Over here in Netherlands all ADSL providers have 12 month contract terms. Getting yourself an ADSL connection takes only 5 days, but getting rid of it can take 364 days if you're unlucky. My provider (xs4all.nl) says that the customer may cancel the contract upon price changes, but you'll have to check their website to find out about that in advance. Funny thing is, they used to have a 'fair use' policy, but since they don't enforce that anymore since there were so few excessive users.
I've always had a suspicion about them [earbud headphones] negatively affecting hearing, and recent studies back up my natural skepticism.
Can you clarify this? Regarding hearing damage, I'd say there shouldn't be a difference whether you listen to 85 dB (A) through earbuds, large headphones, or loudspeakers. However, you need less acoustical power with earbuds since they are closer to the eardrum, so if other people can hear your earbuds, that's a much worse sign than if other people can hear your over-ear headphones.
I don't use headphones and don't crank it up to the point my ears hurt,
My point was that 85 dB(A) is already damaging even though it doesn't sound very loud, let alone hurt one's ears. But your criterium that you want to be able to have a conversation over the music sounds reasonable.
For your information: I tested with a decibel meter how loud 70 dB(A) and 85 dB(A) are on a headphone. Well, 85 dB sounds to me like a nice listening volume, and someone sitting very close to you in the train might even hear some noise escaping from your headphone. (I used an over-ear open headphone). It boggles my mind what people in the train are doing to their ears when I hear their music coming out of their earbuds over the background noise from 3 meters distance.
As you can guess, 70 dB is actually quite soft. It might work in a quiet environment, but anywhere else you will clearly hear environmental sounds.
if they have foolishly agreed to supply you with a certain level of connectivity regardless of what you are using it for, then they cannot simply turn around and say "oops, we've changed our minds
Isn't there usually a clause like "The provider can change the conditions; in such a case the customer is allowed to terminate the agreement without the normal notice period"?
IIRC flourescent lamps are more efficent at producing light when run on RF AC compared with AF AC.
The main reason is that the power supply can be much smaller when running at 10 kHz or so compared to 50 Hz. In the latter case, it is a ballast in series with the tube, consisting of a big and heavy induction coil. In the former, it is more like a switching power supply. More expensive components (at least if you only need to convert a few watts), but also much smaller. RF can mean anything between 3 Hz and 300 GHz.
bulb manufacturers don't use the same filament precicely because it lasts too long
It's much more down to earth: there's a simple relationship between light yield and lifetime (from wikipedia:
Light output is approximately proportional to V^3.4
Power consumption is approximately proportional to V^1.6
Lifetime is approximately inversely proportional to V^16
More light for your watt means the bulb burns out more quickly. They are now tuned for 1000 hours, which -mind you- means about $10 in electricity during the lifetime. If you want to increase the lifetime, put it on a dimmer.
According to Wikipedia, http://en.wikipedia.org/wiki/Lasik">3 to 6% of the Lasik patients still have complications after 6 months... You seem to be the one out of twenty with bad luck.
(I personally would not take a 1:20 chance to spoil my eyesight, however myopic I am.)
After having your teeth drilled without Novacaine it's understandable that you're suffering from memory loss or blocking out the trauma as previously reported
Come on, I have plenty of fillings and almost all of them have been done without anesthesia. Only when they extracted the wisdom teeth and when they had to work for 60 minutes to place a crown, I asked for anesthesia. Actually, with the wisdom teeth I didn't have an option and with the crown I'm still not sure that it was necessary. On the other hand, I tried eating a bacon sandwich while the anesthesia was still working (two hours afterwards) and I started chewing my tongue which I didn't notice before I could taste the blood on the left side of the tongue.
Yes, it hurts when there is only a millimeter of hard tissue between the drill and the nerves. But the bone itself does not contain any nerves and most of the drilling is just a lot of annoying noise. The time it actually hurts is less than a minute. I normally try to solve calculus problems in my head to distract myself from the pain.
Nothing beats being able to talk, smile, drink and eat directly after the dentist takes his tools out of your mouth, rather than have a numb and tingling feeling for 3-4 hours.
I was referring to your remark about 'reconstructing the signal from the beating', where you appeared to be suggesting that that is impossible. My apologies for misunderstanding you.
