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What I said was correct, although simplified.

You are obviously misinterpreting what I said, as out of the multiple points you are attempting to make, only one applies to what I said.

ie: I said nothing about reflection generating the electrical signal. I know how cone cells work. OBVIOUSLY you must absorb SOMETHING to create a signal.

Now, to settle your misconception of the cone cells and what colors they pick up, if you look at the graph that the other poster provided, you will see what I was saying: that there ARE NO receptors which pick up RED, BLUE or GREEN at their peak sensitivity!

One receptor picks up a range from red to green, the other a range from reddish orange to purplish blue, the last one picks up from green to violet.

enjoy.

Ouch! I'm not sure where you got this (mis)information, but it is entirely incorrect.

The photoreceptors (cones) in our eyes are named for the colors they are sensitive to, not the colors they appear. The 'Red' photoreceptors in our eyes are most responsive to RED light, not cyan. If you pick up any book on vision or do a cursory google search you can find graphs showing the response curves for each type of cone and how they overlap in the visible frequency spectrum. See here for example.

Of course in much of our atmosphere, we definitely do not have pure, clear air. There are particulates, there are water droplets, there is all manner of crud. These particles are much more effective scatterers, and they are the primary targets of the instrument being tested. (The instrument name, CALIPSO, stands for Cloud Aerosol LIDAR and Infrared Pathfinder Satellite Observations, after all.)

Computer : one that computes
Compute : to determine especially by mathematical means.

Hardware(simplest form) can compute without software(exp).
Software(simplest form) can not computer without hardware.

So, i would say the hardware IS the computer, and software is whats computed.

Turkey does not lose mass to the vacuum (even water).
Turkey is a 11 cm radius sphere of density 1.0 (about the density of water) which puts it at just over 12 pounds.
Molar mass is 25: Water has a molar mass of 18, and in humans is about 65% of the body. use this as a guess as to the Turkey's water content, neglecting all other molecules the molar mass would be 18/.65=27.6. Subtract a fudge factor for other molecules (which are mostly much bigger, but there are some more molecules in there) and call the total molar mass 25. (smaller numbers here mean a larger total number of molecules estimate.)
Temperature of a cooked turkey should be about 355 K, as any cook who uses a Kelvin thermometer will tell you.
The emissivity is .5. This wild-assed guess is made because cooked turkey should be brown, but not black (which would be emissivity 1)

In addition, this computation in general assumes that the ambient temperature can be neglected, conduction and convection can be neglected (probably reasonable assumptions in earth orbit) and that the temperature of the turkey remains uniform throughout- this last is most problematic and is expected to result in underestimation of cooling time required.

Anyhow, this massive approximation results in:
After an hour (3600 seconds) our turkey is near room temperature (295 K)
After an hour and a half or so, our turkey reaches the freezing point of water and stops there for a while- it takes a lot of energy for water go from liquid to solid. (Our first assumption that the water did not escape as a gas implies some sort of airtight seal; water freezing near 273 K makes sense if the internal pressure is roughly 1 atmosphere)

If you google around the web, you'll see that LEDs are poised to become the primary source of lighting in coming years; they already last longer and can produce powerful lighting more easily than bulbs, so all that's left is for the cost to come down.

My thought is, monitors out of LEDs can wait until they're already tested and used in the mass market for lighting. Until then they'll be a poor choice for pretty much anything below Jumbotron proportions, and there's still a good lifespan for LCD technology besides.

But then, I'm thinking economically here.

It appears the Beeb has confused peak speed with average speed.

According to the US Department of Agriculture, the Great Circle distance from Paris to Tokyo is 6033 miles. Let's round that to 6000 mi. The speed of sound varies with temperature, but using 750mph makes the math easy (at aircraft altitudes, the speed of sound is closer to 700mph).

If it could hold the fuel, the Concorde at Mach 2 (1500mph) could do 6000 miles in four hours. If the EADS jet achieves Mach 4 (3000mph), it could do 6000 miles in two hours. If the entire distance were covered at cruising speed.

My impression (purely from being a passenger) is that it takes half an hour or so for a typical commercial airliner on a 1000 mile flight to reach cruising speed and altitude; the plane will then be at cruising speed for about 60 minutes, and then another 30 minutes is spent in deceleration. Of the 2 hours spent in the air, only half of the time is actually spent at crusing speed.

