"$40?!? My cheapest textbook is twice that amount!"
You bastard!
I bought a solid state physics textbook back in my undergrad days--it cost more than an equivalent weight of silver bullion. I haven't weighed any of my other textbooks, but I wouldn't be surprised if it wasn't the only one worth its weight in silver....
I just want to take a moment to talk to all the retards.
So, you spend your real money in order to get pretend money in your online games.
Then, for the privilege of spending that pretend money - in a pretend world, on pretend things - you pay more real money, every month.
I spent some real money the other day on a pretend world. It was a world created by Arthur C. Clarke. I was entertained for a few hours, and now that pretend world full of pretend things sits on my shelf.
Yesterday I went to the local video store, where I spent some more real money on yet another pretend world. Today, I returned the video--if I want to visit that pretend world again, I'll have to cough up more real money.
What's the difference between people who spend X dollars per month on Everquest et al. and the people who sink X dollars per month into satellite television? It's all entertainment. People don't usually buy either product with 'useful' ends in mind--they pay the money to be amused and pass the time. It's their money; it's their time. Sure, they could be giving both to more 'worthy' causes, but so could we all.
Actually, I found that kind of amusing when I read it, but now you've got me thinking. The grandparent poster indicates that he's deaf in one ear--really, a relatively minor inconvenience. (My best friend is deaf in one ear; I have to avoid sneaking up on her left side.)
The cause of his hearing loss wasn't indicated, but what might it be? Congenital defect? Progressive degenerative illness? Infection? Trauma? In most of those cases (the three most likely, in fact) he has lost the hearing in one ear, but is unlikely to suffer further health problems. On the other hand, obesity is a risk factor for all kinds of ways to die--including heart disease, the leading killer in developed nations.
On reflection, I have to agree--I'd rather be deaf in one ear than fat, too.
Im sorry. We waste way too much time energy and money prolonging the lives of halfdead people.
Can you furnish us with a list of medical conditions you consider not worth treating? Or would you prefer to set a dollar figure beyond which we should let you die?
An extra four or five years can make a tremendous difference to people, to their families. 'Half dead' or not, some people have something to live for.
As described in the article, these bikes are custom handcrafted jobs--works of art, not mass-produced articles. Though no price is mentioned, you know what they say. "If you have to ask, you can't afford it...."
From the article,
"Building these bicycles is art. It is not something you just do. Every bamboo must be selected and fitted into the frame according to size and quality. The secret lies in treating and handling the material the right way. Learning that takes times and the maintenance takes time as well."
Since all of the pieces are held together with glued, fitted joints--not screws, nails, or spikes--there's a lot of potentially finicky (hence time-consuming and expensive) work involved.
First off, I agree with you completely--this particular vehicle was developed because the engineer involved thought 1) that it was neat and 2) that he might make some money from it. As you say, no shame in that.
Further, I agree with you that in going from gasoline-powered vehicles to electrics, we are indeed (in general) trading one type of pollution for another. Really, this is the sticky point. Admittedly fallible scientists, bureaucrats, environmentalists make educated guesses (sometimes well-informed ones, sometimes less so) about the relative damage caused by each technology. Is the potential environmental damage associated with smelting and handling lead more or less serious than the damage associated with drilling, shipping, and pumping petroleum products? As you say, first world nations do very little to attempt to control lead emissions from smelting in other countries--but they also ignore environmental slips associated with processing and handling hydrocarbons. You ask if I'm concerned about the environment as a whole, or just my own backyard--fair enough, but I can't ignore petroleum spills here or elsewhere, either.
You pointed out that "nobody is allowed to touch old air conditioning systems unless..." What does this encourage? Does this better the environment? Human nature doesn't work that way. You can now go to Wal-Mart and purchase a $40 kit to convert your car AC system from R-12 to R-134. The package warns you that you have to have a "qualified professional" recover the R-12. How many people actually are going to pay the money to do that vs. the people that are just going to crack the valve and let it leak? Been there, done that. I don't know of any backyard mechanic who's actually taken his R-12 in to be recovered.
