The science of Christmas

Christmas is a time of faith, family, and festivities, yet peel back the wrapping and you’ll find a fascinating mix of physics, biology, psychology, and astronomy beneath the glitter.

There’s a kernel of truth in Rudolph’s red nose.

Twinkling fairy lights are an iconic symbol of the season worldwide and their invention is a story of engineering brilliance and aesthetic magnificence. Thomas Edison invented the lightbulb in 1879 and three years later his assistant, Edward H. Johnson, made the first string of electric Christmas lights starting a trend that over time went global. Back in the nineteenth century, Christmas trees were becoming popular, yet adorned with candles, although beautiful, each was a fire hazard. To create a safe alternative, Johnson hand-wired 80 red, white, and blue electric bulbs together, and hung them around a tree on a rotating pedestal, inviting a reporter to witness the dazzling display. At the time the cost of doing this was prohibitive for an ordinary household, but just over a decade later, President Grover Cleveland adorned the Christmas tree at The White House with electric lights, capturing the attention of the nation. With advances in technology and mass production, electric Christmas lights became more affordable for the masses, and now, with the efficiency of modern LED bulbs, we can illuminate entire villages without triggering pesky power cuts.

And why do we find sparkling lights so cheering? It’s because they engage our senses and our emotions, charming both the eyes and the mind and reminding us of previous happy times. Mimicking flickering firelight, their gentle glow triggers the production of serotonin, a mood-boosting hormone, induces a sense of wonder and creates a cosy heart-warming ambiance.

The scents of Christmas also have the power to evoke joy. Whilst in the US and Northern Europe, the crisp, woody aroma of pine trees is synonymous with the season, in the sunny Mediterranean, citrus fragrances blended with cinnamon, cloves and nutmeg, mulled wine, roasted chestnuts, gingerbread and other sweet treats activate the taste buds!  These festive fragrances can have a direct impact on our emotional state by triggering the release of the “happy hormones” dopamine and serotonin in the brain. As smell and emotion are intertwined in our memories, these olfactory stimulants evoke powerful nostalgic responses.

The season’s rituals – decorating, gift-giving, and singing carols – increase our levels of oxytocin

While we’re talking about noses, no Christmas article would be complete without a mention of  Rudolph’s red nose and reindeer biology. Reindeer are uniquely suited to a freezing Arctic environment and their fur is made up of densely packed hollow hairs that provide excellent insulation. We might not see reindeer flying across the sky; yet, while it sounds like a Christmas myth, there’s a kernel of truth in Rudolph’s red nose. Research on reindeer physiology shows that their noses are rich in blood vessels to help them regulate their body temperature in the cold, and this high concentration of capillaries can give reindeer noses a reddish hue, especially during strenuous activities like pulling Santa’s sleigh! (And interestingly, recent studies show that their eyes change colour from gold in summer to a deep blue in winter, enhancing their vision in low wintry light.)

The gentle glow of lights triggers the production of serotonin.

The season’s rituals – decorating, gift-giving, and singing carols – also increase our levels of oxytocin, the ‘bonding hormone’ that underpins many mammalian social interactions: acting generously activates the same reward pathway in our brains as food and sex, leaving us feeling more connected and fulfilled and explaining why giving feels good!

Up in the sky above us, the Star of Bethlehem has intrigued scientists and theologians curious as to whether its appearance was a real astronomical event – and we all love a puzzle at Christmas time, our curiosity also driven by dopamine!

What we know of the Christmas star has been drawn from St Matthew’s Gospel augmented by contemporary interpretation, although no theory aligns perfectly with the biblical account.

The possibilities include that the Star of Wonder was a supernova, a massive star’s explosive death, which shone brilliantly for several weeks before disappearing. Classical depictions of the nativity show the ‘star’ in the style of a comet, suggesting that it moved across the sky leading the three wise men - who were likely to have been skilled skywatchers - to Bethlehem.

Another popular theory suggests the Star was a ‘great conjunction’, an event in which the two bright planets Jupiter and Saturn align in the sky, appearing as a single bright object – or even a similar conjunction of the planets Jupiter and Venus, and the bright star Regulus. Seen in the east, associated astrological readings would have translated this event into an announcement of the ‘King of Kings’: Jupiter is the ‘king’ of the planets whilst Regulus is Latin for ‘prince’ or ‘little king’, and Venus symbolises love, fertility and birth.

And so, although the Grinch (with his Grinch-feet ice cold in the snow) was right that “[Christmas] came without ribbons. It came without tags. It came without packages, boxes or bags,” and whilst the celebration of the birth of Christ is at the heart of Christmas festivities, from the twinkle of fairy-lights to the riddles of the sky above, the excitement of the season is a heady blend of faith, scientific phenomenon and happy hormones! It’s no wonder that we love our Christmas with all the trimmings.