[FiatLuxDave]

This is incorrect. The Earth's magnetic field is about 30 microTesla, not 30 Tesla. Also, the flog floating effect (one of my old profs actually did that experiment!) depends upon the field gradient as well as the field strength.

Field strength is not the same as force. The reason why they don't levitate things bigger than frogs with a 16 Tesla field is because bigger things won't fit into the magnet bore, not because 16 T is too weak. One of the techs who worked on one of those serious magnets (at NHMFL) told me that if they put an iron bar in the middle of the bore, it would generate enough force to lift a 747. Of course, that much force would probably break the floor under the magnet, and it's really hard to fit a 747 into the lab.