Question

Why earth is called as a gigantic magnet

Answer 1

1. The earth is called as a gigantic magnet because north pole of a freely suspended magnet always settles in the direction of the geographic north pole of the earth.
2. It means that the South pole of some gigantic magnet must be near the geographic north pole of that magnet, near the geographic south pole of the earth.
3. Gilbert inferred from this that the earth itself is a gigantic magnet.