There's a happy medium here, and I've explained it before. Local government should lay conduit throughout the city through which the free market can pull its copper or fiber. The free market includes not only for-profit major telcos but also not-for-profit cooperative local telcos.
That sounds overly complicated and expensive and risks customers becoming captured (if vertical integration is allowed) i.e. "No you can't change ISPs, you're on our fibre." That's a good way to not achive competition.
Better would be to do it like we do here in Sweden (though sadly not universally) with "Open City Networks" where a (municipal) company, in my case the local energy/district heating company, also laying fibre and installing CPEs etc. (They're all basically the same anyway). The competition is at the ISP level, where I have a choice of 8-10 ISPs/telecom providers/IP-tv providers. If I want old fashioned cable TV there's only one provider, but I'm happy with it, and there's plenty of IP-tv providers. Due to market pressure we even have the old elephant monopoly telco (now private since many years) installing Open City Networks, i.e. where you don't have to have them as the ISP, but have a choice.
Cost is about $40 for 100/100 Mbps, including IP-telephony. TV is on the order of $20 and up depending on the usual cable TV crap.
I'm not one of these, I don't know any of these, but I can't think of any reason why it is moral to force these people (under threat of legitimate violence) to pay other people's personal expenses.
How are they any more personal than expenses incurred when the police investigates a crime that you've been the victim of? Or, perhaps a better example, when the fire department helps put out a fire, that if left to itself would lead to much greater damage?
Answer: That's how society, especially risk management through insurance, works. Put another way. Why should these ingrate people's little pet peeves be allowed to cost society twice as much for a worse outcome? What gives them the right to make other's pay so much more for nothing in return? Their right to selfishness is after all killing people. If they want to live in a society like that, why would it be wrong for the majority to just say "Fine go start one somewhere else, you're not welcome here."?
I used to do that. But then I came to the realisation that I was running a server anyway, and I always wanted a workstation handy, so I've gone the way of the big iron on consolidated everything onto one machine. It's my router/firewall, file server, web server, workstation and everything else. It sits in my living room and for maximum convenience I even don't bother with different user accounts. Instead I use Chrome and my wife uses Firefox so that we can access our email, surfing sessions etc. just by switching windows. Runs Ubuntu 12.04 LTS with Mate desktop.
Since it's consolidated I can spend more money on better components (CPU, 32 GB memory, raid storage etc.) and I save a couple of hundred dollars per year in electricity alone from not running a separate file server etc. like I used to. It also means less to manage. (The kids use another computer with windows 7 and when they mess that up, it's no major hassle. They just have to do without until I get around to fixing it. Which is good for them anyway...:-)
Well yeah, I'm in Sweden, and we have so much fresh water that we just let the surplus run straight out into the ocean. And you know what. There's not a lot stopping diverting a bit of that water to raising animals and then let it out into the ocean (having been used for fertilisation first of course, yes agg runoff into our water ways is an environmental problem, but that's almost all industrial fertiliser, not cow piss).
So by that token, there's no problem. (Hint there are problems, but that isn't one of them). It's not as if we could build a pipe line and ship our excess water to Africa where it would be put to better use...
Kind of reminds me of the country side of my family complaining about city folk who move out their way. "First they move outside the city, then they complain about the smell of cow shit, where did they think they were moving?"
Well, there's that. On the other hand agriculture has changed dramatically in my lifetime. When I was a wee lad much of my family where small hold farmers with a dozen-twenty cows etc. That's all gone. Today it's mega farms that are in many cases owned, not by the farmers themselves, but by agriculture corporations. Feed lots have replaced pastures etc. Now it's not as bad here as it is in some places I've seen in the US. Not yet at least. But there's a large difference of scale especially on the local surroundings between running a small farm with ten pigs you can scratch behind the ears when the inclination strikes you, and a 1000 pig industrial farm. That place can stink up the entire countryside like you wouldn't belive...
I see. You mean that there are people who would make that fine a distinction. While I don't think there are enough of those people to make a difference in a poll like this, your point is well taken.
But likewise, if you would ask random people
1. Is astronomy scientific?
OR
2. Are celestial maps scientific?
I bet the latter questions would get significantly less positive answers.
Yes, but that's predicated on the idea that people wouldn't know what "celestial maps" meant and that they likewise wouldn't know what "horoscopes" meant. I don't think you'll be able to find support for that. Many more people (the overwhelming majority) would probably be familiar with the term horoscope and know what it entailed, than would know about "celestial maps".
