Electromagnetism

Before the advent of technology, electromagnetism was perhaps most strongly experienced in the form of lightning, and electromagnetic radiation in the form of light. Ancient man kindled fires which he thought were kept alive in trees struck by lightning.

Much of the magic of nature has been put to work by man, but not always for his betterment or that of his surroundings. Electricity at high voltages can carry energy across extended distances with little loss. Magnetism derived from that electricity can then power vast motors. But electromagnetism can also be employed in a more delicate fashion as a means of communication, either with wires (as in the telephone), or without them (as in radio communication). It also drives our electronics devices (as in computers).

Magnetism has long been employed for navigation in the compass. This works because Earth is itself a huge magnet, thought to have arisen from the great heat driven convection currents of molten iron in its center. In fact, it is known that Earth's magnetic poles have exchanged positions in the past.