Fortunately, this is all based on the idea that a black hole barely bigger than a proton is somehow stable, which we doubt very much.
The formula for the lifetime of a black hole is t = 8.4 x 10^-17 * M^3, where M is in kilograms and t is in seconds; as the mass decreases, the lifetime decreases very rapidly. A 1000kg black hole will have a lifetime about equal to the mass of the universe. A 1kg black hole has a lifetime of 10 attoseconds.
Of course, during that 10 attoseconds, the entire mass of the black hole evaporates away as energy --- and there is a lot of it in a 1kg mass; roughly the equivalent of 23 megatonnes, assuming I haven't dropped a decimal place or three...
There was an Italian prisoner of war camp in the Orkney Islands, north of Scotland; a lot of the prisoners of war decided not to go back to Italy after the war and stayed there, marrying locals.
The place is worth a visit; among other things, the prisoners painted frescoes on the ceiling of the Nissen Hut they were using as a chapel. It's gorgeous, and still an active church.
Which is already biosynthesisable (from a bunch of different sources), which will already work in all sorts of different engines, for which there's already a massive distribution and support infrastructure, and which is more efficient than petrol anyway?
But what is there to learn on the moon, that can't be learned on Earth? All it is is a rock. A rock without an atmosphere and 1/6 gravity.
If we knew that, we wouldn't need to go there, would we?
But for a start, we'd learn huge amounts about practical engineering in environments with no atmosphere and 1/6 gravity, and I'm sure there'd be all kinds of interesting knock-on effects of that. Not to mention the effects of low gravity on the human body (which has never been studied before), which could well lead to new insights in medicine. And all that's just spin-off knowledge from the primary purpose of any lunar expedition, which will most likely be scientific like astronomical or cosmological.
...we'll learn stuff that will turn out to be useful in really unlikely, impossible-to-predict ways.
Pretty much the same answer as with any pure science initiative, really. Remember: economics may come and go, but knowledge is the only investment that will pay dividends for eternity.
Yep, right. Got an Apple Performa sitting right next to my IBM XT. You mean you don't keep vintage computer hardware around?
Way too much of it.
(Apple Perfoma? Pah. I have an Acorn Risc PC sitting next to my computer desk! Currently used, er, to hold up my company laptop. But it boots and everything.)
Now all I need is a machine that can read a 3.5 inch floppy.
It's worse than that. Apple floppy disks were written with constant linear velocity --- i.e., as the head moves towards the centre of the disk, the rotation speed goes up so that the magnetic medium still passes the head at the same velocity.
PCs, and therefore all modern hardware, use constant angular velocity floppy disks --- the disk spins at a constant speed, so that the speed at which the magnetic medium passes the head varies depending where the head is. Yes, this is clearly a bad idea, but that's PCs for you.
This means that no modern hardware can read old Apple floppy disks. It's just not possible. You'll need an old Macintosh floppy drive and (probably) an old Macintosh floppy drive controller to plug it into, which basically means you need an old Macintosh. You still have yours, right? Right?
Have fun!
Re:Difficult since hackers hide behind huge NAT
on
China's Cyber-Militia
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· Score: 1
It's hard to prosecute hackers and spammers when they hide behind the Great Firewall of China. The information is of course in the NAT logs, but these are controlled by their government.
You do know that the Great Firewall is not, in fact, a NAT? It's just a simple filtering service applied on the master gateways to the outside world. It does proxy DNS, but that's it; all other packets are either passed through unchanged or blocked entirely, depending on the firewall policy.
Go look at the Wikipedia article; it's got a reasonable amount of technical information.
...except for the proprietary BIOS software, the proprietary microcode in the video card, wireless card, I/O controller, hard disks, floppy disks, monitor, keyboard, mouse, POTS modem, ADSL modem, power control microcontroller, and all the other little bits of electronics with embedded CPUs on your desk.
