Can anyone shed light (sorry, bad pun) on the following:
1) The 5 year solar sail propelled mission to Pluto - is there a way to decelerate as you reach Pluto? Actually, is it really 5 years constant thrust or does the solar sail's thrust decrease as an inverse square law as you get more distant from the sun?
2) Can you sail "upstream" into the solar wind? Is it possible to tack and jibe in a solar sail propelled craft?!
Anyone got any suggestions how a positronic brain works exactly? The Star Trek TNG writers gave Data one too, probably as a nod to Asimov (spelled with an 's' BTW). I've never seen even a vague excuse for a description of how one works. However we can do some maths to try and see how much energy is involved.
A single positron/electron has a rest mass of about 0.511 MeV (million electron volts). A proton is in the region of 938 MeV. Converting electon volts to Joules (with Google) tells me "one electron volt = 1.60217646 x 10^-19 Joules".
So, one electron/positron annihilation will release (2 x 511) MeV == 1.63742434 x 10^-10 Joules. Assuming the positronic brain has a few billion of these, then allowing them all to react with each other will release a few joules of energy - this will take the form of gamma rays anyway, so things nearby will get irradiated, not blasted by a big explosion.
Interestingly, this might explain something in one of Asimov's robot stories called Victory Unintentional. A robot interacting with life forms on Jupiter (Asimov didn't have the benefit of modern space probe data) apologises to a native Jovian for killing some bacteria-type samples in a lab as a result of the robot emitting radiation.
Well, it's possible that you could network boot one of these, though you then need to add the cost of a boot server somewhere. Might be worth it if you're deploying lots of 4-head workstations.
In my experience of these, NVidia cards worked better. ATI cards were fussy about the order in which they were booted, and sometime which PCI slot they were in. However I have managed to get one of these things set up with an AGP GeForce 2MX, a PCI Radeon 7000, and a PCI Matrox Millenium II:)
Ignoring those people who say "why would 4 users share one monitor", here's why this system could be useful...
For those without large IT budgets, you can provide basic computer access to several users using fewer components (just 1 case, 1 CPU, 1 motherboard, 1 HDD, RAM, and 4 cheap graphics cards and heads) and less electrical power. Think developing countries, small businesses, schools, charities.
It could also allow your parents/spouse/children to use the computer/Internet at the same time without having to fight over the computer or buy a whole new second PC.
On the down side it's still difficult to set up, 3D acceleration depends on which cards you use (I couldn't get it working), and not all combinations of graphics cards work. Also with PCIe or whatever it's called, I'm not certain that the Ruby kernel will continue to work.
For those linux geeks interested in experimenting with this, start by checking out the Ruby 2.6 kernel modifications from the Linuxconsole project on sourceforge. Then join the mailing list to get help and advice setting up X etc. There's also a reasonably up-to-date HOWTO in the Linux Doc. Project.
Reading the link, it seems he's a bit of a rocket scientist in hte literally meaning. That's not something to be disrespected. However it's vague as to what his exact contribution to India's rocket programme was. I expect that these days he's much more of a politician than an engineer. The two professions can overlap a little bit, but I'm sure engineers reading this have plenty of anecdotes about managers making political decisions counter to the engineering recommendation (NASA perhaps?).
As for scientists lacking common sense... well I have to agree based on some of my friends (and myself I guess)! But then I also think people are stupid when they open another virus infected e-mail attachment called "harmless-flash-game.exe.vbs"...
"We should take maximum care to ensure that our solution is unique to protect our own defence security solutions implemented on open platforms."
Uh oh. Somebody needs to get a visit from Bruce Schneier next! I suspect that his proposed unique solution would be better off if it was Open Sourced for peer review.
1. "Hey, I was in X country and the price was cheaper/more expensive!"
One trend that appears in most countries relates to the size of city. I was in Vietnam last year and the cost of Internet access in Saigon/HCMC was about 3 times more than in somewhere smaller like the town of Hue ($0.50-1.00/hour).
3. Why do people who live on $1 per day need to worry about internet access?
In Hue, the young man running the place was clearly letting his friends and extended family use the spare PCs for e-mailing etc. Generally the literacy rate in Vietnam seems much higher than in neighboring Cambodia.
