Atoms are sometimes metaphysical bets; sometimes, they are scientific facts; others, phenomenological tools. It is a good idea to not mix up those different concepts. Then, what’s your indivisible?
What’s your indivisible?
The word atom is used in different contexts. First, there is the ‘metaphysical atom’ with a meaning similar to that of the Greeks, as the indivisible. In this context, atom hosts the metaphysical hypothesis that there is an absolute minimum size for things that the universe is made of. This is the meaning meant by Dalton when he wrote:
“Matter, though divisible in an extreme degree, is nevertheless not infinitely divisible. That is, there must be some point beyond which we cannot go in the division of matter. The existence of these ultimate particles of matter can scarcely be doubted, though they are probably much too small ever to be exhibited by microscopic improvements. I have chosen the word atom to signify these ultimate particles.”
Many scientists believe in something like this. But it is not a scientific concept. It is a metaphysical bet. We do not need any evidence to speculate whether matter has a minimum size. It is for free. We can even go beyond and ask ourselves, are there atoms of space, or atoms of time?
Due to a sad accident in the history of chemistry, atom is also the name given to the basic units forming matter. They are clouds of electrons surrounding single nuclei, each one weighing something like 10-26 kg. Chemical atoms are scientific facts with a bad name. If I could choose, I would call them elementons.
It is clear that the chemical atom and the metaphysical atom are completely distinct of each other. But things can always get more complicated, can’t they?
Atom can still have a third meaning, as the basic unity of a phenomenon. In the sense that bit is the atom of digital information; or cell is the atom of a living organism; or – as for some biologists – gene is the atom of evolution. These are the ‘phenomenological atoms’.
My own bet: an atomless universe
Scientific research, far from being passive observation of a nature that gives itself to our discovery and delight, is a dialog with this same nature; a new alliance, as Prigogine used to say. In science, the basic unit of a phenomenon depends on what we are asking nature.
Thus, to find the thermodynamic properties of a gas, like temperature or pressure, the basic unity are molecules. In the analysis of a chemical reaction, where the important information is the distribution of atoms before and after the reaction, the chemical atom is really the basic unity. But if we want to understand the reaction at the level of charge transfers, the indivisibles are photons, electrons and nuclei.
However, the difference between having nuclei as basic units, or having protons and neutrons as those units, is the difference between investigating with few thousand or few million electron-volts of energy.
Go to much higher energies and the phenomenological atoms are quarks, leptons and bosons. Many clever people think that we could go to the next level with hyperdimensional strings.
In the end of the day, nature shows itself as rich as our questions are. In the electron beams that generated the image in old TVs, electrons were rigid balls, which would have made Democritus very happy.
But it is enough that we take a closer look at this electron, and its fermionic features start to manifest. Not that we could split it into smaller particles, it is much more weird, it delocalizes though space as a wave.
Now, it s my turn of making a metaphysical bet: if science is a dialog with nature, atom as an absolute indivisible is a conceptual mistake. While we have imagination, enough energy to put new questions, and the laws of physics allow, we will always be able to find new levels of complexity.
We may just live in an atomless universe.
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- If you missed Part I of this text, here it is.
- Still about Part I, my friend Anderson Tomaz brought to my attention the following passage from the influential text book “Introduction to Elementary Particles” by D. Griffiths:
“It is fashionable to carry the story all the way back to Democritus and the Greek atomists, but apart from a few suggestive words their metaphysical speculations have nothing in common with modern science, and although they may be of modest antiquarian interest, their genuine relevance is negligible.”
Dalton’s quote is from his manuscript notes, Royal Institution lecture 18, January 30, 1810. It is cited in “The study of chemical composition. An account of its method and historical development, with illustrative quotations” by Ida Freund.
- Some books age well.”Order out of chaos” by Ilya Prigogine and Isabele Stengers is one of them.
- A cool trip from the smallest to the biggest things in the universe: