The Drake Equation doesn't tell us everything. For starters, there's the Fermi Paradox. More interesting, imho, are the questions raised by the Great Filter -- namely, are the hard challenges ahead of us, or behind us?
If Hawking says he thinks life elsewhere is likely, then that implies a certain degree of pessimism about our future chances.
I think the Sokal Affair would be harder to duplicate in a field that was actually scientific, ie involving experiments and data. And if you did do it, you'd have to fake the data... and that's a big no-no. The assumption behind peer review is that the authors tend to be honest, but may make mistakes. If they're going to just plain lie, that doesn't usually get noticed until people try to replicate their results. Whether the Sokal Affair is the same thing ethically or not, it's clearly distinct in a practical sense. Of course, the journal in question wasn't peer reviewed, either.
Assuming a pair of 2 meter telescopes on a single orbiting platform, with a 25 minute exposure time and 5 minute re-aiming time, and a 1.5 degree field of view. Each scope could image a 1 degree square every 30 minutes. Or 24 degrees per day. Or a 360 degree circle in 15 days. Or 5 degrees above and below the ecliptic plane twice in under a year. With overlap. 2 years for a more comprehensive +/- 10 degree survey.
Except that you wouldn't find all of them in that survey. They're only easy to spot when they're nearby; for the dangerous ones, in orbits similar to Earth's, that only happens every few years. For the rest, you'd have to hope that it happened to be close by when you were surveying the right piece of sky. You also have to get several images of an asteroid to start computing even an approximate trajectory -- 3 images is a minimum, but that would give awful error bars. Sure, you can go follow up on everything that moved, but it would be nice if your original survey could distinguish at least something about how relevant the asteroid is.
Also, this is a job that's reasonably well suited to terrestrial telescopes, AIUI. No need for a special orbiting scope when you can get better pictures for less money from the ground.
Well, the actual intervention would be more likely to involve painting the asteroid white (with a few years warning solar radiation pressure is enough to change the course) than lobbing a nuke at it, assuming we find it in time. So the "defense system" itself wouldn't be special purpose, it would just be another launch vehicle carrying a probe that could perform a rendezvous.
This is more like the target acquisition half of the defense system -- sure, it's not complete, but "observation" to me implies that we're studying the individual asteroids rather than just trying to find them.
Wireless is really really sucky for huge numbers bits.
No kidding. I tried to send a 2 over a wireless network once, and it came out looking all distorted. Ever since, it's been all Cat5 for me. When I need to send a high-valued bit, it just works better.
No, they shouldn't. That's not to say they have nothing to contribute; obviously they do.
If an untrained observer finds a mistake in the work, then that's useful. If an untrained observer fails to find any mistakes, that says nothing. If a suitably trained observer -- ie, one of the researcher's peers -- goes over the work and fails to find any mistakes, that can be taken as a decent indication that the work is of high quality.
Most hobby engines (including mine) are ablatively cooled -- the combustion chamber is lined with something (usually an epoxy/paper composite, or something similar -- remarkably closely related to Apollo-era heat shields) that chars and outgases, forming a "cool" layer between it and the combustion gases, thereby reducing heat flow. A 1/16" liner will function for 5 seconds or more without any particular design effort, and that's long enough for most amateur rocketry work.
Making them not go boom just takes paying attention to the design. For solid propellants, there's a burn rate (that's dependent on pressure), and then you just have to balance the nozzle throat size against the burning surface area to make sure that it has enough area to escape through (so the pressure isn't too high), but little enough that the pressure is high enough to produce thrust. Then you have to make sure the casing is strong enough to support that, taking into account safety margins and such.
If you're interested, the place to start is probably with commercial motors and either kit-built or scratch-built rockets, and then moving on to potassium nitrate / sugar propellants. Tripoli is the major group that organizes launches (they'll handle details like sites and insurance); there should be a launch at least somewhat within driving distance, and people are generally quite friendly to spectators -- but get in touch with the launch organizers first. Commercial motors are a little pricey (expect to spend perhaps $70 on the motor and $30 on propellant for an I-class motor -- sufficient to launch several pounds of rocket to a few thousand feet), but the reusable motors are well made and provide excellent casings for custom solid propellant work. Richard Nakka has a most excellent page discussing sugar propellants, both in practice and in theory.
