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Indeed. In that paper I linked to they specifically mention 60 GHz as a great re-use candidate exactly because the attenuation due to atmospheric gases/water is so horrendous.

I don't think your assertion that "2.4 GHz was opened up because of its high absorption by water molecules" is entirely true. It's a fact that water does absorb some power from 2.4GHz RF, but the reason microwave ovens are there is because it's dead center in an ISM band where things like that are allowed. There is no absorption peak for water at 2.45 GHz. The caption for figure 1 in the second link sums it up nicely: "The frequency for maximum dielectric loss lies higher than the 2.45 GHz (wavenumber 0.0817 cm-1, wavelength 12.24 cm) produced by most microwave ovens. This is so that the radiation is not totally adsorbed by the first layer of water it encounters and may penetrate further into the foodstuff, heating it more evenly; unabsorbed radiation passing through is mostly reflected back, due to the design of the microwave oven, and absorbed on later passes." If there were a peak at 2.45GHz, you'd boil the water off the first few mm of food and progressively leatherize the food all the way to the center.

Glad to hear the atmospheric physists got the measurements wrong?

"I question a management culture that appeared to assume that the rocket’s inertial reference system that functioned perfectly when fitted into Ariane4 would achieve the same results when fitted into Ariane5." ref

I agree with the way you're going about this, I read not to long ago that people shouldn't have a right to their opinions if they cannot defend them. I also like this kind of discussion as it gives me a reason to clarify my thoughts.

CO2 is transparent to most of the spectrum, but the part that affect the temperature is the infra-red region. Infra-red radiation causes molecules to vibrate across the axis of bonds (exactly how gets into some really messy quantum stuff.) Lower frequencies will either affect molecules magnetically (such as microwaves rotating water molecules) or simply not have enough energy to interact and get bounced off the molecule without interacting (such as radio waves.) Higher frequencies either excite electrons (such as visible light) or cause bonds to break (UV and higher.) IR is in the sweet spot for causing heat. The range of wavelengths that can cause heating are 700 nm - 1 mm (1,000,000 nm).

CO2 strongly absorbs radiation at around 4,250 nm and 15,000 nm, both of which being right in the IR field. O2 absorbs at 687 nm and 760 nm, right on the edge of the spectrum. N2 does not really absorb at frequencies below 100 nm. Water (for some reason wikipedia doesn't mention the spectrum of water) absorbs very strongly across the whole IR range. Without getting too far into the exact details of quantum interactions, both H2O and CO2 have polar bonds, which interact much more strongly with the electromagnetic nature of light. O2 and N2 are both non-polar, so magnetic interactions do not affect them at all.

BULLSHIT. The frequency was chosen for effectiveness of generation (a very simple magnetron) and shielding, and for regulatory compliance - you don't want an oven that leaks in the frequencies that are useful for sensitive radio communications, for example. There are no sharp absorption peaks in water below 3THz. Over the range of 3THz down to 0.3GHz, the absorption decreases smoothly by two orders of magnitude. It'd downright boring. There is a slight dielectric loss peak (less than an order of magnitude's worth!) in pure water that is sharply dependent on temperature and thus is useless in heating scenarios. This is, again, only for pure water. If the water is bound, like it often is in the tissues, the frequency of this dielectric absorption peak goes down by orders of magnitude. So, let's stop with the myths.

...said the physics teacher.

Under pressure, the freezing point of water is lowered. The more pressure, the lower the ice point. To demonstrate:

Assume that a container is indestructible (let's say, a sphere with a perfect seal). It is full of water with no gas in solution or loose in bubbles or anything like that. Just pure water. Now, stick it in a deep freeze. Wait.
Water has the odd property of expanding at around 4C at normal (sea level) pressure. By the time it freezes at 0C under those same pressure conditions, it has expanded to fill 1/8 more volume than it did as a liquid. This is why icebergs float. This is why distilled water ice cubes also float. The liquid water does its thing and... you know the rest. Titanic.

The water in the sphere is prevented from freezing for the simple reason that it has nowhere to go. It has no space to expand into. If it cannot expand, it cannot freeze. How low can you go? I have no idea, having no access to magnetocaloric equipment. But I daresay, you wouldn't meet the conditions required to get the volume of water to contract to the point where it can solidify in the available space, outside of a suitably equipped laboratory or in the shadow of an outer planet.

