Thursday, January 29, 2009

Water is blue ... because water is blue

  Pacific Ocean near Santa Barbara, California

One of the most appealing aspects of the ocean is the colour of the water, ranging from a greyish green to deep blue.

But wait a minute: When I pour water in a glass, it is a clear, transparent liquid. So, what is the cause of the blue colour of the sea? Is it the reflection of the blue sky, perhaps?

The answer is simple, and perhaps surprising: Water is blue, because water is blue.

Blue Oceans,

Actually, water is quite a transparent liquid, but not perfectly transparent. All substances to a certain degree absorb light, and as a consequence, the intensity of a beam of light spreading through matter drops exponentially with distance, as described by the so-called Beer-Lambert law. Pure water appears transparent because it takes a distance of the order of metres to reduce by half the intensity of light passing through it. And, what is most important for the apparent colour of water, the absorption depends on the wavelength of light, hence colour.

The blue curve in the following figure shows the so-called absorption spectrum of pure water (data via Optical Absorption of Water by by Scott Prahl).

The absorption spectrum gives, on the vertical axis, the so-called absorption coefficient as a function of the wavelength of light (as measured outside of the medium). The area marked in yellow corresponds to the range of visible light, reaching from deep blue (at a wavelength of about 380 nanometer) to red (at a wavelength of about 760 nanometer). At the left of the visible spectrum lies the ultraviolet, and at the right, where the absorption curve is climbing and going through several bumps, the infrared.

The absorption coefficient is the inverse of the distance along which the intensity of light drops by a factor of e = 2.718..., and is measured in "inverse centimetre". Hence, an absorption coefficient of a = 10−2 cm−1 means that it takes a distance of d = 1/a = 10² cm = 1 m for the intensity of light to drop by one e-folding.

Now, as we can see, the absorption coefficient is very different at the red end of the visible spectrum than at the blue end. The absorption coefficient is plotted in the figure on a logarithmic scale, and indeed, absorption is about one hundred times stronger at the red end of the visible spectrum than at the minimum of the curve, which at a wavelength just below 500 nanometer still lies in the range of blue.

But this, of course, explains the intrinsic colour of water: when light passes through large amounts of water, its red component is absorbed the strongest, and the blue component the least - and hence, pure water appears to be blue.

... Vibrations,

Actually, the strong increase of the absorption coefficient of water towards the infrared not only causes the blue colour of the ocean. It is also intimately linked to the molecular structure of water.

Molecules of water consist of two hydrogen atoms bonded to one oxygen atom in a kinked shape. Water molecules are not completely rigid, but they can vibrate in different ways. The most important ways of shaking, or "vibrational modes", are a symmetric stretching, called ν1, a symmetric bending, called ν2, and an asymmetric stretching, called ν3:

As with any oscillatory system, vibrations are possible not just for these three modes, but also for higher harmonics - that is, overtones - and for combinations of different modes of oscillation. Indeed, bumps in the absorption curve of water can be identified with a combination of all three modes ("ν1+ ν23"), with a combination of the first overtone of mode 1 and mode 3 ("2ν13"), and with a combination of the second overtone of mode 1 and mode 3 ("3ν13"). For the higher harmonics 2ν1 and 3ν1, the frequency of oscillation is higher, and hence, absorption occurs at shorter wavelengths.

... Heavy Water,

There is, interestingly, a very clever way to check experimentally this explanation of the blue colour of water by the vibration of its molecules: Just look at heavy water instead of normal water!

In heavy water, D2O, the hydrogen atoms contain deuterons instead of protons, and hence have double the mass of "normal" hydrogen atoms. The electromagnetic forces bonding the hydrogen to the oxygen, however, are the same for heavy water and normal water. But this means that the frequencies of the different vibration modes of the molecule shift to lower values. It's the same phenomenon as when different masses are fixed to a spring: the higher the mass, the lower the frequency of oscillation.

As a consequence, one could expect the excitation of vibrations for the molecules of heavy water happens at lower frequencies than for normal water, hence at longer wavelengths. The increase of the absorption coefficient towards longer wavelengths could be expected to set in further in the infrared, barely touching the visible spectrum. And this is exactly what happens!

The following figure shows a measurement of the absorption spectra of normal and of heavy water, taken from WHY IS WATER BLUE? by Charles L. Braun and Sergei N. Smirnov, reproduced from J. Chem. Edu. 70(8) (1993) 612. The scale of the figures is linear, and the curves to the left are just scaled-up for a better visibility of the shape of the spectrum.