My work is with nitrous oxide hybrids, and is somewhat documented at HybridSky. It assumes you have some working knowledge of how hybrid motors work, though; Nakka's site is a much better starting point.
I do build rocket engines, both professionally and as a hobby. Not ion engines, but I have a passing understanding of the physics involved. I know that KE, momentum, and velocity are related;)
Xenon isn't too expensive -- it's expensive enough to make testing obnoxious, but still quite cheap compared to the cost of launching chemical propellants. Interestingly, it got a lot cheaper with the fall of the Soviet Union -- the Soviets only had one model of air liquefaction plant, and since there was only one it had a Xenon tap. They didn't have a lot of uses for it, so they stored it (it was valuable, after all). Then, after the fall, they started selling it, and of course a lot of the equipment is still around, so even after prices recovered total supply was higher.
Talking about adding energy to the craft isn't a terribly useful concept in rocketry, since it depends so much on your frame of reference. Delta-v is much more directly relevant. Of course, you can solve the equations any way you choose, but for a good intuitive sense, delta-v is the metric to use (generally). One obvious case where paying attention to the spacecraft kinetic energy is useful is when looking at delta-v penalties for doing burns higher up in the gravity well (or, inversely, gains for doing them low down as in some forms of slingshot maneuver).
My point about kinetic energy wasn't anything that complicated, though -- it was simply that if you vary the mass of the ion you're using as propellant, the kinetic energy of that ion when it leaves the engine stays the same -- whereas the momentum and velocity change (to first order approximation, anyway). So when looking at the engine behavior, and considering alternate propellants, that's the model to use.
Step 1: Take generic TV / Stereo remote, complete with low power infrared LED (not even a laser).
Step 2: Put hand over LED.
Step 3: Place remote and hand directly in front of detector.
Step 4: Observe that enough IR gets through your hand for the remote to work.
Of course, I have no idea how much IR is needed to have an effect on the brain, or how well it propagates through your skull. But if the answers are "not much" and "more than zero" then this is plausible.
If they're doing a spinning media with serial read and write patterns, that implies that the size of the coherent hologram is vastly less than the size of the disk. Which means that scratches lose the data that is stored on that part of the disk. I have no idea how large a domain they're using, but I'd guess kilobits or less.
If you're Disney, or anyone else with data valuable enough to possibly justify recreating an ancient media format reader, then the correct archive solution isn't a single format. It's a storage facility that has people maintaining the archive and updating formats and verifying that the data is still readable. Rather like a library, complete with librarians.
If you're comparing reconstructing a reader, then reading an ancient 250MB disk is easy -- there is tech now that can read off damaged and warped platters through techniques not dissimilar to electron microscopy, and I guarantee it could handle a far-less-dense 250MB drive without issue. Figuring out the low-level formatting would be no harder than for the holo media, and probably rather easier.
100 year DVDs are $108 for 50. I believe 300 year CDs are similar technology and price.
The question isn't whether the technology to read these in 50 years will exist, it's whether I can buy a reader off the shelf. Sure, for truly critical data, you might be able to reconstruct a reader in 50 years -- but for most purposes, that's not practical. There are plenty of things that I might want to store that long that don't have thousands of dollars worth of budget to recover them. What I really care about is how likely this company is to be making a product that can read the data -- and since they don't seem to be pushing to make this a big standard, it has to be them, not someone else. I put the odds as nonzero, but not so high I'd trust critical data to it.
The tech is very cool and all, but I would be *very* reluctant to trust it for archival purposes.
Huh? The theoretical possibilities aren't important -- what matters is what this drive can do, at least when you start talking about price. Physical holograms can no more hold infinite data than analog film has infinite resolution -- there are limitations somewhere, be they high or low. If you push close to those limitations, it won't be scratch resistant -- how resistant it is to damage depends on how much error correction you have, be it in the form of not using the full available resolution or by using electronic ECC techniques. (Care to guess which one is more efficient? Care to guess which one CDs and DVDs use?)
