S04E04: The Hot Troll Deviation

Sometimes you need a secret decoder ring.  We had a few shout-outs to the world of physics and chemistry tonight.

Starting with the very first line of the episode:

KOOTHRAPPALI:   (TO SHELDON) I’m telling you, if xenon emits ultraviolet light, then those dark matter discoveries must be wrong.

And now you are in on the most controversial discussions in physics today.    We’ve discussed here before that about two-thirds of the matter in the galaxy is a dark, unknown substance: the aptly named “dark matter”.   Meanwhile teams of physicists are working hard to be the first to prove dark matter exists, by capturing one of its interactions in a particle detector.  For whoever detects it first, there is no end to the fame.


Sensitive detectors look for dark matter. A dark matter particle may kick a nucleus in the detector leaving behind detectable energy, such as ultraviolet light.


The race is on.   Many detectors are running.    Each is gambling on different techniques.  But what almost all have in common is they are looking for extraordinarily weak and rare events.   So physicists build their detectors from materials with extremely low radioactivity and place them deep under ground to keep them as quiet as possible.   Two of the running experiments have a signal the authors have claimed is consistent with dark matter.  The first is called  “Dama-Libra” (the Italian group who Leonard talked about to his mother in season two) and the other is called CoGeNT (some physicists need their shift key taken away from them.)

But a new type of detector started working recently.  Xenon is a gas in every breath you take, but being a noble gas just goes along for the ride, never interacting in your lungs.  But xenon can be refrigerated to below -162 degrees F where it becomes a liquid.   When a dark matter particle passes through it, it occasionally will give a single xenon atom a small kick.   That small kick causes the xenon’s atomic nucleus to move a short distance through the liquid—producing free electrons, heat, and light.   The highest frequency light your eyes can see is violet.  But energy deposited in xenon produces light with a  color a little bluer than violet, called ultra-violet light.  You can’t see it but particle detectors can.   The xenon detectors is enormous, 100 kilograms, hence its name XENON-100.  But XENON-100 doesn’t see the tell-tale ultra-violet light from dark matter collisions.   Is it because the others’ dark matter discoveries were wrong?  Or is there just not enough ultra-violet light being produced in the liquid xenon?  That’s what Sheldon and Koothrappali are arguing about.  And so. are. the physicists.

But the whiteboards today had nothing to do with this science.  Today’s whiteboards honored a special guest.  Once while talking to a Big Bang Theory writer, he recommended I watch the film Real Genius (1985).   I didn’t know what to expect but put it in my Netflix queue nevertheless.   When I saw it I was blown away….not necessarily by the story or the characters (which were fine), but by the important part: the scientific sets and dialogue.    It turns out that Real Genius had a scientific consultant,  Martin Gundersen, a professor of physics from across town, the University of Southern California (USC).    Now that I know how much goes into getting sets and stories right, I was in awe of what a great job they had done, from the sets to weaving physics right into the plot line.   So I sent Prof. Gundersen a fan letter.   He  responded and eventually was able to visit the set of The Big Bang Theory during the taping of this episode.


Prof. Martin Gundersen, the science consultant for Real Genius (1985). He recognized the whiteboard in Leonard and Sheldon's apartment during the taping of this episode.


So those of you that are whiteboard fans AND have a good memory know what was on the whiteboards.  It was identical to one of the boards used in Real Genius 25 years ago….



Chris Knight (Val Kilmer) steps out of the way so we can see the original whiteboard in Real Genius (1985).


I don’t want to spoil the plot of Real Genius by explaining how excimer lasers work.  It’s only been 25 years and not everybody has had a chance to see it yet.

Finally, we saw Sheldon make a smell of hydrogen sulfide and ammonia gas.  Hydrogen sulfide smells like putrefying eggs.  And ammonia smells like ammonia.   We were careful not to tell how hydrogen sulfide could really be made since it’s been in the news that people have been hurting themselves and others when making it with household chemicals.   We at The Big Bang Theory are nothing if not socially conscious.  So instead I imagined Sheldon made it with something only available around the lab,  an aqueous solution of hydrogen sulfide.   That immediately produces:

(NH4)2S →H2S + 2 NH3

By now I expect you are running out of the room.

28 Responses to “S04E04: The Hot Troll Deviation”

  1. Drew Scott Says:

    I loved that movie (Real Genius) when I watched it as a kid. A nice nostalgic reference, and another great blog post David.

