The Kilcher Homestead is a 600 acre Pioneer Homestead that has been protected for perpetuity via a ConservatIon Easement. The Kilcher Family has also preserved the Historic Cabin and site as a LIving Museum.
Yes, negative pH is possible, but not in water as a solvent. The range of pH in water is 0 to 14 (to be more precise, it is -1.7 to 15.7, but for simplicity's sake, we start with the usual values.) Thus, what pH indicates is the ability of the acid to form H3O+, which can then donate a proton.
Reasonably pure water in a normal room will have a pH of around 6. This is due to carbon dioxide dissolving in the water to create carbonic acid (H2CO3). While reverse osmosis will remove most of the larger ions, if you leave the water out in the room it will dissolve carbon dioxide from the air.