The six numbers that build a cosmos
Martin Rees's dials — gravity, the nuclear force, dark energy, and three more — and what each one does.
1 min read
In Just Six Numbers, the astronomer Martin Rees argued that our whole universe hangs on roughly six quantities. Get any badly wrong and you get no stars, no atoms, or no time to make either. These are the exact dials in our Universe Tuner.
N — gravity's grip
How strong gravity is compared with the forces inside atoms. Ours is fantastically weak, which is why stars burn slowly and live for billions of years. Crank it up and stars flare and die like matches.
ε — the nuclear glue
How efficiently hydrogen fuses into helium — about 0.007 of its mass becomes energy. A hair lower and nothing fuses; a hair higher and hydrogen burns away at birth, leaving no water and no long-lived suns.
Ω, Λ, Q and D
Ω sets how much matter the cosmos holds; too much and it recollapses, too little and nothing gathers. Λ, dark energy, sets how hard empty space pushes apart. Q, near one part in 100,000, is how lumpy the young universe was — the seeds of galaxies. And D is simply the number of spatial dimensions: three, which alone allows stable orbits and stable atoms.
Six numbers. Nudge any of them and the universe forgets how to make you.