  2. Dianoguy Says:

    Awesome! Love the behind-the-scenes info. Gonna have to get ahold of Real Genius myself sometime soon…

  3. Scott G Says:

    As if BBT wasn’t cool enough to watch as it is, paying homage to Real Genius just took it up even higher (let’s say to ultraviolet) in my personal ratings.

  4. Steve K Says:

    You’d never seen Real Genius before? Wow, they let just *anyone* be a science consultant these days, don’t they?🙂

  5. Zig zag zug Says:

    Hehehe. Trolls


  6. tejaswy Says:

    Love your site bro…

  7. Timon Piccini Says:

    Now,just a question. I’ve worked up North (Northern Canada) on the oil rigs and Hydrogen Sulphide is well known up their, because of it being a poison and very harmful in large amounts. I’ve never worked with it in a lab so I am assuming that the laboratory concoction is only a few PPM of actually Hydrogen Sulphide gas? But then again why did Sheldon have a gas mask?

  8. mango Says:

    The science behind the chemistry, was a bit stretched on this, for the joke’s sake. Hydrogen sulfide is only explosive or flammable at concentrations above 4% but you would be dead within seconds at a concentration of 1%

    • David Saltzberg Says:

      You are assuming the hydrogen sulfide was even distributed around the room. Perhaps a region of overdensity passed by the candle. Also note that Sheldon was wearing a gas mask and Raj claimed he has resistance since he is from India. (That’s a joke.)

      • Timon Piccini Says:

        But it is stretched because you can’t have an immunity to H2S nor can you use a gas mask ( only SCBAs work). Or at least that’s what you learn when you work in an oilfield. Can you correct me David? I’m just curious about use in the lab.

      • David Saltzberg Says:

        Yeah, that’s why I said it was a joke. I’m sticking with the uneven distribution of H2S gas in the room. Don’t try this at home (or the oilfield).

      • Phil Says:

        Old science rule of thumb –
        If it wriggles it’s biology
        If it smells it’s chemistry
        If it doesn’t work – it’s physics.

  9. David Saltzberg Says:

    Well some of you may have noticed that you could *not* have seen those whiteboards. This may be the only episode in the entire series that did not have a scene in the boys’ apartment. I didn’t even think to check that. I noticed it when I watched the episode. At least you can consider this tribute as real “behind the scenes” information. Maybe I will put them up in another episode…and y’all will know why.

    • Zig zag zug Says:

      This is getting crazy! The producers owe you a whiteboard close up, I say! I’m glad I come here to ogle the boards the way they should be. Sometimes I even start to think! (But I never finish!)

      Ammonia has a <25 ppm before danger limit (according to wikipedia anyway lol), and 25 ppm of H2S would be dangerous! The limit would be 8-10 ppm. From http://www.extension.iastate.edu/Publications/PM1963A.pdf we can deduce that at least 0.04 ppm of NH3 and at least 0.0005 ppm of H2S (it IS stinky!)

      I think Sheldon would of used a mixture of Ethanethioic acid to get his ammonia. The reaction:

      C2H4OS + H2O = C2H4O2 + H2S

      is endothermic and more easy to manage!

      And something else that reacts with C2H4O2 (an acid!) to get NH3

      H2N-R + H+ (from C2H4O2) = H3N + R + C2H3O2-

      The -R might be something that reacts unexpectededely to give a volatile combustible! A pentane something? I dunno, chemistry is tricky and has too many curvy arrows. @_@

      I got nothing! ^_^

  10. steve Says:

    this may be a stupid question (i’m not a scientist or anything)
    could it be something else that is kicking the xenon atom?
    how do they know its dark matter?

    will just them saying the xenon atom is kicked by dark matter make it exist?

    • David Saltzberg Says:

      Absolutely there will be a rate of other processes kicking the xenon or otherwise leaving energy in the xenon. The authors always need to estimate the rates of these effects (due to radioactivity and cosmic rays, for example) and then see if there is a statistically significant excess above that. The authors will need to convince everyone they did such calculation correctly, of not just their best estimate, but also over how much it could plausibly range (a “systematic” uncertainty.) For example the CoGeNT result says they cannot rule out more mundate effects or calculate their rates, so it isn’t really a discovery yet. If the experiments ever see a signal in xenon, suddenly everyone will look hard at their background estimates.