Further reading suggests temperatures approaching/lower than about 70K (-203C) to achieve this. Further reading.

With a density of 2 gm /cc, this is likely to be a true water world - a world where a rocky interior is surrounded by thousands of miles of ice (not "our" ice, but Ice XI, X, VII), probably a few 100 km of hot liquid (kept from boiling by pressure), and then a steam bath. Look at this phase diagram, and remember that you are starting at 500 K or so, and the pressure increases greatly at depth, so going down into the planet means you are probably following a nearly vertical (but tilted to the right) line on the phase diagram.

Yes dielectric heating is how microwaves work, that doesn't mean 2.4GHz is special at it.

2.4 GHz is chosen to balance several different issues involved in the dielectric heating of water (different temperatures, good penetration depth, salinity, etc):

http://www1.lsbu.ac.uk/water/microwave.html

If so if there is enough heat to keep water in its liquid state, there might be enough power to at least energize simple singe cell-type organisms

Don't confuse water that is liquid due to pressure and water that is liquid due to temperature. Not saying that it's too cold for life, I think you can get water to around -20 celcius without freezing if you put enough pressure on it (after that it forms ice-trhee, five etc.

You can get some more info on this here and here.

Partly because it seems likely that some of the anomalous properties of water are involved in biological mechanisms -- properties not shared by other liquids. And carbon's properties as a backbone chain in molecules are not matched by other elements, at any temperature or pressure.

Another interesting read .. Software Project Failures Sabina Seifert ...

That definition of heat which you have given is commonly stated in physics or thermodynamics textbooks, and for most things, it's perfectly correct. I really should not have used the words "basic thermodynamics" in the grandparent post, because, yes, as you've stated, photons are a form of heat as the word "heat" is used in thermodynamics. I should have made much more clear the context of my pedantry. ;) I'm just tired of all the people who have the misconception that the molecules in a solid object at room temperature are sitting still, and that there's this magical thing called "IR light" that hot things are somehow full of.

However, you don't hear the term "heat" used unqualified very often in academic literature without some sort of meaningful context. In the English language, heat has dozens of definitions, and you can guarantee that your research will be misunderstood if you say something that might have slightly different meanings to chemists, mechanical engineers, cosmologists, particle physicists, solid-state electronics designers, etc. That's why it's almost always given with a certain context and is typically found in a phrase such as "heat transfer," "heat capacity," "specific heat," etc., which all have very explicit usage and meaning. When most people casually refer to heat, they are referring to the internal energy, a sum of the kinetic energy (actually a very complex thing; the simple water molecule has six vibrational modes) and latent energy from the arrangement state and material phase (again, water has more fun behavior to offer). When most people refer to light, they are referring to a collection of photons. The energy associated with the process of heat transfer is a quantity, whereas photons are a physical object. Quantities and physical objects are not interchangeable in language.

(This whole problem of communication is made even worse by adjectives like "hot," which often refers to temperature, a quantity with a distinctly different nature and meaning than "heat.")

This is really a question of usage and semantics. I would say that light can impart heat to a substance, but photons themselves are transfer particles. Heat transfer is known through three processes, conduction, convection, and radiation; in a specific temperature range, the energies of most photons radiated from an object with perfect emissivity (a black-body) fall into the FIR range. I think conceptually, though, it's a lot better for someone to think of heat as molecular movement and light as electromagnetic particles with a definite energy corresponding to their frequency; explaining to most people that one mechanism of heat transfer that brings bodies into equilibrium is the exchange of photons with energies corresponding to the absorption spectra (ignoring fluorescence and similar phenomena here) of said bodies--but that heat on a molecular level is typically considered a function of particulate motive behavior--only seems to confuse many people, reinforcing the misperception that hot things are hot because they're full of infrared light that slowly leaks out. You would not BELIEVE how many people think something like this.

I don't know where to post in this thread to help everyone who needs it, but here is the first result from a google search for "water phase diagram".

Phase diagrams are extremely helpful. That red dot in the upper right area is the "critical point", and the dashed phase line is meant to convey that the difference between the phases in no longer meaningful.

