24 hours eh? Such little time to learn so much!
I would spend a few learning arabic, sanskrit and latin and one other dead language i have forgotten (not that the ones mentioned are dead but latin is)
I spend some more reading the key books in physics, maths and history
I would take a telescope and gaze at the stars hopefully while observing the northern lights and then swim in the great barrier reef watching all the colours.
I would ask all those I know to forgive me for anything wrong I have done towards them and try to forgive them too.
Lastly I'd write a message to someone I didn't know (like a time capsule) telling them that although the world is slightly messed up they have the power to change it if they wish to do so. All they need to do is take the first step. :D