The sun will be in its current stage for much longer than we can comfortably imagine. A few billion years or so. If we haven't got a nice Star Trek future (go on, admit you want it) within the next million years, we're probably all doomed anyway.
As for asteroids. What good is a manned space program going to do? I would imagine solutions involving long-range detection and nuclear explosions. Possibly a big frikin' "laser"... but do you really thing it'll be like the film "Armageddon"?
The article suggests it will use a mixture of methanol and water. Allowing the public to buy hydrogen in normal retail outlets seems like a real bad idea (though possible good for Darwin awards).
Ideally it could be as normal to fill up your laptop at a petrol station (gas station for the US folk) as you would your eco-unfriendly SUV.
And besides, once you are in space, without having to worry about air resistance, it's trivially easy to build up that extra velocity. Your post makes it sound like getting to Mach 3 is trivial and they need to put in eight times the work to reach LEO. This is simply not true. Getting to 100km through most of the atmosphere has already accomplished most of the work. The rest is easy.
I disagree that it's easy. Although accelerating at a height of 100km isn't too hard, you need to get the fuel and oxidizer up to that height and keep burning it. Carrying enough propellants up through the atmosphere in order to burn your way up to about 7,500 m/s velocity is pretty difficult.
Another way to look at it is to use the equation for kinetic energy (1/2*m*v^2). Since it's proportional to v-squared, if you need 8 times more velocity, that's 64 times more energy. As you say, "The rest is easy.":)
> (which is, of course, impossible).
"If you've done six impossible things this morning, why not round it off with breakfast at Millway's, The Restaurant at the End of the Universe?"
The Z machines and their inventor are also mentioned in a beautiful book, most suitable for geek coffee tables everywhere - "Computers: An Illustrated History" (direct Amazon UK link).
A suitable Father's day present if he's a geek too?
I acknowledge that India has a huge population, with many cities that have over a million inhabitants, but... they don't all have broadband Internet access do they?
I was about to moderate but you changed my mind, thanks.
News for Nerds. Stuff that matters.
It's a public forum, and some people think that this matters. If you consider yourself an uber-geek and beyond politics, please understand that that in itself is a political position. Anyway, most geeks are very political - just mention GNU, FSF, RMS, or MSFT.
I hate to reply to my own post but I looked up the problem with how far back we can see, and wanted to correct myself.
The issue isn't density, since water's pretty dense and still has high transparancey. The problem is that earlier that about 1 million years, most matter was ionised and ionised matter seems to be very good at interacting with photons. So there you go.
The orbit is about 1.5 million km distance from the earth, at something called the L2 Lagrangian. The Webb wiki page has a link to the Lagrangian page, but for the lazy people, it's here. The orbit was chosen to keep the position of the sun constant relative to the telescope, so that the big 'parasol' can be used to shield the infra-red sensor.
As for Hubble, it's been able to give some awesome images, but it has its limits. I was hoping that the JW (henceforth called J-Dubya?!) would be able to start spotting planets around other stars, but it's not designed for that. I'd like to know if it's theorically possible to keep both in orbit and use them in parallel somehow, in the same way that ground-based radio telescopes have been linked together in arrays. Probably not worth the hassle?
The 'infra-red only' sensor troubles me. Since the telescope's aim is to study the Big Bang, the light/photons it'll be receiving will have travelled for a long time/distance and I guess be red-shifted way down to the IR band. This is all very well, but it means that the telescope shouldn't be considered as a replacement for Hubble, which carries out a wider range of observations.
As an aside, I believe that there is a limit to how far back we can look. At some point, probably less than 1 million years (a guess, can anyone help?), the universe was just too dense for photons to travel around unhindered as they seem to these days. Who said it was better back in the old days eh?
Now two questions. First why beryllium? I know that it's lightweight so easier to lift into orbit. Any other reasons? And secondly what happens if a micro-meteor hits this shield? Do we get a permanent bright spot on all subsequent images, like a broken pixel on an LCD display?
Look here, it's not the fault of the USA. They got the stupid idea from us Brits.
What screws it up is that the States use the same names - pound, ton - but they have different values and hence metric conversion rates. So it seems the Americans really do have to do things their own way!