One can see that the bump corresponding to the mode 2ν13 is shifted form a wavelength of about 1,000 nm in normal water to about 1,300 nm in heavy water. There is an analogous shift towards longer wavelengths in all other features, and as result, the absorption spectrum of heavy water in the visible spectrum is nearly flat.

But this means that there are no marked differences in the absorption of light of different colours by heavy water. Thus, heavy water, different from normal water, should be colourless. And indeed, as shown in this photo by Braun and Smirnov, this is really the case!

  While a long tube filled with normal water (left) looks blue due to the absorption of the red component of the visible spectrum, the tube filled with heavy water is colourless (from WHY IS WATER BLUE? by Charles L. Braun and Sergei N. Smirnov).

... and Real Oceans

Beautiful physics is hidden below the blue surface of the ocean. But when I tried to inform me a bit about all this, I've also learned that whole books have been written on the topic, and that "the complexity of sea water as a substance means that its optical properties are essentially different from those of pure water. Sea water contains numerous dissolved mineral salts and organic substances, suspensions of solid organic and inorganic particles, including various live microorganisms, and also gas bubbles and oil droplets. Many of these components [..] absorb or scatter photons." (Light Absorption in Sea Water by Bogdan Woźniak and Jerzy Dera, page 5).

Here is a comparison of the absorption spectra of samples of water taken from different places around the globe (Light Absorption in Sea Water, page 6).

Curve 5, which resembles most the absorption spectrum of water we have seen above, has been measured in a sample taken from the Tonga Trench in the Pacific Ocean, at a depth of 10,000 m. And curve 8, the uppermost flat one, has been measured in surface water from the Gulf of Riga in the Baltic Sea.

From the shape of this spectrum, I would guess the sea near Riga looks more grey than blue.

Edit: The first version of the post falsely claimed that a microwave oven heats up food by setting into vibration the molecules of water. That's not correct: Microwaves, with frequencies in the range between 0.3 GHz and 300 GHz, corresponding to wavelengths from 1 mm to 1 m, have not enough energy to excite the vibrational modes of the water molecule. What the electromagnetic field of microwave frequencies does is to shake the water molecules by grappling them by their electrical dipole moments, and to set them in rotation. A detailed explanation can be found on Martin Chaplins unique site, Water Structure and Science", under Water and Microwaves.

Actually, the wavelength of microwaves is about a factor of 1000 longer than in the infrared and far infrared region where the vibrational absorption bands can be found. The vibrational bands in the infrared, though, make water vapour a strong greenhouse gas.

Thanks to all our readers who have pointed out the mistake to me, especially CIP and Jay!

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  1. Something in the air, because someone pointed me **today** to this and this.

    I think these two articles complement yours nicely :)

  2. But it is the rotational modes of water molecules that absorb microwaves.

  3. Stefan, it's an interesting post as usual. As CIP points out in the above, the microoven works in the GHz frequency range, hence in a few centimeters wavelength range, not micrometers as you wrote. Other than that, very interesting. Thanks!

  4. Hi CIP, Jay,

    the microoven works in the GHz frequency range

    oops, how embarassing... I should have checked that before. I was wondering while writing whether microwaves are indeed micrometer waves, well, actually they are longer by a factor of 1000.

    Thank you very much for the comment, I'll correct the post later today - it will take a bit of editing...

    Best, Stefan

  5. Nice to see one wonder about nature in this way.


  6. Hi Stefan,

    A very nice piece on what constitute to be the majority of what we all are. For any alien space traveller the planet’s overall colour alone would indicate us as a galactic oasis, so it’s not wonder then why there have been so many reported visits:-) More seriously our oceans serve to be our most important temperature and therefore climate modifier. Essentially with out them earth would be not much different then many of the other planets being baked during the day and freezing at night.