As for longevity -- there's no particular reason the plastics in the holographic storage will have any longer life than CDs or DVDs. If they say it'll last 50 years, then I'm inclined to believe they used decent plastics. But, you can get CD / DVD media that's rated for 300 years. It doesn't matter what damage sources holograms are "theoretically" susceptible to, what matters is what *this product* is susceptible to. Perhaps it doesn't delaminate, but what about heat / humidity / CD eating bacteria?
For archival media, my biggest concern would be whether I can find a reader in 50 years. I think the odds of that are a lot better for CD / DVD than for this -- though if I really care, it definitely needs some sort of maintenance program to make sure the data is intact and readable.
Because it's correct. You can put a variety of particles in the front of an ion engine and have them come out the back. The simplest approximation for what speed they come out at is that they all have the same kinetic energy, rather than the same momentum or velocity. Obviously all three change in the process, but the governing equation is closer to "KE += x" than anything else simple. Which makes sense, because the ion is presented with an electric field over a distance -- force times distance is energy.
Four out of Five slashdotters? You must be mad. The only things slashdotters can agree on are that they want to marry CmdrTaco and what concert to see on the honeymoon.
GCNR is nice, but chemical rockets will work too, with a lot less hassle. It doesn't have to reach orbit -- a high enough trajectory that the exhaust from the high-energy stage misses the Earth is good enough. The paper I linked above discusses options for an Orion stage launched from a S-IC booster (first stage of Saturn V).
It's also worth noting that chemical rockets work just fine to the Moon and Mars -- the cost barriers are a result of design decisions, not because it has to be that way. It's not until you start trying to go beyond Mars that nuclear propulsion becomes as important.
Poverty is (ok, should be, but mostly is) a necessary but not sufficient prerequisite for federal aid. So, suppose I'm getting federal aid for some reason, and spending that money on rent (or whatever the government says it should be spent on), but also spending some of my (small) paycheck (that I earned) on entertainment. Should that be banned? If not, why should I be allowed to spend it on movies but not gambling? That is what you were saying, after all:
I still want a law that puts casino patrons on a public assistance black list.
Most of the films I watch are purchased, rented, or borrowed on DVD from friends. I download some of it, but most of it is acquired through channels that properly reimburse the producers. As for the rest -- well, my only excuse is that I don't have a lot of money. It's either download it or watch less, so I think the degree of unethicalness there is limited. (Like you, I think that argument is hollow when people aren't spending any money on such things -- but I think it's a more reasonable one when there's a real mix of the two going on. As a fraction of my current income, my movies and such budget is probably quite normal.)
If you're saying that poor people should be barred from having entertainment, then I think you have some serious delusions about what sorts of systems can actually be made to work without huge amounts of corruption, but at least you're being consistent.
Why is gambling any better or worse than other entertainment, if done responsibly? As far as I can see, either way I end up enjoying myself for a while at the cost of a few dollars. Plenty of people are well aware that it will cost them money but enjoy it anyway. If they're making the choice to gamble with that awareness, what's the problem?
Most users turn on auto-update; instant doesn't add any downsides. If you're worried about that, then you need to do your job as a sysadmin, and this wouldn't change anything there either (since you'd have auto-update turned off in either case). Things requiring a reboot would be handled however they are currently -- just with less latency between the patch being available and everyone having it.
You're right, of course, that there is no easy answer.
You can levitate frogs and such by themselves, without having to support them on a levitating magnet -- see the Youtube video. Of course, that technique doesn't work with superconductors -- the field strength required is higher than they can sustain. Instead, you need a 6 megawatt electromagnet.
I suppose 6 MW to levitate a frog is about as impractical as it gets...
Where do you get $1k/L? A quick google search turns up $3-5 per liter, which is about what I recalled. LN2, of course, is much cheaper -- $0.25 in small quantities, $0.05 per liter or less in very large quantities.
