Gravity has energy as much as electromagnetism has energy. It's a slip of English, so it's not really quite correct to say "gravity has energy", but there certainly is gravitational energy and potential.
What he's asking is where the gravitational self-energy of the sun comes from. The answer, of course, is given in its name "self-energy".:p
At an undergraduate level, it's a fundamental force or field. From a quantum perspective, it's a fundamental, quantizable interaction, treatable by quantum field theory. From a relativistic perspective it's an alteration of space-time caused by the presence of energy. (At least, that's what it is when I explain it so poorly.)
The interaction between two gravitational fields certainly does have energy.
The sun can support fusion because the pressures and temperatures necessary to perform H -> He fusion are generated by the extreme gravitational forces present.
The Sun is just high-pressure, high-temperature gas, which means that the hydrogen atoms are very closely packed (high pressure) and have a lot of energy (high temperature), meaning that there's a good probability two of them will run into each other with enough force to fuse. There's no reason this couldn't be replicated on Earth, though with much more work on our part!
The fission and fusion reactions we use are very specific ones. Don't worry, total energy (that is energy present in the mass of the atoms + energy present in the form of radiation) is preserved in both fission and fusion! But in these reactions some energy changes form -- usually from matter into electromagnetic energy (light).
You couldn't take uranium, break it apart to get energy, then put it together to get energy, and somehow end up with what you started with. Not only that, the "easy" fission and fusion reactions produce materials that are not easy to put through nuclear reactions. Hydrogen is "easy" to fuse into Helium, but Helium does not fuse easily (only nearly-dead stars do so) and is practically impossible to perform fission on. The products given off by uranium or plutonium fission would be very, very difficult to fuse.
The short and off-topic answer to your gravity question is that the gravity of the Sun is produced by the matter that makes up the Sun. Remember that the Sun is made up of many, many particles (atoms). To use the undergraduate-type explanation, each atom making up the Sun exerts some gravitational force on each other atom. If you think about it, you may be able to convince yourself that each particle making up the Sun has a net gravitational force that pulls it toward the group's center. Some calculus reveals that the problem is actually a heck of a lot simpler than it sounds.
This sort of thing is a major element in star formation: the atoms will be pulled toward their collective center until forces pushing them away from the center (in the Sun's case, just the high temperatures and pressures generated) counterbalance the gravitational forces. If somehow there is enough matter that it is pulled toward its center with more force than any outward forces (including the very strong Pauli repulsion) can overcome, a black hole or singularity will result.
Re:Glad I'm not a Californian anymore
on
Tinfoil Hat House
·
· Score: 1
To the people of Scaramento, though, having ugly aluminum siding on a house might be unacceptable. That's the community they've chosen to put together with their regulations. Unless these people happen to have been living there prior to such regulations being created, they've chosen to accept them in exchange for living in that area.
Re:Glad I'm not a Californian anymore
on
Tinfoil Hat House
·
· Score: 1
I'm just not being entirely clear. The Alaskan mentioned that he could build a house out of aluminum foil and nobody would care. I doubt that, is all. It is admittedly different from attaching siding to your house, but I'm not the one that brought up actually *building* a house from foil.
Re:Glad I'm not a Californian anymore
on
Tinfoil Hat House
·
· Score: 2, Interesting
It must be nice to live in a state where there are apparently no kind of building codes. Tell me, does the state require that the schools children go to be built to any kind of specification, or is it okay if they're also made out of materials unsuitable for construction (eg. metal foils)? Is it okay for someone to sell you a house that's not suitable to live in?
While the article isn't very well written, your complaint is just as poor. You might be glad you're no longer a Californian, but I'm almost entirely sure that it's not a California state law they're being charged under.
Sadly, I often hear people say, "I should be able to pay to live in a neighborhood where aren't allowed to buy a house." It's under a similar but more reasonable principle that they're not allowed to cover their house in aluminum junk. They're (perhaps unknowingly) paying to live in an area where ugly houses aren't allowed.
I suppose it's also somehow the State of New York's fault that in my apartment complex we're not allowed to put up satellite dishes.
