In partnership with
AI research, explained in one morning email
Most of what shapes AI next year is sitting in a research paper today. Keeping up with them is a full-time job, and the abstracts don't help.
TLDR AI is the newsletter that does the translating. Each morning you get the handful of papers worth knowing about, curated by Anthropic and ex-Google engineers, with a plain-English summary of what they found and why it matters.
You come away smarter about AI research in the time it takes to finish your coffee.
Free, and delivered to 1.1M+ inboxes every morning.
ONE WILD WORLD — NEWSLETTER
Fact-checked stories about the things you thought you knew.
Written for people who don't mind being corrected — or shocked.
ISSUE 072 · FUN FACTS · USELESS BUT FASCINATING
Monday Belongs to the Moon. Saturday Still Belongs to a Roman God. And Friday Probably Isn't Named After Freya.
You say them every day without hearing them. Every name in your week belongs to something people once worshipped or watched in the night sky: seven moving lights, four Norse gods standing in for Roman ones, and one Roman god who never left.
Seven days, seven wandering lights
Ancient astronomers could see seven bodies that moved against the fixed stars: the Sun, the Moon, Mars, Mercury, Jupiter, Venus and Saturn. They called them all planets, and each got a day. The Romans picked up the habit between the first and third centuries. The earliest evidence is a scrap of graffiti in Pompeii from AD 60.
The odd order comes from astrology. Astrologers ranked the planets by how slowly they seemed to move — Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon — and handed out the 24 hours of each day to them in turn. Whichever planet ruled the first hour gave the day its name. Run that through a week and you get exactly Saturn, Sun, Moon, Mars, Mercury, Jupiter, Venus.
Sunday and Monday: the sky
Monday is the Moon's day. In Old English it was mōnandæg, a straight translation of the Latin Lunae dies — which is why Monday is lundi in French and lunes in Spanish. Sunday is the Sun's day, the Roman dies Solis. In 321 the emperor Constantine made it an official day of rest. Christian Europe later renamed it the Lord's day in the south — domingo, dimanche — but English never bothered.
Tuesday to Friday: the great god swap
When Germanic tribes borrowed the Roman week, they swapped the Roman gods for their own nearest match.
Tuesday is Tiw's day. Tiw, the Norse Tyr, was a god of war, so he replaced Mars — still visible in the French mardi. Wednesday is Woden's day: Odin took the place of Mercury, the French mercredi. In Danish it is onsdag, Odin's day. Thursday is Thor's day. One thunder god replaced another: Thor for Jupiter, the Roman Jove, which is why French has jeudi. Friday took the place of Venus, the French vendredi.
Friday probably isn't Freya's
Friday is usually said to be named after Freya, the Norse goddess of love — a neat match for Venus. The Old English word says otherwise. It was frigedæg: the day of Frigg, Odin's wife. The Norse even called the planet Venus Frigg's star.
The confusion is old. Freya is the closer match for Venus, some early Icelandic writers did call the day Freyjudagr, and the two goddesses were sometimes blended together. But the English Friday belongs to Frigg.
Saturday: the Roman who stayed
Saturn is the only Roman god who survived the swap. Saturday was Sæturnesdæg in Old English, and he is still there.
Scandinavia went a different way. The Danish lørdag and Norwegian laurdag come from the Old Norse laugardagr: washing day.
The same week on the other side of the world
The planetary week travelled east as well as north. In Hindi the days run Ravivar (Sun), Somvar (Moon), Mangalvar (Mars), Budhvar (Mercury), Guruvar (Jupiter), Shukravar (Venus) and Shanivar (Saturn) — the same seven bodies, in the same order, as English.
Japanese does the same with the elements the planets were linked to. Monday is getsuyōbi, the Moon's day. Tuesday is fire, for Mars. Wednesday water, for Mercury. Thursday wood, for Jupiter. Friday gold, for Venus. Saturday earth, for Saturn. Sunday is the Sun's day.
One European language refused all of it. In the sixth century Martin of Braga, an archbishop in what is now Portugal, objected to naming days after pagan gods. Portuguese has numbered its weekdays ever since: Monday is segunda-feira, the “second day.”
BY THE NUMBERS
7
moving lights in the ancient sky — one for each day
AD 60
the Pompeii graffiti that is the earliest evidence of the planetary week
4
English weekdays named after Germanic gods: Tiw, Woden, Thor and Frigg
1
Roman god still in the English week: Saturn
321
the year Constantine made Sunday an official day of rest
Every time you say “Thank God it's Friday,” you are thanking a Norse goddess for a Roman planet.
SOURCES
Wikipedia, “Names of the days of the week,” for the planetary week, the Pompeii graffito, the Germanic substitutions, Constantine, Martin of Braga, and the Hindi, Japanese and Nordic names.
Online Etymology Dictionary, entries for “Monday” and “Friday,” for the Old English forms, the Latin and Greek originals, and the Frigg–Freya question.
OneWildWorld!
Facts you never asked for. Knowledge you can't unsee.
Share this newsletter with someone who likes being corrected.
Increase acceptance rates by up to 50% - with Cherry
When treatment is easier to pay for, more people go for it. Practices using Cherry payment plans have seen acceptance rates rise by up to 50%*. Patients apply on their phones in ~35 seconds, and Cherry approves around 90% of applicants.
See why Cherry is trusted by over 75,000 practices.
* These figures come from Cherry’s provider case studies, so individual results vary. Details at withcherry.com/provider-reviews. Payment options through Cherry are issued by the following financing partners: withcherry.com/financing-partners
ONE MORE THING
You can read our MANY newsletters for free at our website:
Read our archive for free at OneWildWorld.com →