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Slashback: Iridium, Synthesis, Drives
In this household, we obey the laws of physics! Tuesday before last, we mentioned that two scientists had announced what they claim is the first accurate measure of the speed of gravity.
Now, Emperor_Alikar writes "In an article on Space.com, many physicists have criticized the current work on the speed of gravity, calling it 'nonsense' and 'simply incorrect.' Many of them still doubt the claims made by Fomalont and Kopeikin even before the results were even announced. Many of the physicists still hold on to the idea that gravity works instantaneously no matter what the distance, an idea that originated by Newton, but that was argued against by Einstein."
Back from the back from the back from the dead. Checkers writes "Spacedaily.com posted the following two stories about Iridium today. The first story is about the DoD committing the first of three renewal options that will use Iridium through 2005. The second story related story is about an agreement inked between Iridium and Harris Corp. that allows Iridium the right to use Harris' OS/COMET satellite command and control system for the life of the Iridium satellite network."
E.T. was also into this scene. In re: matt simpson writes "Another fantastic Speak & Spell modder is Dave Wright of the band "not breathing". You can check his work out, among other modifications to toys, at www.carrionsound.com Dave has made speak & spell/math/read for Nine Inch Nails, Meat Beat Manifesto, and many other bands. Figured you might be interested in other neat synth hackers :)"
Further evidence, never a good time to buy. SpinnerBait writes "It's seems like Serial ATA Controllers have been on the market forever but where have all the Serial ATA Hard Drives been? The wait seems to finally be over, as HotHardware shows with this review and showcase on a pair of new Seagate Barracuda V Serial ATA drives. This article covers benchmarks with the product in single drive configurations, as well as RAID 0. In addition, they show performance on two different SATA controllers, from Promise and Silicon Image. And oh, those nice thin neat little SATA cables! Gotta love 'em."
We've had a few articles about Serial ATA; I hope it lives up to its reputation.
Just to add to the confusion ... probejockey writes "A current article in the Globe and Mail claims SCO will start collecting licensing fees from some Linux users, not all Linux vendors as previously reported here."
Birds of a feather, separate rooms. Finally, Declan McCullagh sent in a few interesting links yesterday regarding the RIAA and its announced opposition to mandated DRM technologies:
"First, here are the photos from today's press conference.
Second, the supposed news of today's announcement was that the RIAA would no longer pursue mandatory-DRM technologies like the Hollings bill. But it was the MPAA that was behind Hollings from the beginning (September 2001). And when Hollings finally introduced his bill in March 2002, it was the MPAA that endorsed it, while the RIAA pointedly did not."
Thanks to Declan for the links.
Wasn't smart enough to get in, either ... Finally, thanks to the several readers who alerted me by email and in comments that the school variously rendered Cal Tech, CalTech and other things even worse is in fact properly spelled "Caltech."
"In this house, we obey the laws of thermodynamics!" Homer mutters this when Lisa, bored at being out of school, creates a perpetual motion machine.
--
Disclaimer: The above statement probably includes half-truths, because real truth is too complicated.
If the Sun suddenly disappears (hypothetically), would the Earth continue to hold its orbit for 8 or so minutes, or would it go whizzing off into space instantly? Does this new "Speed of Gravity" research change that answer from what it was, say, a year ago?
All general relativists (and for that matter, all physicists) I know think that gravity propagates at the speed of light. In the linked articles, the criticism is that they've measured the speed of light by virtue of the radio photons, not the speed of gravity, which they're claiming.
There's nothing about 'infinitely' fast gravity in the article that I can see, and of the two physicists claiming to disagree with the results, the one who says it is 'nonsense' then refuses to comment any further.
Dr Fish
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As copyright owner of this comment, I authorize everyone to defeat any technological measure which limits access to it.
GPS is a passive system. It can't be overloaded.
You like splinters in your crotch? -Jon Caldara
I am not sure if you completely understand how the GPS system works. I am not sure if I do either for that matter but the GPS system is in very little danger of being "overloaded". It is the actual GPS device that does the triangulation calculations. All the sats do is keep track of their relative position to their peers and broadcast a unique signal. Doesn't matter if 1 device or 1 million devices are earthside it is just a broadcast.
It is not enough to succeed, others must fail. - Gore Vidal
I think the real problem with determining the speed of gravity if indeed it does have a speed is the fact that we can not turn gravity on and off. Some of the first very very very rough measurements of the speed of light were made by a light source standing away from an oberserver and being turned off and on in a way that an algorithm they designed would use the information to tell them the approximate time it took for the light to get to the observer from the source. The problem with gravity is that we can not turn it off and on. Perhaps even like we can with a magnetic field. Just get a wire, run some current through it and use a switch to open/close the circuit. We could then measure the speed of a magnetic field (if it has one). The inability to turn gravity off and on is the key inhibitor to any substantial calculations on its part. And, I'm sure that when we can turn gravity off and on we really won't care that much anymore about trying to determine how fast it travels
GPS can never be overloaded like that. The SVs are broadcast only, they don't give a rat's arse how many things are using them.
