In the final episode of Netflix's wildly popular series "Stranger Things" the fate of not just the characters but the entire world, hangs on a character's ability to remember Planck's constant.
Named for the German physicist Max Planck, Planck's constant describes the behavior of particles and waves, including the particle of light, the photon. Planck's constant is represented by h, and is:
6.62607015 x 10-34 Joule-seconds.
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Recognizing that a molecule was the smallest unit of any substance, Planck wondered if there was a smallest unit of energy, that is, if energy could be "quantized".
By measuring the black body radiation given off by vibrating atoms, Planck determined that when energy transfers, it moves in set amounts called quanta.
He determined that the frequencies of the radiation waves were all multiples of the number he called h. While frequencies of 2h or 3h are possible, a frequency of 1/2h is not. For this discovery, Planck received the 1918 Nobel Prize in Physics.
To determine the energy of a particle such as a photon, Planck's constant is multiplied by the frequency of its wave:
E = hf
Another version of Planck’s constant is called h-bar, and it is the quantization of angular momentum. The angular momentum of a particle such as an electron can only be a multiple of h-bar.
The Keys to "The Upside Down"
In the "Stranger Things" episode, Planck's constant is the code to open a safe that contains keys that will close the gate to "the Upside Down", that other world that takes innocents such as Barb.
When Sheriff Jim Hopper enters the wrong code, it's up to Dustin to reach out via ham radio to his girlfriend from camp, Suzie, to get Planck's constant.
Unfortunately, Suzie wants to sing a duet with Dustin, the theme from the movie "The Neverending Story". After a musical interlude, Suzie reals off Planck's constant as 6.62607004, Dustin relays the information to Hopper, and the safe opens.
However, the answer might, or might not, have come in time to save Hopper, and there's another problem. "Stranger Things" is set in 1985, and back then, Planck's constant would have been its 1973 value, which was 6.626176 x 10-34 Joule-second. The value that Suzie gives Dustin is actually the 2017 value, which was 6.62607004 x 10-34 Joule-second.
Why the Differences?
Planck's constant has changed over the years because scientists have learned to measure it better. Using more sophisticated instruments, in 2018 Planck's constant was updated and adopted as part of the International System of Units. It is now:
6.62607015 x 10-34 Joule seconds.
So, the next time, you're trying to save the world, you'll know what to say.
The 0.7% Solution
Planck's constant plays a part in our very existence. The fusion reaction that takes place on the Sun fuses four hydrogen atoms into one helium atom. In that process, approximately 0.7 percent of the hydrogen's mass is converted into energy via Einstein's famous equation E=mc2.
While that might not seem like a lot, it's been enough to keep out planet toasty for the last 4.5 billion years. Scientists call this 0.7 percent a "Goldilocks number" because it is exactly right to permit life as we know it.
The process of hydrogen fusion is a delicate dance. First, the reaction produces deuterium, an isotope of hydrogen whose nucleus consists of one proton and one neutron. Then, two protons collide, causing one of the protons to shed its electrical charge and become a neutron.
If the efficiency of the hydrogen fusion process was 0.6 percent, the neutron and proton would not bond to each other to form a deuterium atom, and it would be too cold for helium to be created. Since helium is the first step toward producing the rest of the elements, the heavier elements of which you and I are formed, would not be created.
If hydrogen fusion had an efficiency of 0.8 percent, helium would form too easily, and there wouldn't be enough hydrogen left over to create water. Without water, life as we know it wouldn't exist.