[mmmBacon]

@twtw was not arguing that one can induce a current in the vacuum. However, I did say that a surface can arc in vacuum. This is because a surface can emit charges either thermally or in presence of a large electric field. This is correct and didstinct from current induction in media. Please note this phenomenon should not be confused with arc discharge in gas.

See: https://en.m.wikipedia.org/wiki/Vacuum_arc

[twtw]

Right, but that effect is pretty much unrelated to the characteristic impedance of free space and doesn't mean that vacuum is not an insulator.

[mmmBacon]

I’m sorry but I fundamentally disagree. GP said vacuum is a perfect insulator. Comment was in response to that demonstrating that it is not.