On the back of a dollar bill, you can see a pyramid with a flat top. No one has been able to explain why the Great Pyramid would have been built without a capstone. This is an interesting story associated with a visit to the top of the great pyramid. Many tourists have climbed to the top, which is not an easy journey. One such person was Sir Siemen's, a British inventor. He climbed to the top with his Arab guides. One of his guides called attention to the fact that when he raised his hand with outspread fingers, he would hear an acute ringing noise. Siemen raised his index finger and felt a distinct prickling sensation. He also received an electric shock when he tried to drink from a bottle of wine that he had brought with him. Being a scientist, Siemen than moistened a newspaper and wrapped it around the wine bottle to convert it into a Leyden jar (an early form of a capacitor). When he held it above his head, it became charged with electricity. Sparks then were emitted from the bottle. One of the Arab guides got frightened and thought Siemen was up to some witchcraft and attempted to seize Siemen's companion. When Siemen's noticed this, he pointed the bottle towards the Arab and gave him such a shock that it knocked the Arab to the ground almost rendering him unconscious. When he recovered, he took off down the pyramid shouting loudly. What kind of natural phenomena on the top of the Great Pyramid could produce such an electo-static effect? It would be interesting to conduct additional physics experiments on the top of the Great Pyramid.
What could cause this? The shape and height of the pyramid might explain it. Simply because of the difference in height between the top and base, there will be an electrostatic potential between the two.
The electrical field (in terms of the potential) is given by: E⃗ =−∇V⃗
On an ordinary day over flat desert country, or over the sea, as one goes upward from the surface of the ground the electric potential increases by about 100 volts per meter. Thus there is a vertical electric field E of 100 volts/m in the air. The sign of the field corresponds to a negative charge on the earth’s surface. This means that outdoors the potential at the height of your nose is 200 volts higher than the potential at your feet! You might ask: “Why don’t we just stick a pair of electrodes out in the air one meter apart and use the 100 volts to power our electric lights?” Or you might wonder: “If there is really a potential difference of 200 volts between my nose and my feet, why is it I don’t get a shock when I go out into the street? We will answer the second question first. Your body is a relatively good conductor.
So the higher the pyramid, the great the electric potential.
Another thing that can be measured, in addition to the potential gradient, is the current in the atmosphere. The current density is small—about 10 micromicroamperes crosses each square meter parallel to the earth. The air is evidently not a perfect insulator, and because of this conductivity, a small current—caused by the electric field we have just been describing—passes from the sky down to the earth.
That current density is across the very wide area at the base. At the top of the pyramid, that current becomes greatly focused into the much smaller area. The shape of the pyramid effectively acts like a lens.
Incidentally (and significantly I think) those last two quotes come from one of the Feynman Lectures. Feynman is arguably the greatest genius able to communication Physics the modern world has ever known.