Re:Glad I'm not a Californian anymore
on
Tinfoil Hat House
·
· Score: 1
Tin foil is no harder to come by than aluminum or lead foil. Gold foil can be a bit expensive, and any foil is pricy if you want it to be particularly thin. Really what you want, though, is lead-tin alloy foil.
Fortunately the combustion and flash points of mineral oil are fairly high -- considerably higher than you'd want to run a CPU at. Assuming you're keeping track of temperatures somewhere near where your CPU is, and figuring that the oil is hottest there, if you're halfway clever you shouldn't run the risk of causing it to combust.
IIRC, though, mineral oil is not scentless. I wouldn't want that oil vapor around. This sort of thing should be sealed and treated carefully. Sealing it, though, would require some way to remove heat from the system. (I'm thinking a glass computer case with plenty of fans inside filled with mineral oil. Should allow for plenty of conduction through the glass walls + radiative heat loss, though it could end up being too hot for the CPU and certainly warm to the touch.)
Microsoft changed its position from favorable to neutral and after pressure from an outside source, true. But unless they say so it doesn't mean those two are connected. There are a lot of reasons they might have decided that they no longer want to be directly in support of the bill. It's kind of like you how can be against the Patriot Act without hating America, except that Microsoft isn't *against* this bill.
Me: "Why would you assume digital media is necessarily going to last longer than older media?"
You: "Why? Are you really asking this question? Because this is one of the primary concerns when it comes to permanent storage! (I almost feel like saying "duh".)"
The parent to my original reply did make the silent assumption that newer technologies should have greater longevity. I was just pointing out that there are other priorities.
You might think it needs top priority, but clearly the developers of new media disagree with you, as do consumers. They want cheap, convenient, high-density storage.
Of course it's overboard, and intentionally so. As I and others have mentioned elsewhere now, digital media favors two huge design choices over longevity. First, it's dense. You could probably shove the sum total of human knowledge on DVDs and store it in a reasonably sized building. Second, it's designed to be easy to move the information to a newer medium. As long as you have the reading equipment, digital standards make it fairly easy to, say, copy your CDs to DVDs and then your DVDs to whatever they come out with next.
Of course we'll never be able to make something last forever. That's not really what we want, either, we just want it to last a very long time. I'm not even sure why we always want that. I mean, studying ancient text now is primarily to satiate the curiosity of historians. Discovering what Aztecs ate for breakfast rarely helps us. Storing library data for the next couple hundred years, though, that's useful.
A lot of people bring up the problem of standards, like CDs, becoming antiquated. This is really the same problem as looters stealing your messages cut into gold sheets. All bets are off if you don't take care of your stored data. Making permanent storage that you never have to maintain is a whole different problem, and one you probably shouldn't get into. Look at what NASA did when they wanted a message to be permenent so they could send it off to aliens. Cut it into metal that won't degrade quickly. In space, that'll last quite some time. Words cut into stone last a long time if you keep them indoors. If you want digital media to remain usable forever, though, your best bet is to maintain your archives, moving them from one generation of storage to the next while you still have all of the equipment for both.
You certainly want long-term storage to last a long time, and you want to know how long it lasts. Clearly.
That doesn't mean that you should assume that a newer storage technology necessarily has a greater longevity than an older storage technology. There are other design factors in long-term storage, and newer technologies have favored these over permanency.
This would be like assuming that a newer or more expensive car necessarily has better gas milage. It's one of the things you want in a car, right? But it's not the only design factor, so making that assumption would be... unwise.
Well, the nice thing is that books are well-designed. They take advantage of equipment that (basically) every human has and standards that we've all adopted. The standards only change on time scales of the order of a human life.
Of course, they have other design flaws, and just because the standards for interpreting them -- language -- changes slowly doesn't mean it changes at all. There are some texts for which the language they're written in is completely dead.
Why would you assume digital media is necessarily going to last longer than older media?
The trend is not for newer storage methods to outlast older ones by any stretch of the imagination.
Stone inscriptions, stored reasonably well, will last quite a long time. Books printed with appropriate inks and stored well will also last ages. Comparing to those, "antiquated" media like microfiche will be useless much earlier.