The way that many of us were taught about the phases of matter is way too simplistic. "Solid-Liquid-Gas" isn't very helpful once you leave the realm of everyday human experience. If you aren't a physicist, you'll probably have to consult a phase diagram. Intuition is pretty useless.

Almost right, except for the 'triple point'. This is a point on a T vs P graph where three phases (solid, liquid, gas) are all equally likely thermodynamically.

On Mars, the both T and P are lower than the triple point. See here for a phase diagram with T and P for Earth, Mars and Venus labeled. Notice that Mars falls below the triple point on the pressure axis. This is roughly constant - while atmospheric pressure will fluctuate, it won't change by that much.

The same is not true of temperature. The location on the T axis is an average of the surface temps of Mars. If you let sun shine on the 'white solid', it warms up and goes into the gas phase (sublimation). By knowing T, P, and the amount of time it takes for the solid to go away, you can make a pretty good guess as to what it is - water ice.

Curiously, there's a triple point very near the mean the surface conditions on Mars shown on that diagram. It's almost as if water were intended to be useful on Earth _and_ Mars....hummm.

Note the portion where solid and vapor phases are adjacent with no liquid phase in between (sublimation/deposition).

Call me a pedant but that isn't freeze drying. It's just freezing in liquid nitrogen and breaking into a fine powder (because the frozen body is fragile).

Proper freeze drying involved placing the frozen item under a vacuum (below the pressure of the triple point of water, 612Pa) and applying gentle heat. The item will remain frozen (see this phase diagram of water) and water is driven off by sublimation and condensed on a cold trap (usually at least -60C) leaving a completely dry item (be it a scientific sample, food item or body).

Not to be rude, but actually this is incorrect. At low pressures there is some odd behavoir, but on a planetary scale the melting point of water increases with increasing pressure. Ice has several different crystal structures called polymorphs that change as pressure increases. Each requires greater and greater temperature to melt. This is a good page on the water molecule and its behavoir: http://www.lsbu.ac.uk/water/index2.html.

Water is the one of the best green house gases.
It's absorption of IR is a lot higher then CO2.
Water vapour carries a lot of energy as well to drive extrem weather effects.

On the plus side clouds do help reflect sunlight.

handy link
http://www.lsbu.ac.uk/water/vibrat.html

I think almost every substance absorbs UV strongly, since it's at the right frequency to excite atomic and molecular electrons. From the graph here, about halfway down, it would seem water absorbs in the near UV about as well as it absorbs red light (and significantly better than it does in the blue visible region). In the far UV water seems to absorbs as well as it does in the infrared.

Um...so you've never made a magnet in chemistry class? You can even polarize water... (or at least polarize the ions within water...)

Vibration. You assume the whole mass would oscillate/vibrate at some frequency. I'm extremely curious as to why you would believe that. Are you under the impression that typical molecules vibrate in funny patterns?

Physically, water molecules in the liquid form experience Brownian motion, true, random motion due to heat. It's chaotic, though, certainly not regular, doesn't really have a measurable frequency (an intensity, sure, in Temperature). Furthermore, supposing there was a regular vibration of some physical sort in water, and the energy of such vibration were somehow to remain in the water instead of dissipating like most vibrations do (try ringing a bell and then putting it down on a table, eh?) it would be readily disturbed and dwarfed when someone sloshed it around or drank it. It certainly could not be expected to persist in the body beyond the esophagus and, if it did somehow maintain this vibrational quality after that, it is sufficiently weakly-interacting that it oughtn't have any effect on the body. (There are plenty of little quantum states which one could maybe possibly call "vibration" if you were feeling poetic, but they're largely irrelevant at super-atomic scales, or else - like magnetism and electron spins - pretty trivial in effect compared to the effects of fields orders of magnitude more intense.)

If there's any sort of "vibration" left, it's a metaphysical pseudospiritual "vibration".

That is an urban myth. The oceans are blue because pure water is very slightly blue. In large quantities, like lakes or oceans, the blue comes out. If it was just due to the reflection of the sky then large bodies of water would by white on overcast days.