To say that you don't know of any backyard mechanic who has had the R-12 recovered from his car is beside the point. Those who have had their vehicles serviced at a dealership, major chain garage, or law-abiding independent mechanic will have had the Freon recovered from thir A/C system. Yes, there will be individuals who will just dump the refrigerant to the atmosphere, just as there are individuals who will pour used motor oil out on the lawn or into a storm sewer. This doesn't mean that these practices should be encouraged, or tolerated. Also, we don't discourage the use of motor oil because it might be disposed of improperly.
Incidentally, referring to "eviro-nazis" may be viscerally satisfying, but it won't help persuade anyone in an argument--remember Godwin's Law.
So here we are discussing a vehicle that is suppose to do something positive for the environment. The car is packed with lead (which the EPA and enviro-nazis have said is evil) and acid. Somebody pointed out that in an accident you have the potential for an acid spill. When the batteries are shot you are somehow going to have to find a way to dispose of them or contain them until you recycle them.
Valid concerns, but many of these issues have been addressed.
Accidents: Many new lead-acid batteries--and, I expect, all that would be permitted for a production electric vehicle--use either gel cell or absorbed glass mat technology. They will not leak appreciable amounts of anything when punctured. The batteries are also usually located in a fairly protected area on the underside of the electric vehicle. Very few people worry about having a tank full of highly flammable gasoline down there, because modern fuel tanks are very well-engineered--not to mention a necessary evil. Batteries can (and are) made similarly crashworthy.
Disposal: Lead is highly toxic, and it certainly can't be landfilled. Fortunately, the lead in most lead-acid batteries is extremely easy to recover--much more so, in fact, than the metals in NiMH and NiCad batteries. Garages in North America already collect your used motor oil for recycling or safe disposal, and nobody is allowed to touch old air conditioning systems unless the shop is equipped to collect Freon. The cost of disposal or recycling just becomes part of the cost of swapping battery sets.
Yes, it is very likely that additional lead will find its way into the environment if these batteries are adopted on a large scale. But--and there is always a but--it will reduce the dependence on fossil fuels. There would be fewer gasoline stations leaking hydrocarbons into the ground--and there are a lot of leaky underground storage tanks. Not only that, people regularly spill fuel when they fill their cars or (worse) boats. Lead would only be handled directly in a few locations--where it is smelted, and where it is recycled. In contrast, there is a gasoline filling station on nearly every corner. There are fewer points to be monitored, so I would argue that it is easier to control the lead pollution than the hydrocarbon pollution that it replaces.
You make some valid points, but quieter cars can result in more pedestrian accidents as they can't hear them coming.
Surely you jest. Visit your nearest large city, and walk through the downtown. Try to hold a conversation. The amount of background noise is really quite astonishing. You really can't hear any modern car (that hasn't been modded by idiots) until it's practically on top of you.
If a driver wants to be noticed by a pedestrian (or anyone else), he won't rev the engine (again, aforementioned idiots notwithstanding)--he will honk the horn. Most pedestrians should know enough to look both ways before crossing the street anyway.
As for the 4x4/SUV problem, in the UK 4x4 ownership is on the increase due to factors like speed bumps (sleeping policemen).
This explanation is new to me. Thanks for mentioning it--it's very amusing! Do people really go to such lengths to justify the purchase of SUVs? Points for creativity, certainly. Please, someone tell these people that speed bumps!=offroading. Have they considered slowing down as an option, I wonder?
Actually if you read the Canadian Charter of Rights and Freedoms you'll notice that where the Americans believed in "life, liberty, and the pursuit of happiness", the Canadians wrote "life, liberty and security of the person".
Another excellent bit Canadian law is from the Constitution Act, 1867, which in part grants Parliament the power to make laws for the 'peace, order, and good government' of Canada. It sounds to me to be an excellent set of goals for legislators in any nation. It also implies a great deal of trust in elected officials--'good government' is a very open-ended guiding priciple--balanced nicely by the protections afforded by the Charter of Rights and Freedoms.
Our current Prime Minister is a complete embarrassment on the international stage.
