The Fine-Tuning Argument
Tweak the cosmological constant by 1 part in 10^120 and nothing exists. That's the whole argument.
Grounded in the research on the fine-tuned universe
the dials
The universe runs on a set of numbers. The strength of gravity, the mass of the electron, the cosmological constant that drives cosmic expansion. None of them are forced by the math. They could've been anything. The fine-tuning argument says they sit in a freakishly narrow band where life, stars, and chemistry are even possible. Move a dial a hair and you get a dead universe, or no universe at all.
the headline number
The cosmological constant is the poster child. It controls how fast empty space expands. For galaxies to ever form it has to be tuned to roughly 1 part in 10^120. That's a 1 with 120 zeros after it. Roger Penrose, no theist, calculated the low-entropy starting state of the universe at 1 in 10^(10^123), a number so big you can't write the exponent out in the observable cosmos. These aren't fringe figures. Physicists call this 'the fine-tuning problem' and lose sleep over it.