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« NEW VOICES: georgie boy | Main | the electrons in your sunday paper aren't charged »


I have neutrino vision. I can't see a damned thing.

Of course those x-ray specs were a rip-off!

And just try getting your money back from those people!

Nice article. Though comic book lovers/physics nerds are not quite such a rare breed!

But the glass in greenhouses absorbs all visible light except green light, which it reflects and sends back out (which is why we see it).

There is a mistake here somewhere. Glass is transparent to all visible light, or else we wouldn't see it as transparent, but as tinted. A band-gap filter absorbing all visible light except green looks purple! Maybe you meant the plants in the greenhouse, which absorb all light except green?

Don't forget that there are a variety of x-ray wavelengths, some of which are vastly more penetrating than others. Soft (long wavelength) x-rays are quite easily stopped by just about anything, while harder (shorter) wavelength x-rays can penetrate quite a many inches of dense materials.

There's also the issue of x-ray scattering/diffraction, which is used to measure crystals.

As for the glass in greenhouses, early glass commonly had quite a bit of Iron as an impurity, which gives glass a green colour. Modern production techniques have mostly eliminated this effect, though.

A more important aspect, though, for greenhouses, is that glass is mostly impervious to infrared radiation, thus helping to contain the heat produced by the incoming sunlight.


Boris - thank you I realize I misspoke. Or rather, was thinking of my neighbors lean-in greenhouse that was covered in green sheeting to keep the heat in. In my mind I was thinking of green tinted glass. But I did mix up the absorption/reflection there. It gets confusing.

Green tinted glass does appear green because it absorbs all frequencies in the visible spectrum except green, which passes through it like clear glass. This is the general principle behind any color. Of course, no tinted glass is perfect and some light in the other frequencies gets through.


I have no idea what a band gap filter is - although presumably it relates to the band gaps in condensed matter physics and how transitions across the gaps(s) selectively absorb radiation.

How does the purple appearance work? Surely looking at it from either side you only see light coming from the other direction (since no light is reflected - green is passed through and the rest is "absorbed") and since only green gets through it should look green?

So, perhaps the absorption you mention is just temporary and the radiation is then spontaneously emitted (otherwise it would get hot and radiate anyway)? In that case half of the non-green is reflected and half passed on? But since this applies to light falling on the thing from both directions, wouldn't the net effect be zero? Or perhaps the spontaneous emission process uses different transitions to the absorption and so the emitted spectrum differs from the absorbed - but then where's the purple (white - green) gone?

Yours, confused...

I guess we are talking about reflection after all. The photon from spontaneous emission might be random for one electron falling back down the gap, but with zillions of electrons involved at the same time, the probability amplitudes must combine/interfere to preferentially give reflection rather than transmission, but I can't remember how this works on a photon basis. (Also why you get 180 degree phase change with reflection from light material to heavier...)


I think you have again miss stated the situation when you said " Green tinted glass does appear green because it absorbs all frequencies in the visible spectrum except green, which passes through it like clear glass. This is the general principle behind any color." in the comment above. What you said applies to opaque objects.

It seems to me that the situation for a tranlucent object like glass is just the opposite of what you state. All wavelengths are passing through EXCEPT green which is being scattered thus it is the color we see. And for opaque objects, the color we see is the complement of those wavelengths which are absorbed.

I own tachyon glasses so I will see the future and I have seen the past. :)

Superman has "heat vision" right? Why in the world would emitting x-rays be any less plausible for the Man of Steel? =)

The image on the left side at the start of paragraph 9 was created with a back scatter x-ray system not a terahertz system. The next image (on the right) is from a terahertz (a.k.a. millimeter wave) system. I found a version of the original article that published that picture here (Augusta Chronicle).

X-Ray Spex (and those by-mail Amazing Sea Monkeys) were invented by Harold von Braunhut. Because real life is queerer than we can imagine, von Braunhut, who was Jewish, was also a member and financial supporter of the Aryan Nations.