Yes, but remember that the parent poster is considering a move from the United States. President Bush on the international stage is an embarrassment with access to nuclear weapons, who seems bent on actively destructive foreign policy.
I would be the last to claim Jean Chretien is a perfect Prime Minister, but at least he runs a friendly dictatorship, and one where he's clearly responsible for his own opinions. He says what he thinks (embarrassing or otherwise)--he definitely doesn't have a Cheney or an Ashcroft pulling his strings.
To appreciate the test you have to have a basic understanding of what the scramjet does.
I agree completely. So why do you then tell us the following? You have been misled, my friend.
A scramjet seperates the hydrogen and oxygen molecules in the atmosphere and uses the hydrogen molecules as fuel for the engine.
In doing this you have an engine that can go significantly faster, an engine that uses up a fraction of the fuel load of traditional aircraft and an aircraft that expels significantly less harmful waste in the atmosphere then a traditional jet engine.
Quick primer on scramjets, from the top:
In a typical jet engine (see here, for example) air enters through an intake at the front, and passes through several fan stages to compress (and heat) the incoming air. Squirt fuel into this hot air, and the rapid combustion generates exhaust at high temperature and pressure. This high pressure exhaust propels the jet (and drives a turbine which turns the fans in the compressor).
The downside of this design is that it is mechanically complex--those compression stages have large, finely-machined, rapidly-moving parts which are subject to wear, tear, and accidental failure; they also add a significant amount of weight to the engine.
Enter the ramjet. (See also cutaway figure.) Instead of using fans to compress incoming air, a ramjet uses a specially shaped inlet. Air enters the jet inlet at high speed, and then is forced through a narrow aperture. The result is compression without fans. Unfortunately, the ramjet will only work when the jet is travelling at significant speed--there isn't going to be any air coming into the engine if the aircraft isn't moving.
A scramjet is a supersonic combustion ramjet. In a plain vanilla ramjet, the incoming air is slowed while it is compressed to the point where it is travelling slower than sound. Combustion takes place in air that is still moving quite quickly, but not supersonically. Although easier to manage from an engineering standpoint, requiring subsonic combustion places an upper limit on the speed of a conventional ramjet.
The scramjet functions in a similar manner--incoming air is compressed and heated through a properly shaped inlet, then fuel is injected, and the combustion products propel the jet. The defining difference is that combustion takes place in a supersonic airflow; in practice, this dictates certain changes to the basic ramjet design. Again, the scramjet requires significant airspeed before it can be started.
Quite correctly, you note that the fuel for these beasts is often hydrogen, though in principle nearly any air-combustible liquid or gas could be used. The fuel must be supplied, however--a scramjet cannot extract hydrogen from ambient water vapour. The hydrogen scramjet is inherently no cleaner burning than any other air-breathing hydrogen engine. Given its high operating temperature, I would be quite surprised if it didn't generate significant nitrogen oxides in operation.
The Vice President still has an unobfuscated email address. Feel free to email Dick at vice.president@whitehouse.gov. We know who runs the government anyway.
The public cotact numbers and addresses for the White House are readily available here.
Contacting the President should be a process simple enough that anyone in the USA, even those with limited technical, communication, and cognitive abilities could perform.
President George W. Bush
The White House
1600 Pennsylvania Avenue NW
Washington, DC 20500
Not only does it require limited technical ability, it also requires no electricity. A paper letter also usually carries more weight, because you have to get off your duff to send one.
To be fair, I like the system adopted in (among other places) Canada, where you can send snail mail to your government representatives free of charge. Still, stamps aren't that expensive in the States.
Cuba's area is 110,860 km^2, or 1.1x10^11 m^2, which is enough to give each person on Earth a luxurious 17.6m^2 of space, or around 158 sq ft -- about the size of a bathroom or small bedroom.
We can do better than that. Build to a height of twenty storeys. Even leaving half of the island for open spaces--parks, roadways, terrain that is difficult to build on--there's nearly 1600 square feet (180 square metres) per person. Huge! Granted, from that space you'll need to subtract infrastructure--power, water, commercial space--but there's still probably a good hundred square meters/1000 sq ft to play with. I know couples living in smaller apartments than that already.
