Lightning never strikes twice in the same place, they say, though maybe not in Tucson, Arizona, where this photograph was taken. Its location in a bowl of hills means the mid-western city has the highest rate of lightning in the United States.
Modern superstitions about lightning - like protecting your home by placing acorns or holly in the window, or sprinkling salt and laurel leaves on the fire - probably stem from our ancestors' attempts to placate natural forces with objects of value. Laurel, for instance, releases a psychoactive drug if chewed - and is one emblem of the Roman god Jupiter, originally a sky god.
Thunder gods have been worshipped all over the world. Earlier inhabitants of Tucson, the Plains Indians, described lightning as the flashing beak of the great Thunderbird as she flew through the eye of the storm, thunder rolling as she beat her wings. About 8,000 years ago in Europe a cult using an axe as symbol of the thunderbolt hurled by the sky god was dominant. The lightning flash was an early symbol of the God of the Old Testament: people still say "God is angry" when the sky growls and crashes.
In Roman times, all places struck by lightning were sacred to Jupiter or Jove in his aspect as "Fulgur" (lightning thrower). So great was the power of the thunderbolt that Jupiter was the god invoked to honour treaties and oaths. How fitting, then, that the planet Jupiter is constantly blasted by thunderous gas storms.
Around our own world, at any one moment there are 1,800 thunderstorms.
Scientists describe lightning as an intense luminous discharge caused by electrical breakdown between two masses of air, one cold and one warm. Thunder is the noise that lightning makes - or, as the Romans put it, "Jove thunders and the world looks up".