From what I recall, we use newer media forms not because they last longer but because they're more convenient. You can store information much more densely on a DVD than you can on microfiche, which is in turn a more dense storage form than paper, which was a big improvement over marble and clay tablets.
If you really want longevity you should take your microfiche and cut the words into sheets of gold.
Sorry, do you have any kind of a point here, or are you just rambling about scientists and how maybe their opinions don't really matter because you don't like this survey? Where's the beef?
None of the questions you listed have anything to do with "usual worker problems".
Maybe you're not familiar with science. If more than 20% of a group of scientsts say that they've been "directed to inappropriately exclude or alter technical information from a... scientific document" and more than 20% don't think that their organization "strives to substantially incorporate independent peer review in formulating and validating scientific findings" and more than 20% don't think that "scientific documents generally reflect technically rigorous evaluations of impacts to listed species and associated habitats", then you've got one bad batch of scientific documents and an inappropriately-behaving organization. Twenty percent is not a few people easily ignored.
Factoring in the percentage of people who responded to reduce numbers is not valid. Unless you're a statistician who's capable of a reasonable analysis on how representative the sample is and can provide a good estimate for response bias, then you'd better leave that alone. Likewise, the total count of 184 is meaningless.
While clearly the UCS is concerned about a particular topic, the questions are hardly "leading". You try to portray this 20% of scientists as just going along with whatever the survey happens to say. You can't just write off the response like this.
Did they teach you in school not to quote an unabashedly right-wing counter-activist's personal website and try to write it off as some sort of informed document on the history of an organization?
Activistcash is a slightly more reputable, but the information source is so poorly written and clearly deriding the organization that its informational content is questionable.
The percentage of people from the scientific community is irrelevant. They still only survey scientists. The fact that there's the other 90% that's non-scientists but still interested is a good thing.
I was surprised to see Kurt Gottfried mentioned though. He's no longer head of the Physics Department but is a neat guy (and wrote a textbook here).
I'm not sure why you use 15 years. Perhaps I missed something in the article, or it is common knowledge that 15 years is an appropriate length of time to compare recent surveys with in the scientific community.
Regarding "reported no such pressure", I quote the article: "And, although more than half of the respondents said they had been ordered to alter findings to lessen protection of species, nearly 40% said they had never been required to do so."
More than half is not most?
Nice try on playing the "liberal card", but they don't even talk about edicts on endangered species or environmentalism. It's solely a survey on whether or not scientists in Fish and Wildlife, who work for the federal government, have been ordered to alter data (20%) or change findings (>50%). You can say whatever you want about different view in the political arena about conservation, but that's not what we're talking about! Fish and Wildlife is creating scientific reports in which the scientists have been ordered to make statements against their professional judgement, which is not good science.
According to the article, the new rules would apply to places where federal employees check identification -- national parks, airports, and the like.
Take the following: Republican politicians argued that the new rules were necessary to thwart terrorists, saying that four of the Sept. 11, 2001, hijackers possessed valid state-issued driver's licenses. "When I get on an airplane and someone shows ID, I'd like to be sure they are who they say they are," said Rep. Tom Davis, a Virginia Republican, during a floor debate that started Wednesday.
I somehow doubt that this federal ID program (which some say is "tantamount" to a National ID -- you don't say!) would have prevented them from getting valid driver's licenses.
The ID would also be "linked" to various documents so that they can be referenced per person -- documents like those determining immigration status.
If your primary concern with nationalized identification is that your name and birthdate might get in the hands of a marketer (who can do no worse than to annoy you), then you have some serious priority inversion issues.
If people didn't have a problem with you digging up the moon (and it wasn't a huge engineering feat to work that much up there), then you could indeed build an enormous radio telescope there. (Or so I'd think.)
There's less light pollution only half the time. The dark side of the moon, if I recall correctly, isn't actually dark -- it faces the sun as often as the light side. It's the side that never sees the earth, though. This would create a small additional engineering problem regarding communicating with the satellite.
Gravity isn't always an advantage. It has the annoying property of holding gases and things like dust closer to the telescope. Modern telescope designs might prefer freefall operation.
