick your butt back up skyward when it's time to leave. Oh yeah, this would have gotten the job done.
Except that, on the last test flight, some damn fool hit the switches out of sequence. Believe it or not, everyone made it out of there. With that much explodium on board, you'd better believe they had a fire truck close by.
But for that, the hostages might have been home by early November. As it was, on November 2, the Iranian parliament accepted an Algerian mediation plan, and a few days after that, Jimmy Carter lost his re-election bid. The plan was shelved after that.
And by the way: landing a C-130 on a carrier was the least crazy part of this plan. It had been done before, in 1963.
The one that just about everyone's heard of is Operation Eagle Claw. Eagle Claw was a complex operation, involving eight RH-53 helicopters and four C-130 Hercules transport aircraft, three of which were carrying fuel for the return trip. It required close cooperation between elements from the Army, Navy, and Air Force. It also required a bit of luck with weather. The close cooperation worked tolerably well enough. The weather ... didn't. Eagle Claw ended in disaster when one of the helicopters collided with one of the tankers while they were preparing to abort the mission anyway, because they didn't have enough mechanically-fit helicopters to complete the mission.
But that wasn't the end of the matter. They had one more trick up their sleeve. One of the problems with Operation Eagle Claw was that it relied on too much coordination. They decided to simplify matters by using only one aircraft, staging the mission out of the continental United States, using multiple in-air re-fuelings on the way to Iran, and meeting up with a nearby aircraft carrier. The aircraft they chose was a C-130 Hercules, and they would land inside a soccer stadium close by the American Embassy.
"Now hold on a second," I hear you saying. "You can't actually do that." Well, not with a stock C-130, you can't. But this one? It's been modified. Ladies and gentlemen, behold Operation Credible Sport:
Yes, someone looked at a C-130 airframe and said, "You know what this thing needs? Rockets. A whole bunch of rockets." One set of rockets to soak up the high rate of descent. Another set of rockets to slow the beast down once you're on the deck. And a third set of rockets, to kick your butt back up skyward when it's time to leave. Oh yeah, this would have gotten the job done.
Except that, on the last test flight, some damn fool hit the switches out of sequence. Believe it or not, everyone made it out of there. With that much explodium on board, you'd better believe they had a fire truck close by.
But for that, the hostages might have been home by early November. As it was, on November 2, the Iranian parliament accepted an Algerian mediation plan, and a few days after that, Jimmy Carter lost his re-election bid. The plan was shelved after that.
And by the way: landing a C-130 on a carrier was the least crazy part of this plan. It had been done before, in 1963.
Friday, November 11, 2011
Sesquicentennial, Part XVIII: Foreign Affairs
--FIRST -PREV NEXT-
In the modern era, we're accustomed to fast-moving, quick-paced conflicts. The interval between the initial invasion of Iraq and the fall of Baghdad in 2003 could be measured in weeks. The interval between the beginnings of unrest in Libya and the death of Quaddafi could be measured in only months. This, you have to understand, is a fairly new development, especially in American military history. Specifically, it was a response to what happened in the 1973 Arab-Israeli war. One of our take-aways from that conflict is that we wouldn't have time to gear up for any future conflict ... and the new watch-words became "come as you are" and "win the first fight." We appear to have more or less learned the lesson.
But in 1861, we were still over a century away from that revelation. The fall of 1861 moved very, very slowly. This was a deliberate pause on both sides. One of the things clear to everyone after the Battle of Bull Run was that no one was really ready for any of this. Everyone needed time to raise, equip, and train fresh troops. A whole lot of fresh troops.
The Union wasn't having a tremendously difficult time doing any of this. To raise and outfit an army, you need a supply of manpower, ready cash to buy weapons and ammunition, more ready cash to expend ammunition in training, and skilled men to lead and direct the training of your new troops. The Union ran down its list: Manpower? Check. Cash? Check. More cash? Check. Skilled men? Well, sort of. But still check.
