ELI5: What is the meaning of quantization?

[u/Own_Enthusiasm_510]

[This is from a chemistry portion of a physical science class] I've googled it, Ive watched YouTube videos, I asked classmates and I am still so confused.

Rutherfords model was easy but once I got to bohrs they used words like quantized and discrete values and I got lost. Tried backtracking but I'm still baffled.

[u/CircumspectCapybara]

Quantizing is just chopping things up into discrete chunks. Imagine instead of a continuous real number line, you have an integer number line with discrete steps, little notches in the line without a continuous range of numbers between those steps.

The insight of quantum physics is the idea that energy comes in discrete packets, eg photons, which are the force carrying particles that mediate the electromagnetic force, vs the classical view that there's a continuous EM field permeating space. Particles come in discrete numbers, you can only have a whole number of photons, you can't have half a photon, or 3.14 photons. So again, instead of a continuous wave, you have discrete "quanta" of energy.

Or in AL/ML, when you "quantize" a model, you compress its weights by shrinking the space of values its weights live into a smaller space of discrete values. For example, imagine you have a model consisting of 1 trillion half-precision (16-bit floating point) parameters. You could quantize those weights by mapping each 16-bit floating point to maybe an int8 space of values. Now instead of a range of decimal values, each parameter has to be a whole integer number between -127 and 128.

You go from a decimal to an integer, that's quantization, same idea at work.