>Now I don't believe that cell phones are dangerous. But the amount of energy microwaves carry has very little to do with that.
It has a lot to do with it. The mechanism you describe isn't possible for microwaves because the photons simply aren't energetic enough. The energy of a photon is proportional to its frequency - a 1GHz photon has energy of around 4 micro electron volts, a few orders of magnitude lower than molecular binding energies. Gamma ray photons of course have energies which are very large compared to the binding energy of molecules and will blast them apart.
Ouch. Mind you, when I was living in university halls of residence 4 years ago there was no broadband, and dialup was at a higher rate than BT (but not as bad as yours. 1.20 a *minute*? That really is taking the piss.) Those phone companies really shaft you, which is why I used a mobile for all my calls and lived without net access.
For what it's worth, broadband was late coming to the UK (it was first available to me a couple of years ago), but it's quite common now, and not too insanely priced. I pay 28 for 512k up and 256k down (bits per second, sadly), and that's at the higher end of the price range. Not particularly fast compared to the US broadband providers but at least there are no use restrictions or caps, I get 8 IP addresses and I can run whatever servers I like.
Good luck getting BT to respond to any faults, but that's another matter entirely...
> But.... assuming you didn't need a true geo sat (stationary), yes it could 'float' at the altitude if you could get up there.
No, it would drop. The reason geostationary satellites don't is that they're travelling very fast, as you said.
A satellite at that height doesn't have to be geostationary of course - it could be travelling at the appropriate speed but in the wrong direction.
Re:Good news for Mandrake users.
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Mandrake 9.2 RC1
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· Score: 1
My comment was really just a remark on some of the Gentoo zealots' claims (not referring to the original poster here), specifically the "compiling everything yourself good" one.
I tried Gentoo once. Spending days watching my system compile for a dubious performance increase doesn't seem much fun to me. How, exactly, does "compiling for your system" improve performance? Sure, you can select the optimizations you want, but that's not the same as optimizing for your system in particular.
Personally, I'll just trust Mandrake to do a decent job as standard rather than try Gentoo again. But each to their own.
Re:Good news for Mandrake users.
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Mandrake 9.2 RC1
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· Score: 1
> Plus, for added geek factor you compile everything from source. Everything.
>blic right of way or no, the railway does a (mostly) adequate job of getting people from A to B without killing anyone in the process.
Assuming "A" and "B" are city centres or the few areas conveniently close to a railway station. And even if they are, it's unlikely that a single train will go to both A and B. Only a very small fraction of my family's regular journeys can be reasonably achieved by public transport - not everyone lives in London. For what it's worth, I'd agree that cars in London are a nuisance.
The zeal with which some people will support such obnoxious, invasive schemes because they dislike the group targeted is truly depressing. Usually the target is illegal immigrants (ID cards and the like). Of course, motorists are a rather large group and I hope it's going to be more difficult getting this one through.
Your source there seems to say that a heat engine with the typical heat source/cold sink temperatures of a car engine can have a *maximum* efficiency of 48% (which is indeed just thermodynamics). It says nothing about the efficiency actually achieved, and I'd be very surprised if it was anywhere near 48%. (I'd heard around 20-30% , but don't quote me.)
>Students feeling oppressed? Yes. By the faculty/administration? Nope.
>Well, not anywhere NEAR the proportion of being intimidated by other students -- which this should provide a little help with.
That's exactly what I thought when I read about this. As someone who's suffered the sharp end of this, I'd have given anything to have cameras monitor the school. After all, bullies tend not to bully in front of teachers, and they rely on intimidating their victims into not saying anything.
Anything which help *this* problem is a good thing.
That may be so, but the fee is continuous. After 3 years you'll have paid far more than the box is actually worth and you'll *still* have to pay to use it. If you stop paying at any point it's no more useful than a standard Sky digibox. Besides, they charge about 250 for it which is in the same ballpark as non-Sky satellite receivers with such recording facilities built in.
25,000 out of 8 million isn't really that much considering it's been around for quite some time now.
An important difference being that with Sky+ you have to buy the box *and* pay a monthly subscription of 10. Of course, it's not taken off, as people rightly think that paying a monthly fee to use a piece of hardware you've bought outright is a ripoff. (The *only* thing you get for your money is the ability to use the recording features.)
Still, there are rumours that Sky are going to be dropping the charge in the Autumn. Perhaps Sky can't get away with anything after all.
I can't see how you could reasonably claim that gun control caused an increase in gun violence in Britain. Handgun ownership was low even before the ban, and restricted to use in sport - self-defence has not been a legally valid reason to own a gun in Britain for a *long* time, and you need to supply a good reason for wanting a firearms licence before you were allowed to own them. The guns were also required to be stored in locked cabinets, so weren't readily available for defensive purposes.