Re microphones: see the specs for the Neumann U87 (a classical high-end microhone) on the manufacturer's website:
Where do you get the idea that in the old days, microphones could handle high frequencies much better than now?
Apart from the technology, from psychoacoustic research it is known that frequencies above 16-18 kHz contribute extremely little to the listening experience, i.e., music with the range 18-22 kHz filtered out is for most people indistinguishable in double-blind tests from music with that range included. (Although it depends on whether the sound card is resampling the signal from 44 to 48 kHz, producing aliasing along the way) At least that is the picture I get from reading on hydrogenaudio.org.
No amount of digital processng or massaging can recover information that is entirely in between the actual sampling moments, without the sound being so long and periodic that its remnants are eventually picked up in the beats with the sampling rate, and No amount of digital processng or massaging can recover information that is entirely in between the actual sampling moments, without the sound being so long and periodic that its remnants are eventually picked up in the beats with the sampling rate, and the anti-aliasing filters normally wipe that right out.the anti-aliasing filters normally wipe that right out.
That's not the real problem. As long as the signal before DA conversion did not contain any frequency components above 22.05 kHz (the Nyqvist frequency for CD audio), it is perfectly possible to fully recover that information. For more realistic DSPs of the kind used in audio DACs, the cut-off has to be a bit below the Nyqvist frequency, i.e. 20 kHz.
The problem is that any noise above the Nyqvist frequency before the AD conversion will cause aliasing into the audible domain. That's why it's a good thing to do sampling during recording at 96 or 192 kHz. Then you can use a very steep digital lowpass filter before downsampling to 44.1 kHz.
The statement about the high-frequency response of LPs may or may not be true. However, the microphones used in those recordings most certainly did not have any significant frequency response above 20 kHz, so there wasn't any high-frequency information to record other than electronic noise.
I think you'll find that it wasn't the microphone that was picking up that 15KHz signal, but much more likely the mic cable,
Why would that be? According to the response curve of the microphone, it can handle up to 20 kHz (-4 dB) and the recorded signal played through headphones sounds similar to the live television set. Also, I have never noticed that it picks up hum and other non-acoustic signals. This is not a cheap mic like the ones you get for a couple of dollars in a computer store. (If you're interested, it's an Audio Technica AT-853R hooked up to an M-Audio Audiophile 24/96 soundcard)
Its the magnetic coils controlling the flyback that induce
minute occilations in themselves and surrounding metal that cause it
I believe.
Then the question is: what is the difference in a construction between a computer CRT and a television CRT that causes the former to be relatively silent? I always assumed that it is the deflector coils that are driven at the hsync frequency. Those coils are big and actually driven at that kind of frequency.
So to dissolve this dispute, I just did an experiment. With a good microphone, I recorded my TV set and then I looked at the waveform in Audacity. I counted 79+/-0.2 oscillations over 5051 microseconds, which gives an acoustic frequency of 15640 +/- 40 Hz for this PAL television. The PAL standard is 625 lines at 50 Hz, factor 2 interleaved, so the hsync frequency is 625*50/2 = 15625 Hz. This is within the margin of error equal to the observed acoustic frequency, which provides strong support for the hypothesis of the horizontal deflection coils causing the high-pitched tone.
For comparison, NTSC is 525 lines at 60/2 Hz, which gives 15750 Hz.
Note that I used an electret microphone which is not sensitive to the magnetic field emitted by the deflection coils.
CRT tubes generally give off a frequency of about 17Khz
Not in general. CRT television sets may be around that frequency (I think PAL is at 16 kHz, don't know NTSC), but computer monitors are usually in the 60--80 kHz range, except for very old VGA screens that were 31.5 kHz.
I've read claims that the high-voltage circuit for driving the electron gun also produces high-pitched sound, but it is rare that I hear a computer CRT while I often hear a the high buzz from a television before I actually hear the sound from the program. (32 years old and not abusing my ears with loud mp3 players)
It's a good thing to adapt pronunciation to the local language in everyday life, but it doesn't harm to write it correctly. Suppose I wanted to know more about this person:
Google:
Google 1: Results 1 - 10 of about 173 for geir ivarsoy.
