Autumn Equinox Brings Complex But Fun Aspects of Astronomy to Portland, Oregon, Washington



Autumn Equinox Brings Complex But Fun Aspects of Astronomy to Portland, Oregon, Washington

Published 09/24/2020 at 6:43 PM PDT
By OREGON TRAVEL DAILY STAFF

Autumn Equinox Brings Complex But Fun Aspects of Astronomy to Portland, Oregon, Washington

(Portland, Oregon) – We’ve just said goodbye to summer as the autumnal equinox turned the corner from summer to fall on September 22, but there’s more to the story.

Jim Todd, astronomy expert with Portland’s OMSI, said that now those of us living in the northern hemisphere and in Oregon are seeing days that are shorter and nights that are getting longer. Places like the Washington coast or Oregon coast may be seeing sunset a few minutes later than inland, but those are getting earlier and earlier as well.

“This is the moment in time where the Sun’s rays are directly over the equator and the days are nights are nearly equal in length,” Todd said. “The Sun’s rays continue to make their journey south, and as a result, hours of darkness will be longer than daylight.”

This is the reason it's called an "equinox," Latin word meaning "equal."


However, September 25 marks another milestone in this cosmic dance between the Earth and the Sun.

That’s the day when day and night are both extremely close to 12 hours for Portland, Oregon. Todd said sunrise is at 7:01 a.m. and sunset is at 7:02 p.m. The area between Salem and Portland is right on the 45th latitude North. There, Todd said the time it takes for the sun to fully rise and set, which is several minutes, is added to the day and subtracted from the night, and therefore the equinox day lasts a little longer than 12 hours.

“Another reason why the day is longer than 12 hours on an equinox is that the Earth's atmosphere refracts sunlight,” Todd said.

Autumn brings on numerous cultural events, religious rites, and customs around the globe. The Chinese Mid-Autumn Festival is also known as the Moon Festival, which coincides with harvest festivals in Taiwan, Hong Kong and Vietnam.

In Oregon, especially in larger areas where fine beverages and live music are ingrained in the city’s lifestyle, these can have a particularly vibrant significance.

“Locally, modern Harvest Moon festivals with variety of concerts, farmers markets, beer- and wine-tasting, and craft fairs,” Todd said. “The wonderful changing fall color of the trees in the Pacific Northwest is expected for rest of September and well into October this year. This is a perfect opportunity to align sundial as the Sun rises due east and sets due west on the equinox.”