Yes, this is exactly the issue. GPL isn't "more free" than BSD. Quite the opposite. GPL is far less free as it grants the users less freedoms.
And by the same token, the South pre civil war was more free. After all they didn't put any limitations on the owning of slaves. The North on the other hand did. So clearly they were less free.
Nope, that's the funny thing about freedom. The system with more restrictions on your limiting the freedom of others, is more free. Not less.
The real problem is, of course, that for major weapon systems, the US always buys American. Even if it's not really American. As you point out with the Harrier.
Well the 39 would fit right in then. Since it's got so many American parts I'm surprised we're allowed to export it at all to countries that are also vowed by the US. (Engine, weapons, flight control SW, just off the top of my head). If the US bought Gripen they would be buying American...
But yes. It's mainly a question of supporting ones industry, just witness the debacle when the US Air force bought new tankers to replace their ageing KC-135s and Airbus won... "Do it again till you select the right manufacturer, i.e. Boeing!" came back the answer...
Quite a few people on here lately have been talking about how vulnerable aircraft carriers are to anti-ship missiles, and I think that threat is somewhat overstated. Sure anti-ship missiles such as the Exocet racked up an impressive tally in the Falklands War, but they didn't sink the carriers. Why? Because naval commanders realize the risk posed by anti-ship missiles and are willing to risk the destroyer screen to protect the valuable carriers (same techniques were applied against kamikaze). If the Argentinians were able to sink both of the British carriers (or maybe just one), the chances of the British being able to retake the Falklands would have pretty much ended.
Well, the Argentinians only had five (count them; five) missiles and as many aircraft to carry them. One aircraft was kept on the ground as a source of spare parts. They flew in sorties of two aircraft with one missile each and scored three hits sinking two ships. (They also scavenged two shipbased exocetes and fired from land, but that would hardly be a threat to a carrier. One hit, but not substantial.)
Now, they had fourteen planes on order with a similar number of missiles. Had they been operational the British would have been in a world of trouble. For one thing, they didn't bring enough destroyers to sacrifice to such an onslaught. (There's also the question of whether the Argentinians actually hit the Invincible, although obviously not seriously.)
Even so, as it was Rear Admiral Sir Sandy Woodward famously summed it up as "a lot closer run than many would care to believe", only a few things going the other way would very likely have upturned the whole thing. They didn't just lose ships to missiles, but also to bombs, that didn't have the correct fuses. No less than six bombs hit the landing force but failed to explode...
These types of "attacks" are very common in police forensics and hence the forensics community have studies ways of how to do encryption with stored keys that don't store them in memory (to for example avoid cold-boot attacks.
One of the interesting approaches are taken by the TRESOR team. They store encryption keys in CPU registers instead of main memory, making a cold boot attack, or hibernation attack impossible.
They have implementations for Linux and Android phones. The Linux implementation on an Intel with AES-hw support is even slightly faster than doint key expansion in memory! It's an interesting approach, but perhaps a bit over the top for most cases.
.357 is simply a lengthened version of the the.38 Special round, with that additional space being used to hold a lot more powder.
Many would think that, but the main reason is actually to make it not fit most revolvers made for.38 special. Elmer Keith loaded original.38 special to pressures and speeds that are very close to the.357 specs. So there's no shortage of case capacity, since it was originally a black poweder cartridge, you wouldn't expect there to be.
How ever, Elmer Keith used the new N-frame S&W revolvers that could take the beating. It was feared that older revolvers would blow up regularly if people started loading them with such hot.38s. Hence the case was lengthened as a safety feature.
And fusing silicon won't give you even near mc^2. You need anti-matter anihilation for that.
So I'm sorry. You're still off by several orders of magnitude. And being off by that much is what we call being wrong in the sciences. Qualitative arguments don't cut it when your quantities are that far off.
It is not realistic to design nuclear power plants to withstand the maximum energy you could get out of the reaction. That would kill off the nuclear industry.
Well, it hinges on the "maximum energy you could get out of the reaction". A nuclear power plant core is emphatically not in an way shape or form a nuclear bomb pit. If it were then nuclear weapons proliferation would be a fools errand. Everybody who could build a reactor could also build a bomb and that's not remotely true.
As others have mentioned, enrichment is one issue. A civilian reactor runs with between 3%-4% U235 enrichment and a U235 bomb needs over 90%. Also you have to assemble the subcritical parts in such a way as to achieve a supercritical mass for long enough for prompt criticality to occur. Only very few reactor accidents have lead that far and even so, they only developed minuscule amounts of power compared to a nuclear detonation.