Don't most of the problems you list actually get easier to solve as population density goes up?
Food doesn't. Six billion people eat a lot. We can make wonderful efficient use of urban space, pack everyone into the cities until we're all as cozy as the folks in Tokyo--yep, we'd all fit. But growing enough food for all those people given just one continent would be...challenging. If the continent were North America, we'd have to get used to soy products awfully quickly, because cattle are a tremendously inefficient source of calories.
Isaac Asimov's Caves of Steel presents (incidentally) a picture of that sort of world. Nearly all food in the novel is based on genetically engineered yeasts--privileged individuals might enjoy a little bit of chicken now and then. Tremendous effort must be expended to maintain infrastructure--if some disaster were to cut off such a city from its outside sources of water, power, fuel, and food, how long could it survive? How long would present-day Tokyo last?
Sure, it's hard to get the modern infrastructure out to the boonies--but a low-density farming community need never starve. You can live without electricity, without telephone service, without--dare I say it?--broadband internet access. You're screwed without food and water.
I can see it now: thousands of people fleeing the subway when a sensor trips because someone lit up a cigarette underneath one.
Well, so far the radiation detectors in the New York subway system haven't caught any terrorists, but they do ensure that individuals receiving certain types of radiotherapy are being regularly strip-searched. As far as I know, the system isn't causing mass panic, just acute embarrassment.
Sensors detecting what exactly? Anyway can you really see any major city subjecting every vehicle to an inspection.
Sensors detecting radiation. A nuclear bomb is a gamma source that can be detected at a distance unless heavily shielded. See also here. Chemical weapons also may leak signature compounds, which can be detected with the appropriate equipment--though not quite as sensitively.
IANA law enforcement official, but I would be very surprised if there were not already radiation monitors (fixed and mobile) in all of the largest U.S. cities. (Have another article.) They are definitely already installed--and catching innocent people--in New York, and I'm sure that they are in the D.C., too.
It will I guess be like one of those "decisions" a battlefield commander takes, of how much he trusts the intel he is getting...
That's why the smart commander avoids a hardware monoculture through the use of AMD boxen as well. In addition, fast AMD processors may be used in combat as incendiary devices.
Interesting though it may be, commercial space flight is a nuclear proliferation nightmare: what if anyone with (say) $50M to spend could put any payload he wanted, anywhere on the planet, reliably?
Though this is certainly a legal problem--there are restrictions in place on rocket technology for precisely this reason--it is nonsense from a realistic standpoint. I can put any payload anywhere I want to, anywhere on the planet, for a lot less than fifty million dollars. The delivery isn't as fast, but container ships would allow an individual to place a nuclear bomb in any port city in the world. Rent a truck and you can place a nuke in (almost) any city in the United States--D.C. and a few other places have sensors. If you work with chemical or biological weapons, they're virtually undetectable and can really be placed anywhere.
Missiles are for the movies. Smart terrorists use U-Haul.
Slashdot Mirror
I've noticed some technical people have started (usually fondly) calling their users muggles. Anybody else seen this?
Shakespeare's grave is located in Stratford-upon-Avon, at the Holy Trinity Parish Church.
Linkie.
You bastard!
I bought a solid state physics textbook back in my undergrad days--it cost more than an equivalent weight of silver bullion. I haven't weighed any of my other textbooks, but I wouldn't be surprised if it wasn't the only one worth its weight in silver....
So, you spend your real money in order to get pretend money in your online games.
Then, for the privilege of spending that pretend money - in a pretend world, on pretend things - you pay more real money, every month.
I spent some real money the other day on a pretend world. It was a world created by Arthur C. Clarke. I was entertained for a few hours, and now that pretend world full of pretend things sits on my shelf.
Yesterday I went to the local video store, where I spent some more real money on yet another pretend world. Today, I returned the video--if I want to visit that pretend world again, I'll have to cough up more real money.