It would be rather more reasonable to suggest that the ban had no effect whatsoever on gun crime in the UK, and I'd agree with that.
As another poster commented, the microwave oven frequency isn't tuned to a resonance frequency of water molecules at all. The absorption of microwaves by the interaction of the water molecule's electric dipole with the field of the microwave works over a very wide range of frequencies. You wouldn't *want* a strong resonance - you don't want the microwaves to be all absorbed by the outside of the food after all, and the frequency used is definitely not a resonance.
I forgot to mention - if an experiment does contradict this, GR is in very serious trouble. So far, the direct tests of GR have been in the solar system (perihelion advance of Mercury, bending of light, radar echo delay from Venus and the like), where the fields are weak and relativistic effects are small, so more testing is definitely a good thing.
If an object is in free fall, which is the state of an orbiting object, any (local) experiment will behave in exactly the same manner as if it was floating in free space with no gravitational field. This is the principle of equivalence, one of the postulates of general relativity.
My point was that the indistinguishability of a gravitational field and an accelerating frame was true, but only over a region where the field strength doesn't change (i.e. locally). If it does, you can tell the difference. You refer to people hitting the ground after jumping off buildings, but in my example there was no force acting other than gravitation (in yours there was), and yet it was still possible to determine the existence of the gravitational field, which would be impossible in free fall if gravitation and acceleration were completely indistinguishable. You said that it had nothing to do with gravity, but what else could it have to do with? There are no other forces acting.(yes, I know GR doesn't consider gravity a force, but it's convenient to think of it that way here).
To call it "really basic physics" is a stretch too - the equivalence of gravitational and intertial mass isn't trivial by any means. GR would be in trouble if it wasn't true.
ecause your post isn't interesting or informative, its just plain wrong. Go pick up an elementary physics textbook. There is absolutely no physical difference between a strong gravitational field from a reference frame at rest and a weak one as experienced from an accellerating reference frame. General relativity goes as far as to say its absolutely impossible to differentiate between the two.
That's not true either... consider someone free-falling towards a black hole (or anything else with a strong gravitational field). The field at their feet will be stronger than the field at their head, because the strength of a gravitational field falls off with distance, so they'd be stretched by the tidal forces. If gravitational fields and accelerating frames were indistinguishable, he'd feel nothing. Utterly irrelevant for a rollercoaster of course.
(yes, it's true that it's impossible to tell the difference *locally*, but if it were true globally , the General Theory of Relativity wouldn't really have much to say).
So, good attempt at trying to look smart, but it didn't work, kid.
I'm sure the world would cringe more if a maniac became elected POTUS than if he were head of, say, some relatively non-threatening state like Papua New Guinea.
Indeed so. Thank goodness that's never going to happen.
Oh, hang on...
In the mid 90's, we were told that cable modems were a 'year away'. Funnily, we were told this in 96, 97, 98, and 99, when the trials started to roll out. A similar thing occured with DSL.
Odd, I'm sure I've been using this cable modem for a year. OK, so it was late compared to other countries, but it's here. (I know what you're saying though, I remember cable modem trials in 1996ish, nothing came of them though). Broadband still isn't available to everyone, but isn't that the case everywhere?
The price reductions are a big step, and seem to have had success - apparently Pipex have had a large increase in orders recently (and also this). It also means that ISPs can offer useful services (multiple static IPs and the like) for a reasonable price now, whereas before you'd be lucky to get it for less than 50 or 60 quid a month. *Big* improvement as far as I can see.
Yes, m in that case would be the mass of matter + antimatter (e.g. an electron-positron annihilation, each with rest mass 511 keV/c^2 would produce 1022 keV of energy - actually two 511 keV photons (gamma radiation)).
And no, you can't use your scheme. Conservation laws basically require matter-antimatter to be produced symmetrically, in pairs, so to create 1kg of antimatter, you'd also need to create 1kg of matter.
Since you asked, to produce 1g of antimatter you need 1.8 * 10^16 joules (because you make 1g of matter too). A lot. You get the same energy back when it annihilates.
Mass-energy equivalence is demonstrated all the time in particle accelerators, where particle-antiparticle pairs are formed by high-energy collisions. The threshold energies required are mc^2 (in the centre-of-mass frame, more beam energy than mc^2 is required for a stationary target because it recoils and carries some of the energy off). So, yes. matter + antimatter does indeed = lots of energy...
As for the stuff about warp theory... well, people have tried applying general relativity to find ways of travelling FTL, though without accepted success yet... have a search for Alcubierre (though it could be utter crap, I don't know enough about GR to comment!)
In this case he's got a point. At first I shared all my stuff over napster/gnutella, but as soon as anyone tried to upload something from me my download speed *plummeted*, from about 5kb/sec (this is on a 56k modem) to 0.5kb/s. Plus a dialup isn't permanent, and I'm not tying up my phone line when I'm not even on the internet.