Yeah, they should take lessons from random people on Slashdot that don't have the cost details.
Perhaps you could explain your rather curious logic. The article states that they estimate it would cost $1 billion to launch the new probe. The language of the sentence suggests that this is building costs plus launching costs. The estimated cost of repairing the Hubble is about $2 billion. Hence for $1 billion less, we get something that is better. It would, however, cost significant amounts of time. (I've no idea how long a repair mission would take to put together. Also, you could say that the new probe wouldn't be a guaranteed success, but neither is the repair mission.)
Thanks. The name I was looking for is Benford's Law, which is a scale-invariant digit distribution, as any such distribution must be (as well as being applicable to bases other than 10).
Yes, in order to do good steganography you have to replace something that already looks random with something else that looks equally random.
The problem with what was referred to originally is that the least significant bits of an image are not necessarily uncorrelated to (a) position in the image (b) values of neighboring LSBs (c) values of more significant bits at that point. You can bet that a very random-seeming message (eg. an encrypted one) is going to be uncorrolated to these three things, so if your original LSB plane was slightly correlated, you may be able to detect the change by statistical analysis.
That's only true if the original data in the LSB plane was also random. However, chances are that it isn't exactly random. Data, encrypted or no, may have different statistical characteristics than the original data.
There's a good story on something vaugely related that has to do with the frequency of digits in measured numbers. (That is, it isn't equally probable to see every digit -- earlier digits in a number favor lower digits, like "1".) People who were falsifying accounting records were caught because the numbers they used were "too random". This occurs also in people who are trying to make a string of random ones and zeros -- they'll tend to have much shorter strings of the same digit than a sequence that's actually randomly generated. (Four zeros in a row? That's not very random!)
If there was a standard for steganography, it wouldn't be steganography any more.
It's kind of like hiding your key under the doormat. Everyone knows that's where people hide keys, so nobody hides keys there because it's useless now.
Unfortunately, the problem of coming up with such a generic pattern-finding algorithm that it'd be truly useful for trying to detect steganography in general is not an easy problem. It should be quite possible to try a lot of popular methods, though.
Slashdot Mirror
Gravity has energy as much as electromagnetism has energy. It's a slip of English, so it's not really quite correct to say "gravity has energy", but there certainly is gravitational energy and potential.
:p
What he's asking is where the gravitational self-energy of the sun comes from. The answer, of course, is given in its name "self-energy".
At an undergraduate level, it's a fundamental force or field. From a quantum perspective, it's a fundamental, quantizable interaction, treatable by quantum field theory. From a relativistic perspective it's an alteration of space-time caused by the presence of energy. (At least, that's what it is when I explain it so poorly.)
The interaction between two gravitational fields certainly does have energy.
The sun can support fusion because the pressures and temperatures necessary to perform H -> He fusion are generated by the extreme gravitational forces present.
The Sun is just high-pressure, high-temperature gas, which means that the hydrogen atoms are very closely packed (high pressure) and have a lot of energy (high temperature), meaning that there's a good probability two of them will run into each other with enough force to fuse. There's no reason this couldn't be replicated on Earth, though with much more work on our part!
The fission and fusion reactions we use are very specific ones. Don't worry, total energy (that is energy present in the mass of the atoms + energy present in the form of radiation) is preserved in both fission and fusion! But in these reactions some energy changes form -- usually from matter into electromagnetic energy (light).
You couldn't take uranium, break it apart to get energy, then put it together to get energy, and somehow end up with what you started with. Not only that, the "easy" fission and fusion reactions produce materials that are not easy to put through nuclear reactions. Hydrogen is "easy" to fuse into Helium, but Helium does not fuse easily (only nearly-dead stars do so) and is practically impossible to perform fission on. The products given off by uranium or plutonium fission would be very, very difficult to fuse.
The short and off-topic answer to your gravity question is that the gravity of the Sun is produced by the matter that makes up the Sun. Remember that the Sun is made up of many, many particles (atoms). To use the undergraduate-type explanation, each atom making up the Sun exerts some gravitational force on each other atom. If you think about it, you may be able to convince yourself that each particle making up the Sun has a net gravitational force that pulls it toward the group's center. Some calculus reveals that the problem is actually a heck of a lot simpler than it sounds.