The Union was beginning to shake out its pre-War old guard. Some of the retirements, if somewhat unfair, were also necessary. Lieutenant General Winfield Scott, the Army's commanding general, was an old man, and not in the best of health to begin with. If he were younger and more vigorous, he'd probably be the man for the job; but young and vigorous he most assuredly was not. His retirement was expected, and surprised no one. As his replacement, Lincoln selected the brightest of his rising stars: General George McClellan. His earlier success was one of the few bright spots for the Union so far. And if there's anything a former railroad engineer knew, it was organization. And it does have to be said: that fall and that winter, General McClellan molded the broken, dispirited soldiers that slouched around Washington into a tight, disciplined unit: the Army of the Potomac. And he strengthened the defenses surrounding Washington to the point that the Federal capital was now the most heavily-fortified city on Earth. Whatever else you may have to say about General McClellan, you must give him credit for laying the groundwork and forging the tools. He was, in many ways, a perfectly splendid officer.
Down South, a similar story was playing out. The Confederates had the same four needs for army-building. And they ran down the same checklist: Manpower? Check ... for now. Cash? Check, with the same proviso. More cash? Well, we may have to get back to you on that one. Skilled men? Oh yes, plenty! But, without arms and ammunition, what can they do?
The Union blockade was beginning to pinch the Confederacy's coffers. They had virtually no native industry of their own. They knew this going in. Their big plan all along was to gain enough support abroad, from foreign merchants who needed their cotton, so that they could use a powerful foreign fleet to force the Union blockade aside. At which point, they could buy all the arms they needed from the English and French. But ... that consummation was still a long, long way from being concluded.
England, you see, wasn't exactly eager to leap into a military alliance with the Confederacy.
Oh, there's one reason why they might. It'd poke a sharp stick in the Yankees' eyes, and no mistake. London might well be up for that. But, there were two issues lurking in the background that cloud those waters. First, as we said before, war with the Union would mean war with the US Navy. It's a war England would probably win, but it would cost. England wasn't eager to pay that cost. And secondly, the Confederacy was explicitly a slave power. There was an organization in London, the Anti-Slavery Society, headed by a German immigrant named Albert. Ordinarily that would have meant little. But, since Albert's wife was Victoria, by Grace of God Queen of England, Scotland, and all the rest; it mattered a great deal indeed. What the Sovereign wants, the Sovereign tends to get; and Prime Minister Palmerston was going to have to have an outstanding reason if he was going to go before her and ask her to support a slave-holding Power.
The Union damn near gave it to him.
William Yancey, the current Confederate representative in London, was sick and unable to fulfill his duties. So, President Davis had to appoint a couple of replacements: John Slidell of Louisiana and James Mason of Georgia. Their job was to get as much support, official and unofficial, as they possibly could. A direct ship to England couldn't be had, so they made their way out to where they could catch a ship for England. Originally, they made for the Bahamas, but they'd missed an England-bound ship by mere days. Then they heard that an English mail ship would be leaving Cuba soon. So, they sailed for Cuba, and got a ride on the RMS Trent. At that point, they thought they were safely England-bound.
It's more or less at this point that the USS San Jacinto intervenes, and stops the Trent for a cargo inspection. And by "cargo", I mean Messrs. Mason and Slidell, since the captain of the San Jacinto had heard while he was laid up in Cuba following an Atlantic patrol that two Confederate ministers were England-bound on the Trent. (Did anyone bother keeping secrets back then?)
Now, strictly speaking, Captain Wilkes had no legal right to stop the Trent. This seizure was a violation of international law. But, Captain Wilkes took it upon himself to detain the Trent and its passengers, so as to disrupt the Confederacy's diplomatic efforts. It apparently escaped Captain Wilkes' calculations that such an action might well enrage England, and provoke them to enter the War on the Confederacy's side.
This mess would take several months to unwind, over the winter of 1861-1862. Several times, things looked like they might flare up into open war. But, owing to skillful diplomacy by President Lincoln and his ambassador in London, Charles F. Adams, no such war took place. England did embark on a naval construction program. They did strengthen their garrison in Canada. But, after an admission of wrongdoing that wasn't really an admission, Mason and Slidell were released from custody and allowed to board a Royal Navy ship in Provincetown, Massachusetts. So, Captain Wilkes merely delayed the two men for six months or so.
In the end, very little changed. The Confederacy wasn't going to get the recognition it wanted, not yet anyway. But, they did win one key concession from the British: recognition of the Confederacy as a belligerent party. While this meant nothing as far as Her Majesty's Government was concerned, it meant that Confederate ships could use British ports to re-provision, and they could contract with private suppliers for arms and munitions.
