Basically, Mjolnir is a fixed quantum point with sentience. However, it does follow a few rules.
1.) Only those that Mjolnir deems "worthy" can move Mjolnir.
2.) When it is being moved by someone "worthy", it has the same physics as if it were made of steel (unless the wielder desires otherwise, in which case the "weight" will alter).
3.) It obeys the laws of gravity as if it were made of steel (unless above circumstances apply).
The way fixed quantum points move is a bit strange. Being fixed, they don't move. But when Mjolnir wants to change positions, it moves the ENTIRE UNIVERSE around it. Additionally, external forces can move the universe when in contact with these fixed quantum points if they are on the same wavelength. Mjolnir is sentient, and is therefore able to adjust its wavelength to fit the person who it wants to be wielded by. Additionally, because it is sentient, it knows to obey the laws of gravity. This is how Thor and others are able to fly with its help, because Mjolnir doesn't NEED to obey the laws of gravity. Mjolnir can do whatever it wants.
1.) Only those that Mjolnir deems "worthy" can move Mjolnir.
2.) When it is being moved by someone "worthy", it has the same physics as if it were made of steel (unless the wielder desires otherwise, in which case the "weight" will alter).
3.) It obeys the laws of gravity as if it were made of steel (unless above circumstances apply).
I knew it!!!