'Super Science with Drew': Here's why the earth's tilt makes the September equinox possible

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Wednesday, September 22, 2021
This is why we have changing seasons
Drew teams up with the Exploratorium to investigate the reason for every season.

SAN FRANCISCO (KGO) -- The September equinox is here! The word "equinox" is Latin for "equal night," when all parts of the Earth experience close to 12 hours of daylight and 12 hours of darkness.

The exact moment of the September equinox this year is Sept. 22 at 12:20 p.m. PDT. At this time, the sun will be directly above the equator, and each day, it will appear lower in the sky (due to the Earth's tilt and our orbit around the sun) until the December Solstice. The days are changing in length now by minutes!

In this episode of Super Science, Drew dresses up as the earth to demonstrate the importance of our planet's tilt with Exploratorium Science Educator Lori Lambertson.

"The tilt is really important because it's the reason we have our seasons, and it's the reason that the equinox and the solstices are special days," explained Lambertson.

The Earth is tilted 23.5 degrees on its axis, which affects the distribution of the sun's energy across the surface of the planet.

Daylength on the September equinox will be 12 hours, 8 minutes in San Francisco. The day we experience equilux (same amount of daylight as night) will be Sept. 25, when the sun will rise at 7 a.m. and set at 7 p.m.

"If we did not have this tilt, we would not have seasons," Lambertson adds. "Seasons are caused by the tilt, not by a variance in the distance between the earth and the sun."

Visit here for more information on the Exploratorium.

Go here to plan your visit. Masks are required indoors. Handwashing and sanitizing stations are found throughout the museum.