What's the difference between people who spend X dollars per month on Everquest et al. and the people who sink X dollars per month into satellite television? It's all entertainment. People don't usually buy either product with 'useful' ends in mind--they pay the money to be amused and pass the time. It's their money; it's their time. Sure, they could be giving both to more 'worthy' causes, but so could we all.
Spoken like a true American. Bravo.
Actually, I found that kind of amusing when I read it, but now you've got me thinking. The grandparent poster indicates that he's deaf in one ear--really, a relatively minor inconvenience. (My best friend is deaf in one ear; I have to avoid sneaking up on her left side.)
The cause of his hearing loss wasn't indicated, but what might it be? Congenital defect? Progressive degenerative illness? Infection? Trauma? In most of those cases (the three most likely, in fact) he has lost the hearing in one ear, but is unlikely to suffer further health problems. On the other hand, obesity is a risk factor for all kinds of ways to die--including heart disease, the leading killer in developed nations.
On reflection, I have to agree--I'd rather be deaf in one ear than fat, too.
Can you furnish us with a list of medical conditions you consider not worth treating? Or would you prefer to set a dollar figure beyond which we should let you die?
An extra four or five years can make a tremendous difference to people, to their families. 'Half dead' or not, some people have something to live for.
From the article,
Since all of the pieces are held together with glued, fitted joints--not screws, nails, or spikes--there's a lot of potentially finicky (hence time-consuming and expensive) work involved.
Further, I agree with you that in going from gasoline-powered vehicles to electrics, we are indeed (in general) trading one type of pollution for another. Really, this is the sticky point. Admittedly fallible scientists, bureaucrats, environmentalists make educated guesses (sometimes well-informed ones, sometimes less so) about the relative damage caused by each technology. Is the potential environmental damage associated with smelting and handling lead more or less serious than the damage associated with drilling, shipping, and pumping petroleum products? As you say, first world nations do very little to attempt to control lead emissions from smelting in other countries--but they also ignore environmental slips associated with processing and handling hydrocarbons. You ask if I'm concerned about the environment as a whole, or just my own backyard--fair enough, but I can't ignore petroleum spills here or elsewhere, either.
You pointed out that "nobody is allowed to touch old air conditioning systems unless..." What does this encourage? Does this better the environment? Human nature doesn't work that way. You can now go to Wal-Mart and purchase a $40 kit to convert your car AC system from R-12 to R-134. The package warns you that you have to have a "qualified professional" recover the R-12. How many people actually are going to pay the money to do that vs. the people that are just going to crack the valve and let it leak? Been there, done that. I don't know of any backyard mechanic who's actually taken his R-12 in to be recovered.
To say that you don't know of any backyard mechanic who has had the R-12 recovered from his car is beside the point. Those who have had their vehicles serviced at a dealership, major chain garage, or law-abiding independent mechanic will have had the Freon recovered from thir A/C system. Yes, there will be individuals who will just dump the refrigerant to the atmosphere, just as there are individuals who will pour used motor oil out on the lawn or into a storm sewer. This doesn't mean that these practices should be encouraged, or tolerated. Also, we don't discourage the use of motor oil because it might be disposed of improperly.
Incidentally, referring to "eviro-nazis" may be viscerally satisfying, but it won't help persuade anyone in an argument--remember Godwin's Law.
Valid concerns, but many of these issues have been addressed.
Accidents: Many new lead-acid batteries--and, I expect, all that would be permitted for a production electric vehicle--use either gel cell or absorbed glass mat technology. They will not leak appreciable amounts of anything when punctured. The batteries are also usually located in a fairly protected area on the underside of the electric vehicle. Very few people worry about having a tank full of highly flammable gasoline down there, because modern fuel tanks are very well-engineered--not to mention a necessary evil. Batteries can (and are) made similarly crashworthy.
Disposal: Lead is highly toxic, and it certainly can't be landfilled. Fortunately, the lead in most lead-acid batteries is extremely easy to recover--much more so, in fact, than the metals in NiMH and NiCad batteries. Garages in North America already collect your used motor oil for recycling or safe disposal, and nobody is allowed to touch old air conditioning systems unless the shop is equipped to collect Freon. The cost of disposal or recycling just becomes part of the cost of swapping battery sets.
