Monthly Archives: July 2019

Long time ago in Bethlehem

The custom of naming years after whoever wore the crown lasted well into the time of the Roman Empire.

Two thousand and some years ago, a baby was born in the town of Bethlehem in Galilee—in the country we now call Israel. The baby was Jesus, son of Mary, the Holy Spirit in human form. He would grow up to begin a ministry that led to His crucifixion and resurrection—in order to save all of humankind. Jesus is the Redeemer; the Christos in Greek; the Mashiach in Hebrew.

The Christian evangelist Luke wrote about the Nativity before there were numbered years. How could he put a date on Jesus’ birth? Here’s how: Luke tells us that Jesus was born while Augustus was emperor of Rome and Quirinius was the governor of Syria. Luke knew his readers would remember when those guys were in charge and place Jesus’ birth in that time.

1 In those days a decree went out from Emperor Augustus that all the world should be registered. 2 This was the first registration and was taken while Quirinius was governor of Syria. 3 All went to their own towns to be registered. 4 Joseph also went from the town of Nazareth in Galilee to Judea, to the city of David called Bethlehem, because he was descended from the house and family of David. 5 He went to be registered with Mary, to whom he was engaged and who was expecting a child. 6 While they were there, the time came for her to deliver her child. 7 And she gave birth to her firstborn son and wrapped him in bands of cloth, and laid him in a manger, because there was no place for them in the inn.

In fact, it would be 5 more centuries before someone thought of numbering the years.

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The ancient cheeks

In the ancient world there wasn’t a numbering of years as we have today. People would remember years or events by who was king at the time. For the ancient Greeks time was a cycle, so they didn’t think of time as a progression of numbered years, as we do. The Greeks of each city-state named the years after whoever was their archon (AR-kon—ruler or king) at the time. Later on the Greeks numbered years by a 4-year cycle, called an olympiad. The Olympic games were held every fourth year, then the cycle started over.

For what it’s worth, the Olympic athletes supposedly competed in the nude. The tradition may have begun when one runner somehow lost his gym shorts during a race. Okay, you guys. No. I’m absolutely not going to draw a cartoon of naked Greek runners. What a buncha sickos!

Well, okay. Maybe one cartoon.

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Bend me your years

Rome’s second king, Numa Pompilius, felt kind of bad about those unnamed extra winter days, so he came up with two new months: Januarius and Februarius. King Numa tacked his new months onto the beginning of the year, which bumped all the other months back. That wasn’t such a big deal for the first four months, which were named for gods (Mars, Aphrodite, Maia, Juno)—but it’s darned awkward for the other months, which were named for their numbered positions in the year. ‘September’ means ‘seventh month’ but now it’s the ninth. October means eighth, but it’s the tenth. November means ninth, but it’s the eleventh. December means tenth, but it’s the twelfth.

The calendar year still kept coming up 10 days too short, so every 2-3 years a leap month—Intercalaris—was added.

In 45 bc, Julius Caesar reformed the Roman calendar by uncoupling it from the Moon—no more figuring out lunar cycles. He must have decided that having a set number of days in a year—365—meant fewer headaches when running something as big as the Roman Empire. Julius ditched the leap month. But because a year is actually 365 days and 6 hours, he added an extra day (February 29) every fourth year—the Leap Year.

What about Quintilis and Sextilis? Quintilis (means ‘fifth month,’ now it’s the seventh) was renamed July for Julius Caesar and Sextilis (means ‘sixth month,’ now it’s the eighth) was renamed August for Caesar Augustus (Julius’ nephew and Rome’s first emperor).

This was the Julian Calendar. It’s more or less the same one we use today.

Julius Caesar reforming the calendar.

Romulus’ days were numbered

Romulus’ 10-month calendar featured adorable wolf puppies on every slab.

The original Roman calendar was invented by Romulus, the first king of Rome, around 753 bc. The calendar started the year in March (Martius) and consisted of 10 months, with 6 months of 30 days and 4 months of 31 days. The winter season didn’t get any months with names, so the calendar year only lasted 304 days with 61 extra days in the winter. Everybody stayed home during those 61 days and looked at seed catalogues.

Here are the months of Romulus’ calendar:

Martius – 31 Days
Aprilis – 30 Days
Maius – 31 Days
Junius – 30 Days
Quintilis – 31 Days
Sextilis – 30 Days
September – 30 Days
October – 31 Days
November – 30 Days
December – 30 Days

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We locked a bunch of astronomers in a room and you’ll never believe what happened next!

Roman astronomers trying to get the lunar and solar cycles to match up. I threw a couple of Sun-worshiping Druid priestesses in there, too.

A big headache with ancient calendars is that they had to be constantly updated to make them agree with the movements of both the Moon and the Sun. Months are based on the Moon’s cycles. Years are based on Earth’s orbit around the Sun. ‘Calendae’—we say ‘calends’—is a Latin word for ‘first day of the month.’ ‘Ides’ is the day in the middle of each month. Astronomers (scientists who study the stars and planets) would first determine the ides (when the moon will be full) for each month and calculate the rest of each lunar cycle/month from there. It is a tricky business to get the twelve cycles of the Moon to work out to be the same amount of time the Earth orbits the Sun.

