In 2012, a team of students from Sheffield University (UK) developed a system that made it possible to know the perfect way to decorate a Christmas tree. The team has developed a calculator that, based on four mathematical formulas, predicts the perfect number of balls, trends, and lights that were needed to optimize tree decoration in height. So, to decorate a 180 cm tree, you need to have: 37 balls, 565 centimeters Christmas lights and 919 centimeters can. As far as the size that the star is to crown, it is calculated by dividing the height of the tree in centimeters by 10.
"We hope that our formulas will make Christmas easier for everyone," the authors of this original mathematical application, called Treegonometry (the word "trigonometry" and the word "tree" in English), said. In addition to home use, the app will also be of great benefit to public administrations and private companies who want to give a Christmas touch and place one of the great trees commonly seen in city squares around the world. For example, the spruce commonly found in Trafalgar Square (London) has an average height of 21 meters, so 433 balls will be needed to be perfectly decorated.
This custom of decorating trees comes, as almost all ancient traditions, by Celtic peoples in Northern and Central Europe. Many of their gods present and worship through trees, and in the winter a festival is celebrated in honor of the birth of the sun and the divine god Frey. It is decorated with a tree, which is Igrasil, the wooden world of Scandinavian mythology, where are the kingdoms of men, gods, and other beings.
It is also common to keep trees indoors because, as their leaves never fall or lose their green color, they are considered a symbol of life and rebirth. The most widespread belief is that the holy Boniface, a German evangelist, takes advantage of this pagan tradition to give it new meaning and adapt it to Christian beliefs. He replaced Odin's worship through a tree with pines representing God, and it was also decorated with apples (a symbol of the original sin) and candles (a symbol of the light of Jesus).
source: Very interesting