Google 2: Results 1 - 10 of about 10,300 for geir ivarsøy.
Temperature is, by definition, the average velocity of the molecules.
Show me a physics textbook that claims such a definition. Temperature is defined in terms of entropy change per unit of energy added to the system. As you may know, entropy is not just the average velocity.
Are you trying to correct me or not... I can't tell... but friction doesn't exist at a molecular level.
The reorientation time of water molecules (with or without a forcing microwave field) is pretty close to what you would expect based on treating water molecules as spheres in a viscous medium. But yes, on a molecular scale the friction consists of dissipating the energy into low-frequency collective modes. In the case of water, you need to dissociate hydrogen bonds (which are not considered molecular bonds) with neigboring molecules if you want to reorient a water molecule. This appears as a resistance against reorientation, which you may call friction.
Microwaves get the water molecules to have a greater average velocity (it's temperature goes up).
You are confused with temperature in the gas phase. In the condensed phase, the thermal energy is in low-frequency collective excitations (i.e. phonons in crystalline materials) where the velocity of individual particles is not very well defined.
Any mechanism that could potentially be unknown would be able to occur from background radiation or sunlight.
The background radiation on earth in the microwave range is completely neglegible to what is emitted by a mobile phone. Look up the Planck equation for black-body radiation.
Disclaimer: IAAPHD (I am a Ph.D., on the topic of infrared spectroscopy of water)
Your list is full of errors. Is that physics lab of yours in high school? Don't believe that you know everything about physics just because you passed your high school exam.
1. Radiation that has the resonant frequency of molecular bonds can give a LOT of energy to the molecules that make us up. That's how a microwave oven works. The EM waves have the same frequency as the resonant frequency for water molecules.
No, vibrational resonances in molecular bonds are in the range 30--100 THz (that is a factor 20,000 above the 2.4 GHz in a microwave oven). And exciting a vibrational mode is not enough to break a molecule. Electronic resonances are even higher, in the visible light. A kitchen microwave works by forcing the water molecules to rotate. The resulting friction is what appears as heat.
2. Radiation can kick off electrons (beta particles) or protons (alpha particles).
This is utter nonsense. Alpha particles are helium nuclei (not protons) that are emitted by the nucleus in certain types of radioactive decay. Electromagnetic radiation is not going to trigger this type of decay. Same for beta decay. However, X-rays (that is EM radiation with a wavelength that is more than 100 times shorter than visible light) can kick out electrons from the shells of an atom, but you don't call that beta decay. But yes, removing electrons from the molecules in your body is unhealthy.
Anyway, just because you cannot think of a mechanism for microwaves to be harmful doesn't mean that there is no such mechanism. For example, a photon of visible light carries way too little energy to synthesize an ATP molecule. Still, plants do manage to produce ATP in photosynthesis because they have a highly complicated molecular light-harvesting system that collects the energy from many photons in order to synthesize a single ATP molecule. Something like that could happen with microwaves: with the help of enzymes, living cells produce all kinds of unstable molecules as an intermediate step that leads to the desired reaction product. In this unstable state, the small energy of a microwave photon might be enough to trip the reaction into the wrong direction.
Don't understand me wrong: I personally don't believe that mobile phone radiation is something to worry about, especially given all the other well-known risks in life that we take(*), but that's not a reason to dismiss the risk based on a wrong understanding of physics.
(*)other risks in life: overweight, excessive consumption of sugar and saturated fats, smoking, participating in traffic, radon gas in houses from rocky soils, sunburn, dangerous situations at home, etc., etc..
So we could have concert quality sound with only one speaker, at least according to this product site stereolith.
As far as I can tell, it is a stereo pair of loudspeakers encapsulated in a single box, with the speakers radiating sideways. Nice idea, but it means that the sound reaches your ear after reflecting from the walls, which are outside the control of the speaker manufacturer. You could in principle create a pleasant effect this way, but only if the stereo track was recorded and mixed with this playback system in mind.
