Quantum mechanics rule life (Introduction)

by David Turell , Thursday, May 30, 2019, 05:42 (2003 days ago) @ David Turell

The important Pauli exclusion principle:

https://www.forbes.com/sites/startswithabang/2019/05/28/this-little-known-quantum-rule-...

"It might make you wonder how this occurs. How do atoms, made of atomic nuclei and electrons, which come in less than 100 varieties, give rise to the enormous diversity of molecules, objects, creatures and everything else we find? We owe the answer to one underappreciated quantum rule: the Pauli Exclusion Principle.

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"Most of us barely give a second thought to the Pauli Exclusion Principle, which simply states that no two identical fermions can occupy the same exact quantum state in the same system.

"Big deal, right?

"Actually, it's not only a big deal; it's the biggest deal of all. When Niels Bohr first put out his model of the atom, it was simple but extremely effective. By viewing the electrons as planet-like entities that orbited the nucleus, but only at explicit energy levels that were governed by straightforward mathematical rules, his model reproduced the coarse structure of matter. As electrons transitioned between the energy levels, they emitted or absorbed photons, which in turn described the spectrum of each individual element.

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"The Pauli Exclusion Principle — and the fact that we have the quantum numbers that we do in the Universe — is what gives each individual atom their own unique structure. As we add greater numbers of electrons to our atoms, we have to go to higher energy levels, greater angular momenta, and increasingly more complex orbitals to find homes for all of them. The energy levels work as follows:

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"Each individual atom on the periodic table, under this vital quantum rule, will have a different electron configuration than every other element. Because it's the properties of the electrons in the outermost shells that determine the physical and chemical properties of the element it's a part of, each individual atom has its own unique sets of atomic, ionic, and molecular bonds that it's capable of forming.

"No two elements, no matter how similar, will be the same in terms of the structures they form. This is the root of why we have so many possibilities for how many different types of molecules and complex structures that we can form with just a few simple raw ingredients. Each new electron that we add has to have different quantum numbers than all the electrons before it, which alters how that atom will interact with everything else.

"The net result is that each individual atom offers a myriad of possibilities when combining with any other atom to form a chemical or biological compound. There is no limit to the possible combinations that atoms can come together in; while certain configurations are certainly more energetically favorable than others, a variety of energy conditions exist in nature, paving the way to form compounds that even the cleverest of humans would have difficulty imagining.

"But the only reason that atoms behave this way, and that there are so many wondrous compounds that we can form by combining them, is that we cannot put an arbitrary number of electrons into the same quantum state. Electrons are fermions, and Pauli's underappreciated quantum rule prevents any two identical fermions from having the same exact quantum numbers.

"If we didn't have the Pauli Exclusion Principle to prevent multiple fermions from having the same quantum state, our Universe would be extremely different. Every atom would have almost identical properties to hydrogen, making the possible structures we could form extremely simplistic. White dwarf stars and neutron stars, held up in our Universe by the degeneracy pressure provided by the Pauli Exclusion Principle, would collapse into black holes. And, most horrifically, carbon-based organic compounds — the building blocks of all life as we know it — would be an impossibility for us.

"The Pauli Exclusion Principle isn't the first thing we think of when we think of the quantum rules that govern reality, but it should be. Without quantum uncertainty or wave-particle duality, our Universe would be different, but life could still exist. Without Pauli's vital rule, however, hydrogen-like bonds would be as complex as it could get."

Comment: As usual quantum mechanics is at the base of our reality.