Meditation on the Galaxy

It was fairly late in the evening and we had reduced the number of lights on in the house, as was customary to help get in the mood for sleep. My wife went out on the deck for a while. I read at the dining room table. A few minutes later she came in smiling and spoke as if she was sharing a great little secret: "Come on outside. I have a surprise for you!"
I could only guess that it was some kind of sky sight, as she knows how much I like astronomy. When I first went out I said "I can't see a thing. It will take a few minutes for my eyes to get dark-adapted." Meanwhile in this oblivious state I mused: aurora? meteors? Slowly, magnitude by magnitude ever fainter stars came into my vision. When it clarified down to the fourth magnitude I saw it: the Milky Way in rare dark-sky splendor.
Once she got me out there, nobody could tear me away. I sat way back in a lounge chair and tried to remember what had attracted me so early in life to the stars.
Lacking any new insight on that topic, I decided to take an imiginary star trip. I felt no particular attraction to any one star, so I tried to imagine the sight before me for what it really was: the foreground stars are like nearby trees, the fainter ones can be imagined as a look into the woods, finally the Milky Way is like the deep forest, a general blur in which individual trees cannot be distinguished. It was not long before I succeeded in perceiving the heavenly sight that way. (The illustration at the left is intended to help visualize stars of farther and farther distances showing as fainter and fainter individuals and finally, the most distant ones blending into the distant general blur.)

What we call the Milky Way is actually a view of our own galaxy seen edge-on, since we are near the outer edge looking in to where the majority of our "neighbor" (astronomically speaking of course!) stars are.
It then recurred to me that every night we are privileged to look out the window of Spaceship Earth. And what a sight it is. It would be easy to assume that everything in the Universe is lined up the same way. But the reality is that the relative angles of planetary orbits in solar system is way off from the plane our Milky Way galaxy. The illustration at left is adapted from an image in a page by blogger Plantigrade. Imagine that you are on the little Earth globe, looking up. The red line represents the Ecliptic, the plane in which everything in the Solar System travels. Our galaxy is tilted about 123º to that plane. That is why our summer view of the Milk Way is over our heads.These nights it is actually running from horizon to horizon passing directly overhead, not at all aligned with the Earth's axis of rotation.

I suppose that if the motion of Earth as the Sun drags us around and around galaxy's center were like a train, then we would be riding sideways in our seats, like guy on the right!