Comment Re:How is this different from holding a Compass? (Score 1) 289
Evolutionarily, we at least have the vestiges of a "sense" of magnetic bearing - our brains contain tiny magnetite crystals, similar to (though much smaller and fewer) those found in birds, which do function to give them a sense of absolute direction. So whether or not we can reactivate that sense, we at least (probably) have the underlying wiring necessary to use it.
As for the cross-modality of this... Judging by TFA and other similar experiements about which I've read, I would say that we can indeed awaken that sense by providing an alternate means of inputting the relevant data (in this case, via touch).
But to compare this to looking at a normal compass, the biggest difference, I would say, comes from it providing constant and passive feedback about the local magnetic environment. Looking at a compass will indeed tell you which way to call "North", but you don't "experience" it as anything but a name for the way the needle points. If instead, you always had an accurate sense of North, I would expect it to affect you much more strongly - Your proprioception would suddenly include an absolute orientation rather than merely relative positioning.