Yes, I use vgetty as an answerphone --- I have it set up so that messages get ogg compressed and emailed to me (because I'm much more likely to actually *get* them that way than I would if I simply relied on noticing the flashing light on the answering machine).
What software is available that can make use of the modem in full duplex mode? I know, for example, that Asterisk can't, and requires weird proprietary hardware rather than a standard modem, which is a shame, because modems are practically free these days.
I'm assuming that the actual work gets done by magic, and just calculated what the mass of the Earth is, turned into energy. At this scale, you can't get away from the fact that mass and energy are equivalent.
In fact, if you could collapse the Earth into a black hole, there'd be very little change in the amount of energy in the system --- because most of the energy is tied up in mass, and that mass isn't going anywhere. You will get some losses in radiation, debris flung off etc, but they'll be insignificant in comparison.
A black hole with the mass of the Earth has, at one Earth-radius, a gravitational attraction of 1g. (In other words, if you were on the far side of the moon, and the Earth suddenly turned into a black hole, you wouldn't notice.) Closer, it would be much higher. Half an earth radius from the black hole it'd be 4g, a quarter of an earth radius it'd be 8g, etc --- one kilometre away it'd be 4 million g, and one metre away it'd be 3x10^14 g. That's gonna hurt.
So if somehow you were to magically create the 5x10^41 Joules of energy necessary to create a black hole the size of the Earth, on the Earth, I suspect we'd probably know immediately, subject to light speed limits, as the direction of down shifts abruptly followed a few seconds later by the disintegration of the planet and collapse into a accretion disc of white hot plasma. That is, those parts of the Earth that are not blasted outwards by the collapse event, which is what astrophysicists would call 'violent'.
(Of course, *now* I realise that you were actually originally talking about the end result after the consumption of the earth by a tiny black hole, but I've done all the maths now, dammit. So I'm going to post anyway. Besides, once the tiny black hole reaches about.1 earth mass it's still going to be pretty spectacular.)
If you place your massy spacecraft near an asteroid and let go, the two will mutually attract each other and eventually collide. The centre of gravity of the system won't change.
So, in order for this to work at all, you need a manouevering system on the spacecraft in order to maintain its separation from the asteroid.
The thing is, though, that from a pure orbital mechanics point of view, this is absolutely equivalent to simply mounting the spacecraft's thrusters on the asteroid itself. In fact, using the gravitational tractor is probably going to be rather less efficient, because the geometry of the system is such that you have to fire your thrusters towards the asteroid --- and a certain amount of your thruster exhaust is going to bounce off the asteroid's surface, imparting momentum in the wrong direction to the asteroid.
The only things I can think of that the gravity tractor does for you that direct acceleration doesn't is:
With the gravity tractor, you don't have to manipulate the asteroid in any way; this may make the engineering considerations easier, as you don't have to worry about the rock collapsing under your rocket's thrust, etc;
The gravity tractor operates on the entire mass of the asteroid, rather than applying thrust to one point and relying on the asteroid's integrity to distribute the thrust. This avoids embarassing situations where the asteroid simply disintegrates rather than accelerating, or leaving stuff behind.
But, given the type of accelerations we're talking about --- which will be the same regardless what technique you're using --- I wouldn't imagine that either of these would be a problem in practice. So, what makes the gravity tractor so much better than just using rockets? Indeed, what makes it better than alternative approaches like spraying the asteroid with aluminium powder (which raises the albedo, causing increased photon pressure, which alters the orbit over time)?
Well, that sucks. Still, this is rocket science. Never mind, there's always next time.
Incidentally: why does the RocketCam footage always cut off the instant anything goes wrong? That's happened on all the Falcon 1 flights so far. Even if the vehicle gets destroyed by Range Safety, you'd expect at least a few seconds between something going wrong and the decision to terminate being made. Instead, every time we apparently transition from flying (relatively) normally to no data. Given that RocketCams typically have their own downlink connection and, I assume, power, I'd have thought that we should see something --- indeed, on termination there's a chance that we could see some views of the debris before everything goes silent.