You might as well say that since E=mc^2 and the buildings contain a lot of concrete the possible energy is off the charts. There is no reasonable way to make even a small nuclear explosion by running a commercial (or other) reactor outside specs. It'll blow up (disassemble) due to other forces long before it can reach anything even resembling a nuclear explosion.
That's not to say that it's a good idea to build or run reactors (like RBMK) that have failure modes even remotely similar to spontaneous rapid disassembly, or that there isn't a lot that could be done to improve reactor safety design, but you don't have to design for a nuclear blast containment, not even by a long shot.
That's a common misconception. Obfuscation can provide security is the attacker doesn't have the means to de-obfuscate, isn't smart enough to find it, or doesn't have the time/resources to get it.
But in this day and age of almost exclusively class breaks that's not a realistic threat model as it hinges on the fact that you're the only one that does that particular obfuscation. So getting NetworkManager to do something "better" would be pointless. The attacker would not only have access to that information as it would be spread far and wide, his tools would deobfuscate automagically.
Obfuscation would work for the likes of the NSA, and then on top of everything else as icing on the cake. For the rest of us, not so much.
You're right. People are plain stupid! Why do we even give them the right to vote?
You did. And this is what they came up with. Did you think this piece of legislation didn't come from your elected representatives? And this in the US of all places where your politicians don't seem to be able to agree and a single thing, they obviously found consensus on this issue.
So what's the problem? By your account, people obviously saw the error of their ways and thought they'd wanted a bit of help getting rid of their old habits, while retaining the right to bitch and moan no doubt. And hence had this law enacted. Representative democracy the way its supposed to work, no way around that...
I live in a house with resistance electric heating; and I prefer the quality of light from incandescent lamps. So, I swap them twice a year. Winter, incandescent lamps approach 100% efficiency for me. I also use them outdoors, in places where I need instant start in cold weather, and in specialty uses, like my range hood with an inbuilt and CFL-incompatible dimmer. Point is, I do it intelligently.
Odds are you're not getting 100%. In Sweden (where we made the switch a few years ago) this was studied as we have a large proportion of houses with resistance electric heating. Some of the cheapest electricity in Europe will do that. They showed that even in that situation, and with our cheap electricity the average house would still save 20% from switching to CFLs.
There are a range of reasons but the main ones are that lights don't come with thermostats. Thermostats are usually quite bad at taking such small and "noisy" added heaters into account, the heat ends up in the wrong place (i.e. the ceiling, where it doesn't add to convection) and the lighting season lasts longer than the heating season to name a few.
Now, I live in a house with district heating (because it came with a nice 100Mbps fiber), and I made the switch several years ago and I don't miss incandescents one bit. Just not having to change them all the bloody time and not having the armatures burn out from excessive temperatures makes getting rid of them worthwhile to me.
"Profiling" is a form of rational statistical analysis with a big social problem attached. If you have a known population of people with a propensity to behave in a certain way, then the rational thing to do is to look closely at that population.
No. Unfortunately that's not true. Profiling works for very small groups and types of behaviour, or groups and behaviours with a high degree of certainty. I.e. people standing close to the shelf at the supermarket and are glancing furtively left and right are probably shoplifters (specific behaviour that is not common among non-shoplifters), or "don't swim with crocodiles" (they'll try and eat you almost every time).
None of this is true when it comes to terrorism. Especially when you take the base-rate fallacy into account. Even if all terrorists to date are Arab males age 18-40 (for the sake of argument as that's not true by a long shot), looking at that group exclusively won't catch you any more terrorists since almost none of the Arab males age 18-40 are actually terrorists. Terrorism is just too uncommon. Even though you'll increase your relative certainty by just looking at the aforementioned Arab males, your probability in absolute terms will still be so close to zero as to make the whole endeavour useless. And that's even ignoring terrorist organisations identifying this fact and actively recruiting operatives that don't fit that profile.
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There's a happy medium here, and I've explained it before. Local government should lay conduit throughout the city through which the free market can pull its copper or fiber. The free market includes not only for-profit major telcos but also not-for-profit cooperative local telcos.
That sounds overly complicated and expensive and risks customers becoming captured (if vertical integration is allowed) i.e. "No you can't change ISPs, you're on our fibre." That's a good way to not achive competition.