    I also found your section on heavy water quite interesting never realizing before it was more colourless then the most common form. I should be ashamed as Canada makes (separates) more of the stuff then any other nation. It has to do with the nuclear reactors we developed using this as a reaction modifier. With the aversion to nuclear as a power source there hasn’t been much of a market for it as of late. Just recently however, a few scientists have claimed that it could be the long sought elixer of life in being able to extend life span. Perhaps then there is a market for it after all. So I can imagine one of the marketing slogans being “heavy water the, clear choice for longer life” :-)



  7. Yes, and that's why light gets bluer and dimmer as you go deeper into the oceans (with some contribution from other things.) But if you are looking at the surface of the water, significant light is reflected from the surface and that influences how it looks

  8. Dear Stefan,

    Thanks so much for finishing this post! Yes, microwaves are in the centimeter range. How do I know that? Because if the rotating plate doesn't work, the fish only unfreezes on one side. Related question: Is glass green? Best,


  9. Microwave ovens are off-resonance for water. Energy deposition penetrates rather than chars the surface.

    Clean silicate glass is colorless. Fe(II) impurities in cheap glass color it green. Added pyrolusite (MnO_2) oxidizes Fe(II) to Fe(III) that is nearly colorless in the matrix. That glass does photoredox with UV, turning a lovely lavender ("desert glass").

    Corporate BS sells soda-lime kitchenware branded "Pyrex". Look at an edge. Pyrex borosilicate is colorless to a foot thickness. If you see green yer bein' screwed.
    The pure water spectrum is revised,

    Appl. Opt. 38 1216 (1999); water
    Appl. Opt. 25 877 (1986); heavy water

  10. Wow, thanks for the fascinating post. I'd always heard conflicting and unsatisfying explanations for the colour of water, so it's great to have the basics laid out so cleanly.

    Re microwaves, I've always been suspicious of the 'it heats water!' explanation. Microwave ovens certainly do, but it's always seemed to me they heat fat a lot faster. Is there just a lot of water in that kind of material, or could it be exciting hydrocarbon chains as well?

  11. The Indian physicist C V Raman won a Nobel prize in 1928 for the Raman Scattering phenomenon that explains why the sky is blue.

  12. Also odd about heavy water: it does not support life! Rats drinking it will die in due course. It would be a strange murder method, since most crime labs wouldn't be able to tell the difference (no chemical distinction.) I wonder if anyone has made use of this in a story ...

  13. Absorption of microwaves by water is nearly completely explained classically. Polar water molecules are rotated by the electric field. If the wavelength is too short, the water molecules have no time to gain rotational ke before the polarity of the em field shifts. If too long, collisions interupt befor much rotational energy is gained. The sweet spot is near 80 GHz.

    Fat absorbs microwaves poorly - not much water or other polar molecules. Protein absorbs like crazy - lots of water and salt. This phenomenon is used in some imaging techniques.

    Ice doesn't absorb well either. You still have polar molecules, but most of them are locked into the crystal lattice and unable to rotate.

  14. Hello Stefan,
    thanks for that enlihgtening post!
    I remember a "pool" of crystal clear water from deep wells in lime stone
    underground a pulp factory I worked with some 30 years ago.
    This pool was the central barometric head
    of the plant, about 30 meters above
    ground in a big building. this pool was abot
    3 meters deep and lined with snow white tiles. There you cold see
    the true color of water!
    But now to the explanation of the
    "blue sea" You gave: Where is the
    white background in some meters depth you need as a reflector to
    "see through" some meters of water?
    If there is some scattering out of
    the water, this would be blue,
    but this blue would habe the same
    reason as the blue color of the sky.
    I still think that the main reason
    for the blue is reflection of the
    sky blue. Taking photos with some
    polarisation filters could solve this question.

  15. How much influence does the colour of the sky actually have on the observed colour of the sea? Where I live the sea is, more often than not, a nice "Riga-grey". On sunny days it is very, very blue. Viewed from shore the sea is still pretty much grey, but from a distance of 3 or 4 miles inland, the blue is quite vivid. Under thick cloud cover, the sea is grey-coloured when viewed from shore or from inland. (North Sea, esturine environment with lots of sediment.)

    Although I don't doubt the intrinsic "blueness" of water, I do think that the colour of the sky has an important role to play.