Cold water is denser than ice. So compressing H2O near its melting point actually tends to melt it rather than freeze it. Extremely high pressure can turn this back into solid state again.

Gliese 436 b is supposed to be at a surface temperature of 520 Kelvin. The phase diagram of H2O indicates that for certain "exotic" forms of ice to form at that temperature, you need more than 10^9 Pascals of pressure. It would be interesting to calculate the gravitational force on the surface of the planet, and at what depth pressures of 10^9 Pa can be created by gravity, from the known data about the mass and size of the planet.

Do the friggin study :

1)Get a few dozen lab rats (baby rats if you RTFA and are still worried),

2)Put them near a wi-fi base station for a few months

3)Dissect and observe if tumors have formed

4)Repeat as necessary, with other organisms if you wish (perhaps the uninformed media wh**es?)

Now tell me: where in that list is there ANY room for a bunch of moronic talking heads on an alarmist docudrama to offer their OPINION? Farking incompetent buncha loonies! Bah ...

Rants aside, people really need to grow up and get over this knee-jerk reaction they have with "radiation". In case it hasn't been said already, EVERYTHING emits radiation. Fancy names like gamma rays, xrays, alpha, beta, etc etc (ad nauseum) are just names that were given to things BEFORE we figured out the physical principles that governed them. Someone needs to construct an equivalent of the dihydrogen-monoxide parody for radiation methinks :P.

Anyway, I found a very nice website for laypeople that explains the behavior of water exposed to different parts of the EM spectrum (water is a good prototypical substance as it is so ubiquitous in our body): http://www.lsbu.ac.uk/water/vibrat.html.

A special focus on the microwave region (1mm to 30cm wavelengths) can also be linked from that page. A few seconds of Googling found the following articles:

http://www.techdirt.com/articles/20061212/080748.s html - A year ow wi-fi is equivalent to 20 minutes on a cell phone :P.

http://www.timesonline.co.uk/tol/life_and_style/he alth/features/article665419.ece - The original article. Notable quote:

"When we have conducted measurements in schools, typical exposures from wi-fi are around 20 millionths of the international guideline levels of exposure to radiation. As a comparison, a child on a mobile phone receives up to 50 per cent of guideline levels. So a year sitting in a classroom near a wireless network is roughly equivalent to 20 minutes on a mobile. If wi-fi should be taken out of schools, then the mobile phone network should be shut down, too -- and FM radio and TV, as the strength of their signals is similar to that from wi-fi in classrooms."

IMO, the most comprehensive study was done recently by a Danish team: http://www.techdirt.com/articles/20061205/170444.s html and this is what came out of it:

A new Danish study tracked 420,095 people who've been using mobile phones for up to two decades or more, and found absolutely no evidence of a substantial cancer risk. The study is the largest yet disproving any cancer link, but the debate over the topic is like a b-horror film villain, who just keeps popping up after you're sure the last blow killed him. Science means little to the significant number of people who have made cancer via wireless their personal techno-bogeyman, so no study in the world is likely to change their minds and put this debate in the morgue.

Especially note the lines I have highlighted in bold.

Here's the original story for the Danish study in the Guardian: http://blogs.guardian.co.uk/technology/archives/20 06/12/07/mobile_phones_dont_trigger_cancer_says_st udy.html

And just to assure the tinfoil pholks :P,

Not true.

H2O crystals can be turned up to 11.

There is only a critical point between the gas and liquid phases. Solid phases do not have critical points with other phases. The solid-liquid phase boundry continues, it just isn't always demarcated due either to running off the edge of the chart or lack of data.

And the link you point to doesn't have any information on water phases. Another comment points to this page which has a really nice water phase diagram. http://www.lsbu.ac.uk/water/phase.html As you can see there are several solid phases that can exist at 573 K at somewhere over 1000 atmospheres (10^9 Pascals).

... to save you all the trouble: Phase diagram of water and ice.

Next time hyperlink it, parent!

as I'm sure my fellow chem nerd slashdotters are saying over and over in other posts: "No, at the pressures we're talking about here the 3-phase diagram is insufficient. Check the real thing:"

http://www.lsbu.ac.uk/water/phase.html

And anybody who talks about critical temperatures and pressures in relation to whether a solid forms is wrong, you can still make a solid above the critical T/P.