And if you want to be really picky, you could also talk about the proprietary chip and CPU designs in every single piece of silicon in all of the above. Not to mention the patented and extremely commercial fabber techniques needed to make it all (in China). Free, it's not.
Now that there are genuinely free (as in speech) IC designs out there on places like opencores.com, is it possible to make completely free computers? Even single-board jobs?
Because with that particular camera, taking an RGB photo involves making three separate exposures with different filters, transmitting the result back to Earth, and combining them. Given that the lander has been on the ground for less than 24 hours so far, they're still at the quick-glance-around-to-see-where-we-are stage and don't want to waste bandwidth taking the same picture three times. Give them time. Given the PR value of RGB images I'd expect some to start showing up within a few days.
(In fact a two-colour image has shown up already, but it's not true RGB and probably isn't what you're looking for.)
Not necessarily if it's a sailboat.
A boat that size usually depends upon the weight of its crew to keep it balanced. Similarly, unless it's got an absolutely immense keel, it can easily tip over into the water.
Actually, building self-righting / uncapsizable boats is pretty straightforward. Remember that the keel needs to be heavy enough to offset the tipping moment of the sails; normally this means they're really, really heavy. Also remember that the keel is submerged in water, which means that its effective weight is rather lower than it would be in air.
With a bit of forethought, you end up with a boat which will tip over until the keel starts coming out of the water, and then it'll just stop --- any additional heel will cause more keel to emerge, which will cause the effective weight of the keel to increase hugely, which will prevent any further heeling.
Even if by some miracle you do end up with the boat upside down, it's unstable in that attitude and will right itself. Yes, the sails will cause huge water resistance, but that resistance is proportional to the speed of motion through the water; it won't stop the self-righting, it'll just cause it to happen slowly. (Also, the sails will act to prevent the capsize in the first place, for exactly the same reason.)
What tends to happen these days on decently designed boats is knock-down; a gust of wind causes the boat to be knocked onto its side, up to the point where the keel's righting moment offsets the tipping moment of the wind against the sail. This can be very hazardous to the crew, but hey, no crew! When the gust passes, the boat will right itself (usually even if it's filled with water).
The biggest risk is that all this process is extremely violent; the boat's being slammed about hugely. You run a very real risk of bits of the boat actually breaking. The tension at the base of the mast is huge at the best of times, and if the mast breaks under strain and doesn't come completely free of the boat it can very easily smash through the bottom of the hull. Which Would Be Bad. That's one of the reasons why people like unstayed masts these days; if you get dismasted, you don't end up with a huge, heavy, sodden and very dangerous lump of stuff smashing about on top of your boat --- you're much more likely to lose it completely overboard. Much safer.
While this does tend to apply to yachts rather than dinghies, which as you say largely use humans for ballast, you really do get yachts that size --- the difference is largely design rather than size. My father designed, built and sailed a highly successful yacht only a little bigger --- 15 feet, I believe. It was a bilge keel gaff rig with two monster lumps of concrete for the keel, and slept three. It would heel comfortably to about 45 degrees and then just stop. My father tried quite hard on several occasions to get the cabin windows in the water (much to my horror) and failed every time...
And it had the passive backplane (which meant that the processor was on an ISA card and plugged into one slot, and the RAM was on another ISA card and plugged into another slot)!
And the full-length HDD/FDD/serial port card (WTF?) had not just one but *two* monster ribbon cables connecting to the hard drives in order to achieve the staggering data throughput of, nearly, a megabyte a second! Beat that, SATA!
Mine ended up getting skipped. I wish I'd known how much in demand they are now, I'd have kept it...
I used to have an uber-expanded 8088 computer of about the same vintage: a Zenith Z150 with passive backplane, ethernet, 1.5MB of RAM, 3.5" floppy, Hercules graphics --- and *two* 20MB Seagate MFM drives. Those things were awesome. Not only was the revving-jet-engine noise as they spun up seriously cool, but when the machine was turned on I didn't need any heaters on in the room...
