Katie Oppenheimer: Can you explain quantum mechanics to me?
J Robert Oppenheimer: Well, this glass, this drink, this table, uh… our bodies, all of it. It is mostly empty space. Collections of small energy waves linked together.
Katie Oppenheimer: with what?
J Robert Oppenheimer: Attractive forces are strong enough to convince us that matter is solid, to prevent my body from passing through yours.
Fast forward to the year 2023, where Mario Barbati is a theoretical chemist and physicist researching the interactions of light and molecules. He is also Professor of Chemistry at Aix-Marseille University in France. Writing this week to TimeBarbati says thatThere are no empty spaces inside an atom.
“the an empty atom The image is probably the most frequently repeated error in popular science.”
It’s not clear who created this legend, but it’s almost certainly Carl Sagan in his classic TV series Universe (1980), played a decisive role in its publication. After questioning how small the nucleus was compared to an atom, Sagan concluded, “Most of the mass of an atom is in its nucleus; electrons, by comparison, are just clouds of moving fluff. Atoms are essentially empty space. Matter is mainly composed of nothing.” I still remember how deeply those words ran into my mind when I heard them as a child in the early 1980s. Today, as a professional theoretical chemist, I know that Sagan’s statements fail to capture some of the fundamental features of atoms and molecules…
The misconceptions that fuel the idea of an empty atom can be dismantled through careful interpretation of quantum theory, which describes the physics of particles, atoms and subatomic particles. According to quantum theory, the fundamental units of matter—such as electrons, nuclei, and the particles that make them up—can be pictured as either waves or particles. Leave them to develop on their own without human intervention, acting as erratic waves in the form of continuous clouds. On the other hand, when we try to observe these systems, they appear to be localized particles, like bullets in the classical world. But accepting quantum predictions that nuclei and electrons fill space as continuous clouds has a bold conceptual price: it implies that these particles do not vibrate, spin, or spin. They inhabit a small, motionless world where time only occasionally plays a role…
A molecule is a body at rest without any internal motion. Quantum clouds of all nuclei and electrons remain absolutely constant for a molecule with a well-defined energy. Time doesn’t matter…but time does come into play when one molecule collides with another, triggering a chemical reaction. Then the storm hits. Quantum stability explodes when parts of the electron cloud flow from one molecule to another. Clouds mix, reshape, merge, and split. Nuclear clouds rearrange themselves to adapt to the new electronic configuration, and sometimes even move between molecules. For a fraction of a picosecond (10-12 seconds or a billionth of a millisecond), the storm rages and reshapes the molecular landscape until rest is restored in the newly formed compounds.