  16. Some more remarks to wimc:
    @ Bee :
    Yes, most glas is slightly green.
    in a glas workshop I remember from university,
    there was a rack to store glas tubes, any diameter from some 4 mm
    up to about 50 mm outside.
    The tubes were 2 meters long.
    One could look at the cut ends of the
    glas tubes, obviously they were of two brands.
    One "kind" looked green, the other
    "black". The green one was Duran 50
    (Schott) the other from Wertheim
    Both glasses were identical for
    practical uses, but one of them had the green color (FeII) "masked" by
    addition of some complementary
    colored ion.
    I heard about that D2O is poisonous,
    but that always was second hand information.
    Do You have some "hard" information?
    BTW: "no chemical distinction" is
    not correct. In that case it would not be poisonous!
    Isotopes cause chemical distinction, predominantly on reaction velocities.
    (Of course only in such cases,
    when a bond to the isotopic atom is broken/formed)
    @ multipe posters:
    "rotation of water molecules"
    in microwave ovens.
    There is no rotation of molecules involved in this process.
    The tremendous absrption (k=3 !)
    at about 30 GHz is due to relaxation of orientational polarisation
    in bulk water, where rotation of water molecules
    does not occur.
    Water has a very peculiar structure due to "hydrogen bonds",
    adaption to electrical polarisation
    is done by the (maybe tunneled)
    shift of protons along the axis
    of that hydrogen bonds.
    This process (a kind of Kohlrausch
    mechanism) is also responsible for
    the extraordinary mobility of
    protons in aqueous solution.
    I dont know the frequency of the
    rotational spectrum of water vapour, but that value would show that
    orientation relaxation in bulk water
    is really a different process.

  17. Somebody should mention the blue grotto on Capri, which is unbelievably intensely blue (I mean this) because most of the light there arrives through an underwater opening several meters deep.

  18. Me again (North Sea anon)

    A nice experiment you can do at home is to fill your bath tub three-quarters full of water. If you have a white coloured bath, then you should be able to see that the water has a distinct greenish blue tint to it. This is especially noticeable at the waters edge, against the white wall of the bath.

    Unless there is some other effect going on here that I've missed, then this a pretty good way to see the real colour of water.

  19. Hi Stefan,
    interesting read
    and as 'clear' as water

    It helps to clean the water in the pool, if you use blue tiles in the swimming pool if one wants the pool water to appear blue

    Blue skies and green glass next Bee?

  20. Great post! Who with a soul could fail to be thrilled by those bumps labelled by integer linear combinations of frequencies?

    I never knew heavy water wasn't blue.

    I think there's a physics FAQ on this subject, which may need updating thanks to your post.

  21. Hi John,

    “I never knew heavy water wasn't blue.”

    Well you’ve certainly made me feel a little better, as like I said to Stefan this was a surprise to me also. Actually as you point out the whole absorption spectrum being different only within primarily the visible band width is fascinating in itself. It’s like this relation to the visible spectrum and water coupled with the mass of the sun one has further serves to tighten the Goldilocks’ parameter or at least what many perceive it as being.



  22. Phil:...serves to tighten the Goldilocks’ parameter....

    Please explain yourself.

    IN contrast to the spectrum, if taken to a "whole nother level" :) it would seem fitting that such a description in regard to wonderment about nature (A psychological depth to meaning)could be "revealed in such a way." It doesn't have to be related to "intelligent design" in such a "wonderment status."

    Such melancholy can be very blue( a dirtied colour) too:) It's as if, we can become better informed in the "light of that reason."

    I know Einstein would despise these allocations in their "earlier context" and most scientists too. They of course would verge on Newton's other works.:)


  23. North sea, the problem with bath water is that in the US at least it is not pure water but filled with chlorine and other *stuff* so a bath tub full of water would not be a very good example.

  24. Thanks for all the interesting comments!

    With respect to the colour of the ocean, well, I am not sure how big can be the influence of the actual reflection of the sky. But in clear water, I guess it's safe that some light will penetrate the surface, and will be scattered around in the water - hence, it will look blue even without some reflecting white floor.

    Actually, sediments, minerals, and organic stuff seem also to have quite a big influence. I haven't seen this grotto in Capri, but I remember the amazing colour of the Mediterranean sea around Elba. Not sure if the water there is especially pure, or has some special content of finely dispersed floating stuff that may play a role?

    I didn't know about the "colour" of heavy water before either - this paper from the the Journal of Chemical Education is really great in this respect. Actually, the post is more or less a resume of that paper, and of a few remarks in Nassau's Physics and Chemistry of Colour ;-)

    Thanks also for the comments about the toxicity of heavy water and the mechanism of the microwave oven! Georg, can you give me a pointer at some references?