Yes, indeed --- I'm rather excited by the new MIPS-based mini laptops that are just becoming available. Not for use as a laptop; for use as a server --- for under $100, you get an adequate processor, adequate memory, UPS, console, flash disk, decent I/O capabilities via USB, and all this in a miniscule form factor and using practically no power. The fact that it uses MIPS rather than ia32 or ARM would give you a small edge security-wise, too.
But I'd still really like an A9-based mini-ITX board.
The new Cortex-A8 ARM processor consumes 300mW; less than a tenth that of the Atom. The Atom is marginly faster, but not much so --- the figures I've found show that a Cortex develops about 2.0 Dhrystone MIPS per MHz, vs about 2.4 for the Atom. Plus, the Cortex is a CPU core, not a discrete chip; most actual products couple it with an on-chip OMAP DSP engine, which is ideal for doing things like video encoding or decoding or OpenGL. With Atom you end up having to couple it with a dedicated GPU...
What sticks out more, though are numbers like "63,434 watts". Uhmm... no? Besides being a clearly invalid measurement, it should probably be expressed at watt-hours.
Well, no; a watt-hour is a measurement of energy, being one watt (a joule per second) applied over one hour. It's precisely equivalent to 3600 joules. If you want to measure power, that is, the rate of energy consumption, then watts are the right unit.
(Although I wish people would just use joules and joules per second instead; it would save all this confusion. At least it's better than the motor industry, who have decided that watts are insufficiently confusing and have opted for horsepower instead, each of which are equivalent to approx. 746 joules per second. Sigh.)
(And besides, the article actually said 63434 watt-seconds --- i.e., one joule per second applied for one second, i.e. one joule. So why they didn't say so in the first place I don't know.)
The Soyuz module with a crew of 3 delivers about 1 ton of cargo. The Shuttle with a crew of 7 can deliver 57 tons of cargo.
24 tonnes to LEO, actually. And if you want to lift cargo, you're hardly going to use a Soyuz. Use a properly designed heavy-lifter instead, such as a Proton or an Ariane 5, and launch your astronauts seperately in a Soyuz; that way you don't have to man-rate your heavylifter, which saves you vast amounts of money. The Shuttle's main problem is that it's designed to be a man-rated lifter and a cargo heavylifter and an on-orbit habitation module and a heavy cargo return vehicle and an aeroplane, which means it does everything badly rather than doing one thing well.
Where do you get your figures from? According to nationalpriorities.org (which given its bias would tend to overestimate, if anything), it 'only' costs $340e6 per day.
(You may be amused to know that that would pay off my mortgage in slightly more than 30 seconds.)
The old images were taken on real photographic film, which was then brought back to Earth and developed. Hugely expensive due to having to ship all that mass around, and only feasible at all on sample-return missions, but the quality is superb. The new images are taken using digital cameras, JPEG compressed, and transmitted back using the Deep Space Network; as a result, the quality is much lower. (On the other hand, shipping photographic film back from Mars is a little beyond our technical expertise right now.)
It is possible to take high-resolution pictures from Mars, but it's not done very often because it takes too long --- a couple of weeks for a decent panorama; dozens of low-resolution pictures need to be taken, transmitted back, and then pieced together (mostly by hand). It's far more cost-effective to use low-resolution pictures. At that distance bandwidth is the main limitation; they've just been upgraded to a 256kbps connection, and the DSN only listens to them in short windows.
This is less of a problem for spacecraft nearer Earth; JAXA's Kaguya lunar probe can send back HDTV video, for example, although still not live.
i have a FAT formatted usb drive, and windows XP refuses to format it as anything other than fat, or fat 32...
Go hunt down the command line FORMAT command; you can use this to format the USB key as NTFS. If you're working off one, like I used to do, this makes all the difference. Not only is it much more robust it also supports things like symlinks, proper access flags, compressed files, etc. *And* with an NTFS file system XP will let you turn off the option to flush the cache after every write, which vastly speeds things up. (You just have to remember to unmount it before removing the device.)
Actually, it confers "the ability to fold space. That is, travel to any part of universe without moving."
Actually actually, the space folding is done using the Holtzman drive, which is a perfectly ordinary machine. The Navigator merely navigates, plotting a safe path through the non-space/time foldspace. The spice grants the Navigator the limited prescience required to do this.
