Stellar Nucleosynthesis
Stellar nucleosynthesis is the process by which stars forge elements heavier than hydrogen. The Big Bang produced primarily hydrogen and helium; nearly everything else in the periodic table was synthesized inside stars and distributed through the universe when those stars died.
The mechanism is nuclear fusion under extreme temperature and pressure. In the core of a star like the sun, hydrogen nuclei (protons) fuse into helium — the process that powers the sun's light and heat. As a star exhausts its hydrogen, it collapses further, raising the temperature and pressure until helium fuses into carbon and oxygen. In more massive stars, the process continues: carbon into neon, oxygen into silicon, silicon into iron. Iron is the end of the line — fusing iron requires energy rather than releasing it, so a massive star's core collapses catastrophically in a supernova.
The supernova explosion disperses the newly synthesized elements into space, seeding interstellar clouds that eventually collapse into new stars and planetary systems. The elements that make up the Earth — and the atoms in every living organism — were forged in the cores of stars that died before the Sun was born.
Feynman's Glass of Wine
Feynman uses stellar nucleosynthesis as the payoff of his argument that physics is not separate from biology or chemistry. Looking at a glass of wine: the water molecules in it contain oxygen forged in stellar cores; the carbon in the alcohol was built the same way; the iron in your blood traces back to a supernova. "All the atoms of our body were once part of the sun," and before that, earlier stars. The atoms are not young. They are cosmic.
This is the final refutation of the idea that "physics" and "life" are different kinds of things. Life is made of atoms; atoms are made in physics; therefore life is physics — not in a reductionist sense that collapses the interesting questions of biology, but in the sense that all of it is continuous.
Connections
- atomic-hypothesis — the atoms forged in stars are the same atoms that make up life
- conservation-of-energy — fusion releases energy by converting mass; E = mc²
- dna-double-helix — the carbon, nitrogen, and phosphorus in DNA are stellar products