Do people generally bring gravity meters (or whatever this may be called)?
There are lots of theories on gravity, one being that it is not a product of earth's magnetic core but a biproduct of time-space, by which we are being held onto earth rather than stuck to it like a paperclip to a magnet. I don't know if gravitational anomalies are the cause of objects floating by but the fluctuation of some type of force may be the cause of some type of inter-dimensional rippling effect that would cause things to "disappear" for a time (and maybe appear in another dimension?).