Yes, it is very likely that additional lead will find its way into the environment if these batteries are adopted on a large scale. But--and there is always a but--it will reduce the dependence on fossil fuels. There would be fewer gasoline stations leaking hydrocarbons into the ground--and there are a lot of leaky underground storage tanks. Not only that, people regularly spill fuel when they fill their cars or (worse) boats. Lead would only be handled directly in a few locations--where it is smelted, and where it is recycled. In contrast, there is a gasoline filling station on nearly every corner. There are fewer points to be monitored, so I would argue that it is easier to control the lead pollution than the hydrocarbon pollution that it replaces.
Surely you jest. Visit your nearest large city, and walk through the downtown. Try to hold a conversation. The amount of background noise is really quite astonishing. You really can't hear any modern car (that hasn't been modded by idiots) until it's practically on top of you.
If a driver wants to be noticed by a pedestrian (or anyone else), he won't rev the engine (again, aforementioned idiots notwithstanding)--he will honk the horn. Most pedestrians should know enough to look both ways before crossing the street anyway.
As for the 4x4/SUV problem, in the UK 4x4 ownership is on the increase due to factors like speed bumps (sleeping policemen).
This explanation is new to me. Thanks for mentioning it--it's very amusing! Do people really go to such lengths to justify the purchase of SUVs? Points for creativity, certainly. Please, someone tell these people that speed bumps!=offroading. Have they considered slowing down as an option, I wonder?
Actually, this is the only space-based hamburger related object we need to worry about.
Yes, it's a good thing that kids don't have access to pornography or alcohol now...
Another excellent bit Canadian law is from the Constitution Act, 1867 , which in part grants Parliament the power to make laws for the 'peace, order, and good government' of Canada. It sounds to me to be an excellent set of goals for legislators in any nation. It also implies a great deal of trust in elected officials--'good government' is a very open-ended guiding priciple--balanced nicely by the protections afforded by the Charter of Rights and Freedoms.
Our current Prime Minister is a complete embarrassment on the international stage.
Yes, but remember that the parent poster is considering a move from the United States. President Bush on the international stage is an embarrassment with access to nuclear weapons, who seems bent on actively destructive foreign policy.
I would be the last to claim Jean Chretien is a perfect Prime Minister, but at least he runs a friendly dictatorship, and one where he's clearly responsible for his own opinions. He says what he thinks (embarrassing or otherwise)--he definitely doesn't have a Cheney or an Ashcroft pulling his strings.
To be fair, this is Slashdot.
It gets worse....
I agree completely. So why do you then tell us the following? You have been misled, my friend.
A scramjet seperates the hydrogen and oxygen molecules in the atmosphere and uses the hydrogen molecules as fuel for the engine. In doing this you have an engine that can go significantly faster, an engine that uses up a fraction of the fuel load of traditional aircraft and an aircraft that expels significantly less harmful waste in the atmosphere then a traditional jet engine.
Quick primer on scramjets, from the top:
In a typical jet engine (see here, for example) air enters through an intake at the front, and passes through several fan stages to compress (and heat) the incoming air. Squirt fuel into this hot air, and the rapid combustion generates exhaust at high temperature and pressure. This high pressure exhaust propels the jet (and drives a turbine which turns the fans in the compressor).
The downside of this design is that it is mechanically complex--those compression stages have large, finely-machined, rapidly-moving parts which are subject to wear, tear, and accidental failure; they also add a significant amount of weight to the engine.
Enter the ramjet. (See also cutaway figure.) Instead of using fans to compress incoming air, a ramjet uses a specially shaped inlet. Air enters the jet inlet at high speed, and then is forced through a narrow aperture. The result is compression without fans. Unfortunately, the ramjet will only work when the jet is travelling at significant speed--there isn't going to be any air coming into the engine if the aircraft isn't moving.
