A Brief Explanation of Planck's Constant and the Birth of Quantum Physics
Planck's constant is a pretty important part of modern physics, but it's also pretty confusing. Maybe you were wondering what it was while reading about the new kilogram definition. Well never fear, because this video from PBS Space Time will tell you everything you need to know about Planck's constant/
In the late 1800's, physics was facing a crisis. Physicists were trying to model atomic vibrations, but they kept getting it wrong. All the physics they knew at that point said it should look a certain way, but reality looked completely different and no one knew why.
The problem would be solved by a man named Max Planck. Previous physicists had assumed that atomic vibrations were continuous; that is, they could vibrate at any frequency. Planck decided to assume that atoms could only vibrate at certain frequencies that were whole number multiples of some base frequency, which he called h. In other words, atoms could vibrate at the h frequency, or 2h, or 3h, but not 2.5h.
This was a really bizarre assumption, but it worked. It turns out that atoms (and a lot of other stuff) can only take certain specific values. In physics, we say that atomic vibrations are quantized. Planck's discovery would ignite a flurry of research in a new field of physics called quantum mechanics. That h constant that Planck discovered would eventually be called Planck's constant, and it literally puts the "quantum" in "quantum mechanics."
Source: PBS Space Time
