# [amsat-bb] Re: Earths Magnetic Field strength

Patrick McGrane N2OEQ at aceweb.com
Wed Feb 21 07:56:56 PST 2007

```Greetings- I wont bother with your disinformation and please dont take my writings out of context.
You must use a blackberry or something, your like a hawk on the BB. Bye Bye, pat n2oeq

Everyone else; always look at the basic ideas or the "big picture"

------- Original Message -------
>From    : Robert Bruninga[mailto:bruninga at usna.edu]
Sent    : 2/21/2007 9:34:44 AM
To      : amsat-bb at amsat.org
Cc      :
Subject : RE: [amsat-bb] Re: Earths Magnetic Field strength

> I moved a handheld compass towards a heavy... speaker magnet.
> When the compass was a few inches away from the magnet,
> it changed direction from North to the direction of the
magnet.

As someone else pointed out earlier, that is because of the
gradient or difference in "force" on one end versus the other.
One end of the compass was an inch or so closer to one pole of
the magnet than the other end.

But in space, the pole of your spacecraft magnet that you are
trying to repel, is only one foot closer to the Earths pole,
than the other pole which is attracted.  So the difference in
distance of the force that is pulling to the one that is pushing
is only 1 foot out of say 21,120,000 feet to the Earth's pole.
Hence the net force difference is a 21 millionth SQUARED or
.00000000000004 of the force that you observed on the compass.

Or something like that.
Bob

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