Changing and Unchanging Cycles
On New Year’s Eve, as we hum “Auld Lang Syne” and drink a cup of kindness, we celebrate the end of one year and the beginning of another. It might feel like a big deal to us here on earth, but from an astronomical perspective, it’s just a day like any other — as one planet circles one star, the sun, out of the galaxy’s billions. But since we arbitrarily impose a beginning and an end on our equitable distribution of days, let’s reflect on some of the cycles that dominate our existence: the big ones over which we have no control, the smaller ones we might hope to influence, and those about which we don’t yet know. This way, we can make some resolutions that will outlast the echoes of our song.
Patterns and repetition are comforting because they help us remember and understand events. Phenomena that occur on a regular basis generally have an underlying reason. The cosmos provides us with numerous examples. Isaac Newton deduced the law of gravity that allows us to predict elliptical orbits around a central object’s gravitational pull. This is how the Milky Way attracts the sun, which takes roughly 240 million years to orbit the galaxy’s center. And as we all know, the earth, along with all the other planets in our solar system, orbits the sun. The earth’s cycle takes a year — hence the holiday and festivities before us.
The planets in the solar system are joined by objects with lesser celebrity status, such as asteroids and comets. Dwarf planets orbit too. “Dwarf planet” is a new category that includes the demoted Pluto, but also other objects of similar size that have been discovered since the 1990s — objects that are big enough to take notice of (and are spherical) but not —> Read More