Stereo sound boils down to this: a human has two ears, so in principle you need two sound channels to record spatial information. Unfortunately, when you playback the music through loudspeakers, the two separate channels are mixed with each other and with unpredictable room reflections. If you wanted to recreate the full sound field as it was during the performance, you would need to cover walls, floor and ceiling with loudspeakers, and make the recording with a corresponding llarge number of tracks. This is not practical, so stereo recordings are mixed such that they will sound reasonable with two loudspeakers, one 30 degrees to your left and the other one 30 degrees to your right, both at equal distances. You don't need a center channel since the part of the stereo signal that is equal for the left and right speakers will appear right in between. However, this only works if the speakers are at exactly symmetric locations with respect to the listener. If you are sitting on the couch with three persons, then only the one in the middle will have agreeable stereo sound, while the one sitting on the left will mainly hear the left speaker and the one on the right the right speaker. So here is the advantage of having more than two speakers: the listener position becomes less critical when you add a central speaker. With the additional two side speakers (numbers 4 and 5) you can widen the sound stage without creating a hole in the middle.
Anyway, as long as recordings are mixed for normal stereo configuration, it does not make sense to change the playback configuration like with the one-speaker system, since what you hear will not be what the sound engineer had in mind during the mixing process. (Of course, it might be that you just like the distorted stereo image better, but now it is no longer a matter of the objective quality of the reproduction.) You can in principle upgrade a stereo signal to a 5-speaker signal to make the listener position less critical.
I've only ever seen one real 5.1 setup with proper speaker placement. In the "ideal" setups you see in advertisements, the couch is always in the middle of the room, with the rear speakers in the back where they belong.
No, with 5.1 the rear speakers are on the SIDE of the listening position. That's the whole idea of 7.1, that you get speakers behind the listener.
Standardized connectors. It's one thing to have a variety of devices that use different voltages, but having a variety of 5V devices each of which uses its own style of plug & jack defies all common sense.
Actually there is a standard that relates the plug size to the voltage, in order to prevent you from frying a 3 V device with a 12 V power supply:
EIAJ RC-5320. Unfortunately manufacturers don't seem to bother very much.
I'm guessing, at that speed, the rock will just pass through your ship creating a nice cylindrical hole. Any thoughts?
From the point of view of the rock, all that would happen is that a solid object inside that spaceship is going to create a nice cylindrical hole in the nonmoving rock.
Come on, even a few electrons in vacuum that slam into a solid target at a velocity of c/2 (about 10^5 eV) will generate loads of X-rays by kicking out electrons that are in the deepest shells inside the atoms. With heavier particles such as atomic nuclei, the electrons around the nuclei will certainly not be able to keep the projectile nuclei out. It is likely that you will get some nuclear reactions as the atoms constituting the rock literally go through the atoms constituting your spaceship.
Design your site in valid XHTML / HTML 4.0.... create a custom stylesheet just for them.
That is a myth. A mobile phone normally has a 1.5 inch screen of 80x100 or 100x150 pixels, capable of displaying 8-12 lines of 20-30 characters (i.e. 150 to 360 characters). With CSS you are not going to be able to make a normal webpage with 10 kB of text to be practical on such a small screen, simply because you need to scroll down 50 screens just to see the bare text and links. Apart from that, these users might be paying EUR 0.01 for every kB of data transfer.
If you want to be accessible by a mobile phone rather than a PDA you have to redesign the whole site (see for example slashdot.org/palm).
Actually, my phone won't even display a page if it is more than about 2 kB, HTML tags included. I use it to read the news headlines when in the train and sometimes to look up something on the web through the Google WML proxy. Unfortunately, Google won't deal with interactive websites, such as dictionaries and public transport time tables, so that's IMO where it pays off most to build a mobile-friendly site: information services that one could need while traveling.
The real solution would be to get off your lazy ass and hit the power switch when you are done watching instead of turning the TV off with the remote.