And, GPS would never be the sole means of guidance for all weapons, by virtue of the fact that it only really works well against targets at known positions. Only laser and TV guidance work well against moving targets.
If you haven't already seen one, Iridium Flares are really quite impressive.
They're toast, though, no matter what half-assed "intellectual property" scheme they come up with. I mean, really - who're you going to stay friends with? A girlfriend who gave you your toothbrush back and said, "Bye, and thanks for all the fish," or one who boiled your fucking cat alive? SCO is kicking its customers in the nuts while they walk out the door; they might squeeze a little cash out of them on the way, but they're only hastening the exit. Did I mention that SCO is toast? That quote alone should get them on FC Translation: "We're desperate and rudderless, checking under sofa cushions for spare change. Got any?"
This isn't as much "normalization" as it is "don't take so many drugs when you're designing tables."
The thing is, you wouldn't know the Sun disappeared till 8 minutes after the fact anyways. Wouldn't it be so cool that here we are whizzing off into space for 8 minutes while the sun is still shining brightly.
"What's this strange force pulling us off into space?"
"It's actually the lack of the sun's gravity. The sun must've disappeared!"
"Let's enjoy the last 8 minutes of sunlight while we can! Woohooo!"
<tim><
Hypothesis: The speed of gravity == infinite
:-)
If the above hypothesis where true then one could (theoretically) build the following device: At place A we have a measurement tool that measures the gravitational pull of an object at place B. At place B we move the object back and forth based on a coded pattern (sending information). At spot A the difference in gravitational pull allows us to decode the pattern (reading information). The time it takes to send this information is based on the time it takes for the gravity 'waves' to reach from point B to point A. Our hypothesis says that this time is 0 so it means that we can now build a device that can send information FASTER then the speed of light. Einstein allready proofed that there is nothing faster then the speed of light.
Conclusion: The hypothesis is FALSE.
(disclaimer: bah, I'm no physicist, so don't flame me for not writing the above proof in a perfect physicist lingo...I tried
No, no, no! The contraversy over the results of the gravity measurement surrounds the MEASUREMENT TECHNIQUE, not the conclusion. You would have to look *really*, *really* hard to find a working physicist who thought that the influence of gravity was instantaneous. You'd have an easier time finding a "Pacifists for Bombing Iraq" organization to join.
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What I'm listening to now on Pandora...
The problem with jamming GPS is that, to do that, you need to transmit a signal.
When you transmit a signal, you make yourself vulverable to things that can sense that signal; e.g., missiles that home in on radio transmissions.
So yes, you could jam a wave of GPS-guided weapons. But if the wave of attacks includes a handful of gravity bombs or other weapons that seek those frequencies, you couldn't do it twice...
Still, a smart jamming strategy might help protect a hardened target.
.
Eloi, Eloi, lema sabachtani?
www.fogbound.net
For one thing, if gravity was instananeous it could conceivably be used to send information anywhere in the universe with zero ping time. Imagine a gravity-wave wireless link that would enable us to communicate with civilizations in other galaxies. Imagine playing Q3 with an alien on a planet in M3 and still having a 20ms ping.
Now imagine sending energy via gravity waves. With the right technology you (in energy form) could be beamed, Star Trek style, to another galaxy. You could go visit your alien buddy for a lan party and be back in time for dinner.
Unfortunately, the notion of energy (and indirectly, matter) moving at infinite velocity seems to violate the entire theory of relativity. Moving you from here to another galaxy instantly certainly seems to violate the theory of relativity.
Out of every benchmark I've seen of the new Seagate Barracuda V S-ATA drives, _none_ of them benchmark against it's parallel ATA brother, but instead benchmark it against either an older generation drive, or a drive of another manufacturer completely.
Look, if you want to know how SATA performs, benching one of these 'cuda V drives against a western digital p-ata drive isn't going to tell you anything. Those drives from Seagate aren't all that fast compared to drives from Maxtor or WD (or IBM/Fujitsu).
Expecting SATA to speed anything up is pretty ridiculous - the drive mechanism is what determines performance in current hard drives - we're nowhere near ATA drives that can match even ATA100 speeds (even burst rates are only reaching ATA66 speeds, if that!).
SATA won't increase your speed, PERIOD. New generation drives with higher data density, etc., are what speed up drives. The interface doesn't matter in speed.
FYI.
If the speed of gravity isn't infinite, then I think you get a paradox when two bodies are orbiting each other.
:-)
Let's say we have two bodies, body 1 and body 2, both orbiting a central point.
Both of them are getting pulled in towards the central point by the other one. Right?
But if the speed of gravity isn't infinite, each body will be pulled not exactly towards the center, but towards the point at which the other body used to be, a certain time ago.
Try this experiment: You will need:
1 friend
2 tennis balls
1 roundabout (the circular playground variety)
Stand on a point on the circumference of the roundabout, and get your friend to stand opposite you. Spin the roundabout so you are both orbiting the central point.