Eventually the Navigators become obsolete, replaced by Ixian semisentient machines known as Compilers that perform the same task without needing melange. A good thing too, because by that point Arrakis is rubble and sandworms are pretty much extinct.
Details courtesy of Wikipedia (and my lack of a social life).
Notice your accelerator foot barely above idle on the highway... Half the time my foots off the gas completely. [...] At cruising speed you may only need 1 KW to keep going.
The reason why you don't have to keep your foot on the accelerator is that the engine management computer (or, more likely, a shaped cam in the carburettor) is automatically feeding in enough fuel to keep the engine happy. There's a reason why it's eating a gallon of petrol every 30 miles or so.
And if your car consumes 1kW at cruising speed, you're either cruising at walking speed or riding a scooter --- 20 or 30kW is rather more realistic...
An "Instant Battery" is also called a generator. Honda makes tiny little ones that weigh about as much as a toddler, or perhaps as heavy as a fat feline house-cat. Strap a one quart gas can to it and an extension cord and you're set.
No use, I'm afraid.
One of those little electric generators will produce, maybe, one or two kilowatts. Unfortunately the Tesla's engine consumes about two hundred kilowatts. Even allowing for driving very slowly to make the most efficient use of the energy, you're simply not going to be able to get enough charge into the car's battery in a reasonable enough time to be useful.
(People don't realise it because they measure car engine powers in horsepower and electrical engine powers in kilowatts, but car engines are ludicrously powerful. My crappy 1200cc Ford Fiesta produces enough power to run my entire house with all the heating turned on four times over. Cars use phenomenal amounts of power, and there's a reason why they're not powered by the kind of tiny lawnmower engine that you get in those generators...)
wow that is amazing. I can't believe this is the first time I'm hearing about Malbolge. I used to collect odd programming languages. I would have thought that Funge-98 was the craziest. Now, I'm not so sure. Malbolge seems like its more of a difficult to exploit buffer overflow than a language. Then again, maybe thats the point.
Unfortunately people have done cryptanalysis of Malebolge and have managed to find an, er, exploit: it's now possible to actually write programs for it on purpose, rather than having to do brute-force searches of the program space until you find one that matches. See this link for details. If you're really brave, here is an implementation of 99 green bottles in Malebolge. (You may be interested to note that the program is roughly twice as long as its output...)
I highly recommend the ClearType Tuner [microsoft.com]. There's a web version, but the control panel applet is nicer I think because changes are immediately shown.
Yeah, except I can't use ClearType. Not only do I hate the effect, it won't work on my monitors.
Also, the ClearType Tuner goes to such great lengths to avoid telling you what it's doing that it's pretty much useless --- I know what settings I want, but it won't let me set that. All it does is present samples and say 'Which of these do you like best?' How should I know? I don't use that font, or that font size, or that monitor, or that colour...
A secondary factor may be the settings of the different computers you have the LCDs attached to - if (God forbid) you're using Windows systems, check that both have "Cleartype" enabled and that it has been tweaked for that particular monitor's arrangement of RGB on the screen. It really does make a difference.
It doesn't to me, because I have a dual-headed system with two monitors with different orientations. (In fact, even on a single monitor I find it gives unpleasant rainbow tinges to all the characters, no matter how it's configured.)
In general I loathe the Windows font rendering system. It seems to insist on applying such aggressive hinting to the fonts that they show up far too spindly and with distorted shapes. On Linux, I use the Gnome control panel to turn the hinting all the way off, which gives slightly fuzzier characters but with far more even contrast and better shapes; does anyone know how to do this on Windows?
They're tiny, they have usable keyboards and a decent screens, they run for about a week on a few AA batteries, they have enough CPU to run proper diagnostic tools using the built-in scripting language, and they have built-in serial ports (although, alas, they're non standard). The Psion 5 will run Linux, but they've both got lots of useful built-in software on ROM. They're also pathetically cheap; 10 dollars for a Psion 3...
I have a Microsoft Internet Keyboard, and I love it. Nice key feel despite being a membrane keyboard, good size, enough extra keys to be useful without being silly, it's dirt cheap, it's robust, and it has one extra incredibly handy facility --- it's designed for maintenance.