How long would it take for the EADS-SS to reach Mach 4? And how long would it take it to slow down from that speed to the typical 150mph (+/-) landing speed that current runways are designed for? I doubt the typical passenger is prepared for Michael Schumacher / John Force g-forces on takeoff and landing.

Let's say the EADS-SS takes 45 minutes to reach Mach 4, and another 45 minutes to drop back to landing speeds. Assuming linear acceleration and deceleration, that's an hour and a half spent at an average speed of 1500mph. So 2250 miles of the trip takes 1.5 hours. Transiting the remaining 3750 miles at Mach 4 (3000mph) would take another 1.25 hours, for a total trip of 2.75 hours. [Ignoring any ground taxi times or other delays.]

I would think, fuel-wise (which is basically the only marginal cost of airplane flight), that going from Mach 2 to Mach 4 is more expensive than going from Mach 1 to Mach 2. On the other hand, Mach 1 -> 2 is done in denser air than Mach 2 -> 4, so maybe not.

This could be a great question for a final exam in Engineering Analysis and Synthesis.

Quill essentially affirms Bellas Hess.

There's a four-prong "Complete Auto" test which has been used as a criterion for the validity of state taxes on interstate commerce:

1. The tax must be applied to an activity with a "substantial nexus" with the taxing state
2. The tax must provide fair apportionment between the states
3. The tax must not discriminate against interstate commerce
4. The tax must be fairly related to services provided by the taxing state

Relevant quotes from the cases:

State taxation falling on interstate commerce ... can only be justified as designed to make such commerce bear a fair share of the cost of the local government whose protection it enjoys.

... The Court has never held that a State may impose the duty of use tax collection and payment upon a seller whose only connection with customers in the State is by common carrier or the United States mail.

... If Illinois can impose such burdens, so can every other State, and so, indeed, can every municipality, every school district, and every other political subdivision throughout the Nation with power to impose sales and use taxes.

The very purpose of the Commerce Clause was to ensure a national economy free from such unjustifiable local entanglements. Under the Constitution, this is a domain where Congress alone has the power of regulation and control.

Other references:

Annette Nellen's Home Page, especially Timeline Review of Activities Related to Discussions on Internet Taxation

Sales and Use Taxation of Internet Transactions

In other news, Barnes & Noble Inc. has offered to buy back the shares of BN.com -- could this eventually mean BN.com will have to collect sales taxes on internet sales to all states which have Barnes & Noble retail stores?

http://hyperphysics.phy-astr.gsu.edu/hbase/electri c/ohmmic.html

Shouldn't you provide attribution for that?

VERY different reactor designs. The reactors that are being designed today have built-in safe guards to prevent any sort of meltdown condition. Those old style reactors in the 50s and 60s (when most accidents happened) where manually controlled and were extremely dangerous to operate. You'll note that these days the US has at least 2-3 dozen nuclear reactors steaming around the world, and yet no major accidents have been reported.

You might find this page interesting. It details many of the accidents that have occurred. Note the dates. We HAVE gotten better.

Easy :)
"Warmth" : presence of an extra compensation capacitor or high second order harmonic distortion :)
"Depth" : Frequency response above 70 Hz is without significant jumps/falls (compare graphs of "high rated speakers" :) )
"Presence" : Described in here :)

Pure zero resistance would prevent electric fields from entering a block of superconductor (the change in magnetic fields will induce eddy currents) to counter any change in the local magnetic field) and this effect is called perfect diamagnetism.

The Meissner effect is different: it's a phase change effect -- it takes energy to expel the magnetic field. If the magnetic field is strong enough, the material may never superconduct. In any case, the transition temperature T_c is actually a function of the local magnetic field.

Furthermore, if you boost the field enough, you can quench the superconductivity and initiate resistance heating -- it can get nasty with high currents. Is the magnetic expulsion perfect? Sometimes it is, and sometimes not, because of flux pinning.

Since we often want to use superconductors to either make high magnetic fields (like in magnetic resonance imagers) or to carry large currents (that induce high magnetic fields) the Meissner Effect, and the magnetic dependence of the transition temperature are important considerations for practical superconductors.