Dry ice is more expensive than LN2, because you have to pay for the CO2, rather than just liquefying air. But if you don't actually need dry ice, then dry ice temps are certainly cheaper to reach than LN2 temps.
Slashdot Mirror
Oh really?
The Drake Equation doesn't tell us everything. For starters, there's the Fermi Paradox. More interesting, imho, are the questions raised by the Great Filter -- namely, are the hard challenges ahead of us, or behind us?
If Hawking says he thinks life elsewhere is likely, then that implies a certain degree of pessimism about our future chances.
I think the Sokal Affair would be harder to duplicate in a field that was actually scientific, ie involving experiments and data. And if you did do it, you'd have to fake the data... and that's a big no-no. The assumption behind peer review is that the authors tend to be honest, but may make mistakes. If they're going to just plain lie, that doesn't usually get noticed until people try to replicate their results. Whether the Sokal Affair is the same thing ethically or not, it's clearly distinct in a practical sense. Of course, the journal in question wasn't peer reviewed, either.
Except that you wouldn't find all of them in that survey. They're only easy to spot when they're nearby; for the dangerous ones, in orbits similar to Earth's, that only happens every few years. For the rest, you'd have to hope that it happened to be close by when you were surveying the right piece of sky. You also have to get several images of an asteroid to start computing even an approximate trajectory -- 3 images is a minimum, but that would give awful error bars. Sure, you can go follow up on everything that moved, but it would be nice if your original survey could distinguish at least something about how relevant the asteroid is.
Also, this is a job that's reasonably well suited to terrestrial telescopes, AIUI. No need for a special orbiting scope when you can get better pictures for less money from the ground.
Well, the actual intervention would be more likely to involve painting the asteroid white (with a few years warning solar radiation pressure is enough to change the course) than lobbing a nuke at it, assuming we find it in time. So the "defense system" itself wouldn't be special purpose, it would just be another launch vehicle carrying a probe that could perform a rendezvous.
This is more like the target acquisition half of the defense system -- sure, it's not complete, but "observation" to me implies that we're studying the individual asteroids rather than just trying to find them.
No kidding. I tried to send a 2 over a wireless network once, and it came out looking all distorted. Ever since, it's been all Cat5 for me. When I need to send a high-valued bit, it just works better.
No, they shouldn't. That's not to say they have nothing to contribute; obviously they do.
If an untrained observer finds a mistake in the work, then that's useful. If an untrained observer fails to find any mistakes, that says nothing. If a suitably trained observer -- ie, one of the researcher's peers -- goes over the work and fails to find any mistakes, that can be taken as a decent indication that the work is of high quality.
Most hobby engines (including mine) are ablatively cooled -- the combustion chamber is lined with something (usually an epoxy/paper composite, or something similar -- remarkably closely related to Apollo-era heat shields) that chars and outgases, forming a "cool" layer between it and the combustion gases, thereby reducing heat flow. A 1/16" liner will function for 5 seconds or more without any particular design effort, and that's long enough for most amateur rocketry work.
Making them not go boom just takes paying attention to the design. For solid propellants, there's a burn rate (that's dependent on pressure), and then you just have to balance the nozzle throat size against the burning surface area to make sure that it has enough area to escape through (so the pressure isn't too high), but little enough that the pressure is high enough to produce thrust. Then you have to make sure the casing is strong enough to support that, taking into account safety margins and such.
If you're interested, the place to start is probably with commercial motors and either kit-built or scratch-built rockets, and then moving on to potassium nitrate / sugar propellants. Tripoli is the major group that organizes launches (they'll handle details like sites and insurance); there should be a launch at least somewhat within driving distance, and people are generally quite friendly to spectators -- but get in touch with the launch organizers first. Commercial motors are a little pricey (expect to spend perhaps $70 on the motor and $30 on propellant for an I-class motor -- sufficient to launch several pounds of rocket to a few thousand feet), but the reusable motors are well made and provide excellent casings for custom solid propellant work. Richard Nakka has a most excellent page discussing sugar propellants, both in practice and in theory.
