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Author Topic: Is 'ground' the same on all planets?  (Read 484 times)

Offline thedoc

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Is 'ground' the same on all planets?
« on: 19/07/2016 17:50:02 »
Bobby Bissett  asked the Naked Scientists:
   - Is 'ground' the same on all planets? For instance, if we could connect a grounded wire from Earth to a grounded wire from another planet, would there be a voltage difference between them? Would there be a giant static discharge, and what might happen to everything on Earth if "ground" suddenly became much more positive or negative
What do you think?
« Last Edit: 19/07/2016 17:50:02 by _system »


 

Offline chris

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Re: Is 'ground' the same on all planets?
« Reply #1 on: 19/07/2016 22:05:36 »
Fantastic question - evan and Alan, this is right up your streets!
 

Offline evan_au

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Re: Is 'ground' the same on all planets?
« Reply #2 on: 19/07/2016 22:42:42 »
Quote from: Bobby Bissett
Is 'ground' the same on all planets?
A large object like a planet has a moderate* electrical capacitance.
Assuming that the planet has some electrical conductivity, when you touch the ground with a charged object, the charge will spread itself out around the planet, and the charged object will be discharged. So Matt Damon could still produce a spark when he steps out of his Mars rover.

Planets are continually bombarded by electrically charged particles from the Solar wind and cosmic ray particles, so they will build up some charge; we don't notice it because this charge is spread out around the whole planet. And the charge would not be excessive, because the influx of particles is overall electrically neutral.

So there could be some random voltage between different planets. The solar wind is partially ionized by the Sun's ultraviolet light, so this would tend to discharge the planets. Energy from voltages between planets will probably be dwarfed by lightning effects within the atmosphere of a single planet.

There is one spectacular example in our Solar System, where the moon Io orbits within Jupiter's powerful magnetic field. Sulphur emitted by Io's volcanos forms an electrical generator which carries currents estimated at 3 million Amps and 400,000 Volts.
See: https://en.wikipedia.org/wiki/Io_(moon)#Interaction_with_Jupiter.27s_magnetosphere 
..but Jupiter also has very active lightning!

*Correction: The Earth has a capacitance of about 710uF.
You can buy capacitors of 1 Farad that you can hold in your hand (but with a much lower breakdown voltage than the Earth).

...Just as well I checked; I thought the Earth's capacitance was larger (closer to a Farad...)
See: https://en.wikipedia.org/wiki/Capacitance#Self-capacitance
« Last Edit: 20/07/2016 12:51:25 by evan_au »
 
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Offline chris

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Re: Is 'ground' the same on all planets?
« Reply #3 on: 19/07/2016 23:27:08 »

There is one spectacular example in our Solar System, where the moon Io orbits within Jupiter's powerful magnetic field. Sulphur emitted by Io's volcanos forms an electrical generator which carries currents estimated at 3 million Amps and 400,000 Volts.
See: https://en.wikipedia.org/wiki/Io_(moon)#Interaction_with_Jupiter.27s_magnetosphere 
..but Jupiter also has very active lightning!

WOW!
 

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Re: Is 'ground' the same on all planets?
« Reply #3 on: 19/07/2016 23:27:08 »

 

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