Questions regarding inhuman speed.

[Kujinata]

Long story short, I made a 20th level character that if using the run action can go past Mach 4. My gaming group has always played using physics which poses several questions. Wouldn't this person just disintegrate? If so how fast can he go without harming himself? Would he die from pure sonic damage? Can he run on water? Can he run up walls?What about people nearby? How would they be affected by the sonic boom that he produces? Please feel free to make your own rulings on this subject, usually pathfinder covers everything but this appear to be a gray area. I may have missed some additional rulings feel free to add whatever you like to this conversation.

[The Mortonator]

Say what now? Are you sure your decimal point was in the right place?

If you have a magic item or su, breaking physics is kinda what those do.

[Shiroi]

I'd like to see the build, that's a thing I'm trying to do myself with a character.
And yes, without protection you pretty much hit a flat wall of air and take falling damage and sonic damage equal to *nope, do not want*.