If you turn it over and undo four screws, the entire top shell lifts off the part with the electronics in it, with the keys clipped into it. As the top shell is curved and extends down to table level at the front, this means that you've removed all the plastic that gets exposed to finger touch. Now all you need to do is to unclip the keys from the shell (and each one is in a little bucket that stops coffee and crumbs getting into the rubber membrane), and put keys and shell into the dishwasher. Once done, clip the keys back on, screw the shell back down to the works of the keyboard, and you have a bright, shiny new clean keyboard. And you didn't even have to unplug it.
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Yes, I use vgetty as an answerphone --- I have it set up so that messages get ogg compressed and emailed to me (because I'm much more likely to actually *get* them that way than I would if I simply relied on noticing the flashing light on the answering machine).
What software is available that can make use of the modem in full duplex mode? I know, for example, that Asterisk can't, and requires weird proprietary hardware rather than a standard modem, which is a shame, because modems are practically free these days.
I'm assuming that the actual work gets done by magic, and just calculated what the mass of the Earth is, turned into energy. At this scale, you can't get away from the fact that mass and energy are equivalent.
In fact, if you could collapse the Earth into a black hole, there'd be very little change in the amount of energy in the system --- because most of the energy is tied up in mass, and that mass isn't going anywhere. You will get some losses in radiation, debris flung off etc, but they'll be insignificant in comparison.
A black hole with the mass of the Earth has, at one Earth-radius, a gravitational attraction of 1g. (In other words, if you were on the far side of the moon, and the Earth suddenly turned into a black hole, you wouldn't notice.) Closer, it would be much higher. Half an earth radius from the black hole it'd be 4g, a quarter of an earth radius it'd be 8g, etc --- one kilometre away it'd be 4 million g, and one metre away it'd be 3x10^14 g. That's gonna hurt.
So if somehow you were to magically create the 5x10^41 Joules of energy necessary to create a black hole the size of the Earth, on the Earth, I suspect we'd probably know immediately, subject to light speed limits, as the direction of down shifts abruptly followed a few seconds later by the disintegration of the planet and collapse into a accretion disc of white hot plasma. That is, those parts of the Earth that are not blasted outwards by the collapse event, which is what astrophysicists would call 'violent'.
(Of course, *now* I realise that you were actually originally talking about the end result after the consumption of the earth by a tiny black hole, but I've done all the maths now, dammit. So I'm going to post anyway. Besides, once the tiny black hole reaches about .1 earth mass it's still going to be pretty spectacular.)
If you place your massy spacecraft near an asteroid and let go, the two will mutually attract each other and eventually collide. The centre of gravity of the system won't change.
So, in order for this to work at all, you need a manouevering system on the spacecraft in order to maintain its separation from the asteroid.
The thing is, though, that from a pure orbital mechanics point of view, this is absolutely equivalent to simply mounting the spacecraft's thrusters on the asteroid itself. In fact, using the gravitational tractor is probably going to be rather less efficient, because the geometry of the system is such that you have to fire your thrusters towards the asteroid --- and a certain amount of your thruster exhaust is going to bounce off the asteroid's surface, imparting momentum in the wrong direction to the asteroid.
The only things I can think of that the gravity tractor does for you that direct acceleration doesn't is:
But, given the type of accelerations we're talking about --- which will be the same regardless what technique you're using --- I wouldn't imagine that either of these would be a problem in practice. So, what makes the gravity tractor so much better than just using rockets? Indeed, what makes it better than alternative approaches like spraying the asteroid with aluminium powder (which raises the albedo, causing increased photon pressure, which alters the orbit over time)?
Well, that sucks. Still, this is rocket science. Never mind, there's always next time.
Incidentally: why does the RocketCam footage always cut off the instant anything goes wrong? That's happened on all the Falcon 1 flights so far. Even if the vehicle gets destroyed by Range Safety, you'd expect at least a few seconds between something going wrong and the decision to terminate being made. Instead, every time we apparently transition from flying (relatively) normally to no data. Given that RocketCams typically have their own downlink connection and, I assume, power, I'd have thought that we should see something --- indeed, on termination there's a chance that we could see some views of the debris before everything goes silent.
