Don Melrose, also at Sydney, points out that the gas in the middle of the galaxy might already be so strongly ionised, and thus such a good electrical conductor, that current would leak away rather than build up into a concentration like the Snake.

ECONOMIST: Here be serpents

Their method was based on the observation that electrical currents will be induced in a conductor (such as water) when it is faced with a magnetic field that varies over time.

ECONOMIST: Blue moon