If I had a connection which would allow normal internet use to be unaffected (or minimally affected) by people getting my files, I'd have no problems sharing, but there's no way I'd do it at the moment. It causes far too many problems.
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>Now I don't believe that cell phones are dangerous. But the amount of energy microwaves carry has very little to do with that.
It has a lot to do with it. The mechanism you describe isn't possible for microwaves because the photons simply aren't energetic enough. The energy of a photon is proportional to its frequency - a 1GHz photon has energy of around 4 micro electron volts, a few orders of magnitude lower than molecular binding energies. Gamma ray photons of course have energies which are very large compared to the binding energy of molecules and will blast them apart.
Ouch. Mind you, when I was living in university halls of residence 4 years ago there was no broadband, and dialup was at a higher rate than BT (but not as bad as yours. 1.20 a *minute*? That really is taking the piss.) Those phone companies really shaft you, which is why I used a mobile for all my calls and lived without net access.
For what it's worth, broadband was late coming to the UK (it was first available to me a couple of years ago), but it's quite common now, and not too insanely priced. I pay 28 for 512k up and 256k down (bits per second, sadly), and that's at the higher end of the price range. Not particularly fast compared to the US broadband providers but at least there are no use restrictions or caps, I get 8 IP addresses and I can run whatever servers I like.
Good luck getting BT to respond to any faults, but that's another matter entirely...
> But.... assuming you didn't need a true geo sat (stationary), yes it could 'float' at the altitude if you could get up there.
No, it would drop. The reason geostationary satellites don't is that they're travelling very fast, as you said.
A satellite at that height doesn't have to be geostationary of course - it could be travelling at the appropriate speed but in the wrong direction.
My comment was really just a remark on some of the Gentoo zealots' claims (not referring to the original poster here), specifically the "compiling everything yourself good" one.
I tried Gentoo once. Spending days watching my system compile for a dubious performance increase doesn't seem much fun to me. How, exactly, does "compiling for your system" improve performance? Sure, you can select the optimizations you want, but that's not the same as optimizing for your system in particular.
Personally, I'll just trust Mandrake to do a decent job as standard rather than try Gentoo again. But each to their own.
> Plus, for added geek factor you compile everything from source. Everything.
What about the compiler?
>blic right of way or no, the railway does a (mostly) adequate job of getting people from A to B without killing anyone in the process.
Assuming "A" and "B" are city centres or the few areas conveniently close to a railway station. And even if they are, it's unlikely that a single train will go to both A and B. Only a very small fraction of my family's regular journeys can be reasonably achieved by public transport - not everyone lives in London. For what it's worth, I'd agree that cars in London are a nuisance.
The zeal with which some people will support such obnoxious, invasive schemes because they dislike the group targeted is truly depressing. Usually the target is illegal immigrants (ID cards and the like). Of course, motorists are a rather large group and I hope it's going to be more difficult getting this one through.
Your source there seems to say that a heat engine with the typical heat source/cold sink temperatures of a car engine can have a *maximum* efficiency of 48% (which is indeed just thermodynamics). It says nothing about the efficiency actually achieved, and I'd be very surprised if it was anywhere near 48%. (I'd heard around 20-30% , but don't quote me.)
>Students feeling oppressed? Yes. By the faculty/administration? Nope.
>Well, not anywhere NEAR the proportion of being intimidated by other students -- which this should provide a little help with.
That's exactly what I thought when I read about this. As someone who's suffered the sharp end of this, I'd have given anything to have cameras monitor the school. After all, bullies tend not to bully in front of teachers, and they rely on intimidating their victims into not saying anything.
Anything which help *this* problem is a good thing.
That may be so, but the fee is continuous. After 3 years you'll have paid far more than the box is actually worth and you'll *still* have to pay to use it. If you stop paying at any point it's no more useful than a standard Sky digibox. Besides, they charge about 250 for it which is in the same ballpark as non-Sky satellite receivers with such recording facilities built in.
25,000 out of 8 million isn't really that much considering it's been around for quite some time now.
>Sounds very much like Sky+ in the UK
An important difference being that with Sky+ you have to buy the box *and* pay a monthly subscription of 10. Of course, it's not taken off, as people rightly think that paying a monthly fee to use a piece of hardware you've bought outright is a ripoff. (The *only* thing you get for your money is the ability to use the recording features.)
Still, there are rumours that Sky are going to be dropping the charge in the Autumn. Perhaps Sky can't get away with anything after all.
I can't see how you could reasonably claim that gun control caused an increase in gun violence in Britain. Handgun ownership was low even before the ban, and restricted to use in sport - self-defence has not been a legally valid reason to own a gun in Britain for a *long* time, and you need to supply a good reason for wanting a firearms licence before you were allowed to own them. The guns were also required to be stored in locked cabinets, so weren't readily available for defensive purposes.
