Slashback: Iridium, Synthesis, Drives

Slashback tonight with word on the (groan) fate of Iridium, more Speak n' Spell modding, examples of Serial ATA oozing to market, the RIAA versus mandatory DRM, and more. Read on for the updates.

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."

Comments

For you proper Simpson's nuts -

[spaten-optimator]

"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.

Re: For you proper Simpson's nuts -

[Roblimo]

You are getting the Simpsons' house confused with Timothy Lord's family's house.

I have been to Timothy's house and I will tell you, they obey the laws of *physics* there, and he and his family are not cartoons. (Except maybe his brother.)

- Robin

Iridium and GPS

[The Bungi]

1. Put satellites in orbit
2. ???
3. Profit!!

It seems they've filled in the '???' part - sell 'em to the DoD.

I couldn't help but think about the GPS system though. As the military shifts from laser guidance systems for bombs and cruise missiles to GPS-based ones, the GPS network becomes more and more critical and overloaded. Is the Iridium network being used only for simple voice/data communications or is there a dual-use capability (targeting, whatever) in the network as well?

Re:Iridium and GPS

[axjms]

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.

Re:Iridium and GPS

[Russ Steffen]

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.

Re:Iridium and GPS

[angst_ridden_hipster]

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.

.

Re:Iridium and GPS

[cristofer8]

About the GPS missiles, I recently took a tour of the Trident Missile facility in California (Moffet Field) with my school. The trident missiles, which are basically our doomsday machine, not only don't rely on GPS, but don't even really have any electronics. The gov is so worried about radiation and interference and such, that they use pressurized tubes to send signals, and orient themselves by actually looking for certain stars through a little hole in the side. Of course, they refused to explain how the "magic inertia" device worked.

Re:Iridium and GPS

[Wyatt Earp]

The problem with jamming GPS munitions is the fact that the aircraft dropping a GPS bomb has GPS up above the jamming.

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& ie =UTF-8&oe=UTF-8

http://www.darpa.mil/spo/programs/gpsguidancepac ka ge.htm

http://www.globalsecurity.org/military/systems/m un itions/jdam.htm

"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_re le ase_980423n.htm

"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.

Re:Iridium and GPS

[marcsiry]

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.

Okay, answer me this:

[TClevenger]

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?

Re:Okay, answer me this:

[Anonymous Coward]

Does this new "Speed of Gravity" research change that answer from what it was, say, a year ago?

No, it just changes what the physicists tell you.

Re:Okay, answer me this:

[DAldredge]

That would be a BAD THING. I line with current US economic thinking BAD THINGS do not exist. So your question is not a valid question. You must be a terrorist supporter...

Re:Okay, answer me this:

[Mac Degger]

An interesting question like that deserves an interesting answer. Too bad it's "we don't know".

Welcome to the wonderfull world of science, where a smart person can ask more than a more informed person can answer :)

Re:Okay, answer me this:

[dougmc]

If the Sun suddenly disappears (hypothetically), would the Earth continue to hold its orbit for 8 or so minutes

If you believe that gravity obeys the speed of light (I do), yes.

would it go whizzing off into space instantly

If gravity is instantaneous, yes.

Of course, it's not that simple. The sun can't suddenly disappear.

It could explode. Assuming that it forms a sphere with all the mass at the outer edge, the gravity that the Earth feels wouldn't change at all until the mass reached the Earth's orbit, and then it would immediately drop to zero (I forget the law that tells us that the gravity of a spherical body is the same as if all the mass was contained at one point in the center.)

Unfortunately, the mass would come at the Earth at less than the speed of light, so this wouldn't be a good test. That, and it would kill us all, so if you do find a device to make the Sun blow up, I suggest not using it for this.

The Sun could be grabbed away by some massive force -- but the source of this `massive force' (super massive spaceship? God? Galacticus?) would have gravity too, and that would affect us. That, and the Sun couldn't leave at more than the speed of light, so even that's not a good test.