Here's some links from Google, so that I can be a karmawhore.
Uhm, I thought planes stored fuel in the wings. So I guess you need some flexible fuel tanks now too? Tell you what, I'll just pour the kerosene into this nice rubber bag and...
Also, I would guess these wings aren't going to be very strong. I don't think they will safely be able to transmit the lift that they generate along their length to the body of the aircraft.
Might work for small UAVs though, since they're smaller, and lighter.
I guess it's a chemical laser, and probably uses things like flourine gas (nasty nasty nasty, but very energetic). You can read some info about these kinds of things here
This old report from 1999 actually suggests it uses some other strong oxidisers like hydrogen peroxide and halogens - chlorine and iodine.
Basically you don't want to be breathing these things in, but you there's a lot of energy available in their reactions.
Slashdot Mirror
1) The 5 year solar sail propelled mission to Pluto - is there a way to decelerate as you reach Pluto? Actually, is it really 5 years constant thrust or does the solar sail's thrust decrease as an inverse square law as you get more distant from the sun?
2) Can you sail "upstream" into the solar wind? Is it possible to tack and jibe in a solar sail propelled craft?!
A single positron/electron has a rest mass of about 0.511 MeV (million electron volts). A proton is in the region of 938 MeV. Converting electon volts to Joules (with Google) tells me "one electron volt = 1.60217646 x 10^-19 Joules".
So, one electron/positron annihilation will release (2 x 511) MeV == 1.63742434 x 10^-10 Joules. Assuming the positronic brain has a few billion of these, then allowing them all to react with each other will release a few joules of energy - this will take the form of gamma rays anyway, so things nearby will get irradiated, not blasted by a big explosion.
Interestingly, this might explain something in one of Asimov's robot stories called Victory Unintentional. A robot interacting with life forms on Jupiter (Asimov didn't have the benefit of modern space probe data) apologises to a native Jovian for killing some bacteria-type samples in a lab as a result of the robot emitting radiation.
In my experience of these, NVidia cards worked better. ATI cards were fussy about the order in which they were booted, and sometime which PCI slot they were in. However I have managed to get one of these things set up with an AGP GeForce 2MX, a PCI Radeon 7000, and a PCI Matrox Millenium II :)
For those without large IT budgets, you can provide basic computer access to several users using fewer components (just 1 case, 1 CPU, 1 motherboard, 1 HDD, RAM, and 4 cheap graphics cards and heads) and less electrical power. Think developing countries, small businesses, schools, charities.
It could also allow your parents/spouse/children to use the computer/Internet at the same time without having to fight over the computer or buy a whole new second PC.
On the down side it's still difficult to set up, 3D acceleration depends on which cards you use (I couldn't get it working), and not all combinations of graphics cards work. Also with PCIe or whatever it's called, I'm not certain that the Ruby kernel will continue to work.
For those linux geeks interested in experimenting with this, start by checking out the Ruby 2.6 kernel modifications from the Linuxconsole project on sourceforge. Then join the mailing list to get help and advice setting up X etc. There's also a reasonably up-to-date HOWTO in the Linux Doc. Project.
As for scientists lacking common sense... well I have to agree based on some of my friends (and myself I guess)! But then I also think people are stupid when they open another virus infected e-mail attachment called "harmless-flash-game.exe.vbs"...
Uh oh. Somebody needs to get a visit from Bruce Schneier next! I suspect that his proposed unique solution would be better off if it was Open Sourced for peer review.
One trend that appears in most countries relates to the size of city. I was in Vietnam last year and the cost of Internet access in Saigon/HCMC was about 3 times more than in somewhere smaller like the town of Hue ($0.50-1.00/hour).
3. Why do people who live on $1 per day need to worry about internet access?
In Hue, the young man running the place was clearly letting his friends and extended family use the spare PCs for e-mailing etc. Generally the literacy rate in Vietnam seems much higher than in neighboring Cambodia.
As for asteroids. What good is a manned space program going to do? I would imagine solutions involving long-range detection and nuclear explosions. Possibly a big frikin' "laser"... but do you really thing it'll be like the film "Armageddon"?