More specifically, you mean to write:

(1) H-2 + H-2 -> He-4 + gammas

Or,

(2) H-2 + gamma -> H-1 + n (We'll ignore the electrons)

And the alternate one you discuss is either:

(3) H-2 + H-2 -> He-3 + n + gamma

or

(4) H-2 + H-3 -> He-4 + n + gamma

(I believe this is the one the tokamak project is using. I'm inevitably wrong on this.)

His reaction, from the article description, is probably:

(5) H-1 + H-2 -> H-1 + H-1 + n

I have no evidence to back this up, other than the fact that they never spoke of Helium really being produced, and the lack of tritium in the discussions. By the way, we can also do a some calculations, to determine the Q-value of these reactions: (using This chart of the Nuclides Table .)

Q=(m_init-m_final)c^2 =>

(5) Q= -2.2 MeV In other words, These ionized atoms would have to be travelling quite fast. (It is endothermic after all.)

What about the ones that release energy? How fast do they have to be moving?

Well, from this page we're talking the temperature would have to be between 4 x 10^7 and 4 x 10^8 K, which is kinda hot. You may be able to make a lot of assumptions about the occasional fast moving particle using temperature distribution graphs.

There's useful web based app here which, using my previous assumptions, gives a total potential energy for the entire cable of 67 x 10^15 Joules

So, given 1 megaton is approx equal to 4x10^15. that still works out at about 16 megatonnes. The difference this time is that the calculation is of the potential energy due ot gravity of the cable. If it comes down - this is how much energy will be released.

As for speed, remember that different parts of the cable all want to travel at the orbital velocity for their height - so the earth's rotation will tend to wrap the cable around the equator, accellerating all the time as you pointed out. It might take days - I have no idea how to calculate it. I doubt it would take more than a week all told.

But my degree is in software, not hardware. Any rocket scientist want to set us both straight?

When you burn a cd does ambient light destroy the medium? No. Just like a strong enough light source (for example, the burning laser in your xDRW drive) could destroy or alter the data on it. There is not going to be a strong enough field to do this accidentally, the fields put off by electronics are too small to be of much concern. If there even was a problem, parity algorythms could be used the same way they are in larger magnetic media (RAID). It is certain that a stong enough magnetic field could depolarize the data but I doubt the field is that "loose". Furthermore a magnetic field is inversly proportional to the square of the distance to the source ( E~1/[R^2] ) which decays rather rapidly as the distance increases. Electronic devices may operate at a high frequency but the power (amplitude)is too low to low to generate the field that would be required. Electic/Magnetic Field Equations

question: Is that charge spoken of a static charge? If it is, how big is that charge compared to typical static charges?

A coulomb is just a certain number of electrons. Magnetic forces act on any charged particle in motion, so the units for the strength of a magnetic field are the amount of force on a certain number of charged particles moving at a certain speed.

How much is a coulomb? Besides saying that it's 16 billion billion (1.6e19) electrons, it's easier to think about what that amount of electrons will do:

If you raise one coulomb of electrons to 100 volts potential, and then let them pass through a light bulb over the course of one second, you would get 100 Watts of light+heat from that light bulb. To light the bulb continuously at that voltage, 1 coulomb per second of electrons needs to pass through it.

The handy name for coulombs per second, of course, is the ampere, or amp.

Really makes you think: some modern CPUs come close to using 100 watts of power, at, say, 3 volts. That's over 30 amperes of current, or somewhere on the order of 450 billion billion electrons being shoved through every second.

- Peter

They do indeed--but that has precious little to do with why the sky is (usually) blue. Refraction occurs when light passes from a medium with one refractive index into another, and bends in so doing. There are lots of websites on the topic. The amount of bending that occurs depends on the material and on the wavelength of the light. Typically, materials have a higher index of refraction for shorter wavelengths--this dependence of refractive index enables prisms to separate light into component colours.

