From http://what-if.xkcd.com/73/
The physicist who mentioned this problem to me told me his rule of thumb for estimating supernova-related numbers: However big you think supernovae are, they're bigger than that.
Here's a question to give you a sense of scale:
Which of the following would be brighter, in terms of the amount of energy delivered to your retina:
A supernova, seen from as far away as the Sun is from the Earth, or
The detonation of a hydrogen bomb pressed against your eyeball?
Applying the physicist rule of thumb suggests that the supernova is brighter. And indeed, it is ... by nine orders of magnitude.
Holy shit.
To think that the supernova needs to be ~31622 AU and it's as bright as a fucking H-bomb pressed against the eye...
However big you think supernovae are, they're bigger than that, indeed.