Half a loaf was better than none. The Confederacy would have as much arms as it could buy and smuggle through the Union blockade. That would allow them to field an army. For how long, no one knew yet. President Davis hoped it would be long enough.
In the modern era, we're accustomed to fast-moving, quick-paced conflicts. The interval between the initial invasion of Iraq and the fall of Baghdad in 2003 could be measured in weeks. The interval between the beginnings of unrest in Libya and the death of Quaddafi could be measured in only months. This, you have to understand, is a fairly new development, especially in American military history. Specifically, it was a response to what happened in the 1973 Arab-Israeli war. One of our take-aways from that conflict is that we wouldn't have time to gear up for any future conflict ... and the new watch-words became "come as you are" and "win the first fight." We appear to have more or less learned the lesson.
But in 1861, we were still over a century away from that revelation. The fall of 1861 moved very, very slowly. This was a deliberate pause on both sides. One of the things clear to everyone after the Battle of Bull Run was that no one was really ready for any of this. Everyone needed time to raise, equip, and train fresh troops. A whole lot of fresh troops.
The Union wasn't having a tremendously difficult time doing any of this. To raise and outfit an army, you need a supply of manpower, ready cash to buy weapons and ammunition, more ready cash to expend ammunition in training, and skilled men to lead and direct the training of your new troops. The Union ran down its list: Manpower? Check. Cash? Check. More cash? Check. Skilled men? Well, sort of. But still check.
The Union was beginning to shake out its pre-War old guard. Some of the retirements, if somewhat unfair, were also necessary. Lieutenant General Winfield Scott, the Army's commanding general, was an old man, and not in the best of health to begin with. If he were younger and more vigorous, he'd probably be the man for the job; but young and vigorous he most assuredly was not. His retirement was expected, and surprised no one. As his replacement, Lincoln selected the brightest of his rising stars: General George McClellan. His earlier success was one of the few bright spots for the Union so far. And if there's anything a former railroad engineer knew, it was organization. And it does have to be said: that fall and that winter, General McClellan molded the broken, dispirited soldiers that slouched around Washington into a tight, disciplined unit: the Army of the Potomac. And he strengthened the defenses surrounding Washington to the point that the Federal capital was now the most heavily-fortified city on Earth. Whatever else you may have to say about General McClellan, you must give him credit for laying the groundwork and forging the tools. He was, in many ways, a perfectly splendid officer.
Down South, a similar story was playing out. The Confederates had the same four needs for army-building. And they ran down the same checklist: Manpower? Check ... for now. Cash? Check, with the same proviso. More cash? Well, we may have to get back to you on that one. Skilled men? Oh yes, plenty! But, without arms and ammunition, what can they do?
The Union blockade was beginning to pinch the Confederacy's coffers. They had virtually no native industry of their own. They knew this going in. Their big plan all along was to gain enough support abroad, from foreign merchants who needed their cotton, so that they could use a powerful foreign fleet to force the Union blockade aside. At which point, they could buy all the arms they needed from the English and French. But ... that consummation was still a long, long way from being concluded.
England, you see, wasn't exactly eager to leap into a military alliance with the Confederacy.
Oh, there's one reason why they might. It'd poke a sharp stick in the Yankees' eyes, and no mistake. London might well be up for that. But, there were two issues lurking in the background that cloud those waters. First, as we said before, war with the Union would mean war with the US Navy. It's a war England would probably win, but it would cost. England wasn't eager to pay that cost. And secondly, the Confederacy was explicitly a slave power. There was an organization in London, the Anti-Slavery Society, headed by a German immigrant named Albert. Ordinarily that would have meant little. But, since Albert's wife was Victoria, by Grace of God Queen of England, Scotland, and all the rest; it mattered a great deal indeed. What the Sovereign wants, the Sovereign tends to get; and Prime Minister Palmerston was going to have to have an outstanding reason if he was going to go before her and ask her to support a slave-holding Power.
The Union damn near gave it to him.
William Yancey, the current Confederate representative in London, was sick and unable to fulfill his duties. So, President Davis had to appoint a couple of replacements: John Slidell of Louisiana and James Mason of Georgia. Their job was to get as much support, official and unofficial, as they possibly could. A direct ship to England couldn't be had, so they made their way out to where they could catch a ship for England. Originally, they made for the Bahamas, but they'd missed an England-bound ship by mere days. Then they heard that an English mail ship would be leaving Cuba soon. So, they sailed for Cuba, and got a ride on the RMS Trent. At that point, they thought they were safely England-bound.
