"How do we know he didn't invent the thing?"

By Phil Plait | March 16, 2009 3:01 pm

Science Daily is reporting that a team led by Artem Oganov (Stony Brook University) and Yanming Ma (Jilin University in China) have discovered something pretty cool: at pressures of about 3 million atmospheres, sodium becomes transparent.

Normally, at room temperature and pressure, sodium is an opaque, whitish metal. At higher pressure, over a million times the Earth’s atmospheric pressure, it turns black. And at 1.9 million atmospheres it starts to becomes transparent at red wavelengths. Although it hasn’t been directly shown, the scientists expect at 3 million atmospheres it will becomes as transparent as glass.

The reason this is so interesting is that, for one, it wasn’t predicted until recently. No one knew what would happen to sodium under such pressures. I read the explanation of what’s going on at the link above, and as I understand it metals are opaque because they have electrons that are free to flow around the atoms in the metal. Electrons are very good at absorbing light, so metals are opaque (as well as good conductors due to the free electrons). At very high pressures, the electrons get locked up in spaces between the atoms and cannot move. This allows light to pass through the material (and I assume makes them insulators as well).

Another interesting aspect of this is that pressures like this are common deep inside planets. How heat gets transferred out from the cores of planets depends in part on how well light can pass through the materials, so anything that furthers our knowledge of this will help understand how planets work.

Sodium is not a material that, by itself, can be used in construction and so on, like, say, aluminum. But how far are we from proving Scotty right?

CATEGORIZED UNDER: Cool stuff, Science

Comments (48)

  1. MacRat

    “3 million atmospheres”

    Very practical…

  2. Scotty and Bones in ST: The Voyage Home.

    That, and the other remarkable moment trying to talk to the computer using a mouse.

    And for the article, well… it’s only a matter of time. Good thing and I believe is a remarkable historical coincidence, when a discovery is made, there have been at last one other cientist performing the same research.

    As how it happened to Galileo and Harriot: the first that got it published, the first that gets the credit! 😉

    Live long and prosper!

  3. rob

    “(and I assume makes them insulators as well).”

    yup, it would make them insulators as well, since the electrons are localized.

  4. John V
  5. jest

    This is why science and research is so important.

    Though it makes sense I suppose… A diamond doesn’t start out as a clear material either.

    The question is, if you were to make a sheet of transparent sodium, and expose it to normal atmospheric pressures, would it degrade or hold its shape?

  6. Oh Boy! I’m gonna make a sodium-walled aquarium! Oh wait….

  7. make a sodium-walled aquarium!

    That’ll be awesome! Briefly.

  8. Elwood Herring

    Elwood’s 1st law: Knowing that something can be done is 50% of the way towards achieving it.

  9. James

    Question: How do you generate those types of pressures to do that type of research?

  10. “A keyboard. How quaint!”

  11. ND

    Elwood Herring,

    ND’s 1st law: Not knowing that something is impossible to do is 50% of the way towards achieving it.

  12. ND


    they probably generated this the presuare on a really tiny volumen. Maybe on a sample that started out as a cube with 1/2 cm side. I’m totally guessing here. It probably involved several elephants.

  13. Tom Woolf

    How to generate 3 million atmospheres?

    – Get fat ladies (and fat men) from traveling shows to stand on one infinitesimally small point;

    – Start collecting all the hot air from politicians and restrict to one small chamber. With enough politicians (will need to be a bipartisan effort) it may be possible. Definitely possible if talking head blowhards from cable “news” shows join in;

    – Put 2 atmospheres in a room together, a Barry White album, and hope the gestational period is really short. Given enough time, who knows? (But make sure the Barry White album keeps playing);

    – And the most logical way to get 3 million atmospheres…. Start by investing 6 million.


  14. Ah, for mine own eyes to see,
    Clearly through an allotropy.
    Electrons run aground of sea,
    Stuck in their localities.
    Metallurgy under pressure,
    3 million skies- the utmost measure.
    Testing still has yet to come,
    if only I could be there for the fun.

