Does the earth behave like a magnet how do you prove it

Take any item that's magnetized.  With a sharpie or a drop of nail polish, make a small mark on one end of the item.  Then, hang it up by a thread, in such a way that its two ends are at the same height off the floor, and it's free to turn on the thread.  

After it settles down and stops turning and wiggling, it'll come to rest with the marked end pointing in the same direction EVERY TIME you try this.  

The only thing that makes a magnet point in the same direction every time is another magnet.

the amount of current in the coil