People often ask me why we don’t do nighttime programs in July at Perkins Observatory, and the answer is a simple one.
There is no nighttime in July, at least the kind of nighttime that is useful for doing a public astronomy program.
The longest period of daylight is, of course, on the summer solstice, which this year happens on June 21. However, the latest sunset doesn’t happen until June 27. (People often ask me about the disconnect between the longest day and the latest sunset. It’s too complicated to explain here. Go to the library and get an old astronomy book. Look up the “equation of time.”)
At the beginning of July, the sun doesn’t set until around 9 p.m., and we end up waiting more than an hour for the sun to get far enough below the horizon to produce the blessed darkness we need to point a telescope at anything interesting.
Starting a program at 10 p.m. is unacceptable to most people, so we opt to do daytime programs in July at Perkins Observatory.
Of course, that choice limits our observing options to some degree. Luckily, we can observe the star that caused our nighttime woes at Perkins in the first place.
This year, we will be holding our Celebration of the Sun programs on July 14, 21, and 28 starting at 4 p.m.
The sun’s light is deadly to your eyes, so you should never look at the sun by yourself. However, we are trained professionals with special equipment at Perkins Observatory. At our sun celebration programs, we will observe the sun safely using special solar-safe telescopes and eclipse glasses. We’ll talk about the sun and the features you will see on it. We will do tours of the observatory, emphasizing its solar features. And we’ll launch rockets, you know, for the kids.
The sun is certainly worth celebrating.
It dominates our neighborhood, which we call the solar system in honor of the star at its center. Those other stars with planets are stellar systems. Our stellar system is called the solar system after the sun’s real name, Sol. And that is as it should be. The sun makes up 99.9 percent of the substance of our solar system. The planets are an afterthought.
The sun is a (nearly) million mile hydrogen bomb exploding with the power of trillions of hydrogen bombs every second.
That grand explosion keeps us alive every second of our lives. In fact, without the sun’s energy, life would not exist at all on planet Earth. Life is a lucky consequence of our orbit’s location. If our planet did not orbit the sun at just the right distance in the narrow band that astronomers have dubbed the Goldilocks zone, Earth would be too cold, like Mars, or too hot, like Venus.
Its light provides us with food. Through the process of photosynthesis, plants convert the light from the sun into their material substance. Animals eat the plants, and we eat both the plants and animals.
The sun heats up our atmosphere and over the short term is one of the determining factors in our weather. Over the long run, the amount of energy the sun produces varies in a complex set of rhythms that is the main factor in our long-term climate.
We miss the sun deeply when it nearly abandons us in the winter and joyously celebrate its return in the springtime.
For most of human history, the sun was the main way we measured the passage of a day. Humans slept at night. They got up when the sun rose, engaged in their daily labors, and returned to their abodes at sunset to hide from the dangers lurking in the night. Midday, or noon, was when the sun reached its highest point in the sky.
In a civil society, we expect to start work at, say, 8 a.m. It doesn’t matter much to our bosses if we have to drive to work in the dark. In a simpler time, say, 100,000 years ago, we let the sun set the rhythms of our lives.
The trouble is that the sun and humans keep a distinct and separate set of times. Civilized people require a uniform and unvarying clock. However, you’ll find no tick mark on Earth’s orbit to mark off the length of a year and no special place on Earth where the sunrise is more important than another.
Our clocks are perfect circles. Their hands must move at unvarying speeds. The hands meet precisely at the circle’s center. Earth’s orbit is not a perfect circle around the sun. It’s an ellipse (a sort-of egg shape), and the sun is not at the absolute center of that ellipse.
Also, Earth is tilted 23 degrees with respect to its orbit, which causes the seasonal changes in the first place.
The result is that the sun keeps its own time, and human time works with limited success to match it. As Earth spins from west to east, the sun rises in the east. In New York, the sun rises earlier than it does in central Ohio and reaches its highest point in the sky (i.e., “noon) earlier than it does here.
Noon is by definition the point when the sun is highest in the sky. If we measured time by the sun, the clock time of local noon would vary significantly from place to place, and temporal chaos would ensue. Every locale on the planet would have to keep its own time.
The result is a set of strange temporal compromises. The oddest one is the time zone. On any given day in summer, local noon occurs in central Ohio at about 1:35 because of cursed Daylight Saving Time and the simple fact that we are about half way into the time zone.
And the human-measured time of local noon varies significantly from that 1:35 p.m. because of the elliptical nature of Earth’s orbit, which causes the sun to appear to move faster across the sky when Earth is closer to the sun and slower when the sun is farther away.
One consequence of all this is that in July, the sky is not completely dark until well after 10 p.m. July is tough sledding for lovers of the night who also need to get some sleep. Consequently, we do our programs in the daytime and observe the one astronomical object we can see. If you can’t beat it, join it.
This year’s Celebration of the Sun is a bittersweet one for me. I’ll be retiring as director of Perkins Observatory on July 31. I’m kind of hoping that my old friends and some new ones will join me at the last programs I will do officially at the “O.” So, come on down.
Our Celebration of the Sun programs will be held this year on Saturday afternoons, July 14, 21 and 28. They begin promptly at 4 p.m. Tickets are $10 for adults and $8 for children and seniors when they are arranged in advanced. The cost increases by $2 if you buy them at the door. Spaces are limited, so I strongly recommend that you purchase your tickets ahead of time by calling the observatory at 740-363-1257.
Of course, we’re still doing nighttime programs in June at 9 p.m, and Perkins will continue to do them throughout the year. If you’d like one more crack at me at night, call the number above to purchase tickets.
Tom Burns is director of the Perkins Observatory in Delaware.