Better would be to do it like we do here in Sweden (though sadly not universally) with "Open City Networks" where a (municipal) company, in my case the local energy/district heating company, also laying fibre and installing CPEs etc. (They're all basically the same anyway). The competition is at the ISP level, where I have a choice of 8-10 ISPs/telecom providers/IP-tv providers. If I want old fashioned cable TV there's only one provider, but I'm happy with it, and there's plenty of IP-tv providers. Due to market pressure we even have the old elephant monopoly telco (now private since many years) installing Open City Networks, i.e. where you don't have to have them as the ISP, but have a choice.
Cost is about $40 for 100/100 Mbps, including IP-telephony. TV is on the order of $20 and up depending on the usual cable TV crap.
I'm not one of these, I don't know any of these, but I can't think of any reason why it is moral to force these people (under threat of legitimate violence) to pay other people's personal expenses.
How are they any more personal than expenses incurred when the police investigates a crime that you've been the victim of? Or, perhaps a better example, when the fire department helps put out a fire, that if left to itself would lead to much greater damage?
Answer: That's how society, especially risk management through insurance, works. Put another way. Why should these ingrate people's little pet peeves be allowed to cost society twice as much for a worse outcome? What gives them the right to make other's pay so much more for nothing in return? Their right to selfishness is after all killing people. If they want to live in a society like that, why would it be wrong for the majority to just say "Fine go start one somewhere else, you're not welcome here."?
I used to do that. But then I came to the realisation that I was running a server anyway, and I always wanted a workstation handy, so I've gone the way of the big iron on consolidated everything onto one machine. It's my router/firewall, file server, web server, workstation and everything else. It sits in my living room and for maximum convenience I even don't bother with different user accounts. Instead I use Chrome and my wife uses Firefox so that we can access our email, surfing sessions etc. just by switching windows. Runs Ubuntu 12.04 LTS with Mate desktop.
Since it's consolidated I can spend more money on better components (CPU, 32 GB memory, raid storage etc.) and I save a couple of hundred dollars per year in electricity alone from not running a separate file server etc. like I used to. It also means less to manage. (The kids use another computer with windows 7 and when they mess that up, it's no major hassle. They just have to do without until I get around to fixing it. Which is good for them anyway... :-)
So by that token, there's no problem. (Hint there are problems, but that isn't one of them). It's not as if we could build a pipe line and ship our excess water to Africa where it would be put to better use...
Kind of reminds me of the country side of my family complaining about city folk who move out their way. "First they move outside the city, then they complain about the smell of cow shit, where did they think they were moving?"
Well, there's that. On the other hand agriculture has changed dramatically in my lifetime. When I was a wee lad much of my family where small hold farmers with a dozen-twenty cows etc. That's all gone. Today it's mega farms that are in many cases owned, not by the farmers themselves, but by agriculture corporations. Feed lots have replaced pastures etc. Now it's not as bad here as it is in some places I've seen in the US. Not yet at least. But there's a large difference of scale especially on the local surroundings between running a small farm with ten pigs you can scratch behind the ears when the inclination strikes you, and a 1000 pig industrial farm. That place can stink up the entire countryside like you wouldn't belive...
I see. You mean that there are people who would make that fine a distinction. While I don't think there are enough of those people to make a difference in a poll like this, your point is well taken.
But likewise, if you would ask random people 1. Is astronomy scientific? OR 2. Are celestial maps scientific? I bet the latter questions would get significantly less positive answers.
Yes, but that's predicated on the idea that people wouldn't know what "celestial maps" meant and that they likewise wouldn't know what "horoscopes" meant. I don't think you'll be able to find support for that. Many more people (the overwhelming majority) would probably be familiar with the term horoscope and know what it entailed, than would know about "celestial maps".
So no cigar.
Well you fooled me at least, so it wasn't a complete loss. :-)
And for being lazy, you can tell my the huge amount of debt the countries carry
Yes well: Sweden 38.2% of GDP, Luxembourg 20.8% of GDP, Finland 53.1% of GDP, and Denmark 45.6% of GDP. (From the CIA world fact book, est. for 2012).
From the same source: USA 70% of GDP (and that's apparently not counting it all).
"Huge" debts indeed... So we're lazy? Well it takes one to know one I guess...
Of course he did. Newton's laws of motion are wrong...
Sure, but there's being wrong and there's being wrong.
Yes, this is exactly the issue. GPL isn't "more free" than BSD. Quite the opposite. GPL is far less free as it grants the users less freedoms.