    Cheers, Stefan

  25. Hi Michael, and North Sea Anonymous ;-)

    I have also noticed the phenomenon of the greenish colour of water in a white bathtub - and with German water that contains not that much chlorine. But then, the water around Frankfurt is very hard... And there was a window in the ceiling, so there mighty have been reflections from the sky. It's probably not so easy to disentangle all the factors that may mask the "true" colour of water ;-)

    Actually, the colour of the North Sea is a very good example - I know it a bit from the Friesian coast in the Netherlands. And indeed, the sea there looks very grey when the sky is overcast, and more blue on clear sunny days, so that reflections of the sky indeed seem to be the dominant factor for the visual appearance. And what's more, the water is full of fine sediments and sands anyway, so it may be quite hard to see the "natural blueness" of water at the North Sea shore.

    Cheers, Stefan

  26. Hi Plato,

    “Please explain yourself.”

    It’s simply if one takes carbon based life as what one is limited to, that is to have beings like ourselves then if you have a larger sun or a smaller one (star) that will with the former produce more EM in the high band or latter the low band you end up with any water (oceans present) being more absorptive and therefore heat up considerably more then ours do. So it seems to me in such circumstances one would have less chance to have a great deal of water in the end.

    It therefore seems to me that planets with larger bodies of liquid water would be those whose sun (star) puts out much of its EM in the visible spectrum such as our own, with roughly half being that quantity. So for instance as M Class stars being the most prevalent, with surface temperatures between 2000-3000 K they would emit in primarily the infrared range which water more readily absorbs.



  27. Hello Stefan,
    some very "classic" reference for
    Water in oscillating electric fields:
    Pohl, R.W. Elektrizitätslehre,
    S 162, 19. Aufl, Springer (1964)
    (Pohls textbook was a kinf of bible for me as a boy :=))
    The extrmly broad absorption is another
    hint to the mechanism.
    Analog processes for other liquids are at much lower frequencies
    (eg Glycerol) or the absorption
    is much weaker.
    Water is a "ganz besonderer Saft" indeed.
    BTW, in infrared spectroscopy it is quite common to see faint
    harmonics of strong lines, e. g.
    the first harmonic of C=O (around
    1700 wavenumbers)
    I think the asymmetry of the potential of vibrational modes
    enhances this forbidden transitions.

  28. Addendum:
    The fundamental of C=O vibration
    is at 1700 wavenumbers, of course,
    the 1st harmonic is at 3400.

  29. Hi Phil,

    So many excellent informative resources in this blog posting and comment section. Thanks for responding.

    A point of clarification?

    To our knowledge the intrinsic blueness of water is the only example from nature in which color originates from vibrational transitions.WHY IS WATER BLUE?


    As we know from Einstein’s theory of special relativity, nothing can travel faster than c, the velocity of light in a vacuum. The speed of the light that we see generally travels with a slower velocity c/n where n is the refractive index of the medium through which we view the light (in air at sea level, n is approximately 1.00029 whereas in water n is 1.33). Highly energetic, charged particles (which are only constrained to travel slower than c) tend to radiate photons when they pass through a medium and, consequently, can suddenly find themselves in the embarrassing position of actually travelling faster than the light they produce!

    The result of this can be illustrated by considering a moving particle which emits pulses of light that expand like ripples on a pond, as shown in the Figure (right). By the time the particle is at the position indicated by the purple spot, the spherical shell of light emitted when the particle was in the blue position will have expanded to the radius indicated by the open blue circle. Likewise, the light emitted when the particle was in the green position will have expanded to the radius indicated by the open green circle, and so on. Notice that these ripples overlap with each other to form an enhanced cone of light indicated by the dotted lines. This is analogous to the idea that leads to a sonic boom when planes such as Concorde travel faster than the speed of sound in air
    What is Cerenkov Radiation

    Stefan's post then reminded me of, "talks about rainbows." :)

    Hopefully not to detract form the perspective of the blog posting or comment section, but to expand it's thinking? I know my head is filled.:)

    Carbon forms the backbone of biology for all life on Earth. Complex molecules are made up of carbon bonded with other elements, especially oxygen, hydrogen and nitrogen. It is these elements that living organisms need, among others, and carbon is able to bond with all of these because of its four valence electrons. Since no life has been observed that is not carbon-based, it is sometimes assumed in astrobiology that life elsewhere in the universe will also be carbon-based. This assumption is referred to by critics as carbon chauvinism, as it may be possible for life to form that is not based on carbon, even though it has never been observed.Carbon based life


    Carbon was not created during the Big Bang due to the fact that it needs a triple collision of alpha particles (helium nuclei) to be produced. The universe initially expanded and cooled too fast for that to be possible. It is produced, however, in the interior of stars in the horizontal branch, where stars transform a helium core into carbon by means of the triple-alpha process. It was also created in a multi-atomic stateCarbon

    Still trying to get to the essence of your explanation in my mind.:) I am trying to "hear" right.