This sort of thing is a major element in star formation: the atoms will be pulled toward their collective center until forces pushing them away from the center (in the Sun's case, just the high temperatures and pressures generated) counterbalance the gravitational forces. If somehow there is enough matter that it is pulled toward its center with more force than any outward forces (including the very strong Pauli repulsion) can overcome, a black hole or singularity will result.
To the people of Scaramento, though, having ugly aluminum siding on a house might be unacceptable. That's the community they've chosen to put together with their regulations. Unless these people happen to have been living there prior to such regulations being created, they've chosen to accept them in exchange for living in that area.
I'm just not being entirely clear. The Alaskan mentioned that he could build a house out of aluminum foil and nobody would care. I doubt that, is all. It is admittedly different from attaching siding to your house, but I'm not the one that brought up actually *building* a house from foil.
It must be nice to live in a state where there are apparently no kind of building codes. Tell me, does the state require that the schools children go to be built to any kind of specification, or is it okay if they're also made out of materials unsuitable for construction (eg. metal foils)? Is it okay for someone to sell you a house that's not suitable to live in?
While the article isn't very well written, your complaint is just as poor. You might be glad you're no longer a Californian, but I'm almost entirely sure that it's not a California state law they're being charged under.
Sadly, I often hear people say, "I should be able to pay to live in a neighborhood where aren't allowed to buy a house." It's under a similar but more reasonable principle that they're not allowed to cover their house in aluminum junk. They're (perhaps unknowingly) paying to live in an area where ugly houses aren't allowed.
I suppose it's also somehow the State of New York's fault that in my apartment complex we're not allowed to put up satellite dishes.
Tin foil is no harder to come by than aluminum or lead foil. Gold foil can be a bit expensive, and any foil is pricy if you want it to be particularly thin. Really what you want, though, is lead-tin alloy foil.
Fortunately the combustion and flash points of mineral oil are fairly high -- considerably higher than you'd want to run a CPU at. Assuming you're keeping track of temperatures somewhere near where your CPU is, and figuring that the oil is hottest there, if you're halfway clever you shouldn't run the risk of causing it to combust.
IIRC, though, mineral oil is not scentless. I wouldn't want that oil vapor around. This sort of thing should be sealed and treated carefully. Sealing it, though, would require some way to remove heat from the system. (I'm thinking a glass computer case with plenty of fans inside filled with mineral oil. Should allow for plenty of conduction through the glass walls + radiative heat loss, though it could end up being too hot for the CPU and certainly warm to the touch.)
Just to point out, as some probably already have:
Microsoft changed its position from favorable to neutral and after pressure from an outside source, true. But unless they say so it doesn't mean those two are connected. There are a lot of reasons they might have decided that they no longer want to be directly in support of the bill. It's kind of like you how can be against the Patriot Act without hating America, except that Microsoft isn't *against* this bill.
Nobody said it should be assumed?
Me: "Why would you assume digital media is necessarily going to last longer than older media?"
You: "Why? Are you really asking this question? Because this is one of the primary concerns when it comes to permanent storage! (I almost feel like saying "duh".)"
The parent to my original reply did make the silent assumption that newer technologies should have greater longevity. I was just pointing out that there are other priorities.
You might think it needs top priority, but clearly the developers of new media disagree with you, as do consumers. They want cheap, convenient, high-density storage.
Of course it's overboard, and intentionally so. As I and others have mentioned elsewhere now, digital media favors two huge design choices over longevity. First, it's dense. You could probably shove the sum total of human knowledge on DVDs and store it in a reasonably sized building. Second, it's designed to be easy to move the information to a newer medium. As long as you have the reading equipment, digital standards make it fairly easy to, say, copy your CDs to DVDs and then your DVDs to whatever they come out with next.
Of course we'll never be able to make something last forever. That's not really what we want, either, we just want it to last a very long time. I'm not even sure why we always want that. I mean, studying ancient text now is primarily to satiate the curiosity of historians. Discovering what Aztecs ate for breakfast rarely helps us. Storing library data for the next couple hundred years, though, that's useful.
