One thing is clear: Santa is an expert physicist

We are in the midst of the Christmas holiday season, a time when the magic of the unknown brings festivities to life for many children. It is a similar wonder that motivates many scientists, and none so more as the mystery of dark energy and dark matter.

The term "dark matter" refers to objects we cannot see in the universe. The theory was originally hypothesised by the astronomer Fritz Zwicky in the 1930s but only began to gain attention in the 1970s, when Vera Rubin and Kent Ford identified the first evidence of this strange substance.

Observing the stars in our nearest galaxy, Andromeda, they were confused that the galaxy was moving much faster than they had expected. The only viable explanation was that it contained more matter than they could identify. This unknown, invisible content has been labelled “dark matter”, and many more observations and images from telescopes have provided us with further evidence of its existence. However, we do not know what it is made of.

Further adding to this mystery, in the 1990s two independent teams of astrophysicists tried to calculate how fast the universe might be slowing down in its expansion. Instead they found that the expansion of the universe was speeding up: this reversed process could only be caused by something counteracting gravity: a “dark energy”. Calculations have since confirmed that dark energy and dark matter make up roughly 95 per cent of the universe. It’s fascinating to think that we can only see about 5 per cent of what is actually around us.

The existence of dark matter and energy has revolutionised our concept of the universe, and whole new fields of research have been born in an attempt to explain what exactly they are. This mystery may well lead to a rethink of the Standard Model, since, as one theory goes, perhaps these dark materials are made up of particles we cannot yet observe and have not yet predicted. Theoretical astrophysicists are trying to define new mathematical theories to explain these mysteries, which experimental astrophysicists can then prove or refute based on their research evidence.

While there are some things we cannot yet explain in the world around us, there are a few things about the story of Christmas we are fairly sure of. We know that the star of Bethlehem, which purportedly led three Magi to a manger, was most likely a planetary grouping with Jupiter, where one or more planets were aligned to create an eye-catching spectacle in the night sky around 1-6 BC.

The biggest mystery of the season, however, is how Santa Claus can possibly deliver presents to all of the children on the planet in one night. One theory is that he uses Einstein’s special theory of relativity, whereby time runs at different rates for different observers moving relative to each other. (This could also explain why time seems to move so slowly for excited children.) However, in order for this to occur, his reindeer would have to be moving at incredible speeds, which, even with a shining red nose, they likely could not sustain without wearing proper protective equipment.

Another theory suggests he might use a warp drive, similar to what we see in Star Trek and mathematically proven as a possibility by Miguel Alcubierre of Cardiff University. However, this would require an enormous amount of energy to contract space-time in front of the sleigh and expand space-time behind the sleigh, so, unless Mr Claus is holding an enormous secret about energy production, this is not likely to be his mode of transport.

The answer might lie in quantum mechanics, which allows for matter to be transported great distances in a short amount of time. But for Santa to use quantum mechanics to travel around the world would again take an enormous amount of energy. It may be the case that a deep knowledge of dark energy and dark matter solves the mystery of Santa’s magic. One thing is for certain: Nicholas must be a really good physicist.

Other Christmas-themed research has found that singing carols will add to your general health and wellbeing. So, while you ponder the physics of the night sky on Christmas Eve, it might be appropriate to hum a little Silent Night.