The apparent colour of the sky depends not on refraction (air has an index of 1.003, only a shade more than vacuum's 1.000) so light bends very little passing through the atmosphere. The important effect is Rayleigh scattering. Light with shorter wavelengths is scattered much more strongly--red and yellow light from the sun follows a fairly direct path to the viewer, so the sun appears as a yellow disc. Blue light is scattered repeatedly by the atmosphere, resulting in a diffusely blue sky. Interestingly, if you take a long exposure photograph on a moonlit night, the sky will still show up as blue from scattered moonlight.

Incidentally, I would call the 'sky' blue, even though the gases of the atmosphere are (except around cities) colourless. That's the colour you see when you look up, in the direction of what a layperson would call the sky. Oh, and I am a physicist.

If you look at a blue ball through the edge of a prism and it looks red, is the ball still blue? I think so.

If you look at a 'blue' ball through the edge of a prism, it will look blue or black--if it reflected large amounts of red light, then it wouldn't appear blue without the prism in the first place.

I would call you a pedant, if you were right.

I would still call you a pedant--and a condescending one, at that--even though you're a little iffy on scattering of light. If you would like some further pedantry, I would be pleased to explain why the sky is red at sunset.

For the rest of us, RGB centered at our own visual peaks makes the most sense of any encoding scheme possible. Not only can we not see another color,

Not true. We can see colors that monitors can't display -- IIRC, mainly deep purples. Oh, of course, as long as we're using modern monitor technology with RGB additive, storing images in RGB makes perfect sense. However, in general, there are other more general schemes; wavelength+amplitude would be one, and CIE is an internationally accepted standard to describe human vision.

Ah, here we are. A little graph showing how much of the human vision RGB can't cover. Check it out!

but it wastes space in the image (ie, some optimal conversion function can, by physical necessity, reduce those four colors to an RGB triad indistinguishable from the original quartet by a normal human.

And more manipulation could reduce it to TWO numbers, related to wavelength and frequency. And even more could reduce it to two numbers related to the eye's response to wavelength and frequency. I don't think that's been done, but the CIE system reduces to three numbers.

More information does seem better, agreed. However, due to the physiological limitations of human vision, this scheme does not convey any more information, thus my biggest complaint. It seems everyone else missed this as nothing more than a meaningless marketing ploy.

I'm sure it's occurred to you that if you disagree with everyone else, it's sometimes possible that you're missing something.

So you all go out and buy this toy so you can brag about having "better" color, and I'll continue taking perceptually identical pics with my boring 'ol RGB cam that cost $800 less. :-)

We'll have to wait to see real reviews to make a judgement on this one -- the previews I've seen look very positive, regardless of filter technology. It looks like it's a substantial improvement on other cameras in the same price range.

-Billy

i think the + and - parts you are refering to is the pn junction.

What about the implications of people changing due to a Big Brother presence? Are we willing to make the classroom, which in some ways it is one of the most important structures in society a Panopticon? How can we pretend to respect computer privacy in society, but at the same time do this to what should be the cusp of free speech?

Shouldn't they be going for a NAND gate? Or a NOR gate?

The issue of American spelling of various words, has been of great interest to me this year, as I simultaneously start to write my PhD thesis and also learn the German language.

I live in New Zealand, yes one of those countries colonised by the great British empire. Here of course we write with the British spelling (ie. English spelling used by the rest of the world). However this is under threat from the ever prevalent American spelling, mostly due to the internet, and things like Microsoft Word and e-mail spell checkers defaulting to the US spelling (Yes I know how to change it but very many people do not - Actually I use LaTeX so this is a moot point for me). Teachers used to mark this alternative spelling quite harshly, but now I feel they are giving up.

This raised a few issues, for me mostly when I find information on the internet I am conscious to try with both spellings. I got caught out in Bugzilla with this.

Interestingly the changes the US have made to the language not only include spelling changes, But also grammatical. An example is "to dream" the American is: "dreamed" whilst the British is: "dreamt". These grammatical differences are seen in all American movies and TV shows shown around the world.

I am not American bashing in any way, but these issues are non-trivial.

inertia....as in "Moment of inertia"

I'm curious when they will make platters about 1 inch across and stack them on a shaft a few inches long and lay them flat in a drive case, instead of a few vertical slow platters, a whole bunch of horizontal fast small platters.