Anyone know anything about this?
...he's going to be the only person in academic history to actually generate any income from selling his Ph.D thesis.
Yes, indeed --- I'm rather excited by the new MIPS-based mini laptops that are just becoming available. Not for use as a laptop; for use as a server --- for under $100, you get an adequate processor, adequate memory, UPS, console, flash disk, decent I/O capabilities via USB, and all this in a miniscule form factor and using practically no power. The fact that it uses MIPS rather than ia32 or ARM would give you a small edge security-wise, too.
But I'd still really like an A9-based mini-ITX board.
Am I supposed to be impressed?
The new Cortex-A8 ARM processor consumes 300mW; less than a tenth that of the Atom. The Atom is marginly faster, but not much so --- the figures I've found show that a Cortex develops about 2.0 Dhrystone MIPS per MHz, vs about 2.4 for the Atom. Plus, the Cortex is a CPU core, not a discrete chip; most actual products couple it with an on-chip OMAP DSP engine, which is ideal for doing things like video encoding or decoding or OpenGL. With Atom you end up having to couple it with a dedicated GPU...
Well, no; a watt-hour is a measurement of energy, being one watt (a joule per second) applied over one hour. It's precisely equivalent to 3600 joules. If you want to measure power, that is, the rate of energy consumption, then watts are the right unit.
(Although I wish people would just use joules and joules per second instead; it would save all this confusion. At least it's better than the motor industry, who have decided that watts are insufficiently confusing and have opted for horsepower instead, each of which are equivalent to approx. 746 joules per second. Sigh.)
(And besides, the article actually said 63434 watt-seconds --- i.e., one joule per second applied for one second, i.e. one joule. So why they didn't say so in the first place I don't know.)
24 tonnes to LEO, actually. And if you want to lift cargo, you're hardly going to use a Soyuz. Use a properly designed heavy-lifter instead, such as a Proton or an Ariane 5, and launch your astronauts seperately in a Soyuz; that way you don't have to man-rate your heavylifter, which saves you vast amounts of money. The Shuttle's main problem is that it's designed to be a man-rated lifter and a cargo heavylifter and an on-orbit habitation module and a heavy cargo return vehicle and an aeroplane, which means it does everything badly rather than doing one thing well.
Where do you get your figures from? According to nationalpriorities.org (which given its bias would tend to overestimate, if anything), it 'only' costs $340e6 per day.
(You may be amused to know that that would pay off my mortgage in slightly more than 30 seconds.)
The old images were taken on real photographic film, which was then brought back to Earth and developed. Hugely expensive due to having to ship all that mass around, and only feasible at all on sample-return missions, but the quality is superb. The new images are taken using digital cameras, JPEG compressed, and transmitted back using the Deep Space Network; as a result, the quality is much lower. (On the other hand, shipping photographic film back from Mars is a little beyond our technical expertise right now.)
It is possible to take high-resolution pictures from Mars, but it's not done very often because it takes too long --- a couple of weeks for a decent panorama; dozens of low-resolution pictures need to be taken, transmitted back, and then pieced together (mostly by hand). It's far more cost-effective to use low-resolution pictures. At that distance bandwidth is the main limitation; they've just been upgraded to a 256kbps connection, and the DSN only listens to them in short windows.
This is less of a problem for spacecraft nearer Earth; JAXA's Kaguya lunar probe can send back HDTV video, for example, although still not live.
i have a FAT formatted usb drive, and windows XP refuses to format it as anything other than fat, or fat 32...
Go hunt down the command line FORMAT command; you can use this to format the USB key as NTFS. If you're working off one, like I used to do, this makes all the difference. Not only is it much more robust it also supports things like symlinks, proper access flags, compressed files, etc. *And* with an NTFS file system XP will let you turn off the option to flush the cache after every write, which vastly speeds things up. (You just have to remember to unmount it before removing the device.)
Actually, it confers "the ability to fold space. That is, travel to any part of universe without moving."
Actually actually, the space folding is done using the Holtzman drive, which is a perfectly ordinary machine. The Navigator merely navigates, plotting a safe path through the non-space/time foldspace. The spice grants the Navigator the limited prescience required to do this.
