Question

hw do we knw tat earth is a magnet?and at every point on the earth's surface,isn't the magnetic field different,if nt why?

Answer 1

http://en.wikipedia.org/wiki/Earth%27s_magnetic_field

Earth has magnetic field, which can be measured. Simplest and oldest application to do it is to use a magnetic compass.

The magnetic field varies depending on:
* the shape of terrain,
* magnetic materials under the ground (iron ore etc.)
* etc.
Here is a good summary: http://en.wikipedia.org/wiki/Earth%27s_magnetic_field#Magnetic_field_variations

and here is a very interesting article:
http://en.wikipedia.org/wiki/Magnetic_anomaly

Answer 2

okie.so was the magnetic compass,discovered after discovering tat earth has a magnetic field?

Answer 3

but if magnetic compass wasn't discoverd ,thn hw did they find tat earth has a magnetic field?well,i wanna knw hw they actually found out?

Answer 4

Magnetic compass was discovered long before before anyone knew anything about magnetic fields.

Just like electric current was discovered long before anyone knew about electrons :-).

Answer 5

thnxx!but hw did it all happen?

Answer 6

I don't know. I think the question is as hard as "how was bread invented" or "how was the wheel invented". It happened so long time a go. Here is something:
http://en.wikipedia.org/wiki/Compass#History

Answer 7

hmm!thnxx 4r answering ma question,u hav been a gud help to mee!:)

Answer 8

but the comparison with electric current they had a principle that positive charge carries current so they found out ! buet what was the principle behind compass in the first place ?