I slightly miss those old MFM drives. While modern ones are far more sophisticated and generally better in every way, the old drives had a kind of mechanical elegance to them that the new ones don't. Also, big chunky rectangular red access LEDs.
Hey. We've had 12 years of Howard, almost. Imagine if you have another 4 years of Bush ahead of you. The US would be screwed too.
How's Rudd working out, now you've had him a bit? While he seemed to be a really big improvement over Howard at first (of course, a decaying rat corpse would have been an improvement over Howard), he's kind of dropped off the internation news since then, and I'd be interested to hear what he's like now.
If you want an idea of why Slashdotters enjoy him, check out his (free to read) non-fiction piece In the Beginning was the Command Line.
Also check out Mother Earth, Mother Board, which is a fast-moving, gripping, action packed, 42000 word essay on... the history and practice of submarine cable laying. Really. It's awesome. Read it. (He used bits of it for the background in Cryptonomicon, so if you've read that you may find it a little familiar.)
I've never quite understood how that allowed them to find the age of things. How do you know that is when the rock formed? You know the age of the atoms the rock is made of, not the age of the rock.
Ah, but rock's not made out of atoms --- it's made out of molecules. The molecules only work properly if they're made up of the right combination of atoms. Let's say that the environment the rock's formed in contains Foonium. Foonium is unstable and decays into Barnium, which is stable. They're chemically different; Foonium forms Foonium Oxide, but Barnium's an inert metal. So, when the rock's formed in lots of hot air, it ends up containing lots of Foonium Oxide --- but no Barnium, because the Barnium's so inert it doesn't take part in the rock-making process.
Millions of years later, some of that Foonium has decayed into Barnium. Since we know that the rock was formed with 100% Foonium and 0% Barnium, we can use the ratio to figure out how long it's been since it was formed.
My fingers land right on the middle of the keys; there's no fumbling around the edges until I get good purchase on the middle and finally press it.
No, you don't --- but you do get loads of feedback from the shape of the key that lets you know where you hit the key. This allows you to continuously adjust the position of your hands and fingers so that you continue to hit the middle of the keys.
That's why it's so easy to adapt to a keyboard of a different size. If it was simply a matter of 'knowing where the keys are', it would be impossible. Instead, you continuously adapt based on the kinaesthetic feedback you get from your hands. It's not something you notice consciously unless you look for it --- or until you try typing on a keyboard that doesn't provide those subtle cues.
Try an eee some time; okay, the keyboard's small, but it's not that small --- it's so hard to type on because the keys are flat. Which is a really dumb idea and I don't know why they did it. But even the eee is better than a real, old-fashioned membrane keyboard... like on the ZX81. *shudder*
Otherwise one task suddenly taking a lot of CPU will starve all tasks with lower priority until it is done.
I recently worked on a mobile phone platform (not based on VxWorks) which had a mechanism for sending messages to specific threads. There was a system wide 150-slot message queue. There was a background thread that ran at low priority that was supposed to do non-real-time things like UI work. This thread was a message receiver. The system did not support timeslicing.
Can you see the problem yet?
If the background thread didn't get enough CPU time, it wasn't able to keep up with the incoming messages that would get posted by high-priority threads. This meant the queue would fill up, and once the queue filled all the way up, the system would reboot. The end result was that since the system didn't support timeslicing, if any thread running at the 'background' priority spent too long running without yielding, the message receiver thread would get starved of CPU, and splat. They were using a low-priority background task to handle high-priority system critical operations. When we queried them on this, they said, "Well, we don't really plan task priorities; we just adjust everything on an ad-hoc basis until it works."
Really? I guess vxWorks is an acquired taste then, because I'd be extremely happy to be given the opportunity to use vxWorks again.