Eventually the Navigators become obsolete, replaced by Ixian semisentient machines known as Compilers that perform the same task without needing melange. A good thing too, because by that point Arrakis is rubble and sandworms are pretty much extinct.
Details courtesy of Wikipedia (and my lack of a social life).
I've heard the same thing from UK coworkers. Just be thankful you never had any of the government cheese they gave out years ago. Mmmm, tasty!
Suddenly, I now get one of the jokes in The Great Brain Robbery...
The reason why you don't have to keep your foot on the accelerator is that the engine management computer (or, more likely, a shaped cam in the carburettor) is automatically feeding in enough fuel to keep the engine happy. There's a reason why it's eating a gallon of petrol every 30 miles or so. And if your car consumes 1kW at cruising speed, you're either cruising at walking speed or riding a scooter --- 20 or 30kW is rather more realistic...
Ancient Greek had a dual form, although it was mostly used only for nouns that had natural pairs (eyes, oxen, etc).
No use, I'm afraid.
One of those little electric generators will produce, maybe, one or two kilowatts. Unfortunately the Tesla's engine consumes about two hundred kilowatts. Even allowing for driving very slowly to make the most efficient use of the energy, you're simply not going to be able to get enough charge into the car's battery in a reasonable enough time to be useful.
(People don't realise it because they measure car engine powers in horsepower and electrical engine powers in kilowatts, but car engines are ludicrously powerful. My crappy 1200cc Ford Fiesta produces enough power to run my entire house with all the heating turned on four times over. Cars use phenomenal amounts of power, and there's a reason why they're not powered by the kind of tiny lawnmower engine that you get in those generators...)
Unfortunately people have done cryptanalysis of Malebolge and have managed to find an, er, exploit: it's now possible to actually write programs for it on purpose, rather than having to do brute-force searches of the program space until you find one that matches. See this link for details. If you're really brave, here is an implementation of 99 green bottles in Malebolge. (You may be interested to note that the program is roughly twice as long as its output...)
...are they going to call it Blahctivision or (my favourite) Actilizzard?
Yeah, except I can't use ClearType. Not only do I hate the effect, it won't work on my monitors.
Also, the ClearType Tuner goes to such great lengths to avoid telling you what it's doing that it's pretty much useless --- I know what settings I want, but it won't let me set that. All it does is present samples and say 'Which of these do you like best?' How should I know? I don't use that font, or that font size, or that monitor, or that colour...
It doesn't to me, because I have a dual-headed system with two monitors with different orientations. (In fact, even on a single monitor I find it gives unpleasant rainbow tinges to all the characters, no matter how it's configured.)
In general I loathe the Windows font rendering system. It seems to insist on applying such aggressive hinting to the fonts that they show up far too spindly and with distorted shapes. On Linux, I use the Gnome control panel to turn the hinting all the way off, which gives slightly fuzzier characters but with far more even contrast and better shapes; does anyone know how to do this on Windows?
Nah, if you really want a dirty word, try 71077345...
Go get a second-hand Psion 3 or Psion 5 off ebay.
They're tiny, they have usable keyboards and a decent screens, they run for about a week on a few AA batteries, they have enough CPU to run proper diagnostic tools using the built-in scripting language, and they have built-in serial ports (although, alas, they're non standard). The Psion 5 will run Linux, but they've both got lots of useful built-in software on ROM. They're also pathetically cheap; 10 dollars for a Psion 3...
I have a Microsoft Internet Keyboard, and I love it. Nice key feel despite being a membrane keyboard, good size, enough extra keys to be useful without being silly, it's dirt cheap, it's robust, and it has one extra incredibly handy facility --- it's designed for maintenance.
If you turn it over and undo four screws, the entire top shell lifts off the part with the electronics in it, with the keys clipped into it. As the top shell is curved and extends down to table level at the front, this means that you've removed all the plastic that gets exposed to finger touch. Now all you need to do is to unclip the keys from the shell (and each one is in a little bucket that stops coffee and crumbs getting into the rubber membrane), and put keys and shell into the dishwasher. Once done, clip the keys back on, screw the shell back down to the works of the keyboard, and you have a bright, shiny new clean keyboard. And you didn't even have to unplug it.