Many centuries ago, people knew of only seven metals. That also was the number of known “planets” – the five true planets that are visible to the naked eye, plus the Sun and Moon. So each metal was associated with a planet – gold with the Sun, silver with the Moon, for example. Another metal with a good match was quicksilver. It’s the only metal that’s liquid at everyday temperatures, so it was associated with the quickest planet: Mercury. And it was even given the planet’s name. The planet moves back and forth between the morning and evening sky every few months. That quick motion is where the planet got its name. Mercury was the Roman messenger god, who flitted across the heavens on winged heels. The only spacecraft to study the planet from orbit didn’t find any trace of the metal mercury on its surface. And if there’s any of it near the planet’s equator, it would go through all three everyday phases of matter. At night, the planet is so cold that the metal would be frozen solid. At noon, it’s so hot that it would vaporize, forming a gas. And for much of the rest of the daytime, it would be a liquid – quicksilver puddles on a quicksilver planet. Mercury will stand close to the Moon during the dawn twilight tomorrow. It looks like a fairly bright star, to the lower right of the Moon. The brighter planets Venus and Jupiter align to their upper right – the planets of copper and tin. Script by Damond Benningfield