It’s a mid-February morning as I sit down to write. In the distance, Mts. Wrightson and Hopkins are, in the early sun, gleaming white from a recent snow storm. Closer to my window, though, it’s just a lot of brown. In a month or so, I tell myself, it’ll look different. The higher elevations may remain quite cold, but down here, dormancy will give way to an explosion of green.
Despite the havoc that man-made climate change is having on our environment and weather patterns, we haven’t been able, mercifully, to alter basic astronomy. The coming Spring Equinox reminds us that interactions between planets and stars remain out of reach of human interference. In the midst of so much worry, Spring is coming and there’s nothing we can do about it.
Our planet spins like a child’s toy, a very fast one. It takes 24 hours to complete one revolution. To do so means we’re traveling about 1,000 miles per hour. None of us feel the motion. Likewise, we also don’t realize that we’re spinning at a 23.4% angle. We’re tilted. The most likely explanation for this is that something quite immense slammed into Earth billions of years ago and knocked us out of whack. It is this, and not our imperfect orbit around the sun, that has given us a planet with seasons.
Earth’s average distance to the sun is around 93,000,000 miles. Because ours is an elliptical orbit, there are times when that distance is closer to 90,000,000 and other times when it extends beyond 94,000,000 miles. Seems significant but is isn’t. Indeed, we’re furthest away during Summer. It’s all about the axial tilt.
Take a paper cup and drive a stick through the bottom so that the stick extends past the top as well. Set it at a slant, as if you’re in the process of pouring water from it. Now, make a mark on the side of the cup about 2/3 to the top. Walk it around a stationary object, your imaginary sun. If you look at your “orbit” like a clock, you’ll see that the mark you made is the same distance and angle to the sun at the “12:00” and “6:00” positions. Those are the equinoxes that occur in March and September. However, the “3:00” and “9:00” positions are opposites. At “3:00” our mark leans away from the sun. At “9:00” it leans in. Winter and Summer.
Apparently, all the planets are tilted to varying degrees. The strangest one is Uranus, at nearly 90 degrees. It’s on its side. Pluto, now called a dwarf planet, is closer to being upside down at 122 degrees. Our tilt has minor fluctuations, but is generally steady. A change of even a few degrees would have an enormous impact. It’s another example of nature’s perfection. Astronomers refer to certain exoplanets as being in the “Goldilocks” zone, the distance that might make them “just right” and suitable for life. For us, 23.4% is our “Goldilocks” tilt. We can’t improve upon it.
So, now that Spring is here, going outside to observe the night sky becomes easier. One of the great constellations to look for is Leo, the Lion. Its most distinguishing feature is the backwards question mark that forms its head. It’ll be high in the east in the early evening. Use a phone app to locate it and its brightest star, Regulus.
For modern astronomers, Leo serves not only as a home to numerous exoplanets orbiting a number of its stars, but also as a kind of picture frame marking out the parameters to approximately 70 galaxies hundreds of millions of light years away. You’ve got the skin-deep beauty and the majesty that lies much further within. It’s that duality that makes it a favorite site in the Spring sky.
For all of us welcoming the change in the weather, we see on the surface of the ground a hint of what is to come. With a bit of patience and perseverance there’s so much more to welcome. And, so it is with Leo, a lion at ease with our prying eyes.