It's not easy to measure this :)

Re:Okay, answer me this:

[Guppy06]

"would the Earth continue to hold its orbit for 8 or so minutes, or would it go whizzing off into space instantly?"

Yes and yes.

For an observer on Earth, the planet will start leaving the star system as soon as the sun vanishes.

For an observer equidistant from both the sun and the earth, the earth will start flying out of the star system ~8.5 minutes after the sun vanishes.

For an observer on/near the sun, the earth will start to leave its path ~17 minutes after the sun vanishes.

And they're all right. Ain't relativity grand?

Re:Okay, answer me this:

[Grog6]

How about doing the experiment outside the space station, with two smaller masses orbiting each other.
Have to get far enough away that the gravity generated by the space station wouldn't affect your setup, and other details, But; Somewhere, in orbit, we should be able to do this experiment.

Two masses, one lead and dense, one made of a less dense material easy to disperse rapidly.

After the two masses are orbiting each other, we detonate one, (make one out of TNT) , while recording positions of the other, (in 3d) and see what happens.

the amount of debris hitting the orbiting body can be determined and taken into account;

The resultant path should show whether it's instantaneous or not. (does it's path change before the debris reaches it?)

What else am I missing?

Re:Okay, answer me this:

[Scott Carnahan]

The matter would become energy .. and energy doesn't create gravity .. so .....

According to general relativity, energy does make a contribution to gravitational effects. Einstein's field equations include the stress-energy tensor, which for each point in spacetime gives information about the energy (including mass-energy) density, momentum density, and stress (e.g. pressure) associated to all forms of matter and all non-gravitational fields [MTW].

The problem is that if you assume Einstein's field equations, you automatically get the assertion that gravity "travels" at c, the speed of light in a vacuum. Any alternative theory regarding speed would have to include some change in the field equations, which have made some very strongly verified predictions in the last 85 years. On the other hand, if you had some alternative theory that did not have the same dependence on the stress-energy tensor, and if it predicted a gravitational change from an annihilation event, then you might be able to test its validity using such an experiment.

Infinite speed gravity?

[Doctor Fishboy]

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

Re:Infinite speed gravity?

[Doctor Fishboy]

What I was saying in my first comment was that the majority of physicists believe gravity has a finite propagation speed, whilst the /. tagline suggested that few physicists do. The experiment itself is being questioned by physicists thinking they're measuring the speed of light, not gravity. Apart from the Newton quote, none of the modern physicists thought that gravity propagated 'infinitely' fast - it's another usual /. not-quite-right headline.

> After all, GR certainly doesn't agree with quantum mechanics

Not sure if I agree with you there - I don't recall that QT is inconsistent with GR. The problem is that it is very, very hard to test a QT of gravity because the hypothesized quanta of gravity are 10^41 times smaller than those of electromagnetism and nuclear forces.

Anyway, they came up with a speed of gravity (if that is what they measured) of plus or minus 20 percent of the speed of light, so if they were measuring gravity, it is consistent with GR.

Dr Fish

Re:Hey Y'all

[Sloppy]

Check your user preferences, messages. Readers decide how much the bonus is worth. Set it to 1 instead of the default, 0, and you'll see the old behavior.

Me fail GPS ? That's unpossible!

[OldMiner]

GPS is a passive system. It can't be overloaded.

Can we turn gravity off?

[bleckywelcky]

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 :) (although we probably will have already).

Re:Can we turn gravity off?

[Guy Harris]

Couldn't you collide some matter and antimatter? If you had some mass and then it co-annihilates, it should be like turning gravity off.

No, it shouldn't. A matter-antimatter annihilation isn't really an "annihilation" in the sense that the "nihil" in "annihilation" might suggest; instead, if, for example, an electron and positron mutually annihilate, you get a pair of photons, and the total energy of the photons is equal to the total energy (rest energy, from rest mass, plus kinetic energy) of the incoming electron and positron.

The photons have a gravitational field just as the electron and positron did. (Mass isn't the source of gravity - energy and momentum, and the flow thereof, are.)