It's more or less at this point that the USS San Jacinto intervenes, and stops the Trent for a cargo inspection. And by "cargo", I mean Messrs. Mason and Slidell, since the captain of the San Jacinto had heard while he was laid up in Cuba following an Atlantic patrol that two Confederate ministers were England-bound on the Trent. (Did anyone bother keeping secrets back then?)
Now, strictly speaking, Captain Wilkes had no legal right to stop the Trent. This seizure was a violation of international law. But, Captain Wilkes took it upon himself to detain the Trent and its passengers, so as to disrupt the Confederacy's diplomatic efforts. It apparently escaped Captain Wilkes' calculations that such an action might well enrage England, and provoke them to enter the War on the Confederacy's side.
This mess would take several months to unwind, over the winter of 1861-1862. Several times, things looked like they might flare up into open war. But, owing to skillful diplomacy by President Lincoln and his ambassador in London, Charles F. Adams, no such war took place. England did embark on a naval construction program. They did strengthen their garrison in Canada. But, after an admission of wrongdoing that wasn't really an admission, Mason and Slidell were released from custody and allowed to board a Royal Navy ship in Provincetown, Massachusetts. So, Captain Wilkes merely delayed the two men for six months or so.
In the end, very little changed. The Confederacy wasn't going to get the recognition it wanted, not yet anyway. But, they did win one key concession from the British: recognition of the Confederacy as a belligerent party. While this meant nothing as far as Her Majesty's Government was concerned, it meant that Confederate ships could use British ports to re-provision, and they could contract with private suppliers for arms and munitions.
Half a loaf was better than none. The Confederacy would have as much arms as it could buy and smuggle through the Union blockade. That would allow them to field an army. For how long, no one knew yet. President Davis hoped it would be long enough.
Friday, November 04, 2011
It's About Time
A while back, a group of physicists at CERN reported a remarkable result: they had observed a beam of neutrinos traveling faster than light. Which, near as we can tell, ought to be impossible. They are currently attempting to repeat their experiment to verify their results, and are also looking into possible measurement errors.
One recent rebuttal was interesting. They claim that, if they really were moving faster than light, they ought to have shed energy in the form of specific particles, which the CERN experiment did not detect.
Another theory holds that something that's moving faster than light is also moving backwards in time. Leading to the physicists' joke: "We don't serve faster-than-light neutrinos here," said the barman. A neutrino walks into the bar. I'm not sure I buy the theory, but then again, I pretty much hate time travel in all its forms.
Another competing theory caught my attention: the neutrinos only seemed to be traveling faster than light, because the laboratory used GPS satellites as a time reference. Since the satellites were also moving with respect to the experiment, that motion also has to be accounted for, leading to a margin of error that almost exactly covers the gap.
"Now, wait one second," I can hear you saying. "GPS satellites are used to find where you are. What do clocks have to do with it?" Everything, my friend. Everything. The clock is by far the most important thing a GPS satellite carries. It's the key to the whole process.
You see, one of the things we think we know about the Universe is that light always moves at the same speed. We're fairly sure about that. At least, we haven't been able to design an experiment to disprove that fact. So, if you have two clocks, and Clock A broadcasts a time signal to Clock B, then the difference between Clock A's time at arrival and the received time from Clock B tells you the instantaneous distance between the two clocks. With me so far?
Now, each of the GPS satellites is continually broadcasting two pieces of information: an identifier, and a time signal. The identifier tells you which satellite it is, and that information plus your current time should tell you where that satellite ought to be. So, once your GPS receiver gets a signal from Satellite A, it compares the broadcast time with the current system time, and computes a distance. Using that distance, and the satellite's position, it figuratively draws a circle on the globe. You're somewhere on that circle.
That's not enough. So, it looks for a second signal. If it can find Satellite B, it compares Satellite B's broadcast time with the current system time, converts that into a distance, and draws another circle on the globe. Now, those two circles intersect in at most two places. So, you're at one, or the other. You still don't know which.
