Almost every case of fine-tuning discussed so far concerns nuclear reactions and their consequences, in the realm of the very small. This is what could happen if the universal constants and parameters were not fine-tuned:
- Either
there would be no hydrogen in the universe, and the stars
would last too short a time for life to appear.
- Or
the fusion of hydrogen to give helium would not be possible,
so there would be no stars.
- Or
oxygen or carbon, essential elements for life, would
not be generated in stars.
In all these cases, concepts and ideas are drawn from particle physics, astronomy, and cosmology.