Now throw your tennis ball at your friend. Chances are you will miss, because your friend will have moved by the time the ball gets there. So now change your aim so that the ball actually hits your friend. Get your friend to do the same.
When you've got things sorted, you should get the tennis balls hitting you from slightly 'front-on' compared to the center of the roundabout.
So what this means is that if gravity has a speed, then each orbiting body will be pulled by the phantom ghost of the other one, which will appear to be slightly behind the center of rotation. Therefore, the two bodies will keep on accelerating, pulling themselves up by their shoelaces, until the orbits around the central point become so huge that the effect isn't very big at all.
In other words, orbits won't be stable if gravity has a speed.
If we assume that 2-body orbits are stable, then gravity must be instantaneous, but this introduces a communication paradox (as pointed out by many other posters).
So we have a paradox! If you were God, would you make gravity have a speed, or not? Or do you make it so friggin' hard to measure that people give up and argue over which physicist has the bigger reputation?
I am artificially intelligent.
Now getting back to what someone asked earlier, what would happen if the sun were to be removed, would the earth spin off or stay in place for 8 minutes. To answer you question i use will use einstien's theory of gravity. He equated space to a 2-d surface, like a trampoline, gravity would warp that surface and create indentions. Ok say i put a bowling ball (sun) on the trampoline, and put a baseball (earth) in orbit of it. Now lets say i pick up the bowling ball quickly (almost instaneously), the baseball does just go off in a straight line, right?. What if i did it slowly?
Now saying that, you all know that you just simply can't move a mass such as the sun faster than the speed of light, heck you can't even make an bowling ball go faster than the speed of light, but the problem is relativity doesn't quite work for very large or very small objects. My theory is that gravity can move faster than the speed of light but the mass that generates it can't so you could never use it to create any paradox that was suggested.
A Fatal OE Exception has occurred, Sig will now reboot.
The problem with jamming GPS munitions is the fact that the aircraft dropping a GPS bomb has GPS up above the jamming.
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The aircraft is connected to the bomb in flight with a databus. The plane gives the weapon updated location via the bus up to the point of release.
The bomb knows where it was, the bomb also has a ballistics computer updating the rate of decent and distance to target.
So when the weapon gets into the jamming region, it still knows where it was when it was dropped, and knows how fast/far is dropped and where the target was. The weapon still falls relativly close to the target, the CEP just increases.
I've read the CEP doubles when GPS is off/jammed. Which is still much better than a dumb iron bomb.
http://www.google.com/search?q=jdam+gps+jamming
http://www.darpa.mil/spo/programs/gpsguidancepa
http://www.globalsecurity.org/military/systems/
"Once released, the bomb's INS/GPS will take over and guide the bomb to its target regardless of weather. Guidance is accomplished via the tight coupling of an accurate Global Positioning System (GPS) with a 3-axis Inertial Navigation System (INS). The Guidance Control Unit (GCU) provides accurate guidance in both GPS-aided INS modes of operation (13 meter (m) Circular Error Probable (CEP)) and INS-only modes of operation (30 m CEP). INS only is defined as GPS quality hand-off from the aircraft with GPS unavailable to the weapon (e.g. GPS jammed). In the event JDAM is unable to receive GPS signals after launch for any reason, jamming or otherwise, the INS will provide rate and acceleration measurements which the weapon software will develop into a navigation solution."
http://www.boeing.com/news/releases/1998/news_r
"A new anti-jam Global Positioning System (GPS) developed by Boeing has successfully defeated jammed environments in two successive drop tests, allowing the test vehicles to strike well within their designated target areas."
"In the most recent test, the AGTFT test vehicle was dropped into a high-power GPS-jammer environment from 44,000 feet and achieved direct military code GPS acquisition within 8 seconds. While descending through wind shears of up to 110 mph, the test vehicle continued to track GPS satellites in the jammed environment and ultimately struck within 6 meters of the target.
In an earlier test, the AGTFT test vehicle was dropped from 44,000 feet into a low-power GPS-jammer environment and achieved direct military code GPS acquisition within 12 seconds. The test vehicle descended in the jammed environment through wind shears of up to 105 mph, continuously tracking GPS satellites and striking within 3 meters of the target."
Those tests were conducted in 1998.
Many GPS guided weapons have inertial guidance as a backup. If they lose guidance from the satellites, they remember where they where, and roughly what direction and how far they had to go to hit their target.
This article claims that GPS jamming reduces the accuracy of a 200 lb JDAM to +/- 100 feet; considering the destructive power of those weapons, the difference is academic against all but hardened targets.
The frequencies are fixed; they'll only change when the next generation of GPS satellites are launched, a prospect that hasn't even been planned yet. Anyhow, any sort of technological countermeasures deployed by Iraq against its much more powerful enemies are going to be a speed bump at best- they're hopelessly overmatched. Their best bet will be evasion, deceit, and propoganda- the only things that (barely) worked for them in Gulf War I.
Marc Siry || interactive media professional, motorcycle enthusiast ||