I laughed hard at such fails I found in the physics textbooks I've had in the past.

Perhaps it was being overly cautious in stating what is complete fact vs. what is probable and deduced from observation?

I'd say it's more the fact that scientists have trouble with the obvious and refuse to accept it despite evidence.

Me not included.

How old is this book? (look for the copyright in the front of the book)

2006. Then again, it's not like modern scientists really understand this particular subject using mainstream theories that ignore electrical phenomenae.

As someone who is studying planetary science, I can maybe elaborate on this a bit. While electric currents are responsible for the planet's magnetic field, the details of how this current forms, and what types of interior processes obstruct or benefit this current are a little more fuzzy.

Also, the planets rotation doesn't come from the current, but during formation the planet gains rotational energy as material collides with the protoplanet. Which way it rotates has to do with what direction the protoplanetary disk is rotating (materials farther out impart more rotational energy as they hit the protoplanet in the direction of their motion around the sun). The rest is angular momentum and the planet getting knocked on its side or something by larger orbiting bodies. Faster rotation (higher rotational energy) probably speeds up whatever internal reactions are contributing to the electric current, but this is speculation (i.e. the physicists studying it don't have a working model yet), and we aren't really sure how one contributes to the other.

But then again, I'm not really into astromagnetophysics or whatever they call it these days so just go with whatever floats your cosmological boat.

A magnetosphere is created thusly (my theory):

Planet rotation "stirs" its fluid/molten core/mantle

The physical motion of the core/mantle simulates current electricity (imagine copper wire traveling in tandem with the electrons)

The planet's rotation affects the electrical current's flow, creating a magnetic field

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Possible testing procedure for this theory:

Take a dead car battery (where the ionized materials inside have reach an equilibrium), and then rotating it on an axis really fast. (don't try this at home)

There may be a necessity of having a spherical test item instead of a battery box.

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P.s. feel free to test it in a lab Baz, even if it's just for the heck of it. ;)

Well yes this is true, we wouldn't expect (*I'm not ruling this out) to see a magnetic field around a planet that never or hasnt recently had a convective interior. This is one of the reasons why Mars is the way it is. It's interior cooled and became less active, its magnetosphere weakened, solar rays pelted the atmosphere, reacting with it and the planets surface, effectively turning it into one big rust bucket. So it's obvious convection has a lot to do with it, but there are a lot of other factors (such as what regions of the interior are convective and which aren't, and what directions they are convecting in) that play into this.

And I could be wrong, but I'm pretty sure we knew all of this back in 2006 (I'm pretty sure this knowledge has been circulating since at least the 80s back when they were analyzing data from the various 60s and 70s spacecraft), so I'm a little boggled as to why the author of that textbook didn't know about it, perhaps he was too lazy to explain it...