The water at the bottom of the marianna's trench is very close to freezing, but in this case, the pressure is actually what keeps if from freezing. Water has a strange property where the liquid form can (at certain temp/pressures) have a greater density than the solid form (ice). This is why ice floats, and also what makes ice skates work (the pressure of the skate turns the top layer of ice into a thin film of water. If you compress ice at 0 degrees celsius it will turn into water, while compressing water at 100 degrees celsius will eventually result in hot ice. The phase diagram for H2O can be found here

There is an Ice-IX, but it only exists at a combination of very low temperature (less than 140K) and very high pressure (~300MPa). Raise the temperature, and there will be a conversion to another polymorph of ice (or to liquid water). This site has some good information on the phases of water, especially the ice polymorphs.

This one is better, and it's got crystal structures http://www.lsbu.ac.uk/water/phase.html

Sorry, I appear to have left of the hyperlink in that post.

Yes, liquid water under pressure at room temperature will indeed solidify. You need a hell of a lot of pressure, and the crystal form will be one of the other 12 known forms of ice, not the familiar ice(I) we know and love. In this case, it's actually ice(VII), a high pressure form consisting of two interpenetrating cubic lattices. The interpenetrating lattices allow more water to squeeze into a smaller space than in the liquid. Water is a truly unique substance, from a physical chemistry standpoint. It often acts in ways that go against your physical intuition about how stuff should act. The obvious example everyone knows is the fact that the solid form is less dense than the liquid (so that ice floats), but there are many others. Lots of good reliable info here: http://www.lsbu.ac.uk/water/

Or you can just decrease the pressure. I remember seeing a demonstration once where water was placed in a beaker that was sealed at a near-vacuum. Even whenever submerged in liquid nitrogen, the water was still boiling and steaming.

You can't have liquid water at liquid nitrogen temperatures. The coldest you can possibly have liquid water is about 250K at 200MPa.

http://www.lsbu.ac.uk/water/phase.html

Tim.

Protons resonate at 2.4 GHz approximately (which is the frequency used in microwaves to resonate the H's in the {H}_2{0} molecules in your food and heat it.

Nope. Protons resonate at higher frequencies, as do water molecules. 2.4 MHz is not where water absorbs the most energy. That's an urban legend. You want microwaves to enter to food and heat it inside. Please read this and stop spreading this false story.

No, it isn't.

http://www.lsbu.ac.uk/water/vibrat.html

Four. It is fact that water expands when heated.

Actually, its physicly possible. There are several ice phases (http://www.lsbu.ac.uk/water/phase.html/, and just above 10e9 Pa pressure and less than 200 K there are two forms of amorphous ice (LDA and HDA) that dont form crystals (to rupture cell membranes). So actually, one needs to raise the pressure to 10e9 Pa fisrt and start lowering the temperature. Bingo. And thats technologicaly feasible - dip a body in some fluid so that lungs are full of it, connect arteries to same fluid - start circulation to get rid of blood - then raise pressure to 10e9 Pa as fast as possible without creating shockwaves. Than cool as fast as possible to get to LDA.

That's a pretty odd microwave then, since most of them operate at 2.45 GHz, which is chosen because of the way it causes liquid water molecules to vibrate. See this article, particularly the graphs showing dielectric temperature as a function of frequency. It's pretty clear that a 10GHz microwave oven would be a lot less efficient at heating water than a conventional 2.45 GHz one, although I suppose you could choose a multiple of 2.45GHz and probably still have a functional product.

Overall, unless your goal was to build a miniature microwave (a 21st century E-Z Bake Oven?), I don't know why you'd want to use 10GHz instead of 2.4Ghz ones. The tolerances of parts in the magnetron and waveguide would have to be much tighter, I think, and this would almost certainly cause it to be more expensive.

There are twelve known physical types of ice. Look at the phase diagram carefully. Even at 10,000 gigapascals there are forms of ice. Most of these types are denser than water. What we typically think of as "water ice" is specifically called Ice-1 (there are two subtypes, cubic and hexagonal). Ice-2 through Ice-10 are all denser than water, with Ice-10 being 2.5 times as dense. That's some heavy ice. Ice-11 is less dense than water, but Ice-12 is again denser.

