一週七天：神、行星和月亮

Have you ever wondered why the days of the week have such strange names? The answer takes us back to ancient astronomy and the gods of northern Europe. The ancient Romans named the seven days after the seven moving objects they could see in the sky: the Sun, the Moon, Mars, Mercury, Jupiter, Venus and Saturn. When the Germanic peoples of northern Europe adopted the seven-day week, they replaced most of the Roman gods with their own. Sunday is the Sun's day, and Monday is the Moon's day – those two are easy. Tuesday is named after Tiw, a Germanic god of war, who took the place of Mars, the Roman god of war. Wednesday is Woden's day. Woden, also known as Odin, was the chief Germanic god, and he replaced Mercury. Thursday belongs to Thor, the god of thunder, who took Jupiter's place. Friday is named after the goddess Frigg, who replaced Venus. And Saturday is the only day that kept its Roman name: it's Saturn's day. You can still see the Roman names clearly in other languages. In French, Tuesday is mardi (Mars's day), Wednesday is mercredi (Mercury's day) and Friday is vendredi (Venus's day). Interestingly, Japanese uses exactly the same system. Japanese week names follow the Sun, the Moon and five planets, which in East Asia were linked to fire, water, wood, metal and earth. So Tuesday, kayōbi, is "fire day" – the day of Mars, the fire star. The names travelled to Japan through China centuries ago. Whether you're speaking English, French or Japanese, you're still naming your week after the sky.