Drum storage with a difference. At 10,000 RPM or worse, those suckers would precess like crazy. Perhaps they could use paired contra-rotating shafts, good bearings and hope nobody used them for a mobile app. Or build them into Segways. (-:

Right. I would have made this comment if it hadn't already been here. I'd also like to mention the CHARA project, located at Mount Wilson Observatory. This *is* the equivalent of the VLA, but in the optical domain.

I'm no astronomer, but I saw it when I went up there for a tour, and it looks very cool. Really fascinating that, in spite of it's close proximity to the 'light pollution' of Los Angeles, Mount Wilson is still doing Real Astronomy.

Well, I don't think you can use these forms of the equasions, since photons have no mass. They do have kenetic energy, IIRC.

Momentum at relativistic speeds is different than classical momentum (mv).

Yes, I'll probably die from being pedantic.

And what exactly does that link have to say about human perception of loudness? It is about speaker efficiency, which is NOT what we were discussing. We are talking a subjective measure of loudness.

"loudness" in acoustical psychophysics is (grossly) defined like this:

Say I have the ability to measure the sound pressure intensity coming to your ears. ie. the "sound pressure level", which I can express with decibels. I play one tone and you listen to it. I then ask you to adjust the tone to be half as "loud". You do this. Thus, I have a relation between what you perceive is half as "loud", and what the sound pressure level is for that "loudness".

The "loudness" is purely subjective and perceptual. Different people will report different sound pressures as being half as loud, for the same starting value. But, averaged over lots of people, we get a representative curve.

The point I made is that although 6 dB represents a drop in the power level by half (or a halving of the intensity of the measured signal by a sound pressure meter), most people would require about a 10 dB reduction in intensity to report a halving of "loudness". ie. The slope of the curve is different. In fact, it is not non-linear, but most reference books on acoustics will have a curve showing perceived loudness to measured dB, for a standardized tone.

There is an adjusted scale, that compensates for this, that is called the "Sones" scale. So a halving of the value on the Sones scale, would be a halving of the loudness (for the "typical" person)

Sadly, things are even more complex than this, as frequency content also changes percevied loudness.

And, to back all this up, here is a usefull link I googled:


http://hyperphysics.phy-astr.gsu.edu/hbase/sound /l oud.html#c2

And this one on sones:

http://hyperphysics.phy-astr.gsu.edu/hbase/sound /p hon.html#c2

And what exactly does that link have to say about human perception of loudness? It is about speaker efficiency, which is NOT what we were discussing. We are talking a subjective measure of loudness.

"loudness" in acoustical psychophysics is (grossly) defined like this:

Say I have the ability to measure the sound pressure intensity coming to your ears. ie. the "sound pressure level", which I can express with decibels. I play one tone and you listen to it. I then ask you to adjust the tone to be half as "loud". You do this. Thus, I have a relation between what you perceive is half as "loud", and what the sound pressure level is for that "loudness".

The "loudness" is purely subjective and perceptual. Different people will report different sound pressures as being half as loud, for the same starting value. But, averaged over lots of people, we get a representative curve.

The point I made is that although 6 dB represents a drop in the power level by half (or a halving of the intensity of the measured signal by a sound pressure meter), most people would require about a 10 dB reduction in intensity to report a halving of "loudness". ie. The slope of the curve is different. In fact, it is not non-linear, but most reference books on acoustics will have a curve showing perceived loudness to measured dB, for a standardized tone.

There is an adjusted scale, that compensates for this, that is called the "Sones" scale. So a halving of the value on the Sones scale, would be a halving of the loudness (for the "typical" person)

Sadly, things are even more complex than this, as frequency content also changes percevied loudness.

And, to back all this up, here is a usefull link I googled:


http://hyperphysics.phy-astr.gsu.edu/hbase/sound /l oud.html#c2

And this one on sones:

http://hyperphysics.phy-astr.gsu.edu/hbase/sound /p hon.html#c2

The quote from Goslins article/interview IMHO tries to say that computer programs are often more complex coded then the problem they try to solve requires.

And where does it say that ? Nowhere - you're taking something that you know and reading it into a quote that doesn't say it. Judge the article not by what you already think, but by what it says, and you'll find it says nothing, but flatters the reader. Now take Brook's argument about the essential and accidental complexity of software (that I alluded to originally), the causes, the complexity of the problem and that of the solution, and you get some insight into complexity in software. Not just some glib statement.