And by the same token, the South pre civil war was more free. After all they didn't put any limitations on the owning of slaves. The North on the other hand did. So clearly they were less free.
Nope, that's the funny thing about freedom. The system with more restrictions on your limiting the freedom of others, is more free. Not less.
The real problem is, of course, that for major weapon systems, the US always buys American. Even if it's not really American. As you point out with the Harrier.
Well the 39 would fit right in then. Since it's got so many American parts I'm surprised we're allowed to export it at all to countries that are also vowed by the US. (Engine, weapons, flight control SW, just off the top of my head). If the US bought Gripen they would be buying American...
But yes. It's mainly a question of supporting ones industry, just witness the debacle when the US Air force bought new tankers to replace their ageing KC-135s and Airbus won... "Do it again till you select the right manufacturer, i.e. Boeing!" came back the answer...
Quite a few people on here lately have been talking about how vulnerable aircraft carriers are to anti-ship missiles, and I think that threat is somewhat overstated. Sure anti-ship missiles such as the Exocet racked up an impressive tally in the Falklands War, but they didn't sink the carriers. Why? Because naval commanders realize the risk posed by anti-ship missiles and are willing to risk the destroyer screen to protect the valuable carriers (same techniques were applied against kamikaze). If the Argentinians were able to sink both of the British carriers (or maybe just one), the chances of the British being able to retake the Falklands would have pretty much ended.
Well, the Argentinians only had five (count them; five) missiles and as many aircraft to carry them. One aircraft was kept on the ground as a source of spare parts. They flew in sorties of two aircraft with one missile each and scored three hits sinking two ships. (They also scavenged two shipbased exocetes and fired from land, but that would hardly be a threat to a carrier. One hit, but not substantial.)
Now, they had fourteen planes on order with a similar number of missiles. Had they been operational the British would have been in a world of trouble. For one thing, they didn't bring enough destroyers to sacrifice to such an onslaught. (There's also the question of whether the Argentinians actually hit the Invincible, although obviously not seriously.)
Even so, as it was Rear Admiral Sir Sandy Woodward famously summed it up as "a lot closer run than many would care to believe", only a few things going the other way would very likely have upturned the whole thing. They didn't just lose ships to missiles, but also to bombs, that didn't have the correct fuses. No less than six bombs hit the landing force but failed to explode...
Sure you would. You would even get that holy grain of academia "external funding", from the oil companies...
These types of "attacks" are very common in police forensics and hence the forensics community have studies ways of how to do encryption with stored keys that don't store them in memory (to for example avoid cold-boot attacks.
One of the interesting approaches are taken by the TRESOR team. They store encryption keys in CPU registers instead of main memory, making a cold boot attack, or hibernation attack impossible.
They have implementations for Linux and Android phones. The Linux implementation on an Intel with AES-hw support is even slightly faster than doint key expansion in memory! It's an interesting approach, but perhaps a bit over the top for most cases.
But why does the government have to force me to use a different device?
Because you're stupid. Same with seatbelt laws, same with not polution the environment etc. etc.
That's why we have representative democracy.
.357 is simply a lengthened version of the the .38 Special round, with that additional space being used to hold a lot more powder.
Many would think that, but the main reason is actually to make it not fit most revolvers made for .38 special. Elmer Keith loaded original .38 special to pressures and speeds that are very close to the .357 specs. So there's no shortage of case capacity, since it was originally a black poweder cartridge, you wouldn't expect there to be.
How ever, Elmer Keith used the new N-frame S&W revolvers that could take the beating. It was feared that older revolvers would blow up regularly if people started loading them with such hot .38s. Hence the case was lengthened as a safety feature.
Not using the same neutrons they don't.
And fusing silicon won't give you even near mc^2. You need anti-matter anihilation for that.
So I'm sorry. You're still off by several orders of magnitude. And being off by that much is what we call being wrong in the sciences. Qualitative arguments don't cut it when your quantities are that far off.
It is not realistic to design nuclear power plants to withstand the maximum energy you could get out of the reaction. That would kill off the nuclear industry.
Well, it hinges on the "maximum energy you could get out of the reaction". A nuclear power plant core is emphatically not in an way shape or form a nuclear bomb pit. If it were then nuclear weapons proliferation would be a fools errand. Everybody who could build a reactor could also build a bomb and that's not remotely true.