Iridium Flares

[FrostedWheat]

If you haven't already seen one, Iridium Flares are really quite impressive.

Re:Add me to the list.

[anotherone]

users can decide what the bonus is worth for themselves, so if you've got the bonus set to 0 it won't show up.

SCO is toast

[legLess]

My brother used to run a motorcycle courier service in LA, and the only bill higher than his liability insurance (think about it - what type of guy wants to be a motorcycle courier? how safe is he going to be?) was his SCO license. These folks have been squeezing blood out of the turnip for years, and now that people have abadonded their turnip (to further torture the analogy) SCO is looking for other vegetables.

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.

Chris Sontag, hired in October as senior vice-president of SCO's Operating Systems division, leads the intellectual property organization, sources said. Earlier in his career, Mr. Sontag led marketing and product development for Novell...

Did I mention that SCO is toast? That quote alone should get them on FC

Our Unix IP is a significant asset. And for several months, we have been holding internal discussions, exploring a wide range of possible strategies concerning this asset," the company said in a statement Monday. SCO hasn't decided how exactly to collect more Unix revenue, the company added.

Translation: "We're desperate and rudderless, checking under sofa cushions for spare change. Got any?"

Re:SCO is toast

[IntlHarvester]

Flame on, but read the article.

Sources said SCO plans to charge for use of two software "libraries," ... A source said SCO libraries that accompany the SVR4 and OSR5 versions of Unix may be used with UnixWare and OpenServer, respectively, but using them in conjunction with Linux is prohibited by the software's licence.

"There's a little bit of ignorance on the part of some customers," a source familiar with the plan said. But at the same time, the source added, "there are customers using the libraries that know they're not supposed to be using them."

Using the libraries allows programs designed for SCO Unix to be run, unmodified, on Linux machines in conjunction with a package called Linux-ABI. That's a key step for companies moving servers from SCO Unix to Linux with minimum disruption.

For those who don't know, "Linux-ABI" used to be called IBCS -- "Intel Binary Compatibility Standard" -- and you can guess from the name that it was an (old) attempt to standardize the ABI between different x86 Unixes. A long time ago, Linux users needed this to run commercial software like Oracle or WordPerfect.

It sounds like either Linux-ABI steps on SCO patents, or certain customers are shipping SCO libraries to run on top of Linux-ABI (which is outright copyright violation). In either case, this only affects about 0.001% of Linux users.

In short, all 2000 posts eariler were probably a massive over reaction.

Re:SCO is toast

[js7a]

all 2000 posts eariler were probably a massive over reaction

Maybe those 2000 posters are the ones with software using Linux-ABI.

CALTECH

[Anonymous Coward]

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."

And of course, "Caltech" is pronounced: sall-TEESH

Glad I could clear that up!

We wouldn't know it.

[Timothy Chu]

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><

Measuring the speed of gravity

[Anonymous Coward]

Okay, we can't make the sun disappear and watch what happens to the earth's orbit (and really, why would you want to?)

BUT - what if scientists create an amount of matter and anti-matter, and using very sensitive equipment measure the gravity effect it has on say a hanging weight (ala the two really heavy bags suspended next to each other). Then, all of a sudden combine the matter and anti-matter and measure how quickly the gravity "disappears". (BTW, the antimatter can be "held" in a magnetic field, as opposed to wearing really thick gloves)

Okay, there's a lot of work to be done before this could even be considered, let alone be done in the garage of /.'ers, but are there any arguments against this being possible?

I'm not sure if the energy released by the matter/anti-matter combination would interfere in any way (it probably would, for all I know). Also, it's probably not practical to generate a significant amount of anti-matter, and I believe it may have a very short half-life. Also, do we have equipment sensitive enough?