  30. Hi Georg,

    cool, Pohl's classic textbook, that's a nice reference, thanks a lot! And you can now even read it online, as there has been a new edition.

    The plot of the frequency dependence of the dielectric constant of water - and its absorption coefficient - in the gigahertz region is now on page 184.

    I've learned something about microwave ovens ;-)

    Best regards,


  31. Hi Phil, Plato

    thanks for pointing out this "goldilock" phenomenon about the minimum in absorption around at optical frequencies... that's an interesting point of view!

    Hi Philramble,

    phenomenon that explains why the sky is blue.

    I don't want to be nitpicking, but to avoid confusion - the dominant contribution to the blueness of the sky comes from the frequency dependence of elastic Rayleigh scattering of light at air molecules.

    When light scatters off molecules, it can excite, say, vibrational modes of the molecules, and hence the scattering is inelastic. That's then Raman scattering, which thus can be used to measure vibrational excitation energies with light of optical frequencies.

    Cheers, Stefan

  32. Hello Stefan,
    a new "Pohl"! This is incredible.
    Is there a renaissance for such textbooks?
    For me it was one of the oldfashined
    textbooks with drawings instead of
    photographic pictures (and some more
    oldfashioned things) I loved since my boyhood. (50ty years ago that I first had a Pohl in hands)
    I bought a 19th edition some years ago as a kind of reminiscense.

  33. Hi Plato,

    Yes as you point out there are proposed alternativesto life’s base, yet for many reasons such as its shear abundance and reactivity make it overwhelmingly the best choice. This abundance is sort a counterbalance to the Goldilocks premise, since it would seem to allow life to be formed wherever given the opportunity within the confines of other factors.

    The bottom line in all this is that from the very outset the universe had to wait for the eventual evolution of these elements through the action of star formation and death. So the road to life requires a time span and evolution that exceeds the time of existence of an individual system. In that context I often remind those with gold wedding rings that it is a very appropriate symbol of unique origin and eternity, as it’s made of a element that could not be produced in a star like our own but predates it to one or many that was much larger and ended in a Supernova explosion from which it was born.

    Like Carl Sagan so often reminded, we are creatures of star stuff, who now ponder the stuff and the process from which we formed; which when one thinks about it is truly remarkable. That is despite the debate that needlessly worries if life is born of consciousness, we should be content that our universe is undoubtedly a birth place of it and for me that is what is truly awesome.

    In this context you might be interested that Leonard Susskind cares this one step further in his new book ,“The Black Hole War” , which I’m currently reading where he says in the introduction:

    “The truth of course, is that all complex life forms have built-in instinctive physics concepts that have been hardwired into their nervous systems by evolution. Without this preprogrammed physics software, survival would be impossible. Mutation and natural selection have made us all physicists, even animals. In humans the large size of the brain has allowed these instincts to evolve into concepts that we carry at a conscious level.”



  34. Hi Phil,

    That was a very deep and thoughtful comment. I would most certainly like to try and respond in kind with that standard.:)

    Not to long ago while standing in the bookstore, I held Susskind's book you reference in my one hand, while in the other, I held "Symmetry and the Beautiful Universe, by Leon M. Lederman with Christopher T. Hill.

    The Symmetry book won out, although, I would like to acknowledge that the "historical perspective of Susskind would have to be accounted for," while one reads the current summation of Susskind's book call the Black Hole wars you point out.

    Susskind had to set it up in a "previous incarnation" so, that that book could lead one to understand what he is surrounding his arms about, in his points of view. Where he is today.

    "The protagonists were Stephen Hawking and his army of General relativists on one side. For the first fifteen years, it was mainly Gerard 't Hooft and myself on the other. Later a band of string theorists came to our aid." The Cosmic Landscape, by Leonard Susskind, page 326, para 2.

    From your quote then Phil....

    The truth of course, is that all complex life forms have built-in instinctive physics concepts that have been hardwired into their nervous systems by evolution.Phil's reference to Blackhole Wars by Susskind.

    So I do recognize how Susskind embraces Lee Smolin's views as you speak, as to why I think there is a collaboration taking place beyond our talking. See here for a more detail explanation.