As others have mentioned, enrichment is one issue. A civilian reactor runs with between 3%-4% U235 enrichment and a U235 bomb needs over 90%. Also you have to assemble the subcritical parts in such a way as to achieve a supercritical mass for long enough for prompt criticality to occur. Only very few reactor accidents have lead that far and even so, they only developed minuscule amounts of power compared to a nuclear detonation.
You might as well say that since E=mc^2 and the buildings contain a lot of concrete the possible energy is off the charts. There is no reasonable way to make even a small nuclear explosion by running a commercial (or other) reactor outside specs. It'll blow up (disassemble) due to other forces long before it can reach anything even resembling a nuclear explosion.
That's not to say that it's a good idea to build or run reactors (like RBMK) that have failure modes even remotely similar to spontaneous rapid disassembly, or that there isn't a lot that could be done to improve reactor safety design, but you don't have to design for a nuclear blast containment, not even by a long shot.
"Made to order?" Hmm, so the creationists are right after all. There is a creator and he clearly likes science...
Could have been worse I guess.
That's a common misconception. Obfuscation can provide security is the attacker doesn't have the means to de-obfuscate, isn't smart enough to find it, or doesn't have the time/resources to get it.
But in this day and age of almost exclusively class breaks that's not a realistic threat model as it hinges on the fact that you're the only one that does that particular obfuscation. So getting NetworkManager to do something "better" would be pointless. The attacker would not only have access to that information as it would be spread far and wide, his tools would deobfuscate automagically.
Obfuscation would work for the likes of the NSA, and then on top of everything else as icing on the cake. For the rest of us, not so much.
Why? Is Europe's location somehow significant to average Americans?
Well you know, you might like to bomb us sometime. Then it comes in handy to know where it is!
You're right. People are plain stupid! Why do we even give them the right to vote?
You did. And this is what they came up with. Did you think this piece of legislation didn't come from your elected representatives? And this in the US of all places where your politicians don't seem to be able to agree and a single thing, they obviously found consensus on this issue.
So what's the problem? By your account, people obviously saw the error of their ways and thought they'd wanted a bit of help getting rid of their old habits, while retaining the right to bitch and moan no doubt. And hence had this law enacted. Representative democracy the way its supposed to work, no way around that...
I live in a house with resistance electric heating; and I prefer the quality of light from incandescent lamps. So, I swap them twice a year. Winter, incandescent lamps approach 100% efficiency for me. I also use them outdoors, in places where I need instant start in cold weather, and in specialty uses, like my range hood with an inbuilt and CFL-incompatible dimmer. Point is, I do it intelligently.
Odds are you're not getting 100%. In Sweden (where we made the switch a few years ago) this was studied as we have a large proportion of houses with resistance electric heating. Some of the cheapest electricity in Europe will do that. They showed that even in that situation, and with our cheap electricity the average house would still save 20% from switching to CFLs.
There are a range of reasons but the main ones are that lights don't come with thermostats. Thermostats are usually quite bad at taking such small and "noisy" added heaters into account, the heat ends up in the wrong place (i.e. the ceiling, where it doesn't add to convection) and the lighting season lasts longer than the heating season to name a few.
Now, I live in a house with district heating (because it came with a nice 100Mbps fiber), and I made the switch several years ago and I don't miss incandescents one bit. Just not having to change them all the bloody time and not having the armatures burn out from excessive temperatures makes getting rid of them worthwhile to me.
"Profiling" is a form of rational statistical analysis with a big social problem attached. If you have a known population of people with a propensity to behave in a certain way, then the rational thing to do is to look closely at that population.
No. Unfortunately that's not true. Profiling works for very small groups and types of behaviour, or groups and behaviours with a high degree of certainty. I.e. people standing close to the shelf at the supermarket and are glancing furtively left and right are probably shoplifters (specific behaviour that is not common among non-shoplifters), or "don't swim with crocodiles" (they'll try and eat you almost every time).
None of this is true when it comes to terrorism. Especially when you take the base-rate fallacy into account. Even if all terrorists to date are Arab males age 18-40 (for the sake of argument as that's not true by a long shot), looking at that group exclusively won't catch you any more terrorists since almost none of the Arab males age 18-40 are actually terrorists. Terrorism is just too uncommon. Even though you'll increase your relative certainty by just looking at the aforementioned Arab males, your probability in absolute terms will still be so close to zero as to make the whole endeavour useless. And that's even ignoring terrorist organisations identifying this fact and actively recruiting operatives that don't fit that profile.