This week Hal talks about the Summer Solstice.
This year, 2016, the longest day of the year, June 20th, the summer solstice, occurs on the same day as a full moon. What is the cosmic significance of this astronomical coincidence? Sorry, absolutely none.
Because the Moon orbits the Earth in just a bit over 27 days, and because our calendar months are either 31, 30, or 28 days long, the Moon will always be doing its own thing, independent of Earth-based calendars. So a full moon on June 20 is no more significant than a full moon on June 21, April 15, or December 25. In fact, the difference in the two calendars means that full moons, new moons, or any phase you wish to pick in between will occur on the same calendar dates roughly every 19 years. So there is no significance to a full moon on the solstice.
So what is the solstice? Your local TV weather person will tell you it is the longest day of the year, but why is that so? Just like getting good service in a restaurant, it all comes down to being properly tipped.
If the Earth orbited the Sun perfectly vertical, relative to its orbit, there would be no seasons, no solstice, and no topic for this episode of Looking Up.
But the Earth is, in fact, tilted, relative to its orbit, by a bit over 23°. This means that the summer solstice, every June, marks the point where, due to the tipping, the sun rises the farthest north of due east and sets the farthest north of due west that will all year. So while it marks the longest day of the year for those of us in the northern hemisphere, it also marks the shortest day of the year for our friends in Australia. After June 20, I hate to say, the days begin to get shorter. So get out and enjoy the sun while you can. Winter is coming.
If you’d like to take a closer look at the Moon, or any of the other wonderful and amazing things in the sky, please visit KRCC.org or CSASTRO.org for a link to information on our monthly meetings and our free public star parties!
This is Hal Bidlack for the Colorado Springs Astronomical Society, telling you to keep looking up, Southern Colorado!