8.9 metres? And that's a portable walkman is it? What will these wacky foreigners think of next? :)
Ideally it could be as normal to fill up your laptop at a petrol station (gas station for the US folk) as you would your eco-unfriendly SUV.
The "rockets won't work outside the atmosphere" arguement was used as a critcism as Goddard in 1920. See this wiki.
I disagree that it's easy. Although accelerating at a height of 100km isn't too hard, you need to get the fuel and oxidizer up to that height and keep burning it. Carrying enough propellants up through the atmosphere in order to burn your way up to about 7,500 m/s velocity is pretty difficult.
Another way to look at it is to use the equation for kinetic energy (1/2*m*v^2). Since it's proportional to v-squared, if you need 8 times more velocity, that's 64 times more energy. As you say, "The rest is easy." :)
> (which is, of course, impossible).
"If you've done six impossible things this morning, why not round it off with breakfast at Millway's, The Restaurant at the End of the Universe?"
'nuff said.
The Z machines and their inventor are also mentioned in a beautiful book, most suitable for geek coffee tables everywhere - "Computers: An Illustrated History" (direct Amazon UK link).
A suitable Father's day present if he's a geek too?
I acknowledge that India has a huge population, with many cities that have over a million inhabitants, but... they don't all have broadband Internet access do they?
News for Nerds. Stuff that matters.
It's a public forum, and some people think that this matters. If you consider yourself an uber-geek and beyond politics, please understand that that in itself is a political position. Anyway, most geeks are very political - just mention GNU, FSF, RMS, or MSFT.
The issue isn't density, since water's pretty dense and still has high transparancey. The problem is that earlier that about 1 million years, most matter was ionised and ionised matter seems to be very good at interacting with photons. So there you go.
The orbit is about 1.5 million km distance from the earth, at something called the L2 Lagrangian. The Webb wiki page has a link to the Lagrangian page, but for the lazy people, it's here. The orbit was chosen to keep the position of the sun constant relative to the telescope, so that the big 'parasol' can be used to shield the infra-red sensor.
As for Hubble, it's been able to give some awesome images, but it has its limits. I was hoping that the JW (henceforth called J-Dubya?!) would be able to start spotting planets around other stars, but it's not designed for that. I'd like to know if it's theorically possible to keep both in orbit and use them in parallel somehow, in the same way that ground-based radio telescopes have been linked together in arrays. Probably not worth the hassle?
The 'infra-red only' sensor troubles me. Since the telescope's aim is to study the Big Bang, the light/photons it'll be receiving will have travelled for a long time/distance and I guess be red-shifted way down to the IR band. This is all very well, but it means that the telescope shouldn't be considered as a replacement for Hubble, which carries out a wider range of observations.
As an aside, I believe that there is a limit to how far back we can look. At some point, probably less than 1 million years (a guess, can anyone help?), the universe was just too dense for photons to travel around unhindered as they seem to these days. Who said it was better back in the old days eh?
Now two questions. First why beryllium? I know that it's lightweight so easier to lift into orbit. Any other reasons? And secondly what happens if a micro-meteor hits this shield? Do we get a permanent bright spot on all subsequent images, like a broken pixel on an LCD display?
I just read that as shooting a hobbits rocket into space is just cool. Yup. Sure is.
What screws it up is that the States use the same names - pound, ton - but they have different values and hence metric conversion rates. So it seems the Americans really do have to do things their own way!
Here's some links from Google, so that I can be a karmawhore.
Columbia Encylcopedia entry
World History Wiki entry
Cooking unit conversions (I always wondered what the hell a 'cup' was)
In space, no one can hear you stream... Sorry!
Let me know if they find a fossilised Babelfish.
Also, I would guess these wings aren't going to be very strong. I don't think they will safely be able to transmit the lift that they generate along their length to the body of the aircraft.
Might work for small UAVs though, since they're smaller, and lighter.
I guess it's a chemical laser, and probably uses things like flourine gas (nasty nasty nasty, but very energetic). You can read some info about these kinds of things here
This old report from 1999 actually suggests it uses some other strong oxidisers like hydrogen peroxide and halogens - chlorine and iodine.
Basically you don't want to be breathing these things in, but you there's a lot of energy available in their reactions.