Naked-Eye Universe—Part 1

Sitting in my outdoor tub, gazing at the dark (late) winter's sky, I can see hundreds of stars, even though my field of vision is significantly reduced by overhead trees and the bulk of the house behind me. Were I to be lying on my back while floating on the ocean or reposed on the flat desert sand, I would be able to count as many as 4,000 stars above me. So tonight, with my limited view, I still may be able to discern as many as a thousand stars. That's not a bad count.

But how deep a view am I looking at? How far “out there” can I see? I know that with my naked eye I can see but a tiny fraction of the number of stars that a telescope could capture. My eyes extend nowhere near as far out as telescopes go. So just how much of the whole universe can my naked eye sample?

Our ancestors were very familiar with the night sky—far more than we moderns. We may occasionally look up, but we are either limited by city lights or are so ignorant of the sky that we quickly lose interest and turn back to our electronic screens. Our ancestors did not possess telescopes (or cell phones), so they had no idea of how far away those stars were. In fact, most of the ancients believed that the stars were all about the same distance away... maybe just a little ways above the trees. So, although they were intimate with their sky, they had little idea of just how large the universe really is.

We moderns, however, know that those stars are not scattered across a hemispherical bowl immediately overhead, but are as far away as billions of light years. (A light year is really a measure of distance. It's the distance that light—the speediest thing in our universe—travels in one year; about 6,000,000,000,000 miles. That's a hell of a distance to try to wrap your head around! So we resort to light years.) So today we know something about the true size of our universe—because telescopes have told us.

But I wander. Back to my soaking in the outdoor tub: I know I can see but a tiny part of it all. How small a part? I look up and see hundreds, if not thousands of stars, and wonder what is the size of my naked-eye universe. It's ever so smaller than the whole enchilada. Astronomers tell me that there are billions of galaxies and trillions upon trillions of stars, but I can see only a wee portion... a much smaller portion of it all.

More naked-eye universe next time...