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.
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.
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….
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.