On Saturday (Jan. 2), the earth will reach the point on its orbit known as perihelion, our closest approach to the sun. Now wait a minute, you might be thinking. Why is it so cold outside and there is snow on the ground if we are actually closer to the sun? The seasons are caused by the tilt of the earth towards the sun, not the distance from it, but I bet you knew that.
Also on Jan. 2, we will be going at our fastest speed for the year, a dizzying 67,794 miles per hour! Compare that with our speed at aphelion, when we are farthest from the sun on July 5, just a lazy 65,556 miles per hour. It is a good thing we are moving so fast; otherwise, we would fall into the sun, which would be bad. I hear it is hot.
The sun is not standing still either. It is moving through the Milky Way galaxy, tugging the earth and all the other planets along with it, at a staggering 500,000 miles per hour. Even at that breakneck speed it still takes the sun 250,000,000 years to make one spin around our galaxy. It is also a good thing the sun is moving. Otherwise, we would fall into the gigantic black hole at the center of the Milky Way. Does that sound bad? You bet it does! If the earth fell into a black hole, it would be squeezed down to the size of a pea. How big would you be? Not very.
The Milky Way is not standing still either. It is falling into the Andromeda galaxy at this very moment at hundreds of thousands of miles per hour. Go outside some clear night and find Andromeda using the W-shaped constellation of Cassiopeia as a guide. This is a great time of year to spot our very distant neighbor. Try to wrap your head around the idea that you are looking downhill in the biggest sense of the word that we puny humans can comprehend. We might actually survive the crash, but it is a few billion years in the future and I doubt if anything will be left of us by then anyway.
Our Milky Way and the Andromeda galaxies are part of a small cluster of several dozen galaxies known as the Local Group, and it is not sitting still either. All of us are swimming through a big grouping of hundreds of galaxies known as the Virgo Super Cluster. We are cruising through that immense backdrop at over a million miles per hour!
Beyond that things start to get a little fuzzy as we start to consider the expansion of space itself which is carrying all the distant galaxies away from each other. The question of how fast we are going in relation to what confuses the issue, but you could say that we are moving almost as fast as the speed of light itself from the most distant galaxies we can see way out there. And you thought you were just sitting still on your couch reading the newspaper!
This time of year is not known for its clear nights, but if we have one be sure to go out there and look at all the bright stars of winter. Jupiter and Saturn, which made a very close pass at the end of December, are now drifting off into the sunset glow in the southwest. Mars is still high in the south and southwest. You can recognize it by its red color. Venus is getting low in the predawn sky and we can all look forward to its return to evening viewing next summer.
One more thing to think about. If we are going so darn fast, why do we not even notice it? The way I like to look at it is that the distances are vast and our lives are so very short.