Our observations of water here on earth are not really representative of all the forms of H2O in nature. On the contrary, a big part of the reason why life is able to exist on this planet is that we are almost exactly at the triple point of water. By the weak anthropic principle, we only observe those forms of water that are conducive to the existence of life.

Water Phase Diagram

Note regions VIII-XI. With enough pressure yes, water will solidify. HOWEVER there is a temperature point at which the water will no longer solidify (not shown on this scale although you can see the "liquid dome" is increasing as temperature increases. Eventually if you go far enough to the right there is a point where only vapor exists, regardless of pressure.

So while GP is correct that pressure will solidify water there is also extreme temperature that will counteract the pressure. One must wonder why water cores don't exist in real life...

Actually, not all forms of ice are less dense than water. Ice V, specifically, is very close to the density of water.

http://www.lsbu.ac.uk/water/phase.html

If you pressurize water enough it will stay liquid up to temperatures of 500-600 degrees Kelvin. See the phase diagram

this is a bit wrong, because water never turns into gas, water can be heated up in air to turn into steam, but it never turns into a *gas*. so it can't be a greenhouse gas.

You're really not helping yourself. When water boils, it goes from a liquid form to a gaseous form. Steam is just vaporized water. But just in case you don't believe me, you're welcome to check these sources for validation.

ofcourse it's responsible for the heating effect in the sunlight, we wouldn't be chatting here in slashdot if we had no air with water around us, we'd freeze to death.
If it's a gas that captures and holds the heat from the sun, warming the ambient temperature above that which it would be without an atmosphere, then it's acting like a greenhouse, and such is a greenhouse gas.

but if you define water as a responsible material for heating up earth in the sun, you should add oxygen and nitrogen too and every other thing that you see.

I'm sure they contribute to some extent, but not nearly to that which water, methane, and carbon dioxide do.

but you should try to look over the border of your "great" country and see that other people use cars that need 6 litres of gas for 100km

Not sure where you are, but that's 39 miles per gallon, and while it is higher than the average car mileage, we have plenty of vehicles that get that kind of mileage and higher. One of my cars (the one I use for leisure) gets about half of that, and the one (the one I drive to work and which is now about 12 years old) gets 75% of that. Not too terrible.

a local heat station running 9 months a year produces far more co2 than cars over here for example
Judging by your e-mail address, you live in Estonia, which has a much colder climate than the average US resident has to protect against, so it's not surprising that you put more into heating than you do into transportation. That does not negate my position that a significant fraction of emitted CO2 is released by vehicles. It may not be that way for you, or for Lithuania, or Finland, but it is that way for many other nations.

power stations may be more effective, but the still shoot out massive amounts of co2, even the electricity that is used to make me type here is produced by burning the old goold coal.

Yes, they do, which is why I am far more comfortable with nuclear power. In fact, some of the electricity I'm using comes from a nuclear power plant, which means that there is zero CO2 being released. During the day, some of the power comes from a solar plant, and perhaps some from wind. Most of the rest for me comes from methane-fired power plants, which are even more efficient than coal.

I don't think that they are different diamond states; they are differing arrangements of carbon atoms to form a structure. If we define "diamond" as the tetrahedrally shaped crystalline form of carbon, then this is a different form of carbon. This would be analogous to the twelve forms of solid water, only one of which we know as "ice".

Actually solids are not a single phase for most substances. Solids can have different states depending on how much pressure is applied. Water, for instance, has numerous phase transiitons in the ice phase. Check out this phase diagram for water.

You're pretty much right. Have a look at the phase diagram for water.

This particular diagram is, coincidentally, marked with the letters "M" "V" and "E" for the conditions which exist on Mars, Venus, and Earth, respectively.

On Mars, the temperature and pressure fall into a regime where water vapor directly sublimates to and from the solid state. No liquid state is present. However, an increase of a few degrees in temperature would push Mars very close to the triple point of water that the Earth currently rests at.

The fact is: if you put energy into a system, the stuff in the system gets hotter. It dosen't really matter if it's 10Ghz, 10Mhz or anywhere in between. As long as it gets absorbed, it makes the object hotter.

Informative post!