My work is with nitrous oxide hybrids, and is somewhat documented at HybridSky. It assumes you have some working knowledge of how hybrid motors work, though; Nakka's site is a much better starting point.
I do build rocket engines, both professionally and as a hobby. Not ion engines, but I have a passing understanding of the physics involved. I know that KE, momentum, and velocity are related ;)
Xenon isn't too expensive -- it's expensive enough to make testing obnoxious, but still quite cheap compared to the cost of launching chemical propellants. Interestingly, it got a lot cheaper with the fall of the Soviet Union -- the Soviets only had one model of air liquefaction plant, and since there was only one it had a Xenon tap. They didn't have a lot of uses for it, so they stored it (it was valuable, after all). Then, after the fall, they started selling it, and of course a lot of the equipment is still around, so even after prices recovered total supply was higher.
Talking about adding energy to the craft isn't a terribly useful concept in rocketry, since it depends so much on your frame of reference. Delta-v is much more directly relevant. Of course, you can solve the equations any way you choose, but for a good intuitive sense, delta-v is the metric to use (generally). One obvious case where paying attention to the spacecraft kinetic energy is useful is when looking at delta-v penalties for doing burns higher up in the gravity well (or, inversely, gains for doing them low down as in some forms of slingshot maneuver).
My point about kinetic energy wasn't anything that complicated, though -- it was simply that if you vary the mass of the ion you're using as propellant, the kinetic energy of that ion when it leaves the engine stays the same -- whereas the momentum and velocity change (to first order approximation, anyway). So when looking at the engine behavior, and considering alternate propellants, that's the model to use.
Step 1: Take generic TV / Stereo remote, complete with low power infrared LED (not even a laser).
Step 2: Put hand over LED.
Step 3: Place remote and hand directly in front of detector.
Step 4: Observe that enough IR gets through your hand for the remote to work.
Of course, I have no idea how much IR is needed to have an effect on the brain, or how well it propagates through your skull. But if the answers are "not much" and "more than zero" then this is plausible.
If they're doing a spinning media with serial read and write patterns, that implies that the size of the coherent hologram is vastly less than the size of the disk. Which means that scratches lose the data that is stored on that part of the disk. I have no idea how large a domain they're using, but I'd guess kilobits or less.
300GB is not sufficiently large, then.
If you're Disney, or anyone else with data valuable enough to possibly justify recreating an ancient media format reader, then the correct archive solution isn't a single format. It's a storage facility that has people maintaining the archive and updating formats and verifying that the data is still readable. Rather like a library, complete with librarians.
If you're comparing reconstructing a reader, then reading an ancient 250MB disk is easy -- there is tech now that can read off damaged and warped platters through techniques not dissimilar to electron microscopy, and I guarantee it could handle a far-less-dense 250MB drive without issue. Figuring out the low-level formatting would be no harder than for the holo media, and probably rather easier.
100 year DVDs are $108 for 50. I believe 300 year CDs are similar technology and price.
The question isn't whether the technology to read these in 50 years will exist, it's whether I can buy a reader off the shelf. Sure, for truly critical data, you might be able to reconstruct a reader in 50 years -- but for most purposes, that's not practical. There are plenty of things that I might want to store that long that don't have thousands of dollars worth of budget to recover them. What I really care about is how likely this company is to be making a product that can read the data -- and since they don't seem to be pushing to make this a big standard, it has to be them, not someone else. I put the odds as nonzero, but not so high I'd trust critical data to it.
The tech is very cool and all, but I would be *very* reluctant to trust it for archival purposes.
Huh? The theoretical possibilities aren't important -- what matters is what this drive can do, at least when you start talking about price. Physical holograms can no more hold infinite data than analog film has infinite resolution -- there are limitations somewhere, be they high or low. If you push close to those limitations, it won't be scratch resistant -- how resistant it is to damage depends on how much error correction you have, be it in the form of not using the full available resolution or by using electronic ECC techniques. (Care to guess which one is more efficient? Care to guess which one CDs and DVDs use?)