And great, Gosling has the idea "things could be better" - but the article shows very little of value other than a "gee-whiz wouldn't it be nice if all the complexity just vanished".

The fact that a number of people read into it things that it doesn't say, and some people say "it must be deep because I don't understand it", implies that it's typical marketing speak - ie techno-babble.

Until he produces something more concrete than "wouldn't it be good" then he has nothing, and definitely nothing new (and bandying around technical speak to fake depth of thought isn't goign to hide it). Lots of other people have followed this logic, and then realised if it was that mechanical then the compilers would be doing it already. Let me say it again - the real insight into refactoring comes from looking at problems again, not from looking at low levels of code.

Funny, that /. - ers pick a single sentence of an article out of context, make a laugh about it, and then declare the whole article, not only the singel sentence to be techno brabble :-)

So nice of you to generalise about me again...

I'm not declaring the article techno-babble on the basis of a single laugh, I'm calling it as techno-babble of which the only parts written to be easily accessible are truisms - a classic bit of marketing spin to flatter middle management and generate "gee isn't he smart" reactions in techies with an interest in the subject.

I like hyperphysics because they link the different areas of physics graphically. A map to knowledge is sometimes more helpful than the actual knowledge.

-metric

This isn't right. You've got the carnot cycle upside down. You want to know how much heat can be transferred per unit of work input, not how much work can be generated per unit of heat available.

A typical efficient air conditioner has an energy efficiency ratio of about 9, this means 9 BTU/hr per watt of electricity used.

or about 2.6 watts of heat extracted from the cold side per watt of electricity consumed.

You can see that your calculation is wrong because it predicts higher efficiency when you pump up a larger gradient, in other words if you are trying to pump heat out of my room directly into the sun's surface it would predict a very high efficiency, obviously the wrong formula.

The formula you've given is for the efficiency of a heat engine trying to extract work from a temperature differential, not for a refrigeration system trying to extract heat using work.

The internet to the rescue: Hyperphysics shows some information on heat pumps.

A typical efficiency is therefore about 300%, whereas if you use the air conditioner to pump heat into ground water (ie. use the earth as a heat sink) you can get very high efficiency, in that case you're acting like a heat pump, ie. heating ground water from a high temperature room.

If the inverse carnot equation held and you had ground water at 55F (286K) and air at 95F (308K), you'd get about 1300% efficiency.

This is clearly the best way to cool your house, use a heat pump to pump heat out of your room into the earth.

Go here. You'll find that microwaves are a range of the electromagnetic spectrum between 3,000 and 30,000 MHz. So you can make some pretty different microwaves. As others have pointed out, microwave ovens make heat by kicking out a specific frequency that water molecules resonate at. This is analogous to hitting that one note in the shower that will sound louder than the others. There are an infinite number of non-water-resonant microwave frequencies to choose from.

The biggest problem with trying to do this is that electromagnetic waves drop off very, very rapidly as they propagate through space, and to counter this you need a huge generator.

Neither will hydrogen {snip}

Sure it will. The effect is the same as with helium -- faster speed of sound in a gas other than air.

However, helium is an inert gas, and hydrogen is a flammable, oxygen-reducing gas, so I wouldn't want to breathe it.

Actually, the human ear has a frequency range of approximately 20 Hz to 20 KHz, not 48 KHz.

http://hyperphysics.phy-astr.gsu.edu/hbase/sound/e arsens.html

I don't blame the technology as such, but the technology does bring out behavior in certain people that makes them more annoying than they would be without the cell phone.

See the article for examples of what I'm talking about. My personal favorite:

During a recent performance of "Death of a Salesman," its star, Brian Dennehy, was startled to hear a cell phone ring near the end of the second act.

Even more disturbing was to hear the phone being answered, and a woman in the audience clearly saying, "It's almost finished," and going on to make dinner plans.

Say what you want about the technology not being to blame -- without a cell phone, this woman would not be engaging in this type of behavior.

The more common mercury vapor lights have a much broader emission spectrum, therefore making filtering out their light much more difficult.

The more common mercury vapor lights have a much broader emission spectrum, therefore making filtering out their light much more difficult.