The last time I had to use it --- which, admittedly, was a while ago --- we had a requirement to do asynchronous I/O. VxWorks didn't support that, so we had to emulate it by using a pool of helper tasks each of which ran a blocking I/O operation. Unfortunately we had a further requirement that asynchronous I/O operations had to be cancellable, and the only way we could find of doing that was by nuking the helper task that was blocked on the I/O operation. Unpleasant, to say the least, especially as we then discovered that on the BSP we were using, half the device drivers had bugs which meant they leaked resources / crashed / made the system hideously unstable if you destroyed the task while they were in the middle of an operation...
Hopefully this has all been sorted out by now, but it still left a nasty scar. I've had much better experience with Nucleus (although it mysteriously does not have mutexes, only semaphores), and while I haven't worked with it, I really like the look of QNX.
Slashdot Mirror
The formula for the lifetime of a black hole is t = 8.4 x 10^-17 * M^3, where M is in kilograms and t is in seconds; as the mass decreases, the lifetime decreases very rapidly. A 1000kg black hole will have a lifetime about equal to the mass of the universe. A 1kg black hole has a lifetime of 10 attoseconds.
Of course, during that 10 attoseconds, the entire mass of the black hole evaporates away as energy --- and there is a lot of it in a 1kg mass; roughly the equivalent of 23 megatonnes, assuming I haven't dropped a decimal place or three...
There was an Italian prisoner of war camp in the Orkney Islands, north of Scotland; a lot of the prisoners of war decided not to go back to Italy after the war and stayed there, marrying locals.
The place is worth a visit; among other things, the prisoners painted frescoes on the ceiling of the Nissen Hut they were using as a chapel. It's gorgeous, and still an active church.
Which is already biosynthesisable (from a bunch of different sources), which will already work in all sorts of different engines, for which there's already a massive distribution and support infrastructure, and which is more efficient than petrol anyway?
If we knew that, we wouldn't need to go there, would we?
But for a start, we'd learn huge amounts about practical engineering in environments with no atmosphere and 1/6 gravity, and I'm sure there'd be all kinds of interesting knock-on effects of that. Not to mention the effects of low gravity on the human body (which has never been studied before), which could well lead to new insights in medicine. And all that's just spin-off knowledge from the primary purpose of any lunar expedition, which will most likely be scientific like astronomical or cosmological.
...we'll learn stuff that will turn out to be useful in really unlikely, impossible-to-predict ways.
Pretty much the same answer as with any pure science initiative, really. Remember: economics may come and go, but knowledge is the only investment that will pay dividends for eternity.
Yeah, the old stuff is really cool and historic, but it's not precisely useful.
Unless you have a Performa and need to read some old Macintosh floppies, of course.
Way too much of it.
(Apple Perfoma? Pah. I have an Acorn Risc PC sitting next to my computer desk! Currently used, er, to hold up my company laptop. But it boots and everything.)
It's worse than that. Apple floppy disks were written with constant linear velocity --- i.e., as the head moves towards the centre of the disk, the rotation speed goes up so that the magnetic medium still passes the head at the same velocity.
PCs, and therefore all modern hardware, use constant angular velocity floppy disks --- the disk spins at a constant speed, so that the speed at which the magnetic medium passes the head varies depending where the head is. Yes, this is clearly a bad idea, but that's PCs for you.
This means that no modern hardware can read old Apple floppy disks. It's just not possible. You'll need an old Macintosh floppy drive and (probably) an old Macintosh floppy drive controller to plug it into, which basically means you need an old Macintosh. You still have yours, right? Right?
Have fun!
You do know that the Great Firewall is not, in fact, a NAT? It's just a simple filtering service applied on the master gateways to the outside world. It does proxy DNS, but that's it; all other packets are either passed through unchanged or blocked entirely, depending on the firewall policy.
Go look at the Wikipedia article; it's got a reasonable amount of technical information.
...except for the proprietary BIOS software, the proprietary microcode in the video card, wireless card, I/O controller, hard disks, floppy disks, monitor, keyboard, mouse, POTS modem, ADSL modem, power control microcontroller, and all the other little bits of electronics with embedded CPUs on your desk.
