27. Cobalt: Mischief Managed

Cobalt is a tricksy little element, which means the scientists who’ve dealt with it the most are some of the cleverest people to have ever walked the Earth.

Featured above: Chien-Shiung Wu doing what she loved most.

Show Notes

Dog People Or Dragon People? Gamers among the audience will recognize “kobolds” as the trap-crafting cave-dwellers from many fantasy role-playing games. This is their origin, as well! However, Dungeons & Dragons is responsible for creating a distinction where previously there was none, as kobolds, goblins, bugbears, boogeymen, and many other creatures from European folklore used to all be different words for the same thing, with the same etymological origin.

Master of DMCA Takedown Notices: You might have noticed that the music played in the background is definitely not Ride the Lightning by Metallica. If you were around for the downfall of Napster, you understand why.

“The Wu Experiment” Would Be A Decent Band Name: Suffice it to say, I simplified things a great deal for the sake of explaining Chien-Shiung Wu’s parity experiment. My aim was to make it as easy to grasp as possible without actually misleading any listeners, so anyone curious could continue studying what Wu did.

First of all, parity symmetry *does* hold true in the vast majority of circumstances, in the same way that you don’t need to employ the theory of relativity when calculating the trajectory of a cannonball. For the strong nuclear force and for electromagnetism, parity symmetry holds up. Wu directly tested the veracity of parity on the weak nuclear force.

And, just for the record, Wu’s experiment suggests that our universe is “a semiambidextrous southpaw.”

Veritasium made a pretty great video recently that explains the experiment in a little more detail:

Nonetheless, this is still kind of a watered-down explanation. That’s kind of necessary. To wit: On the Ask Science subreddit, /u/Greebo24 explained what made cobalt the ideal material for Wu’s experiment:

  1. It is a Gamow-Teller decay with a spin difference of 1 (ground state of 60 Co is 5+, decaying into the first 4+ state in 60 Ni) Quote: “One might point out here that since the allowed beta decay of Co involves a change of spin of one unit and no change of parity, it can be given only by the Gamow-Teller interaction. This is almost imperative for this experiment.” It is required so that the electron helicity and the neutrino helicity are well defined. Both the electron spin and the neutrino spin have to add in a maximally stretched configuration to the Ni 4+ state to get the Co 5+ state. This makes it possible to deduce the neutrino helicity from all other observables.
  2. Co can be polarised “by the Rose-Gorter method in cerium magnesium (cobalt) nitrate, and the degree of polarization detected by measuring the anisotropy of the succeeding gamma rays.” This cools the salt containing the Co down into the mK range.

If that makes sense to you, congratulations, because you’re in the 1% of people who might not be alienated by that kind of heady material.

Ain’t No Blues: Blue is not a common color in nature. Even blueberries aren’t exactly blue. Joe Hanson spends an episode of It’s Okay To Be Smart explaining why that is — and explains how butterflies created the color blue not with pigments or dyes, but with tiny microscopic structures:

And Vsauce2 discusses the “invention” of blue here — more of a slow acknowledgement that blue is its own color, but nonetheless interesting:

Fun Fact: If you search youtube for “cobalt blue” you’re gonna see a lot of spiders. You’ve been warned.

Click To Read Transcript


  1. Scientific American, Channeling Ada Lovelace: Chien-Shiung Wu, Courageous Hero Of Physics. Maia Weinstock, October 15, 2013.
  2. Time, The Manhattan Project Physicist Who Fought For Equal Rights For Women. Joanna Scutts, June 14, 2016.
  3. ThoughtCo, Chien-Shiung Wu: A Pioneering Female Physicist. Jone Johnson Lewis, February 10, 2018.
  4. The New Inquiry, Where State Politics Meets Gender Politics: Chien-Shiung Wu And The Manhatthan Project. Kanta Dihal, January 18, 2018.
  5. Gizmodo, Madame Wu And The Holiday Experiment That Changed Physics Forever. Jennifer Ouellette, December 31, 2015.
  6. Hackaday, There Is No Parity: Chien-Shiung Wu. Will Sweatman, September 28, 2017.
  7. Berkeley Lab, Chien-Shiung Wu, Physicist Who Helped Change The World. May 19, 2015.
  8. Biography.com, Chien-Shiung Wu.
  9. The Atomic Heritage Foundation, Einstein-Szilard Letter. Primary source.
  10. Nuclear, Biological, And Chemical Warfare, p. 76. K. Bhushan, G. Katyal, 2002.
  11. MotleyTech.net, The Man Who Changed War, Peace, And The World. March 29, 2015.
  12. Cambridge Polymer Group, Cobalt Brew: Frothy Foam, Sick Heart. May 18, 2017.

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