Earth's axis - an imaginary line between the north and south poles - is not perpendicular to the sun, but is off by 23 degrees. This is known as axial tilt. Because of axial tilt, we have our seasons: when our hemisphere is tilted towards the sun for half of our orbit around the sun (half of our year), we get more solar radiation. This is felt most strongly as summer. And when we tilt away from the sun for the other half of the year, we get winter. And the exact turning point in the middle of winter, when we (in the northern hemisphere) start to tilt back towards the sun, is technically known as the winter solstice. This annual event is imprinted on the global consciousness. As Christmas.
Newgrange and the winter solstice
How? Let’s start by going to the first large-scale building in human history. We don’t have to travel very far from Dublin (where this post is written), just up the road to County Meath, and Newgrange. On the 21st of December every year, a shaft of light penetrates deep into the heart of this ancient structure. It is believed that the light awoke the souls of the dead buried within, because the world was literally given new life. It is also believed that the appearance of the beam of sunlight was a cause of celebration for the early farmers who lived around the structure. It proved that the gods had decided that enough was enough with the ever-darkening winter days and that light and hope had returned. We can only imagine how it must have felt for people whose very survival depended on the return of spring to see that, clearly spring was on its way. Two minutes' worth of extra sunshine every day.
At around 5,000 years old, Newgrange predates the Pyramids of Egypt and Stonehenge, and it is likely that those mighty structures also had some connection with the solstice, as did structures around the world from Mexico to Easter Island. Imagine the energy and organisation and meticulous study of the sun that went into the construction of Newgrange and the other monuments to the solstice! The solstice was clearly the single most important thing in people’s lives.
Mithraism vs Christianity
If we fast forward to the mighty Roman Empire of the fourth century CE, the official state religion was called Mithraism, a pagan cult that celebrated the sun. On December 25th every year, there was a huge celebration of feasts and games - the Romans did like to party - in honour of the sun god’s birth. They called it Natalis Solis Invicti and it was the biggest party of the year, marking the rebirth of the sun after the winter solstice.
Christianity was gaining a foothold in Rome at the time but, during the early 4th century CE, it looked like Mithraism could come out on top, with Christianity potentially fading away. Church leaders decided ‘if you can’t beat them, join them’. They decided to celebrate the birth of Jesus Christ, which had never been celebrated before. Nobody knew when Jesus had been born. Most likely it was in spring, as that’s the only time of year when shepherds would mind their flocks at night. But that didn’t really matter. It was decided that the 25th of December, the exact date of the sun god’s birthday party, would also be Jesus’s birthday party. When the Roman emperor Constantine was baptised in 337 CE, Christianity became the official state religion of the empire and Christmas became a permanent feature of the calendar.
Merry axial tilt
So, as you enjoy Christmas, with its mix of customs and traditions from all over history, from Queen Victoria to Coca-Cola, remember that the most important thing of all is the winter solstice. Merry axial tilt everyone!
See the sun live: https://www.nasa.gov/mission_pages/sdo/the-sun-now/index.html
Live coverage of the sun entering the chamber at Newgrange, 2017: https://youtu.be/a4Zv3EUmxP4
The sun - NASA
Newgrange - Tjp Finn - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=51765798
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