And if you want to be really picky, you could also talk about the proprietary chip and CPU designs in every single piece of silicon in all of the above. Not to mention the patented and extremely commercial fabber techniques needed to make it all (in China). Free, it's not.
Now that there are genuinely free (as in speech) IC designs out there on places like opencores.com, is it possible to make completely free computers? Even single-board jobs?
Because with that particular camera, taking an RGB photo involves making three separate exposures with different filters, transmitting the result back to Earth, and combining them. Given that the lander has been on the ground for less than 24 hours so far, they're still at the quick-glance-around-to-see-where-we-are stage and don't want to waste bandwidth taking the same picture three times. Give them time. Given the PR value of RGB images I'd expect some to start showing up within a few days.
(In fact a two-colour image has shown up already, but it's not true RGB and probably isn't what you're looking for.)
Remember, if you love something, set it lose...
Actually, building self-righting / uncapsizable boats is pretty straightforward. Remember that the keel needs to be heavy enough to offset the tipping moment of the sails; normally this means they're really, really heavy. Also remember that the keel is submerged in water, which means that its effective weight is rather lower than it would be in air.
With a bit of forethought, you end up with a boat which will tip over until the keel starts coming out of the water, and then it'll just stop --- any additional heel will cause more keel to emerge, which will cause the effective weight of the keel to increase hugely, which will prevent any further heeling.
Even if by some miracle you do end up with the boat upside down, it's unstable in that attitude and will right itself. Yes, the sails will cause huge water resistance, but that resistance is proportional to the speed of motion through the water; it won't stop the self-righting, it'll just cause it to happen slowly. (Also, the sails will act to prevent the capsize in the first place, for exactly the same reason.)
What tends to happen these days on decently designed boats is knock-down; a gust of wind causes the boat to be knocked onto its side, up to the point where the keel's righting moment offsets the tipping moment of the wind against the sail. This can be very hazardous to the crew, but hey, no crew! When the gust passes, the boat will right itself (usually even if it's filled with water).
The biggest risk is that all this process is extremely violent; the boat's being slammed about hugely. You run a very real risk of bits of the boat actually breaking. The tension at the base of the mast is huge at the best of times, and if the mast breaks under strain and doesn't come completely free of the boat it can very easily smash through the bottom of the hull. Which Would Be Bad. That's one of the reasons why people like unstayed masts these days; if you get dismasted, you don't end up with a huge, heavy, sodden and very dangerous lump of stuff smashing about on top of your boat --- you're much more likely to lose it completely overboard. Much safer.
While this does tend to apply to yachts rather than dinghies, which as you say largely use humans for ballast, you really do get yachts that size --- the difference is largely design rather than size. My father designed, built and sailed a highly successful yacht only a little bigger --- 15 feet, I believe. It was a bilge keel gaff rig with two monster lumps of concrete for the keel, and slept three. It would heel comfortably to about 45 degrees and then just stop. My father tried quite hard on several occasions to get the cabin windows in the water (much to my horror) and failed every time...
Better than meeting the GGOD --- the Green Ground Of Death...
Do you mean like Accordian Hero?
And it had the passive backplane (which meant that the processor was on an ISA card and plugged into one slot, and the RAM was on another ISA card and plugged into another slot)!
And the full-length HDD/FDD/serial port card (WTF?) had not just one but *two* monster ribbon cables connecting to the hard drives in order to achieve the staggering data throughput of, nearly, a megabyte a second! Beat that, SATA!
Mine ended up getting skipped. I wish I'd known how much in demand they are now, I'd have kept it...
I used to have an uber-expanded 8088 computer of about the same vintage: a Zenith Z150 with passive backplane, ethernet, 1.5MB of RAM, 3.5" floppy, Hercules graphics --- and *two* 20MB Seagate MFM drives. Those things were awesome. Not only was the revving-jet-engine noise as they spun up seriously cool, but when the machine was turned on I didn't need any heaters on in the room...
