The Day I Became a Planetary Observer

One day in 1971 I was on a great adventure traveling down the coast of Oregon on Highway 101.  At a National Parks visitor center I was reading a display and it informed me that "The full moon always rises at sunset."

"Always?", I thought.  It got me thinking about "why", but it also got me thinking about "how".  I was also forced to admit that I really didn't know much at all about the very Universe that I, being a person living on the Earth, was a part of.

About a year later I was camping in the high country in Yosemite National Park in California, sitting around the campfire and I had an unobstructed view of the night sky, horizon to horizon.  The stars were brilliant and there in the eastern sky was an almost full moon, and that statement, "The full moon always rises at sunset" came to me.

I looked at the moon, low in the eastern sky and I looked over to the western horizon and I imagined where the sun would be below the horizon as it had just set a little while ago. 

Things began to click in my mind and I took a stick and made a simple drawing in the dirt in the fire and moon light.  Then it all fell into place – the moon up in the east, the sun down below the western horizon, and me and the Earth in the middle.  At that moment I could see myself way above the Earth, out in space.  I could see the Earth, the Moon, and the Sun.

There are two very important things to remember here. 1) We are looking down on the Earth from directly above the north pole and the Earth is rotating in a counter-clockwise direction.  2) The moon orbits the Earth once every 28.25 days.  At this point in its orbit, from the Earth it is opposite from the Sun.

The white 'Y' on at the "top" of the earth is me in this story and I was looking eastward and see the full moon appearing just after the sun was disappearing in the west, which created the darkening sky.  The Moon appearing and the Sun disappearing was caused by the rotation of the Earth.

So I was standing right between the Sun and the Moon.  Can you see that only half of both the Earth and the Moon are illuminated by the sun's rays and the other half is in the dark?  So from my vantage point (the 'Y' on the Earth) I was looking at the fully lighted face of the Moon because the Sun was behind me.

Ergo, the full Moon always rises at sunset. 

And from that night forward I could step into The Cosmic Observer mode and imagine myself out in space watching the Moon and the Sun and the Planets moving through space.  This has allowed me several "ah ah!!" moments as I looked up at the night sky and wondered how the planets and the Moon and the Sun all danced together.

Short aside here:  The Earth is spinning in a counter-clockwise direction (toward the east), which is why the moon and stars and sun appear in the east and appear to move across the sky toward the west.  Can you see that when the person 'Y' is looking up at the moon and the Earth is rotating counter-clockwise in 6 hours (1/4 of a 24 hour day) he would then be at the "9 o'clock" position and the Moon would be directly above.