There we go - I've suggested a better experiment, shot it to bits, admitted my ignorance and also taken the piss out of my suggestion a bit! This is the ultimate /. post - no replies necessary!!! (But the replies will still come. So sayeth the spider)

The speed of gravity, a consequence

[Traa]

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 :-)

Re:The speed of gravity, a consequence

[Traa]

actually, you CAN get a really long string from here to china. If you pull it however then each atom in the string will atract a nearby atom to 'stay close' and this information moves at best at the speed of light. So yes, your 'almost instantaneous' will turn out to be the speed of light.

Re:The speed of gravity, a consequence

[kcbrown]

Well, you're thinking along the right lines...

Here's the experiment you really want to perform:

At place A, you place a massive object in front of a light, and move the object back and forth.

At place B, you set up a light detector and a gravity detector (the means by which one builds the gravity detector is left as an exercise to the reader).

You start off with points A and B really close to each other so you can calibrate your equipment (you need to be able to account for the difference between reading the gravity detector and the light detector). Once you do that, you move the points further apart.

Now, if the speed of gravity is instantaneous, then the phase difference between the signal received by the gravity detector and the signal received by the light detector should change as you move the points away from each other.

If the speed of gravity is the same as the speed of light, then the phase difference between the two signals should always be zero (after accounting for the equipment), no matter what the distance between points A and B.

The relationship between the phase difference and the distance between points A and B will give you a clue as to the speed of gravity versus the speed of light, if that of gravity is finite but different from that of light.

IRIDIUM IS EVIL! BOYCOTT!!

[sulli]

I can't believe there's another positive Iridium story on slashdot. Is this due to the visual studio .NET ads?

People, we need to boycott this insidious attempt by Micro$haft and the evil **AA along with Senator Disney and the BSA to control our PCs! Join the EFF, delete your Windows partition, and FIGHT BACK against this menace! Power to the people!

oh, Iridium? oops, never mind.

big-swinging-karma

[Cadre]

hehe, you can assign negative values to people using the karma bonus. That's pretty nice, you can now mod down the big-swinging-cock-because-i've-got-karma people. :-) yaaa

Re:big-swinging-karma

[fermion]

I suppose this is an irony. A poster with lots of top rated posts using the karma bonus to post some dumb ass shit complaining about the moderation and bonus system. I understand. We that have karma to burn just occasionally feel like doing a bit of mischief. I guess having big swinging genitalia does that to a person.

In any case, lest we forget, I quoth the FAQ:
Karma is used to remove risky users from the moderator pool, and to assign a bonus point to users who have contributed positively to Slashdot in the past. It is not your IQ, dick length/cup size, value as a human being, or a score in a video game. It does not determine your worth as a Slashdot reader. It does not cure cancer or grant you a seat on the secret spaceship that will be traveling to Mars when the Krulls return to destroy the planet in 2012. Karma fluctuates dramatically as users post, moderate, and meta-moderate. Don't let it bother you. It's just a number in the database.

And I just always wanted to note that the focus on dick length (not girth?) and cup size (not shape?) certainly lends credence to the concept of computer geeks being male dominated and female unfriendly.

Re:Hey Y'all

[writertype]

I'm guessing someone's a bit peeved at the arrogance of your sig... Exactly who do you write for as a "professional journalist"? Google searches only turn up your Slashdot comments, and I think you need a wider audience than that ;)

Um, why is this worthwhile?

[SuperDuG]

"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."

There are still scientists that argue EVOLUTION. This is nothing new, scientists looking to ride the coat-tails of rising stars in the field by doubting them. Obviously with the results not out before the entire idea was refuted, but this doesn't surprise me. PhD's who are "experts" in their field tend to be arrogant asses when it comes to something they didn't "discover".

Don't believe me, walk on to your local university and sit in on a graduate level class. Some people love to get paid to hear themselves speak.

Argh!!!!!

[volsung]

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.

Re:Hey Y'all

[Otter]

Why Linux Isn't Ready For The Desktop: Chapter LXXIV

Check your user preferences, messages. Readers decide how much the bonus is worth. Set it to 1 instead of the default, 0, and you'll see the old behavior.

