In Firefly episode eight, Out of Gas, the engine breaks, causing the oxygen and heating to go offline on Serenity. For some reason, the gravity stays on. Mal (the captain) is able to move about freely, clearly drawn to the ground. Items are not floating about. The backup engine was not working, as stated by Kaylee (the engineer) when asked about extra time for oxygen.
Is there a rare metal in the Firefly universe that, when no longer near a gravitational pull, emits its own? Or some kind of gravity field that is not created by a piece of machinery that is required to be on? Is this ever addressed?