# The Space Station Grounding Problem **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [September 10, 2002, 10:56pm UTC](https://boards.straightdope.com/t/the-space-station-grounding-problem/127861 "2002-09-10T22:56:53Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![Wikkit](https://avatars.discourse-cdn.com/v4/letter/w/c0e974/32.png) [@Wikkit](https://boards.straightdope.com/u/Wikkit)\ **Post date:** [September 15, 2002, 7:53am UTC](https://boards.straightdope.com/t/the-space-station-grounding-problem/127861/21 "2002-09-15T07:53:02Z")
> [@](#): > > \*Originally posted by calliarcale \* > \*\*As another user pointed out above, it also poses a problem for docking if that additional charge is allowed to accumulate, it could result in a large shock between the ISS and the arriving spacecraft. I would bet that there is some grounding at this time, but it’s not much. I’ve watched videos of dockings and I’ve never seen a _visible_ spark, at any rate. \*\* How would a visible spark even be possible? As pointed out, it’s not absolute vacuum, but it sure isn’t normal atmosphere. When you get an electric arc on the surface, you can see it becasue the air is getting heated to a point where it glows. Without air, you just get electrons jumping around, and I don’t think you’d be able to see that any more than you can see the electron stream in a clear CRT. ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [September 15, 2002, 10:15am UTC](https://boards.straightdope.com/t/the-space-station-grounding-problem/127861/22 "2002-09-15T10:15:27Z")
**Mister.Physics** said: > [@](#): > > The ball is very different than its surroundings - true, which is exactly why it should not be given an “absolute zero” potential. It is very positively charged compared to the “normal” (ie neutral), which is why it is at very high potential. But isn’t that a bit like talking about gravitational potentials, i.e. gravity fields, and heights? You take your lowest point and call that zero, and define all heights off that, and that works fine unless a sinkhole suddenly appears under you and you find yourself at the top of a new potential. 😉 The point is, phyisicists have good reasons for relating to “absolute” voltages, whereas most people (i.e. engineers, technicians, people tinkering with their light sockets, etc) are only worried about the relative difference. It sure makes the math easier to define the common point as zero instead of +237.24. 😉 And if you do suddenly find your ball of protons you’re calling “zero potential” approaching a neutral sphere, the engineer says it’s time to redefine terms. 😉 ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 15, 2002, 4:55pm UTC](https://boards.straightdope.com/t/the-space-station-grounding-problem/127861/23 "2002-09-15T16:55:21Z")
> [@](#): > > The point is, phyisicists have good reasons for relating to “absolute” voltages, whereas most people (i.e. engineers, technicians, people tinkering with their light sockets, etc) are only worried about the relative difference. Actually, the only good reason for physicists to use absolute voltages is uniformity of notation. If physicists the world over had decided to instead set the standard at infinity being at a potential of -3722.6 volts, the physics would all still be the same, and the only difference is that it would be harder to remember. ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [September 20, 2002, 7:00am UTC](https://boards.straightdope.com/t/the-space-station-grounding-problem/127861/24 "2002-09-20T07:00:46Z")
That’s not a good enough reason? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 20, 2002, 8:21pm UTC](https://boards.straightdope.com/t/the-space-station-grounding-problem/127861/25 "2002-09-20T20:21:01Z")
Yeah, it’s a good enough reason, especially since there’s no reason to do it any other way. Likewise, engineers have a good reason (the same good reason, in fact: Uniformity of notation) for calling Earth zero potential. Of course, the two definitions of zero potential aren’t all that far off from each other. [Previous page](https://boards.straightdope.com/t/the-space-station-grounding-problem/127861.md?page=1)