  35. Georg - There is no rotation of molecules involved in this process.
    The tremendous absrption (k=3 !)
    at about 30 GHz is due to relaxation of orientational polarisation
    in bulk water, where rotation of water molecules
    does not occur.

    I don't think that this is quite right. It's true that from a statistical mechanical point of view the absorption mechanism is dielectric relaxation - essentially a lag between the imposed electric field and the polarization of the medium. This lag is what allows the microwave electric field to do mechanical work on the medium (water).

    Microphysically, that lag is due to the moment of inertia of the polarized water molecules. (This point is briefly mentioned in The Feynman Lectures, II-11 and discussed in more detail in Mcquarrie and other Stat Mech books. The root mechanism is the electro-mechanical torque applied to the water molecules and their consequent gain of rotational kinetic energy.

    Microwave ovens work at about 2.5 GHz, far from the peak absorption point at 20 GHz or so. Perhaps this is to promote more even heating - the skin depth would be much less at peak.

  36. Hi Plato,

    I’m not as certain as you that Susskind and Smolin have forged a meeting of the minds in the context of the subquantum realm or the nature of time. I would however agree that when it comes to trusting that the pursuit of physics will ultimately lead us to a unique and revealed truths about our world they would see this commonly.

    As for selecting books when I find myself in a dilemma such that you described. This is when I display a weakness in having no self discipline or restraint for I just buy them both. It’s lucky for me that self indulgence doesn’t extend itself much in the way of other things :-)



  37. Phil:I’m not as certain as you that Susskind and Smolin have forged a meeting of the minds in the context of the subquantum realm or the nature of time.

    I thought to double check and you might be right in this respect in term's of Natural Selection and the Universe.

    Lee Smolin has attempted to explain the very special properties of the world-Anthropic properties-by direct analogy with Darwinian evolution-not in the general probabilistic sense that I explained earlier but much more specifically...Cosmic Landscape, On page 360( Susskind references The Life of the Cosmos)

    While I reference "earlier incarnations" Susskind would not be to happy with that, but like Lee how is it you can disregard your past and find the literature you are producing "is progressive" and leads to formulations that will direct and trend current thoughts in regards to science?

    So one continues to hold to their positions( "but" still open to the process of collaboration in research) and if I mention "symmetry and symmetry breaking" what is the position both men have? It's hidden in their past and in their positioning today.

    No need to "justify this" in face of my comment as to what science should continue to do. I do not discard what the leaders in science are doing but also persevere to distinguish the roads they have and are taking.

    Susskind will lead you to this place "in time" once you are done his book? Decide for yourself of course.

    Tell me later if you recognize the relationship Poincare' and Klein had "is reflective" in today's positioning or not:)

    "I feel" for the string theorists as well, that they understand where things are going and not to be upset. This can come out in "adverse reactions." I have been amazed at their "conduct becoming of gentle wo/man" of moving to continue this collaboration. This is intended for some specific( the brilliant assemblers.)

    Felix Klein thought to be progressive too?:)

    To move forward, as an example of what the "open institute" shall do while it moves in it's direction.

    This means to me to take a view of the Book Susskind now writes in terms of the Black Hole Wars, and to predict where it's "summation shall lead you." So of course, I can speculate and yes, still hold to the science.

    Some might "propose topics" about laptops and quantum computers in relation to the universe. The subject is diverse in historical annotation, might reveal a way one might question the road taken with regard to the tangibility of where science is going?:)

    So of course too, any attempts at at the joining of the "electromagnetic and gravity" in a future "conceptual sense" can help one to imagine what one is to contend with the perceive in reality then, and how it may take on new meaning. I should not jump so far ahead I guess.:)

    So of course, there is a place and focus I have about this "cross over point." How it applies to the "changing ability" of the world in the reality perceived. It's formative qualities.


  38. Hello "Capitalist...."
    Water is special due to that "hydrogen bonding".
    This is a localized and directional bond, inhibiting
    the rotation.
    E.g. here:
    "The water molecule has a very small moment of inertia on rotation which gives rise to rich combined vibrational-rotational spectra in the vapor containing tens of thousands to millions of absorption lines. In the liquid, rotations tend to be restricted by hydrogen bonds, giving the librations."

    Instead of ratational momevents
    water molecules can follow an external field by the jump of a proton along the axis of that hydrogen bond.
    A second proton at the same oxgen atom follows very fast, on the whole the result is as if rotation
    of 109 ° had happened.
    This process is much faster than
    rotations, time for the hydrogen
    jump is about the typical collision frequency in liquids 10^13 Hz.