What I understand is that most American TVs don't have a hard power switch. I think the better solution is to have two separate transformers. A small one dimensioned for the standby circuitry only and a big one for the rest of the electronics, one that is switched off during standby. Losses in a transformer are for a large part independent of the load, so a 60 VA transformer could be 90% efficient at full rating (with 6 W loss), but it might still do 5 W loss when it is idle. (Numbers made up, but you can notice that transformers tend to be warm whether they are used or not)
What I don't understand about this whole thread is that everybody is talking about whether marihuana should be legal or not. It is the same species, but the strains that are cultivated for fiber production are completely different from those for the drugs. If you didn't know: pot consists of the unpollinated flowers of female plants. Hemp plants for the fibers are both males and females and they contain a completely negligible amount of THC (the active compound of the drug). If you tried to hide drug-grade plants between the fiber-grade plants, you would need to prevent pollination (which would spoil the drugs), which is nearly impossible since they are pollinated by wind. Also, the drug-grade and fiber-grade plants look different, so hiding them wouldn't even be that easy.
Anyone know why they don't just burn natural gas or coal at the plants for heat instead?
Aluminium is produced from ore by electrolysis, i.e. by passing a current through molten aluminium ore. Quote from Wikipedia:
Aluminium electrolysis with the Hall-Héroult process consumes a lot of energy, but alternative processes were always found to be less viable economically and/or ecologically. The world-wide average specific energy consumption is approximately 15±0.5 kilowatt-hours per kilogram of aluminium produced (52 to 56 MJ/kg). The most modern smelters reach approximately 12.8 kWh/kg (46.1 MJ/kg).
Slashdot Mirror
Over here in Netherlands all ADSL providers have 12 month contract terms. Getting yourself an ADSL connection takes only 5 days, but getting rid of it can take 364 days if you're unlucky. My provider (xs4all.nl) says that the customer may cancel the contract upon price changes, but you'll have to check their website to find out about that in advance. Funny thing is, they used to have a 'fair use' policy, but since they don't enforce that anymore since there were so few excessive users.
Can you clarify this? Regarding hearing damage, I'd say there shouldn't be a difference whether you listen to 85 dB (A) through earbuds, large headphones, or loudspeakers. However, you need less acoustical power with earbuds since they are closer to the eardrum, so if other people can hear your earbuds, that's a much worse sign than if other people can hear your over-ear headphones.
I don't use headphones and don't crank it up to the point my ears hurt,
My point was that 85 dB(A) is already damaging even though it doesn't sound very loud, let alone hurt one's ears. But your criterium that you want to be able to have a conversation over the music sounds reasonable.
Decrease in hearing with aging is for a large part the cumulative effect of exposure to noise: It has been demonstrated that the most important factor of hearing degradation is not aging alone, but rather the cumulative long-term exposure to environmental and occupational noise that create the harm The standard guideline of 40 h/week at 85 dB(A) is way too lax from a medical point of view; 70 dB(A) (30 times lower acoustic power) would be more reasonable. So you yourself can for a great part affect how much of your hearing you will be losing.
For your information: I tested with a decibel meter how loud 70 dB(A) and 85 dB(A) are on a headphone. Well, 85 dB sounds to me like a nice listening volume, and someone sitting very close to you in the train might even hear some noise escaping from your headphone. (I used an over-ear open headphone). It boggles my mind what people in the train are doing to their ears when I hear their music coming out of their earbuds over the background noise from 3 meters distance.
As you can guess, 70 dB is actually quite soft. It might work in a quiet environment, but anywhere else you will clearly hear environmental sounds.
Isn't there usually a clause like "The provider can change the conditions; in such a case the customer is allowed to terminate the agreement without the normal notice period"?
The main reason is that the power supply can be much smaller when running at 10 kHz or so compared to 50 Hz. In the latter case, it is a ballast in series with the tube, consisting of a big and heavy induction coil. In the former, it is more like a switching power supply. More expensive components (at least if you only need to convert a few watts), but also much smaller. RF can mean anything between 3 Hz and 300 GHz.
It's much more down to earth: there's a simple relationship between light yield and lifetime (from wikipedia:
- Light output is approximately proportional to V^3.4
- Power consumption is approximately proportional to V^1.6
- Lifetime is approximately inversely proportional to V^16
More light for your watt means the bulb burns out more quickly. They are now tuned for 1000 hours, which -mind you- means about $10 in electricity during the lifetime. If you want to increase the lifetime, put it on a dimmer.(I personally would not take a 1:20 chance to spoil my eyesight, however myopic I am.)
