The Moon and Earth are approximately spherical conductive balls and the Earth has a self-capacitance of around 710uF. Is there ever a significant potential difference in the Earth-Moon system? Is there even a way to tell if there is? Presumably the Apollo astronauts didn't expect to be electrocuted on landing.
I was thinking that a huge charge would not build up because they are both bathed in a flow of charged particles from the Sun which I would have thought would equalize the voltage. Is this true?
Also what voltage difference would have to build up for a massive bolt of lightening to jump through space between them?