I slightly miss those old MFM drives. While modern ones are far more sophisticated and generally better in every way, the old drives had a kind of mechanical elegance to them that the new ones don't. Also, big chunky rectangular red access LEDs.
How's Rudd working out, now you've had him a bit? While he seemed to be a really big improvement over Howard at first (of course, a decaying rat corpse would have been an improvement over Howard), he's kind of dropped off the internation news since then, and I'd be interested to hear what he's like now.
I go with gandi.net, who are reasonably price, have decent service, and appear to be fairly white-hat.
You do realise that Nazi is a proper noun, not an acronym, and therefore should not be capitalised?
HTH. HAND.
Also check out Mother Earth, Mother Board, which is a fast-moving, gripping, action packed, 42000 word essay on... the history and practice of submarine cable laying. Really. It's awesome. Read it. (He used bits of it for the background in Cryptonomicon, so if you've read that you may find it a little familiar.)
Ah, but rock's not made out of atoms --- it's made out of molecules. The molecules only work properly if they're made up of the right combination of atoms. Let's say that the environment the rock's formed in contains Foonium. Foonium is unstable and decays into Barnium, which is stable. They're chemically different; Foonium forms Foonium Oxide, but Barnium's an inert metal. So, when the rock's formed in lots of hot air, it ends up containing lots of Foonium Oxide --- but no Barnium, because the Barnium's so inert it doesn't take part in the rock-making process.
Millions of years later, some of that Foonium has decayed into Barnium. Since we know that the rock was formed with 100% Foonium and 0% Barnium, we can use the ratio to figure out how long it's been since it was formed.
No, you don't --- but you do get loads of feedback from the shape of the key that lets you know where you hit the key. This allows you to continuously adjust the position of your hands and fingers so that you continue to hit the middle of the keys.
That's why it's so easy to adapt to a keyboard of a different size. If it was simply a matter of 'knowing where the keys are', it would be impossible. Instead, you continuously adapt based on the kinaesthetic feedback you get from your hands. It's not something you notice consciously unless you look for it --- or until you try typing on a keyboard that doesn't provide those subtle cues.
Try an eee some time; okay, the keyboard's small, but it's not that small --- it's so hard to type on because the keys are flat. Which is a really dumb idea and I don't know why they did it. But even the eee is better than a real, old-fashioned membrane keyboard... like on the ZX81. *shudder*
I recently worked on a mobile phone platform (not based on VxWorks) which had a mechanism for sending messages to specific threads. There was a system wide 150-slot message queue. There was a background thread that ran at low priority that was supposed to do non-real-time things like UI work. This thread was a message receiver. The system did not support timeslicing.
Can you see the problem yet?
If the background thread didn't get enough CPU time, it wasn't able to keep up with the incoming messages that would get posted by high-priority threads. This meant the queue would fill up, and once the queue filled all the way up, the system would reboot. The end result was that since the system didn't support timeslicing, if any thread running at the 'background' priority spent too long running without yielding, the message receiver thread would get starved of CPU, and splat. They were using a low-priority background task to handle high-priority system critical operations. When we queried them on this, they said, "Well, we don't really plan task priorities; we just adjust everything on an ad-hoc basis until it works."
Gah.
The last time I had to use it --- which, admittedly, was a while ago --- we had a requirement to do asynchronous I/O. VxWorks didn't support that, so we had to emulate it by using a pool of helper tasks each of which ran a blocking I/O operation. Unfortunately we had a further requirement that asynchronous I/O operations had to be cancellable, and the only way we could find of doing that was by nuking the helper task that was blocked on the I/O operation. Unpleasant, to say the least, especially as we then discovered that on the BSP we were using, half the device drivers had bugs which meant they leaked resources / crashed / made the system hideously unstable if you destroyed the task while they were in the middle of an operation...
Hopefully this has all been sorted out by now, but it still left a nasty scar. I've had much better experience with Nucleus (although it mysteriously does not have mutexes, only semaphores), and while I haven't worked with it, I really like the look of QNX.