Well, that doesn't really work, either. So, you need a third signal. Now, it looks for Satellite C, and does the same thing. It compares times, finds a distance, draws a third circle ... and now, if the Earth were a perfect sphere, all three circles would meet in harmony in one and only one place. But the Earth isn't a perfect sphere. It's not a perfect anything. It's awfully damned lumpy. So...
So it looks for a fourth signal. Once it finds Satellite D, it goes through the same process. And basically, it finds the point where all four circles more or less meet up. And hey presto, you know where you're at. And, if you have a relatively new unit, it'll also tell you that you need to take the next exit to get to your Aunt Sally's house. Oh, and you need to pick up a loaf of bread and some eggs while you're at it.
But, mad scientists being the innovative chaps that they are, they found a new and interesting "off-label" use for GPS technology. Why worry about synchronizing your clocks if the U.S. Department of Defense has already gone to the trouble of synchronizing one for you? Well, now we think we know a good reason: because it's whizzing around the planet at 17,500 miles per hour, that's why. And if you don't take that into account, weird things might happen.
Although the jury's still out. Weird things might still be happening. We won't know until the re-test is over. Measurements talk, and we just don't have enough of 'em yet.
Still, we should know something in six months or so. Keep your fingers crossed.
One recent rebuttal was interesting. They claim that, if they really were moving faster than light, they ought to have shed energy in the form of specific particles, which the CERN experiment did not detect.
Another theory holds that something that's moving faster than light is also moving backwards in time. Leading to the physicists' joke: "We don't serve faster-than-light neutrinos here," said the barman. A neutrino walks into the bar. I'm not sure I buy the theory, but then again, I pretty much hate time travel in all its forms.
Another competing theory caught my attention: the neutrinos only seemed to be traveling faster than light, because the laboratory used GPS satellites as a time reference. Since the satellites were also moving with respect to the experiment, that motion also has to be accounted for, leading to a margin of error that almost exactly covers the gap.
"Now, wait one second," I can hear you saying. "GPS satellites are used to find where you are. What do clocks have to do with it?" Everything, my friend. Everything. The clock is by far the most important thing a GPS satellite carries. It's the key to the whole process.
You see, one of the things we think we know about the Universe is that light always moves at the same speed. We're fairly sure about that. At least, we haven't been able to design an experiment to disprove that fact. So, if you have two clocks, and Clock A broadcasts a time signal to Clock B, then the difference between Clock A's time at arrival and the received time from Clock B tells you the instantaneous distance between the two clocks. With me so far?
Now, each of the GPS satellites is continually broadcasting two pieces of information: an identifier, and a time signal. The identifier tells you which satellite it is, and that information plus your current time should tell you where that satellite ought to be. So, once your GPS receiver gets a signal from Satellite A, it compares the broadcast time with the current system time, and computes a distance. Using that distance, and the satellite's position, it figuratively draws a circle on the globe. You're somewhere on that circle.
That's not enough. So, it looks for a second signal. If it can find Satellite B, it compares Satellite B's broadcast time with the current system time, converts that into a distance, and draws another circle on the globe. Now, those two circles intersect in at most two places. So, you're at one, or the other. You still don't know which.
Well, that doesn't really work, either. So, you need a third signal. Now, it looks for Satellite C, and does the same thing. It compares times, finds a distance, draws a third circle ... and now, if the Earth were a perfect sphere, all three circles would meet in harmony in one and only one place. But the Earth isn't a perfect sphere. It's not a perfect anything. It's awfully damned lumpy. So...
So it looks for a fourth signal. Once it finds Satellite D, it goes through the same process. And basically, it finds the point where all four circles more or less meet up. And hey presto, you know where you're at. And, if you have a relatively new unit, it'll also tell you that you need to take the next exit to get to your Aunt Sally's house. Oh, and you need to pick up a loaf of bread and some eggs while you're at it.
But, mad scientists being the innovative chaps that they are, they found a new and interesting "off-label" use for GPS technology. Why worry about synchronizing your clocks if the U.S. Department of Defense has already gone to the trouble of synchronizing one for you? Well, now we think we know a good reason: because it's whizzing around the planet at 17,500 miles per hour, that's why. And if you don't take that into account, weird things might happen.
Although the jury's still out. Weird things might still be happening. We won't know until the re-test is over. Measurements talk, and we just don't have enough of 'em yet.
Still, we should know something in six months or so. Keep your fingers crossed.
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