  39. Georg,

    I read your very interesting link on water absorption, including the microwave absorption part. That latter talked about the role that rotation of the dipole played, but nowhere did I see anything about the proton jumps you speak of.

    There are two sort of jumpy phenomena of interest, first the protonation deprotonation reaction which does take place along hydrogen bond axes, but is much too slow (1 kiloHertz) to have anything to do with microwave absorption. The second, hydrogen bonding, libration about the bond, rotation, and rebonding is just ordinary rotation somewhat constrained by the short duration hydrogen bonds.

    I don't see any support for the no rotation idea here anyway, and there is explicit discussion of the Debye rotation with inertial lagging model I mentioned.

  40. Hello "Capitalist...."
    did You always watch out whether
    gas phase or liquid
    water was talked about?
    Where did You read this kHz figure?

  41. Georg,

    link here

    Quote: "Water molecules i are tiny and V-shaped with molecular formula H2O a and molecular diameter about 2.75 Å.g In the liquid state, in spite of 80% of the electrons being concerned with bonding, the three atoms do not stay together as the hydrogen atoms are constantly exchanging between water molecules due to protonation/deprotonation processes. Both acids and bases catalyze this exchange and even when at its slowest (at pH 7), the average time for the atoms in an H2O molecule to stay together is only about a millisecond. As this brief period is, however, much longer than the timescales encountered during investigations into water's hydrogen bonding or hydration properties, water is usually treated as a permanent structure."

  42. I thought I might place a link here to an artistic interpretation that this science work brought to mind.

    Can we not be inspired by this true science and it's wonderments? The refraction of light.

    Reveal that the geometers are trying to "algebraic describe" the world around us, while wanting to see nature as it is. Too much information, and then it becomes chaotic. Who are the brilliant assemblers?

    Let us not forget then that Thales has had own foundational idea about the world too, based on water. See also: Thales Theorem


  43. Hello CapitalistImperialistPig,
    ah, You replaced frequency for time!
    This millisecond is plainly wrong.
    The writer himself seems to have noticed the contradictions to the
    facts regarding hydrogen bonding.

  44. Hi CIP, Georg,

    thank you for your stimulating comments! I think I start to understand ;-)... Actually, the page Water and Microwaves by Martin Chaplin and the references given there are really instructive.

    So, if I get it right, the dielectric response of water fits quite well to the Debye description for polar molecules - however, the relaxation time of 8.3 picoseconds for liquid water at room temperature is so short that it cannot be understood from rigid rotations of the molecule. So what actually is going on, instead, is a rearrangement of the network of hydrogen bonds between neighbouring molecules, somehow?

    Actually, this seems to be quite topical, here are two recent papers I've come across that seem to deal with this problem (I've only seen the abstracts so far...):

    Water inertial reorientation: Hydrogen bond strength and the angular potential (PNAS, 8 April 2008: 105(14) 5295-5300)

    A Molecular Jump Mechanism of Water Reorientation (Science, 10 February 2006:
    311 832-835)

    Cheers, Stefan

  45. Hello Stefan,
    Yes, that is what I meant!
    This picture of the Water structure
    was already state of the art
    when I studied in the 60/70ties.
    Mainly because it was able to explaine the high mobility of H³O+, being about 10 times higer than the mobility of
    all other "normal" Kations e.g. Na+ ion.
    Again this is due to the same rearrangement of protons along the
    axis of O-H..O bonds.
    This is what I called a "Kohlrausch mechanism".
    (Kohlrausch proposed something similar as a general theory of
    electrolytic conduction in days when the existence of ions was unknown)
    I see today it is possible to investigate such processes with fast spectroscopic methods.
    The ominous "millisecond" maybe
    was calculated from the autoprotolysis equilibrium, ignoring that protons can switch over from molecule to molecule
    without ever beeing "free" as a

  46. The effect of sky color depends a lot on the viewing angle because of Fresnel reflection. Without Fresnel, water wouldn't look like water.
    Typically there is also some scattering, although I'm not sure if that happens in pure water. And refraction, but I guess that doesn't change the overall color.
    Very nice post and good comments - thanks!

  47. I'm looking for a article for any description on differences between stretching, asymmetric and symmetric vibrations, ANy help...? Many thanks


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