A lot of people bring up the problem of standards, like CDs, becoming antiquated. This is really the same problem as looters stealing your messages cut into gold sheets. All bets are off if you don't take care of your stored data. Making permanent storage that you never have to maintain is a whole different problem, and one you probably shouldn't get into. Look at what NASA did when they wanted a message to be permenent so they could send it off to aliens. Cut it into metal that won't degrade quickly. In space, that'll last quite some time. Words cut into stone last a long time if you keep them indoors. If you want digital media to remain usable forever, though, your best bet is to maintain your archives, moving them from one generation of storage to the next while you still have all of the equipment for both.
You certainly want long-term storage to last a long time, and you want to know how long it lasts. Clearly.
That doesn't mean that you should assume that a newer storage technology necessarily has a greater longevity than an older storage technology. There are other design factors in long-term storage, and newer technologies have favored these over permanency.
This would be like assuming that a newer or more expensive car necessarily has better gas milage. It's one of the things you want in a car, right? But it's not the only design factor, so making that assumption would be... unwise.
Well, the nice thing is that books are well-designed. They take advantage of equipment that (basically) every human has and standards that we've all adopted. The standards only change on time scales of the order of a human life.
Of course, they have other design flaws, and just because the standards for interpreting them -- language -- changes slowly doesn't mean it changes at all. There are some texts for which the language they're written in is completely dead.
Why would you assume digital media is necessarily going to last longer than older media?
The trend is not for newer storage methods to outlast older ones by any stretch of the imagination.
Stone inscriptions, stored reasonably well, will last quite a long time. Books printed with appropriate inks and stored well will also last ages. Comparing to those, "antiquated" media like microfiche will be useless much earlier.
From what I recall, we use newer media forms not because they last longer but because they're more convenient. You can store information much more densely on a DVD than you can on microfiche, which is in turn a more dense storage form than paper, which was a big improvement over marble and clay tablets.
If you really want longevity you should take your microfiche and cut the words into sheets of gold.
Yeah, I'd like my digital media to last forever.
While they're at it, can they make my car run forever? I also want to stay young forever, if that's not too much trouble.
Sorry, do you have any kind of a point here, or are you just rambling about scientists and how maybe their opinions don't really matter because you don't like this survey? Where's the beef?
None of the questions you listed have anything to do with "usual worker problems".
... scientific document" and more than 20% don't think that their organization "strives to substantially incorporate independent peer review in formulating and validating scientific findings" and more than 20% don't think that "scientific documents generally reflect technically rigorous evaluations of impacts to listed species and associated habitats", then you've got one bad batch of scientific documents and an inappropriately-behaving organization. Twenty percent is not a few people easily ignored.
Maybe you're not familiar with science. If more than 20% of a group of scientsts say that they've been "directed to inappropriately exclude or alter technical information from a
Factoring in the percentage of people who responded to reduce numbers is not valid. Unless you're a statistician who's capable of a reasonable analysis on how representative the sample is and can provide a good estimate for response bias, then you'd better leave that alone. Likewise, the total count of 184 is meaningless.
While clearly the UCS is concerned about a particular topic, the questions are hardly "leading". You try to portray this 20% of scientists as just going along with whatever the survey happens to say. You can't just write off the response like this.
Did they teach you in school not to quote an unabashedly right-wing counter-activist's personal website and try to write it off as some sort of informed document on the history of an organization?
Activistcash is a slightly more reputable, but the information source is so poorly written and clearly deriding the organization that its informational content is questionable.
Try their own website or perhaps even Wikipedia.
The percentage of people from the scientific community is irrelevant. They still only survey scientists. The fact that there's the other 90% that's non-scientists but still interested is a good thing.
I was surprised to see Kurt Gottfried mentioned though. He's no longer head of the Physics Department but is a neat guy (and wrote a textbook here).
I'm not sure why you use 15 years. Perhaps I missed something in the article, or it is common knowledge that 15 years is an appropriate length of time to compare recent surveys with in the scientific community.