Come on, I have plenty of fillings and almost all of them have been done without anesthesia. Only when they extracted the wisdom teeth and when they had to work for 60 minutes to place a crown, I asked for anesthesia. Actually, with the wisdom teeth I didn't have an option and with the crown I'm still not sure that it was necessary. On the other hand, I tried eating a bacon sandwich while the anesthesia was still working (two hours afterwards) and I started chewing my tongue which I didn't notice before I could taste the blood on the left side of the tongue.
Yes, it hurts when there is only a millimeter of hard tissue between the drill and the nerves. But the bone itself does not contain any nerves and most of the drilling is just a lot of annoying noise. The time it actually hurts is less than a minute. I normally try to solve calculus problems in my head to distract myself from the pain.
Nothing beats being able to talk, smile, drink and eat directly after the dentist takes his tools out of your mouth, rather than have a numb and tingling feeling for 3-4 hours.
Re microphones: see the specs for the Neumann U87 (a classical high-end microhone) on the manufacturer's website:
- Neumann U87 historical scanned specifications (pdf): 20-16,000 Hz.
- Modern Neumann U87 Ai specifications: 20-20,000 Hz.
Where do you get the idea that in the old days, microphones could handle high frequencies much better than now?Apart from the technology, from psychoacoustic research it is known that frequencies above 16-18 kHz contribute extremely little to the listening experience, i.e., music with the range 18-22 kHz filtered out is for most people indistinguishable in double-blind tests from music with that range included. (Although it depends on whether the sound card is resampling the signal from 44 to 48 kHz, producing aliasing along the way) At least that is the picture I get from reading on hydrogenaudio.org.
That's not the real problem. As long as the signal before DA conversion did not contain any frequency components above 22.05 kHz (the Nyqvist frequency for CD audio), it is perfectly possible to fully recover that information. For more realistic DSPs of the kind used in audio DACs, the cut-off has to be a bit below the Nyqvist frequency, i.e. 20 kHz.
The problem is that any noise above the Nyqvist frequency before the AD conversion will cause aliasing into the audible domain. That's why it's a good thing to do sampling during recording at 96 or 192 kHz. Then you can use a very steep digital lowpass filter before downsampling to 44.1 kHz.
The statement about the high-frequency response of LPs may or may not be true. However, the microphones used in those recordings most certainly did not have any significant frequency response above 20 kHz, so there wasn't any high-frequency information to record other than electronic noise.
Why would that be? According to the response curve of the microphone, it can handle up to 20 kHz (-4 dB) and the recorded signal played through headphones sounds similar to the live television set. Also, I have never noticed that it picks up hum and other non-acoustic signals. This is not a cheap mic like the ones you get for a couple of dollars in a computer store. (If you're interested, it's an Audio Technica AT-853R hooked up to an M-Audio Audiophile 24/96 soundcard)
Then the question is: what is the difference in a construction between a computer CRT and a television CRT that causes the former to be relatively silent? I always assumed that it is the deflector coils that are driven at the hsync frequency. Those coils are big and actually driven at that kind of frequency.
So to dissolve this dispute, I just did an experiment. With a good microphone, I recorded my TV set and then I looked at the waveform in Audacity. I counted 79+/-0.2 oscillations over 5051 microseconds, which gives an acoustic frequency of 15640 +/- 40 Hz for this PAL television. The PAL standard is 625 lines at 50 Hz, factor 2 interleaved, so the hsync frequency is 625*50/2 = 15625 Hz. This is within the margin of error equal to the observed acoustic frequency, which provides strong support for the hypothesis of the horizontal deflection coils causing the high-pitched tone.
For comparison, NTSC is 525 lines at 60/2 Hz, which gives 15750 Hz.
Note that I used an electret microphone which is not sensitive to the magnetic field emitted by the deflection coils.
I've read claims that the high-voltage circuit for driving the electron gun also produces high-pitched sound, but it is rare that I hear a computer CRT while I often hear a the high buzz from a television before I actually hear the sound from the program. (32 years old and not abusing my ears with loud mp3 players)
Google:
Google 1: Results 1 - 10 of about 173 for geir ivarsoy.
Google 2: Results 1 - 10 of about 10,300 for geir ivarsøy.