Archimedes and his odometer

Archimedes was a Greek mathematician who specialized in measuring space. He was certain that there must be a way to accurately measure how much space is in a circle—area—or how much space is in a sphere or a cylinder—volume (he figured out how to measure volume when he noticed that a certain amount of water spilled out when he got into a bath tub). Archimedes was influenced by other great mathematicians, like Pythagorus and Euclid.

Archimedes invented many wonderful machines, like a screw for drawing up water, or catapults that were used to fight off invading navies. Although we don’t have his plans for it, Archimedes is said to have invented a way to measure distance. This machine is called an odometer.

Archimedes’ odometer operated on the idea that every time a wheel goes around, it travels its own circumference. The odometer adds up those circumferences and marks when the wheel has traveled a mile. In our last post, we showed how a standard Roman chariot wheel goes around 42 times to travel a mile.

We know about Archimedes’ odometer because the Roman military engineer Marcus Vitruvius Pollio (80–70 bc – 15 bc), or Vitruvius for short, wrote about it in his 10-volume book De Architectura. Engineers build stuff. As the Roman Empire expanded, the army took along a corps of engineers to build fortifications; siege engines; bridges; tunnels; aqueducts to provide water; and roads. These engineers did such a good job that you can still find Roman bridges, aqueducts and roads today.

Emperor Caesar Augustus wanted to know exactly how big the empire was and decreed that mile markers should be put up along the newly-built roads. Vitruvius decided to build Archimedes’ odometer to accurately measure the miles.

We only know what Vitruvius’ odometer looked like from a fanciful drawing. We don’t know exactly how it worked. Some people, including Leonardo da Vinci, have come up with some pretty good guesses about how it worked. You can see Leonardo’s drawings here—plus, you can even download plans if you’d like to build one yourself! Now that’s cool.

We do know that every time the chariot wheel goes completely around, it moves other gears. The other gears are set up to mark a mile at the 42nd revolution of the chariot wheel. The trick is gear ratio—meaning some gears are bigger, some gears have more teeth. If the gear on the drive shaft has only one tooth and the gear holding the marbles has 42, the marble-gear moves 1/42 of a revolution every time the chariot wheel goes completely around. At the 42nd revolution, a hole with a marble lines up with a hole underneath the gear and the marble drops into a bucket. Each dropped marble represents one mile traveled.

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Who doesn’t like π?

Pi, or π, is a letter from the Greek alphabet used by mathematicians. π signifies this weird number: 3.14159265359… or 3.14 for short. It is the ratio of a circle’s circumference to its diameter. Circumference is how big around a circle is. The diameter is how wide a circle is from side to side if you draw a line through its center. Diameter x 3.14 = circumference. This is true of any circle, no matter how big or small.

MrNystrom has a great video about how to think about π.

Pi has been around for 4000 years, but Archimedes of Syracuse (287–212 bc) was the first mathematician to calculate π accurately.


Archimedes came up with his best ideas in the bath tub.

So back to the Romans. If you want to measure miles across the Roman Empire, how would you do it? Counting steps and paces as you march along isn’t very accurate—it’s too easy to lose count. What if you used a circle—like a wheel? I mentioned that chariot wheels were made a standard size, like many things in the Roman Empire.


A chariot wheel is 4 feet across at its widest point—that’s the diameter. Let’s calculate a chariot wheel’s circumference—how big around the wheel is. You can calculate the circumference by multiplying its diameter by π. π = 3.14. Four feet x 3.14 = 12.56 feet.

Now, there are 5280 feet in one mile. 5280 divided by 12.56 = 42 revolutions of the chariot wheel. All we have to do now is count every time the wheel goes around. At 42 times, we’ll know we’ve reached a mile.

Counting how many times a chariot wheel goes around still seems like a big pain in the neck, doesn’t it? Archimedes thought so, too.

Side note: March 14, 3/14, is known as π Day. On π Day a grocery store in my town sells pies for $3.14.

pie day559

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Measuring long distances

The Romans were geniuses at organization. The way they organized their government and army/navy is how they could maintain such a huge empire. The Romans found that standardization really helped—from soldiers’ armor to the width of a chariot wheel to money to constructing roads.

Good roads are important to a maintain a huge empire, especially for moving armies quickly from one place to another. It’s vital to know exact distances, too, if you are planning a big march with thousands of soldiers. We know that one Roman mile is 1,000 passus—paces—or 5,000 gradus—steps. The problem is, it’s too easy to lose count of all those steps. How do you measure a mile and know for sure you didn’t lose count?

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Measuring distance in Rome

The Romans borrowed religion, art, architecture and literature from the people they conquered to make a hodge-podge, eclectic culture for themselves. Mostly they borrowed from the Greeks—the Greek gods got Latin names. Ares (the god of war) became Mars. Zeus became Jupiter, Hera became Juno, Poseidon became Neptune, Aphrodite became Venus.

The Romans also borrowed technology. They measured distance the same way the Egyptians and Greeks did, by using parts of a typical grown man for standardized units.

finger—digitus (1/16 of a pes)
thumb-joint—uncia (inch, 1/12 of a pes)
four fingers—palmus (1/4 of a pes)
foot—pes (plural: pedes)
one step—gradus (2.5 pedes)
pace—passus (5 pedes)

For longer distances, a mile (mille passus) was 1000 passus or 5000 pedes. (I hope I’m getting the plurals right—

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