      • steve Says:

        if i understand the cogent project…they have a germanium detector the size of a hockey puck half mile underground…looking for particles of dark matter…which if i understand dark matter..is something that must exist because we cant explain the difference in what we think is the mass of a galaxy- which we cant really measure– and what we can see of the same galaxy?

        isnt that a circular argument like the chicken and the egg…

        i cant explain the mass of a galaxy so ill just make up dark matter to explain it?

      • feldfrei Says:

        @Steve: The point is that the velocity (kinetic energy) of stars circling around the centre of a galaxy is related to the total mass within this circle (potential energy) according to Newton’s law of gravitation and classical mechanics. Based on known rotation velocity as function of the distance from the centre one can estimate the actual mass which is much larger than the visible mass.

        It’s not a circular argument but rather a mismatch of two observation. Thus, either Newtons law and/or classical mechanics must be wrong or there is some kind of massive matter which is invisible.

        There are more observations indicating the existence of dark matter – see: http://en.wikipedia.org/wiki/Dark_matter

  11. Candy Says:

    I would of never of seen the connection with Real Genius.

    Thanks for your posts – I love reading them after watching the episode!

  12. Aaron B. Says:

    My favorite movie; I can quote almost every line of it. Tragic to think younger science geeks are missing it.

  13. steve Says:

    wouldnt newtons law be wrong if there is no gravitational constant?
    how do we know it doesnt fluctuate or change?

    • David Saltzberg Says:

      Actually other explanations for the motions of stars in our galaxy and galaxies among themselves do include modifying the theories of gravity. The theories are called MOND, for MOdified Newtonian Gravity. I think they have trouble explaining all the data, for example the distribution of various types of matter in the aftermath of collisions of clusters of galaxies. But I confess I have never sat down and read their whole argument.

  14. superGrover Says:

    “As soon as we apply a field, we couple to a state, it is radiatively coupled to the ground state. I figure we can extract at least ten to the twenty-first photons per cubic centimeter which will give one kilojoule per cubic centimeter at 600 nanometers, or, one megajoule per liter. ”
    – Chris Knight in Real Genius

    A Martin Gunderson is credited with the role of ‘Math Professor’ in the film. Typecasting?

  15. Erik Says:

    This brings back memories.. When I was 14 (29 years ago) I made some hydrogen sulfide. Stupidly I used concentrated H2SO4. A friend of mine brought it in class and thought it funny to throw it on a class mate. It burned a hole in his sweater. My parents didn’t think that was funny so they took my whole lab apart (took me 2 years to build). Luckily they never caught on to my experiments with potassium chlorate and sugar….

  16. Gregg Says:

    I am still waiting for Chris Knight to appear on an episode of the Big Bang Theory.

  17. Tradução: “S04E04: The Hot Troll Deviation (A Deviação da Troll Atraente)” « The Big Blog Theory (em Português!) Says:

    […] feita por Hitomi a partir de texto extraído de The Big Blog Theory, de autoria de David Saltzberg, originalmente publicado em 14 de Outubro de […]

  18. Michal Says:

    Well, I have no direct experience on generating H2S and NH3 at the same time and space, but let me make some guess based on similar chemicals:
    … H2S is a weak acid, HCl is an acid as well and exists as gas as well as H2S does.
    … Ammonia is a base. As such likes to react with acids, even in gas phase.
    … if you put HCl together with NH3 in gas phase, you get a very nice white fog, as tiny ammonium chloride crystals are formed. Such fog (or shall I be using the proper term aerosol in here?) is pretty stable as the crystals are even electrically charged.

    So I would say H2S does something similar with ammonia. Thus, none would get poisoned by the powerful combination of the two, but they would have real trouble to find the door to open it with mask or without. But the fog “falling” out of the doorway would have been a very nice effect.

  19. Mark Says:

    Shouldn’t Raj be dead, or at least in distress? Hydrogen Sulfide is highly toxic, even at fairly low ppm concentrations (starts out attacking the mucus membranes). And, even before it reaches a lethal concenetration, it destroys the sense of smell, so you no longer notice it as it becomes more dangerous. When we’ve worked with reactions in the lab which can create H2S, we all had to wear personal detector alarms, which alerted at very low concentrations. If it’s dispersed enough in the room that Leonard can smell it in the hall, then its got to be at a danger level throughout the room, not just in isolated pockets.

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