I like the sun and the moon. They have teamed up to give us livable temperatures, a moderate climate, and a dependable, predictable schedule of days. I’m glad they have accomplished such extremely tricky feats. They deserve to be observed with awe and studied very carefully.
I’ve done my share of reading about the sun and the moon and the other objects in our solar system. The sun, particularly, has a lot of features worth studying. It’s a dynamic and frightful orb, but just stable enough to allow Earth to support life. The moon, silent and mysterious, has given humans much to ponder about during long, dark, melancholy nights. It is watched by warriors and lovers, fortune tellers and scientists. Both objects came to exist much like the billions of other stars, planets, and moons in the Universe. But they belong to us, so they are special.
One of the things they have in common is that they move through our sky. They both come and go on regular schedules, not deviating enough from them so that anyone you or I know could detect it. The difference between the movement of the two bodies is that the Earth is a satellite of the sun and so orbits around it. The moon, however, is a satellite of Earth, so it orbits around us. The movement that we see in the sun is actually caused by the Earth’s rotation, not the orbit around the sun. As we orbit the sun, we also rotate. One revolution of Earth on its axis makes for one full day. As we rotate, we see the sun from a continuously changing position.
The observed movement of the moon through our sky is the result of both our rotation and its orbit around us. Just take my word for it, because I’m not going to attempt a scientific explanation. I couldn’t give you one even if I wanted to anyway. My point is that the sun and moon have different agendas when it comes to making themselves observable. They both have schedules, but each is based on its own unique relationship to Earth.
I didn’t used to pay much attention to the rising and setting of the moon, since its position in our sky is obviously not as critical as that of the sun. Things have changed a bit since I’ve been biking to work. I have to consider sunrise when planning my trip. And I’m sure I’ll have to consider sunset later on, when darkness hits here earlier in the day. I want to bike during daylight hours, and because of that I have been monitoring the time of sunrise. I found a nice web page, operated by the US Naval Observatory. You can input a date and then you’ll see precise times of rising and setting. Here’s an example using my birth date:
Friday 8 April 1949 Eastern Standard Time SUN Begin civil twilight 5:48 a.m. Sunrise 6:16 a.m. Sun transit 12:47 p.m. Sunset 7:17 p.m. End civil twilight 7:46 p.m. MOON Moonrise 12:31 p.m. on preceding day Moonset 4:06 a.m. Moonrise 1:48 p.m. Moon transit 9:21 p.m. Moonset 4:39 a.m. on following day
Very nice. If you want explanations of moon and sun transit and twilight, go here.
Now, in checking the sun and moon data for tomorrow morning, I see that civil twilight starts at 6:20 a.m. Sunrise is at 6:49. Sometime between the two I should be able to hit the road. It’s supposed to be clear, so it will be bright enough to bike. What the moon does tomorrow will have little impact on my ride, unless it’s a full moon and people start acting crazy. Nonetheless, it’s interesting to know that I should be able to see the moon early in the morning and perhaps even during my ride. According to USNO, there will be a “waning crescent with 40% of the Moon’s visible disk illuminated.” Sounds absolutely delicious!