It doesn't matter how carefully you wound up your Christmas lights last year, and placed them in a box in an orderly coil. The following year they're always going to be a tangled nightmarish mass of cords and twinkly lights that somehow roped in three pointy star ornaments that poke you from all angles every time you try to fix everything and get it on the tree. 

But, as Joe Hanson from It's Okay To Be Smart says in his new Christmassy video, this phenomenon isn't new. Scientists have been thinking about how things get tangled for centuries, and it turns out, it's just the rules of the Universe.

In 2007, physicists showed that for any cord longer than 2 metres, knots aren't rare, they're almost guaranteed to happen. It also applies to why your earphone buds are a perennial mess. Science makes it so. "Think of it as the most frustrating example of entropy you've ever encountered," says Joe in the video above. "There's always only one way for a string of lights to be untangled, but with a few twists and turns, there's billions, and trillions of ways for them to get tied up."

Now, speaking of twinkly lights, did you know that Rudolph and his very red nose would have had to be a female, according to science? In fact, all of Santa's reindeer, with their impressive antlers, have to be female. Plus they would all have bright blue eyes, and be, rather conveniently, buoyant.

But even with his team of buoyant, blue-eyed lady reindeer, how does Santa make it around the entire world in one day to make all the children happy… according to science? Joe crunches the numbers, and let's just say it all ends in tears and a flaming sleigh. Watch the latest episode of It's Okay To Be Smart above to find out why.

Source: It's Okay To Be Smart