Forgot to add:

There is a quark named "down", but it doesn't necessarily have a spin oriented downward. Like an electron, it has a 1/2hbar spin which can be oriented in any direction to conserve angular momentum.

Here is a click-through standard model chart, and Here is an easy description of electron spin.

Actually, launching a rocket into the sun is extraordinarily difficult, and I think is still beyond our abilities (please, some of you rocket-scientist types out there correct me if I'm wrong....)

The problem is, we're orbiting the sun, and so is anything we launch. Earth's orbital velocity is pretty high (29.8 km/sec according to this).

Any rocket that hit the sun would have to first kill its initial orbital velocity of 30km/sec, or it would "miss" the sun and whip around the sun in a comet-like orbit.

I found a terminal velocity calculator here. I don't feel like hunting up exact numbers, but it looks like a bowling ball isn't gonna manage much more than a few hundred miles an hour. Meteors start out going much faster than that.

This "experiment" has no bearing the behavior of meteors. Sounds like these guys should go review basic physics before they propose dangerous experiments.

Don't believe me? Check out this. Look at the section called "Microscopic View of Copper Wire".

The electric FIELD in the wire moves at nearly the speed of light. The electrons THEMSELVES are barely moving at all!

Read a bit about The Color-Sensitive Cones

"In 1965 came experimental confirmation of a long expected result - there are three types of color-sensitive cones in the retina of the human eye, corresponding roughly to red, green, and blue sensitive detectors. "

Old hat

You're talking about beat frequencies I think.

So you're trying to tell me the billboard has a receiver so sensitive to pick up on the internal oscillator in my car radio. Not only will it pick up on this EXTREMELY low level signal, past all the noise and crap in the air, it will take an aggregate of all the cars in the area and figure the most listened to station.

Yes, it does. TV detector vans in the UK work on this principle -- and no, they don't work off vsync or hsync flyback voltages (well, ok; they use that to tell if you've got a TV) -- they can actually tell which channel you're watching, based on the carrier freq. you're using to decode the VHF/UHF signal.

No... First off your method of demodulating an FM signal is all wrong. You got the first stage right. The RF is broken down into an intermediate frequency (IF) by mixing it with a locally generated signal. But then you are all wrong. The IF is not rectified and filtered in an FM receiver. That is for AM.

In FM, the IF is run past a discriminator circuit. A change in frequency is interpreted as a change in amplitude and thus produces the audio.

Same difference. No; seriously. If you take the signal and pass it through an integrator, you get exactly the same net result. There are more elegant ways of decoding the signal which reduce noise, but this is decoding at its most basic. You did all the hard work when you mixed in the carrier frequency.

Now, if you're encoding stereo on the signal, then yes, you need a discriminator.

Here's a basic mono-FM signal receiver.

As I said, there's not much to it. Note the diodes for rectification of the signal.

If it was so easy to tell what radio frequency one was listening to, what would I (as a member of the US Navy) do? The enemy would know what frequencies we were listening to. That would get them one step closer to breaking our encryption and listening to our messages.

Yup... that's the case. That's why the Navy doesn't use FM for sensitive communications; they use spread spectrum.

Simon

No no no! CD players are designed to focus though 1.2mm of plastic to the surface very very near the "top" side of the CD. See a diagram of CD layers.

It's DVDs that have the same thickness of plastic on both sides, as my original post said.

It is true, though, that some CD-R manufacturers paint on a stronger anti-scratch coating, making it harder to scratch off the reflective coating.

Just FYI: The audio bandwith of stereo FM radio is about 18kHz or less. The stereo pilot signal is at 19kHz, and the Left-Right signal is centered at 38kHz. So the radio receiver is going to need some pretty good filters to produce the full audio bandwidth, and eliminate the 19kHz pilot.

AM radio stations are only 10kHz apart so you are limited to less then 5kHz of clear audio bandwidth.

This web page has some good info. It shows only 15kHz of audio bandwidth for FM stereo which is probably typical, but that is not a limitation of the specification.

Indeed.

The range of humanly audible sound is about 20Hz-20kHz; standard speakers generally do not exceed that range.

So anything coming out of a speaker should be audible.