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Ephemeris: 09/25/2023 – Now that autumn has set in, what does that mean?

September 25, 2023 Comments off

This is Bob Moler with Ephemeris for Monday, September 25th. Today the Sun will be up for 12 hours and 1 minute, setting at 7:34, and it will rise tomorrow at 7:34. The Moon, 3 days past first quarter, will set at 3:34 tomorrow morning.

Now that autumn has set in, what does that mean? The latitude on the Earth where the Sun passes overhead is now south of the equator, and will stay south of the equator until March 19th, our time, next year. The North Pole of the Earth is experiencing a prolonged sunset, starting six months of night, while the South Pole is enjoying an equally long sunrise, for their six months of daylight. The Earth’s seasons are not caused by our distance from the Sun. We’re closer to the Sun now than we were in early July, and will continue to move closer to the Sun until early January. The Earth’s average distance of 93 million miles only varies by a million and a half miles either way. It’s the Earth’s axial tilt that causes the seasons.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT –4 hours). They may be different for your location.

Addendum

Sun's path on the equinox for TC-Interlochen
The Sun’s path through the sky on an equinox day from the Traverse City/Interlochen area in Michigan. The Sun is plotted every 15 minutes. This is a stereographic projection which compresses the image near the zenith and enlarges the image towards the horizon. Created using my LookingUp program.
Earth's position at the solstices and equinoxes
Earth’s position at the solstices and equinoxes. This is a not to scale oblique look at the Earth’s orbit, which is nearly circular. Click on the image to enlarge it. Credit: ESO (European Southern Observatory which explains the captions in German and English.
Categories: Ephemeris Program, Equinox, Seasons Tags: