Master of the Stars: The Romans

According to historians, the Roman empire ended about 1600 years ago. Yet, even today we still see their influence on a daily basis. The way we build bridges and arches, our calendar, most western legal systems, languages...and so on. All of this derived from the Romans. And let’s not forget modern day astronomy. The way we look at the stars and planets today has its basis in the Roman era, even if it was just for the names we gave all those celestial bodies.

The Roman gods are in the sky

In the article about Greek astronomy, we already mentioned Ptolemy. The Greece he lived in was occupied by the Romans, so he would've fitted in this article just as well. But it wasn’t just him that focused on the knowledge of the stars and planets. There were many Roman astronomers that occupied themselves with star mapping by just staring into the skies to see the movement of the constellations.

The Romans knew of 7 celestial bodies in the sky. With the naked eye they could see the sun (sol), the moon (luna), and 5 planets: Mercury, Venus, Mars, Saturn, Jupiter. The planets were given the names of Roman gods. The other 2,5 planets that were discovered much later were also given names of Roman gods.

The Roman calendar

In order to know your zodiac sign, you need to take a look at the calendar to see when your star sign takes place during the year. Guess what, that calendar is almost entirely a Roman invention. The biggest changes made to it were done by a very famous man; Gaius Julius Caesar.

Before Julius Caesar created his calendar, the Roman year was thought to have 10 months.The prefixes sept, oct, nov, and dec meaning seventh, eighth, ninth, and tenth come from Latin. July and August are named after Caesar and emperor Augustus. As early as 600 BC 2 extra months (January and February) were added and the calendar counted 355 days. Every 2 years, a month was added after February as a leap month.

The Julian calendar was introduced in 45 BC. It counted the 12 months we use today, each with the same amount of days. February was given a leap day. At first this day happened every 3 years, this was later changed to every 4 years. The Julian calendar was used until 1582 when pope Gregory XIII introduced his calendar, making minor changes to the Julian calendar.

The daily horoscope for the Roman emperor

The Romans were very interested in astronomy, but perhaps even more in astrology. They wanted to know what the movement of the constellations meant for them. Thrasyllus, born in Egypt, was the personal astrologer of emperor Tiberius. He predicted that Tiberius would become the new emperor. When that happened, Tiberius always kept Thrasyllus close so he could tell him what the stars (the gods) had in store for him. The astronomer and emperor became close friends which lead to Thrasyllus receiving Roman citizenship, an honor not many foreigners would get.

Thrasyllus also predicted that Caligula would be the next emperor after Tiberius. Caligula was having an affair with his granddaughter, so maybe that had something to do with his wishful prediction. One part of Tiberius’ horoscope that Thrasyllus didn’t get right was the year the emperor would die. He said in 36 AD that he was going to live another 10 years. This however meant he saved the lives of a large amount of Roman nobles who were suspected to have been plotting the murder of Tiberius.

As you can see, the Romans were quite influential to our western knowledge of astronomy. But outside of the western world there were other societies with completely different ideas. You'll find out more about those ideas in the next episodes of Masters of the Stars.