I am working on an article which includes terahertz metamaterials. Of course this involves terahertz radiation. Your article is really well written and makes the concepts very clear. It is very informative. Also, I like your prose style. I wish I could use this article as a source, but guidelines don't allow me to use blogs for sources, no matter how good or accurate. Well, here is the article that I have been writing for almost a month. I hope you don't mind me providing you with a link:

However, you have given me some good leads for useable sources. And again, your prose style is excellent. Good job. - Ti-30X

Hey maybe you can give me your opinion on the article if you have time. There is a page for comments here:

Ti-30x - this post actually needs some edits/clarifications that I am meaning to get around to. Until then you might want to hold off directing people this way; still, thank you for the great comments!

Calla, if you want to edit out the links to the article, feel free to do so, if you think that is best. Ti-30X

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    Physics Cocktails

    • Heavy G
      The perfect pick-me-up when gravity gets you down.
      2 oz Tequila
      2 oz Triple sec
      2 oz Rose's sweetened lime juice
      7-Up or Sprite
      Mix tequila, triple sec and lime juice in a shaker and pour into a margarita glass. (Salted rim and ice are optional.) Top off with 7-Up/Sprite and let the weight of the world lift off your shoulders.
    • Listening to the Drums of Feynman
      The perfect nightcap after a long day struggling with QED equations.
      1 oz dark rum
      1/2 oz light rum
      1 oz Tia Maria
      2 oz light cream
      Crushed ice
      1/8 tsp ground nutmeg
      In a shaker half-filled with ice, combine the dark and light rum, Tia Maria, and cream. Shake well. Strain into an old fashioned glass almost filled with crushed ice. Dust with the nutmeg, and serve. Bongos optional.
    • Combustible Edison
      Electrify your friends with amazing pyrotechnics!
      2 oz brandy
      1 oz Campari
      1 oz fresh lemon juice
      Combine Campari and lemon juice in shaker filled with cracked ice. Shake and strain into chilled cocktail glass. Heat brandy in chafing dish, then ignite and pour into glass. Cocktail Go BOOM! Plus, Fire = Pretty!
    • Hiroshima Bomber
      Dr. Strangelove's drink of choice.
      3/4 Triple sec
      1/4 oz Bailey's Irish Cream
      2-3 drops Grenadine
      Fill shot glass 3/4 with Triple Sec. Layer Bailey's on top. Drop Grenadine in center of shot; it should billow up like a mushroom cloud. Remember to "duck and cover."
    • Mad Scientist
      Any mad scientist will tell you that flames make drinking more fun. What good is science if no one gets hurt?
      1 oz Midori melon liqueur
      1-1/2 oz sour mix
      1 splash soda water
      151 proof rum
      Mix melon liqueur, sour mix and soda water with ice in shaker. Shake and strain into martini glass. Top with rum and ignite. Try to take over the world.
    • Laser Beam
      Warning: may result in amplified stimulated emission.
      1 oz Southern Comfort
      1/2 oz Amaretto
      1/2 oz sloe gin
      1/2 oz vodka
      1/2 oz Triple sec
      7 oz orange juice
      Combine all liquor in a full glass of ice. Shake well. Garnish with orange and cherry. Serve to attractive target of choice.
    • Quantum Theory
      Guaranteed to collapse your wave function:
      3/4 oz Rum
      1/2 oz Strega
      1/4 oz Grand Marnier
      2 oz Pineapple juice
      Fill with Sweet and sour
      Pour rum, strega and Grand Marnier into a collins glass. Add pineapple and fill with sweet and sour. Sip until all the day's super-positioned states disappear.
    • The Black Hole
      So called because after one of these, you have already passed the event horizon of inebriation.
      1 oz. Kahlua
      1 oz. vodka
      .5 oz. Cointreau or Triple Sec
      .5 oz. dark rum
      .5 oz. Amaretto
      Pour into an old-fashioned glass over (scant) ice. Stir gently. Watch time slow.