Regarding "reported no such pressure", I quote the article:
"And, although more than half of the respondents said they had been ordered to alter findings to lessen protection of species, nearly 40% said they had never been required to do so."
More than half is not most?
Nice try on playing the "liberal card", but they don't even talk about edicts on endangered species or environmentalism. It's solely a survey on whether or not scientists in Fish and Wildlife, who work for the federal government, have been ordered to alter data (20%) or change findings (>50%). You can say whatever you want about different view in the political arena about conservation, but that's not what we're talking about! Fish and Wildlife is creating scientific reports in which the scientists have been ordered to make statements against their professional judgement, which is not good science.
Unfortunately this isn't what it's for.
According to the article, the new rules would apply to places where federal employees check identification -- national parks, airports, and the like.
Take the following:
Republican politicians argued that the new rules were necessary to thwart terrorists, saying that four of the Sept. 11, 2001, hijackers possessed valid state-issued driver's licenses. "When I get on an airplane and someone shows ID, I'd like to be sure they are who they say they are," said Rep. Tom Davis, a Virginia Republican, during a floor debate that started Wednesday.
I somehow doubt that this federal ID program (which some say is "tantamount" to a National ID -- you don't say!) would have prevented them from getting valid driver's licenses.
The ID would also be "linked" to various documents so that they can be referenced per person -- documents like those determining immigration status.
If your primary concern with nationalized identification is that your name and birthdate might get in the hands of a marketer (who can do no worse than to annoy you), then you have some serious priority inversion issues.
I did say it was a small engineering concern.
If people didn't have a problem with you digging up the moon (and it wasn't a huge engineering feat to work that much up there), then you could indeed build an enormous radio telescope there. (Or so I'd think.)
There's less light pollution only half the time. The dark side of the moon, if I recall correctly, isn't actually dark -- it faces the sun as often as the light side. It's the side that never sees the earth, though. This would create a small additional engineering problem regarding communicating with the satellite.
Gravity isn't always an advantage. It has the annoying property of holding gases and things like dust closer to the telescope. Modern telescope designs might prefer freefall operation.
Yeah, they should take lessons from random people on Slashdot that don't have the cost details.
Perhaps you could explain your rather curious logic. The article states that they estimate it would cost $1 billion to launch the new probe. The language of the sentence suggests that this is building costs plus launching costs. The estimated cost of repairing the Hubble is about $2 billion. Hence for $1 billion less, we get something that is better. It would, however, cost significant amounts of time. (I've no idea how long a repair mission would take to put together. Also, you could say that the new probe wouldn't be a guaranteed success, but neither is the repair mission.)
Thanks. The name I was looking for is Benford's Law, which is a scale-invariant digit distribution, as any such distribution must be (as well as being applicable to bases other than 10).
Yes, in order to do good steganography you have to replace something that already looks random with something else that looks equally random.
The problem with what was referred to originally is that the least significant bits of an image are not necessarily uncorrelated to (a) position in the image (b) values of neighboring LSBs (c) values of more significant bits at that point. You can bet that a very random-seeming message (eg. an encrypted one) is going to be uncorrolated to these three things, so if your original LSB plane was slightly correlated, you may be able to detect the change by statistical analysis.
That's only true if the original data in the LSB plane was also random. However, chances are that it isn't exactly random. Data, encrypted or no, may have different statistical characteristics than the original data.
There's a good story on something vaugely related that has to do with the frequency of digits in measured numbers. (That is, it isn't equally probable to see every digit -- earlier digits in a number favor lower digits, like "1".) People who were falsifying accounting records were caught because the numbers they used were "too random". This occurs also in people who are trying to make a string of random ones and zeros -- they'll tend to have much shorter strings of the same digit than a sequence that's actually randomly generated. (Four zeros in a row? That's not very random!)
If there was a standard for steganography, it wouldn't be steganography any more.
It's kind of like hiding your key under the doormat. Everyone knows that's where people hide keys, so nobody hides keys there because it's useless now.
Unfortunately, the problem of coming up with such a generic pattern-finding algorithm that it'd be truly useful for trying to detect steganography in general is not an easy problem. It should be quite possible to try a lot of popular methods, though.