It would be rather more reasonable to suggest that the ban had no effect whatsoever on gun crime in the UK, and I'd agree with that.
As another poster commented, the microwave oven frequency isn't tuned to a resonance frequency of water molecules at all. The absorption of microwaves by the interaction of the water molecule's electric dipole with the field of the microwave works over a very wide range of frequencies. You wouldn't *want* a strong resonance - you don't want the microwaves to be all absorbed by the outside of the food after all, and the frequency used is definitely not a resonance.
This seems to be one of those persistant myths...
I forgot to mention - if an experiment does contradict this, GR is in very serious trouble. So far, the direct tests of GR have been in the solar system (perihelion advance of Mercury, bending of light, radar echo delay from Venus and the like), where the fields are weak and relativistic effects are small, so more testing is definitely a good thing.
If an object is in free fall, which is the state of an orbiting object, any (local) experiment will behave in exactly the same manner as if it was floating in free space with no gravitational field. This is the principle of equivalence, one of the postulates of general relativity.
My point was that the indistinguishability of a gravitational field and an accelerating frame was true, but only over a region where the field strength doesn't change (i.e. locally). If it does, you can tell the difference. You refer to people hitting the ground after jumping off buildings, but in my example there was no force acting other than gravitation (in yours there was), and yet it was still possible to determine the existence of the gravitational field, which would be impossible in free fall if gravitation and acceleration were completely indistinguishable. You said that it had nothing to do with gravity, but what else could it have to do with? There are no other forces acting.(yes, I know GR doesn't consider gravity a force, but it's convenient to think of it that way here).
To call it "really basic physics" is a stretch too - the equivalence of gravitational and intertial mass isn't trivial by any means. GR would be in trouble if it wasn't true.
That's not true either... consider someone free-falling towards a black hole (or anything else with a strong gravitational field). The field at their feet will be stronger than the field at their head, because the strength of a gravitational field falls off with distance, so they'd be stretched by the tidal forces. If gravitational fields and accelerating frames were indistinguishable, he'd feel nothing. Utterly irrelevant for a rollercoaster of course. (yes, it's true that it's impossible to tell the difference *locally*, but if it were true globally , the General Theory of Relativity wouldn't really have much to say).
So, good attempt at trying to look smart, but it didn't work, kid.
Well, quite.
Indeed so. Thank goodness that's never going to happen. Oh, hang on...
Odd, I'm sure I've been using this cable modem for a year. OK, so it was late compared to other countries, but it's here. (I know what you're saying though, I remember cable modem trials in 1996ish, nothing came of them though). Broadband still isn't available to everyone, but isn't that the case everywhere? The price reductions are a big step, and seem to have had success - apparently Pipex have had a large increase in orders recently (and also this). It also means that ISPs can offer useful services (multiple static IPs and the like) for a reasonable price now, whereas before you'd be lucky to get it for less than 50 or 60 quid a month. *Big* improvement as far as I can see.
>I don't see a benifit especially in storage space >for the red laser format.
>
>Anybody have a reason other than politics?
Blue laser diodes are expensive and have a very short lifetime compared to red ones, at least at the moment.
Yes, m in that case would be the mass of matter + antimatter (e.g. an electron-positron annihilation, each with rest mass 511 keV/c^2 would produce 1022 keV of energy - actually two 511 keV photons (gamma radiation)).
And no, you can't use your scheme. Conservation laws basically require matter-antimatter to be produced symmetrically, in pairs, so to create 1kg of antimatter, you'd also need to create 1kg of matter.
Since you asked, to produce 1g of antimatter you need 1.8 * 10^16 joules (because you make 1g of matter too). A lot. You get the same energy back when it annihilates.
Mass-energy equivalence is demonstrated all the time in particle accelerators, where particle-antiparticle pairs are formed by high-energy collisions. The threshold energies required are mc^2 (in the centre-of-mass frame, more beam energy than mc^2 is required for a stationary target because it recoils and carries some of the energy off). So, yes. matter + antimatter does indeed = lots of energy...
As for the stuff about warp theory... well, people have tried applying general relativity to find ways of travelling FTL, though without accepted success yet... have a search for Alcubierre (though it could be utter crap, I don't know enough about GR to comment!)
In this case he's got a point. At first I shared all my stuff over napster/gnutella, but as soon as anyone tried to upload something from me my download speed *plummeted*, from about 5kb/sec (this is on a 56k modem) to 0.5kb/s. Plus a dialup isn't permanent, and I'm not tying up my phone line when I'm not even on the internet.
If I had a connection which would allow normal internet use to be unaffected (or minimally affected) by people getting my files, I'd have no problems sharing, but there's no way I'd do it at the moment. It causes far too many problems.