I was standing on the beach at the edge of the Pacific Ocean. It was a beautiful, clear, summer afternoon. The sun was just setting. When the sun gets close to the edge of the horizon you can actually see it move. I was watching it move, sinking into the ocean. I know that the sun isn’t really moving. We are, the Earth, spinning away from the sun. I stood there for some time even after it had dropped below the horizon line, the sky glowing orange. Within this broad wash of color the line of the horizon stood out definite. I could see the curve of Earth in the distance. I stood and watched until the sky faded into a deep bluish hue, punctuated by the glow of whitewater from the waves, night was coming on fast and I thought about the horizon.
I wonder how far away that is, that line in the distance. I wonder if I look West across the Pacific or East across the Atlantic, if the horizon would be at the same distance. There must be a mathematical equation that calculates this. It turns out there is. I tried to follow it but…well, hmmm, let’s see… But do I really care? Was that sunset interesting to me in an empirical way or was it just a beautiful sunset on the edge of the Pacific Ocean? I decided I would look further into this and broaden my horizons, so to speak.
What is the horizon? Simply put it is the line that separates the Earth from the sky. It is that point where Earth and sky meet. No matter from where you observe it, there will always be a horizon of sorts. Perhaps you are looking across your own front yard and all you can see is your neighbor’s roof line set against the blue of the sky. Well, that is your horizon. On the other hand you could be in space, looking through a porthole at the Earth in the distance. From there you can truly see the curvature of the earth. The word horizon comes from the Greek word “orizein” which means “to limit”. Okay, that makes sense to me. I looked the word horizon up in the Internet. I found that there are many kinds of horizons. For instance there are Expanding horizons and Visible horizons. There is what is known as the Celestial Horizon. Let’s think about that a moment; I like the way it sounds; the Celestial Horizon. Scientifically speaking it is the circle on the celestial sphere whose plane is at right angles to the visible horizon. Hmmm. What does that mean? I looked further. It is also known as the Rational horizon, whose plane passes through the Sensible horizon and the center of the Earth. There is also a Bubble horizon, which is actually an artificial horizon that is parallel to the Celestial Horizon.
There is, in reference to black holes, what is known as an Event Horizon. I remember there was a horror movie of that name but what really is an Event Horizon? An Event Horizon is evidently the field of gravity in a black hole where space-time is so warped that light cannot escape. Who sits around and figures this stuff out? As I inquired further I found out that there are Kicking horizons, Particle horizons, Cosmological horizons, Isolated horizons, Dynamical horizons. There are Apparent horizons and Absolute horizons. An Absolute horizon apparently calculates as (r=2m) whatever that means. I read about what is known as an Acoustical horizon. I read about it but it’s pretty complicated and I’m not sure I truly understand it.
Wow, and all I was doing was watching the sun set behind the ocean. To me the horizon is the line that separates the earth from the sky whether it is Expanding or Absolute, whether it is Cosmological or Kicking. I have told myself at one time or another to broaden my horizons. In my search into the horizon I looked into the literary aspects of the word. There is a play by Eugene O’Neill, a Pulitzer Prize winner called Beyond the Horizon. It is about two men, brothers, who love the same woman. That could be a problem. One or both of those guys needed to broaden their horizons. Does the word horizon relate to the word horizontal? Hmmm. I could go off on a tangent on that one. But no.
Expand your horizons. Widen your horizons. How many parents have said that to their children? “Come on Billy. Widen your horizons. There’s more to life than just Basketball (or Batman or Soccer or girls or….well maybe not girls, but surely there is more to life than Soccer.) Look beyond the horizon. Saint Brendan looked beyond the horizon when he sailed off in his little open boat. So did Columbus, Cortez, Cabrillo, and Cook. Exploration. New frontiers. Kit Carson, Lewis and Clark, Captain William Bligh. Captain Kirk. John Glenn. Neil Armstrong. Travel. Voyage. Trek.
Weathering Horizon. Sunrise. Sunset. The Green Flash. The Zodiacal Light. Storm clouds on the horizon.
Horizon. The line that separates the Earth from the sky. We can never reach the horizon. The faster and farther we go the faster the horizon recedes into the horizon. That line is always at the horizon. The nature of the word itself is broad. It has already expanded. It is wide indeed. It is something that humans looked at and pondered since before they became human. What is out there? What is beyond that line? Is that the end of the Earth? What is out there?
Let’s go look and find out.