A scramjet is a supersonic combustion ramjet. In a plain vanilla ramjet, the incoming air is slowed while it is compressed to the point where it is travelling slower than sound. Combustion takes place in air that is still moving quite quickly, but not supersonically. Although easier to manage from an engineering standpoint, requiring subsonic combustion places an upper limit on the speed of a conventional ramjet.
The scramjet functions in a similar manner--incoming air is compressed and heated through a properly shaped inlet, then fuel is injected, and the combustion products propel the jet. The defining difference is that combustion takes place in a supersonic airflow; in practice, this dictates certain changes to the basic ramjet design. Again, the scramjet requires significant airspeed before it can be started.
Quite correctly, you note that the fuel for these beasts is often hydrogen, though in principle nearly any air-combustible liquid or gas could be used. The fuel must be supplied, however--a scramjet cannot extract hydrogen from ambient water vapour. The hydrogen scramjet is inherently no cleaner burning than any other air-breathing hydrogen engine. Given its high operating temperature, I would be quite surprised if it didn't generate significant nitrogen oxides in operation.
The public cotact numbers and addresses for the White House are readily available here.
Not only does it require limited technical ability, it also requires no electricity. A paper letter also usually carries more weight, because you have to get off your duff to send one.
To be fair, I like the system adopted in (among other places) Canada, where you can send snail mail to your government representatives free of charge. Still, stamps aren't that expensive in the States.
We can do better than that. Build to a height of twenty storeys. Even leaving half of the island for open spaces--parks, roadways, terrain that is difficult to build on--there's nearly 1600 square feet (180 square metres) per person. Huge! Granted, from that space you'll need to subtract infrastructure--power, water, commercial space--but there's still probably a good hundred square meters/1000 sq ft to play with. I know couples living in smaller apartments than that already.
Don't most of the problems you list actually get easier to solve as population density goes up?
Food doesn't. Six billion people eat a lot. We can make wonderful efficient use of urban space, pack everyone into the cities until we're all as cozy as the folks in Tokyo--yep, we'd all fit. But growing enough food for all those people given just one continent would be...challenging. If the continent were North America, we'd have to get used to soy products awfully quickly, because cattle are a tremendously inefficient source of calories.
Isaac Asimov's Caves of Steel presents (incidentally) a picture of that sort of world. Nearly all food in the novel is based on genetically engineered yeasts--privileged individuals might enjoy a little bit of chicken now and then. Tremendous effort must be expended to maintain infrastructure--if some disaster were to cut off such a city from its outside sources of water, power, fuel, and food, how long could it survive? How long would present-day Tokyo last?
Sure, it's hard to get the modern infrastructure out to the boonies--but a low-density farming community need never starve. You can live without electricity, without telephone service, without--dare I say it?--broadband internet access. You're screwed without food and water.
Well, so far the radiation detectors in the New York subway system haven't caught any terrorists, but they do ensure that individuals receiving certain types of radiotherapy are being regularly strip-searched. As far as I know, the system isn't causing mass panic, just acute embarrassment.
Sensors detecting radiation. A nuclear bomb is a gamma source that can be detected at a distance unless heavily shielded. See also here. Chemical weapons also may leak signature compounds, which can be detected with the appropriate equipment--though not quite as sensitively.
IANA law enforcement official, but I would be very surprised if there were not already radiation monitors (fixed and mobile) in all of the largest U.S. cities. (Have another article.) They are definitely already installed--and catching innocent people--in New York, and I'm sure that they are in the D.C., too.
That's why the smart commander avoids a hardware monoculture through the use of AMD boxen as well. In addition, fast AMD processors may be used in combat as incendiary devices.
Though this is certainly a legal problem--there are restrictions in place on rocket technology for precisely this reason--it is nonsense from a realistic standpoint. I can put any payload anywhere I want to, anywhere on the planet, for a lot less than fifty million dollars. The delivery isn't as fast, but container ships would allow an individual to place a nuclear bomb in any port city in the world. Rent a truck and you can place a nuke in (almost) any city in the United States--D.C. and a few other places have sensors. If you work with chemical or biological weapons, they're virtually undetectable and can really be placed anywhere.
Missiles are for the movies. Smart terrorists use U-Haul.