Show me a physics textbook that claims such a definition. Temperature is defined in terms of entropy change per unit of energy added to the system. As you may know, entropy is not just the average velocity.
The reorientation time of water molecules (with or without a forcing microwave field) is pretty close to what you would expect based on treating water molecules as spheres in a viscous medium. But yes, on a molecular scale the friction consists of dissipating the energy into low-frequency collective modes. In the case of water, you need to dissociate hydrogen bonds (which are not considered molecular bonds) with neigboring molecules if you want to reorient a water molecule. This appears as a resistance against reorientation, which you may call friction.
Microwaves get the water molecules to have a greater average velocity (it's temperature goes up).
You are confused with temperature in the gas phase. In the condensed phase, the thermal energy is in low-frequency collective excitations (i.e. phonons in crystalline materials) where the velocity of individual particles is not very well defined.
Any mechanism that could potentially be unknown would be able to occur from background radiation or sunlight.
The background radiation on earth in the microwave range is completely neglegible to what is emitted by a mobile phone. Look up the Planck equation for black-body radiation.
Disclaimer: IAAPHD (I am a Ph.D., on the topic of infrared spectroscopy of water)
1. Radiation that has the resonant frequency of molecular bonds can give a LOT of energy to the molecules that make us up. That's how a microwave oven works. The EM waves have the same frequency as the resonant frequency for water molecules.
No, vibrational resonances in molecular bonds are in the range 30--100 THz (that is a factor 20,000 above the 2.4 GHz in a microwave oven). And exciting a vibrational mode is not enough to break a molecule. Electronic resonances are even higher, in the visible light. A kitchen microwave works by forcing the water molecules to rotate. The resulting friction is what appears as heat.
2. Radiation can kick off electrons (beta particles) or protons (alpha particles).
This is utter nonsense. Alpha particles are helium nuclei (not protons) that are emitted by the nucleus in certain types of radioactive decay. Electromagnetic radiation is not going to trigger this type of decay. Same for beta decay. However, X-rays (that is EM radiation with a wavelength that is more than 100 times shorter than visible light) can kick out electrons from the shells of an atom, but you don't call that beta decay. But yes, removing electrons from the molecules in your body is unhealthy.
Anyway, just because you cannot think of a mechanism for microwaves to be harmful doesn't mean that there is no such mechanism. For example, a photon of visible light carries way too little energy to synthesize an ATP molecule. Still, plants do manage to produce ATP in photosynthesis because they have a highly complicated molecular light-harvesting system that collects the energy from many photons in order to synthesize a single ATP molecule. Something like that could happen with microwaves: with the help of enzymes, living cells produce all kinds of unstable molecules as an intermediate step that leads to the desired reaction product. In this unstable state, the small energy of a microwave photon might be enough to trip the reaction into the wrong direction.
Don't understand me wrong: I personally don't believe that mobile phone radiation is something to worry about, especially given all the other well-known risks in life that we take(*), but that's not a reason to dismiss the risk based on a wrong understanding of physics.
(*)other risks in life: overweight, excessive consumption of sugar and saturated fats, smoking, participating in traffic, radon gas in houses from rocky soils, sunburn, dangerous situations at home, etc., etc..
As far as I can tell, it is a stereo pair of loudspeakers encapsulated in a single box, with the speakers radiating sideways. Nice idea, but it means that the sound reaches your ear after reflecting from the walls, which are outside the control of the speaker manufacturer. You could in principle create a pleasant effect this way, but only if the stereo track was recorded and mixed with this playback system in mind.
Stereo sound boils down to this: a human has two ears, so in principle you need two sound channels to record spatial information. Unfortunately, when you playback the music through loudspeakers, the two separate channels are mixed with each other and with unpredictable room reflections. If you wanted to recreate the full sound field as it was during the performance, you would need to cover walls, floor and ceiling with loudspeakers, and make the recording with a corresponding llarge number of tracks. This is not practical, so stereo recordings are mixed such that they will sound reasonable with two loudspeakers, one 30 degrees to your left and the other one 30 degrees to your right, both at equal distances. You don't need a center channel since the part of the stereo signal that is equal for the left and right speakers will appear right in between. However, this only works if the speakers are at exactly symmetric locations with respect to the listener. If you are sitting on the couch with three persons, then only the one in the middle will have agreeable stereo sound, while the one sitting on the left will mainly hear the left speaker and the one on the right the right speaker. So here is the advantage of having more than two speakers: the listener position becomes less critical when you add a central speaker. With the additional two side speakers (numbers 4 and 5) you can widen the sound stage without creating a hole in the middle.