  15. Damn … I had to get all the way to the end before I got the title reference: must be a slow brain day

  16. QUASAR

    3 million? Are you sure about that?

    What do they use to make that much pressure?

  17. Somewhat (but not completely) off topic-

    This reminds me of water. I remember way back when I was reading Bad Astronomy (the book) there was a comment on water. It suggested (it seemed without certainty) more than reflecting the sky- it having intrinsic blueness.

    There was an experiment done back in 1993 comparing D2O against H2O, revealing D2O to be clear and H2O to be blue. Strictly speaking it’s not the same as this, but like I said, I was reminded of it.

  18. Torbjörn Larsson, OM

    High pressures? Usually by pressing two diamond tips together. “Diamond anvil cell”, see Wikipedia: “A diamond anvil cell (DAC) is a hand-top device used in scientific experiments. It allows compressing a small (sub-millimeter sized) piece of material to extreme pressures, which can exceed 3,000,000 atmospheres (300 gigaPascals).[1]”

    The diamonds are excellent windows too.

  19. OMG! I love Star Trek IV!
    Computer. Computer?

  20. Chas, PE

    I’m still trying to figure out why glass is transparent

  21. MadScientist

    Fascinating … I wonder what the refractive index would be.

    I’m a bit confused by the explanation of metals being opaque. Metallic sodium is a shiny silvery color and most visible light is reflected, not absorbed – same for aluminum. Whatever is not reflected is absorbed – when the metal is in bulk, visible light just doesn’t shine through. Metals can be vaporized onto glass in very thin layers so that light can actually be transmitted through the metal film – in such a case we have reflection (which is typical of a bulk metal), absorption, and a residual transmission of light. From that we can work out how thin a sheet of metal has to be to block, say, 99.999% of visible light under the assumption that there is no reflection (which is strange because there will be reflection at the surface). Where BA has me confused is how he uses ‘opaque’ – he seems to imply that there is only absorption and transmission and no reflection at all. I guess I’ll have to follow his link to the article …

  22. Ross

    Wait, if I remember correctly from the early BA days you talked about how it would be impossible to see the stars from the enterprise’s observation lounge because the glass would reflect all the ship’s interior lights. Wouldn’t transparent aluminum, theoretically, react differently to the lights inside the ship?

  23. Liz

    That’s the ticket laddy!

  24. Jess Tauber

    On the other hand, there are metallic glasses, created when molten metals are cooled too fast for a crystalline structure to form. From what I’ve seen only opaque forms currently exist (various shades of black).

    Can it be that by tweaking the formula (alloys) we might come up with a variant that traps the current-bearing electrons in their own little lacunae and also can get a nice transparent material, without the extra elbow grease?

    Working metallic glass can be problematic, given that most things one can do to it in normal time frames will heat it, and maybe turn it back into a reflective mess.

  25. Ed

    It sounds like aluminum becomes a metamaterial at high pressure, so we can probably make aluminum or some other metal invisible by structuring it correctly, which is basically what the high pressure is doing to sodium. (look up metamaterial on wikipedia)

  26. R.W. Thomas

    This made my evening.

  27. Elmar_M

    Transparent aluminum has been floating arround the web for a while. I am pretty sure I read something on new scientist, or science daily once. One of these pages anyway. I read something about applications for windows in armored transports, etc.

  28. I think my bicycle pump goes to about 3 or 4 million atmospheres, is does get quite hot though.

  29. Transparent aluminum has been around for decades industrially. Well, aluminum trioxide, better known as sapphire. It’s used for viewports in plasma etching chambers because the etch products won’t stick to it, like they will to glass or quartz. It’s also more transparent over more wavelengths than any other common material (allowing optical sensors to work from far IR to far UV).

    Add some impurities to the structure to give it color, and you have rubies, blue sapphires, etc. If you grow it directly on an aluminum surface you have anodizing.

