CAMBRIDGE — It’s a simple and joyous event taking place this Saturday, starting at 5 p.m. The tree at the bandstand in Spring Valley at the Dorchester County Courthouse is draped with strings of Christmas lights, but has been sitting in darkness every evening, waiting for the Cambridge version of the tree lighting ceremony, made possible by the Christmas Tree Committee. The mayor, or some dignitary, will throw the switch, the bulbs will spring to life, and everyone will cheer. This same tradition is taking place all over Maryland, all over the United States, and in many places in the world. Yes, it’s a world full of grim conflict, but it is also a world of beauty and joy. For more than a 1,000 years, people have been decorating trees. The Romans, pagans, and eventually Christians all decorated their trees to mark or celebrate agriculture, to honor a deity of their faith, to keep alive a custom. The first lighted trees are attributed to Germany, where trees were lighted with candles. Early German immigrants brought the custom to the United States. According to Wikipedia, you could hang candles on your tree in Pennsylvania, but in the Puritan state of Massachusetts, you could be hanged for it. Customs changed and soon so many people were using the dangerous wax candles, that in 1908 insurance companies wanted a law to ban them. Thomas Edison had already invented the electric light bulb when his associate Edward Johnson adapted it to make a light suitable for a tree. In his own home, Mr. Johnson decorated the first electrically lit tree with red, white and blue bulbs. The feat was reported in a newspaper because there was no Facebook. Lighting trees have their own history now. A Belgian holds the record for bulbs on a tree, close to 200,000. Must be blinding — the tree and the electric bill too. The 14th president, Franklin Pierce, brought the first electric-lit tree to the White House. Read up on him and you may conclude it was his only bright idea. The internet offers a fine history of the tradition of Christmas trees, but what’s important to Cambridge this weekend is the continuation of our tradition ... a gathering of people, from babies to grandmothers, children and parents, in short, community ... to witness and celebrate the season with a ceremony that has refreshments, camaraderie, music, and LIGHT.