Today's exercise in open source user-friendliness is making a major change to score display with no notice or explanation. After all, users can simply download the current Slash code from SourceForge CVS, grep for "No Karma Bonus", see what variable the checkbox sets and work back through the source to figure out why display seems to be broken. Oh! It's just a new preference that needs to be set!

Re:Hey Y'all

[Angry Toad]

I'm not even clear on what the point of Karma is anymore.

Isn't this pretty much the death knell of any meaningful value being derived from a good Karma score?

First you can't watch your Karma Value climb to insanely high levels, and now you can't even let other people Check Out The Big Karma Value On Yourself with your bonus. Other people can even mod you down (in their own views) for having a decent karma score.

So what's the point? Why not get rid of it altogether?

Go ahead, mod me down as a troll or whatever, I don't see how it matters.

You'd have a hard time seeing movement at all.

[Christopher Thomas]

Actually, if gravity is instantaneous, then you would percieve the sun as moving away from the earth instantaneously after it vanished due to the earth moving quickly out of orbit. The earth would fling off in a straight line from the sun as soon as it vanished at incredible speed, and the light from where the sun WAS would take longer to reach the earth as the earth moves away.

While you are correct in pointing out that we'd see the light for slightly longer than 8 minutes (with a slight accompanying redshift), the time (and distance) difference is very small.

The time between gravity shutoff and light shutoff is 8 minutes. The Earth's orbital period is about 526,000 minutes. That gives an angle of about 9.6e-5 radians. Over that small an angle, the Earth's orbit is close enough to being straight already that divergence from the path would be negligeable.

Re:You'd have a hard time seeing movement at all.

[Christopher Thomas]

Keep going with that math. 8 light-minutes times (1-cos(9.6e-5)) is about 660 meters of deviation, which is not really "negligible."

Compared to the distance from your terminal to the break room, no.

Compared to the distance between the Earth and the Sun (about 1.5e+11 m), yes, it's most definitely insignificant.

Read the original poster's description of visual effects to see what "significant" in this context would do.

Re:Okay, I'll try:

[glenebob]

"...would the Earth continue to hold its orbit for 8 or so minutes..."

There would be no clue that anything happened to the sun until 8 minutes after it happened. Or so the scientests are telling us. And if you think about it, it seems to make some sense when compared against other relativistic theories.

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.

SATA benchmarks pretty useless thus far

[Tumbleweed]

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.

Speed of gravity paradox

[nebbian]

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? :-)

Re:Speed of gravity paradox

[Forgotten]

Cute thought experiment, but I don't think it matters. The end result of the vector math is still a point in between the bodies (the centre if they're of identical mass). The orbits will appear the same at all times regardless of whether gravity is constrained within light cones or not, and this is why it's such a pickle of a problem. In fact I suspect it's the sort of problem that will lead to other unexpected understanding simply because one has to be so devious to try and measure it.

If you don't believe in the vector math method (that the bodies orbit a central gravitic point, just as, say, a dust ring or ringworld would) try thinking of it this way: each body is orbiting the [displaced phantom of] the other, but because their orbits are complimentary it still doesn't matter. That is, if only one body was affected then the binary system would go spinning crazily away, but because their respective motions necessarily complement one another, it again doesn't matter - with either method, the phantomicitys you're concerned about will exactly cancel each other out.

Same applies if the bodies differ in mass, of course, though the math is a bit harder. ;)

Re:Speed of gravity paradox

[zilly]

OK... your wish is my command. See this article, written by a University of Toronto physicist, that explains in simplespeak the concept of relativistic simultaneity. To wit:

More importantly, the relativistic notion of simultaneity makes it clear that no information can travel faster than light without throwing all our concepts of cause and effect into disarray. Relativity teaches us that if two space-time events are separated so that they cannot be connected by any signal travelling at c or less, then different observers will disagree as to which of the two events came first. Since most physicists still believe that cause needs to precede effect, we conclude that no information can be transmitted faster than the speed of light.