    – Jack

  30. Alan

    For those asking how such pressures are generated, here’s one way: http://en.wikipedia.org/wiki/Diamond_anvil_cell

  31. ElasticPlanet

    I thought I heard once that most, if not all, metals have the potential to become transparent given the right circumstances (mostly pressure).

    I also could be making that up. Am I completely wrong here?

  32. gopher65

    Transparent Aluminum was invented ~3 years ago (initially) for use as armour on military vehicles (replacing bulletproof glass), as well as military aircraft windows.

    So transparent metals are nothing new. Old news.

  33. Steve Morrison

    The Chemist–

    I can’t seem to download the PDF you linked, but this page may be of interest in re the intrinsic blueness of water.

  34. I have perfected a method of mass manufacturing transparent metals. Now, in addition to being perfectly transparent, these metals are also untouchable and unweighable. But I swear they’re there! Military contract, please.

  35. T.E.L.

    This is an example of how progress is made in science: by contemplating and experimenting with conditions which are extreme, that is to say, very different in degree from the familiar. It’s the same reason why particle accelerators have gotten bigger over the years. Progressively extreme circumstances yield new data, with which theories of Nature can be further generalized.

  36. Jeffersonian

    I always thought it weird…
    Sodium only exists in nature as a compound. (Pure sodium being extracted by man and not being stable in air or water).

    Also, opaque ≠ transparent

  37. Jeffersonian

    [oops, …Not opaque ≠ Transparent ]

  38. Regarding the problem of maintaining 3 million atmospheres, etc: just go back to the source…

    “It would take years just to figure out the dynamics of this matrix.”

    “You would be rich beyond the dreams of avarice.”

    I think that covers it.

  39. Trekkies are just like creationists – fit the science to the sacred revelations 😀

  40. brnofeathers

    “How do we know he didn’t invent the thing?”

    I wonder that very same thing every time I see a piece of velcro.

  41. T.E.L.


    Why do you think it’s weird about Sodium?

  42. Sion H

    So what does iron or nickel do at those pressures? I ask as I think it would be cool if the Earth’s core were transparent. Not that I’d ever see it, but just knowing …

  43. Gary Ansorge

    Al2O3 is the formula for sapphire, which, w/o any other contaminants, is transparent, thus this would be a good example of transparent aluminum,,,but I’m still waiting for metallic Hydrogen(theoretically super conductive, transparent to visible light, floats on water and really strong). Besides, it would make a dandy fuel for rockets,,,

    Also, there is now a tetra Nitrogen form with 5 times the explosive power of C4 but I keep wondering if a metallic form of Nitrogen could be made?

    Ah, so many ways to play with matter,,,and the nutters of the world think energy is less crude than matter(as in Yodas comment to Luke “We are beings of light, not this crude matter,,,”)
    Crude my booty! Remember E=hv and E=MC^2???
    Therefore MC^2=hv(v being frequency) which gives
    v=MC^2/h. Thus we have v proportional to Mass, ie, the fatter we are, the higher our frequency,,,

    Dang! My frequency is higher than yours,,,

    Gary 7

  44. papageno

    MadScientist: I’m a bit confused by the explanation of metals being opaque.

    It simply means that light does not travel very far within a metal, that is, light is not transmitted in bulk metals. Most of it is reflected.

    It is possible to work that out (at least in first approximation) if you know the density of free electrons in the metal.

  45. @ Steve Morrison,

    I’m sorry about the page, I’m using the computers at my university library so our institutional license kicks in automatically for the full article- I took it for granted that you’d get the abstract. This link should go directly to abstract if you’re still reading. Actually the only reason I came back to the comments was to look for the link I left here.

    The page you linked about water refers to the same study. That’s actually how I got the study in the first place.

    @Chas PE (though I doubt you’re still following the comments here) What makes glass transparent has a great deal to do with the amorphous nature of glass, all the SiO2 particle are aligned in a non-crystalline pattern due to supercooling. I wrote a little on it here.


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