As for longevity -- there's no particular reason the plastics in the holographic storage will have any longer life than CDs or DVDs. If they say it'll last 50 years, then I'm inclined to believe they used decent plastics. But, you can get CD / DVD media that's rated for 300 years. It doesn't matter what damage sources holograms are "theoretically" susceptible to, what matters is what *this product* is susceptible to. Perhaps it doesn't delaminate, but what about heat / humidity / CD eating bacteria?
For archival media, my biggest concern would be whether I can find a reader in 50 years. I think the odds of that are a lot better for CD / DVD than for this -- though if I really care, it definitely needs some sort of maintenance program to make sure the data is intact and readable.
Because it's correct. You can put a variety of particles in the front of an ion engine and have them come out the back. The simplest approximation for what speed they come out at is that they all have the same kinetic energy, rather than the same momentum or velocity. Obviously all three change in the process, but the governing equation is closer to "KE += x" than anything else simple. Which makes sense, because the ion is presented with an electric field over a distance -- force times distance is energy.
Four out of Five slashdotters? You must be mad. The only things slashdotters can agree on are that they want to marry CmdrTaco and what concert to see on the honeymoon.
GCNR is nice, but chemical rockets will work too, with a lot less hassle. It doesn't have to reach orbit -- a high enough trajectory that the exhaust from the high-energy stage misses the Earth is good enough. The paper I linked above discusses options for an Orion stage launched from a S-IC booster (first stage of Saturn V).
It's also worth noting that chemical rockets work just fine to the Moon and Mars -- the cost barriers are a result of design decisions, not because it has to be that way. It's not until you start trying to go beyond Mars that nuclear propulsion becomes as important.
Poverty is (ok, should be, but mostly is) a necessary but not sufficient prerequisite for federal aid. So, suppose I'm getting federal aid for some reason, and spending that money on rent (or whatever the government says it should be spent on), but also spending some of my (small) paycheck (that I earned) on entertainment. Should that be banned? If not, why should I be allowed to spend it on movies but not gambling? That is what you were saying, after all:
I still want a law that puts casino patrons on a public assistance black list.Most of the films I watch are purchased, rented, or borrowed on DVD from friends. I download some of it, but most of it is acquired through channels that properly reimburse the producers. As for the rest -- well, my only excuse is that I don't have a lot of money. It's either download it or watch less, so I think the degree of unethicalness there is limited. (Like you, I think that argument is hollow when people aren't spending any money on such things -- but I think it's a more reasonable one when there's a real mix of the two going on. As a fraction of my current income, my movies and such budget is probably quite normal.)
If you're saying that poor people should be barred from having entertainment, then I think you have some serious delusions about what sorts of systems can actually be made to work without huge amounts of corruption, but at least you're being consistent.
Why is gambling any better or worse than other entertainment, if done responsibly? As far as I can see, either way I end up enjoying myself for a while at the cost of a few dollars. Plenty of people are well aware that it will cost them money but enjoy it anyway. If they're making the choice to gamble with that awareness, what's the problem?
Most users turn on auto-update; instant doesn't add any downsides. If you're worried about that, then you need to do your job as a sysadmin, and this wouldn't change anything there either (since you'd have auto-update turned off in either case). Things requiring a reboot would be handled however they are currently -- just with less latency between the patch being available and everyone having it.
You're right, of course, that there is no easy answer.
You can levitate frogs and such by themselves, without having to support them on a levitating magnet -- see the Youtube video. Of course, that technique doesn't work with superconductors -- the field strength required is higher than they can sustain. Instead, you need a 6 megawatt electromagnet.
I suppose 6 MW to levitate a frog is about as impractical as it gets...
Where do you get $1k/L? A quick google search turns up $3-5 per liter, which is about what I recalled. LN2, of course, is much cheaper -- $0.25 in small quantities, $0.05 per liter or less in very large quantities.
Dry ice is more expensive than LN2, because you have to pay for the CO2, rather than just liquefying air. But if you don't actually need dry ice, then dry ice temps are certainly cheaper to reach than LN2 temps.