Anyway, as long as recordings are mixed for normal stereo configuration, it does not make sense to change the playback configuration like with the one-speaker system, since what you hear will not be what the sound engineer had in mind during the mixing process. (Of course, it might be that you just like the distorted stereo image better, but now it is no longer a matter of the objective quality of the reproduction.) You can in principle upgrade a stereo signal to a 5-speaker signal to make the listener position less critical.
No, with 5.1 the rear speakers are on the SIDE of the listening position. That's the whole idea of 7.1, that you get speakers behind the listener.
Actually there is a standard that relates the plug size to the voltage, in order to prevent you from frying a 3 V device with a 12 V power supply: EIAJ RC-5320. Unfortunately manufacturers don't seem to bother very much.
From the point of view of the rock, all that would happen is that a solid object inside that spaceship is going to create a nice cylindrical hole in the nonmoving rock.
Come on, even a few electrons in vacuum that slam into a solid target at a velocity of c/2 (about 10^5 eV) will generate loads of X-rays by kicking out electrons that are in the deepest shells inside the atoms. With heavier particles such as atomic nuclei, the electrons around the nuclei will certainly not be able to keep the projectile nuclei out. It is likely that you will get some nuclear reactions as the atoms constituting the rock literally go through the atoms constituting your spaceship.
That is a myth. A mobile phone normally has a 1.5 inch screen of 80x100 or 100x150 pixels, capable of displaying 8-12 lines of 20-30 characters (i.e. 150 to 360 characters). With CSS you are not going to be able to make a normal webpage with 10 kB of text to be practical on such a small screen, simply because you need to scroll down 50 screens just to see the bare text and links. Apart from that, these users might be paying EUR 0.01 for every kB of data transfer.
If you want to be accessible by a mobile phone rather than a PDA you have to redesign the whole site (see for example slashdot.org/palm).
Actually, my phone won't even display a page if it is more than about 2 kB, HTML tags included. I use it to read the news headlines when in the train and sometimes to look up something on the web through the Google WML proxy. Unfortunately, Google won't deal with interactive websites, such as dictionaries and public transport time tables, so that's IMO where it pays off most to build a mobile-friendly site: information services that one could need while traveling.
What I understand is that most American TVs don't have a hard power switch. I think the better solution is to have two separate transformers. A small one dimensioned for the standby circuitry only and a big one for the rest of the electronics, one that is switched off during standby. Losses in a transformer are for a large part independent of the load, so a 60 VA transformer could be 90% efficient at full rating (with 6 W loss), but it might still do 5 W loss when it is idle. (Numbers made up, but you can notice that transformers tend to be warm whether they are used or not)
What I don't understand about this whole thread is that everybody is talking about whether marihuana should be legal or not. It is the same species, but the strains that are cultivated for fiber production are completely different from those for the drugs. If you didn't know: pot consists of the unpollinated flowers of female plants. Hemp plants for the fibers are both males and females and they contain a completely negligible amount of THC (the active compound of the drug). If you tried to hide drug-grade plants between the fiber-grade plants, you would need to prevent pollination (which would spoil the drugs), which is nearly impossible since they are pollinated by wind. Also, the drug-grade and fiber-grade plants look different, so hiding them wouldn't even be that easy.
Aluminium is produced from ore by electrolysis, i.e. by passing a current through molten aluminium ore. Quote from Wikipedia:
Aluminium electrolysis with the Hall-Héroult process consumes a lot of energy, but alternative processes were always found to be less viable economically and/or ecologically. The world-wide average specific energy consumption is approximately 15±0.5 kilowatt-hours per kilogram of aluminium produced (52 to 56 MJ/kg). The most modern smelters reach approximately 12.8 kWh/kg (46.1 MJ/kg).