The article continues...

Nevertheless, velocities greater than c can be observed. Suppose a lighthouse illuminates a distant shore. The rotating lamp moves quite slowly, but the spot on the opposite shore travels at a far greater velocity. If the shore were far enough away, the spot could even move faster than light. However, this moving spot is not a single "thing". Each point along the coastline receives its own spot of light from the lighthouse, and any information travels from the lighthouse at c, rather than along the path of the moving spot. Such phenomena are described as the "motion of effects", and are not forbidden by relativity.

Pretty interesting, no?

Re:Speed of gravity paradox

[NanoProf]

I'm impressed. Very clever, but you've forgotten about the coordinate transformations of relativity. Assuming I remember my grad school E&M correctly, if one does a full calculation relativistically, the force arising from a body moving in a straight line at uniform speed does in fact appear to come from where the body would be predicted to be at the time that the signal is received, not the time that it is sent. Of course, if the body curves suddenly, this simple result breaks down (since own can't anticipate how it would curve). The situation with co-orbitting bodies is more complex, but the basic idea is the same: the full relativistic calculation with retardation effects (i.e. finite signal propagation) eliminates the naive nonphysical effects. One does, however, see things like precession of the perihelion from GR, which is absent in the Newtonian approximation.

Ok, this is what i think

[FS1]

I have seen alot of people here who say that gravity can't travel faster than the speed of light and usually back their response up with relativity. But mind you, relativity is still theory not law. Say for example gravity could travel faster than light, we will say that gravity waves travel at 2x the speed of light. Now say we have a way to measure the effect of gravity waves and not of gravity itself, just going to Heisenberg's uncertainty principle to say we can't measure the intensity of gravity waves unless we change their position. Because we would have to use light or energy or something that goes slower than light to measure the speed of the effects, that renders the results of any such attempt to send information or energy this way useless.

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.

Re:Ok, this is what i think

[egomaniac]

You made a typo in your post.

I believe what you meant to say was "My entire understanding of physics comes from half-remembered articles in Scientific American that I didn't really understand."

library licences are all you need

[boots@work]

Well, you're closer, but you're still not on the money.

It sounds like either Linux-ABI steps on SCO patents, or certain customers are shipping SCO libraries to run on top of Linux-ABI (which is outright copyright violation).

They don't *need* patents. They just need for the SCO C library licence to say that programs developed using it may only be run on genuine SCO Unix. In that case, anyone running such a program would be in trouble -- they wouldn't have to redistribute it.

I suspect the background for this story is that a few long-standing SCO customers with an eye to the future have had a bright young nerd look at how hard it would be to get their vertical application to run on Linux instead of SCO. (Perhaps it's a dental surgery management suite running on Ingres or something similar.) Probably in many cases the customer has a binary app without source access, but that can be fixed with Linux-ABI. It's probably not so hard in most cases.

It's a good deal for the customer: they cut out their SCO licence costs, they get a platform with a bright future, and they have much less trouble finding people who can support and enhance it.

This is a bit bad for SCO, though. Once word gets back to HQ that this is happening, they start to think about methods that can be used to keep their customers locked in. One technique is to exploit the licence that the customer's application vendor originally signed to get the SCO libraries. If SCO were smart enough to put in a "this can only be used on SCO" clause, then they're set!

Anybody who has the source for their applications should be easily able to move to Linux, and probably most of the commercial applications like Oracle already have native ports. Linux-ABI and this licensing strategy really just apply to people with legacy SCO apps who can't, or don't want, to port to Linux.

Microsoft could use such a clause in the Office (or DirectX or MSVC Runtime) licences to put an end to all this Wine, Crossover and Transgaming nonsense, if they wanted to. I think there are enough precedents for that kind of restriction in software licences that it would be possible. For example, lots of driver software comes with a licence saying it may only be used with the vendor's original software. I think this technique is a terrible abuse of customers, like most proprietary software licences. But it would probably work to shake down some more money.