If you have been out looking at the evening sky lately, maybe you could not help but notice the bright planets hanging up there in the southwestern twilight sky. They are millions of miles away from us, dwarfing the scale of things on our little planet.
Do you want to go deep and see into the vast depths of space? How about the most-distant thing visible to the naked eye?
You will need a couple of simple items, a lounge chair and a pair of binoculars. Plenty of warm clothes and a thermos of hot tea will come in handy also. It is best to pick a clear, moonless night and a spot away from distracting lights. Settle back in that chair and look high in the north for the distinctive “W” of the constellation Cassiopeia, the Queen. Use the sharper of the two “Vs” in the “W” as an arrow and point over about the length of the constellation to an insignificant looking fuzzy glow.
If you spot it, congratulations. That is the farthest away thing and the biggest thing you have ever seen! The photons that make up that dim glow have been traveling across an unimaginable vast void of empty space for 2,500,000 years. Remember, those photons are cruising along at 186,282 miles per second. What you are looking at is the combined light of about 600,000,000 stars, the Andromeda Galaxy.
Gazing up at this distant wonder, try to let go of your usual perspective of up and down. Looking up at Andromeda is really looking downhill in the biggest sense of the word. It is much bigger than our own galaxy, the Milky Way, with almost twice as many stars. Bigger means more gravity, and because of all that gravity we are actually falling into Andromeda. At over a million miles an hour. And we are going to crash! When we do, it will be the biggest event in our little corner of the universe. But do not worry, you do not have to go out and buy collision insurance tomorrow. We are talking about billions of years from now.
Gravity at work
I know this whole thing about galaxies colliding is hard to visualize, so here is a little demonstration you can do in the comfort and safety of your own living room. Amaze your friends and family with your knowledge of celestial mechanics. Get two footballs, one for the Andromeda galaxy and one for our own Milky Way galaxy, and place them 30 feet apart on your living room floor. Interestingly, this is just about the scale of the size of the two galaxies and the distance between them.
All you have to do is sit down on your couch and watch closely. In 12,500,000 years the two footballs will move one inch closer together. Now that is gravity at work — the same force that allows you to collapse into your easy chair after a hard day of skiing on the trails.
Now about those planets. On the evening of Jan. 3, if you can find a place where you can see low into the southwest, four planets and a slim crescent moon will be on display about 30 minutes after sunset. Lowest to the horizon, Venus will be barely visible. Next, Mercury will shine dimmer with the moon right under it. Then Saturn and Jupiter are on display all in a line. The next evening the moon will be higher and a lot easier to see. Mercury will be at its best on the evening of Jan. 7. Venus will be riding off into the sunset glow during the first week of January. Look for her at the end of the month in the early morning twilight just above where the sun will rise.