  Core-collapse supernovae presumably explode because trapped neutrinos push
the material out of the stellar envelope. This process is directly controlled
by the weak scale $v$: we argue that supernova explosions happen only if
fundamental constants are tuned within a factor of few as $v \sim \Lambda_{\rm
QCD}^{3/4} M_{\rm Pl}^{1/4}$, such that neutrinos are trapped in supernovae for
a time comparable to the gravitational time-scale. We provide analytic
arguments and simulations in spherical approximation, that need to be validated
by more comprehensive simulations. The above result can be important for
fundamental physics, because core-collapse supernova explosions seem
anthropically needed, as they spread intermediate-mass nuclei presumably
necessary for `life'. We also study stellar burning, finding that it does not
provide anthropic boundaries on $v$.
