Winter Solstice 12/21 at the Cesar Chavez Memorial Solar Calendar

[Chavez Huerta Solar Calendar]

Hello community,

At the turning of each season, we gather to commemorate the passage of time, connecting with our ancestors and people around the world who celebrate seasonal patterns of the sun. These are moments to be together, honoring the seasons of agriculture, the four directions, and the four key virtues of Chávez – hope, determination, courage, & tolerance. Join us this month for a celebration of the returning of the light! 

Sunday, December 21st, 2025 – 4 pm to 5:15 pm
Celebrate the Astronomical and Cultural significance of the Winter Solstice and festivals of earth’s resting season.
Chávez / Huerta Virtue:  Tolerance / Non Violence

Led by Alan Gould, Lawrence Hall of Science and Bryan Mendez of the Space Sciences Lab, UCB      

Cesar Chavez Memorial Solar Calendar
Perimeter Trail, Berkeley, CA 94720
(Rain cancels but some brave souls often show up anyway!)

Join the Solar Calendar's Google Calendar if you want to be automagically reminded each season. 

Share with friends! 

[Chavez Huerta Solar Calendar]

Happy Solstice 2025!

This message is sent to you because the gathering at the Chavez-Huerta Solar Calendar in Berkeley might be storm-dampened to the point where you're reluctant to go in person. Some will still celebrate in a light rain, but it will be informal. 

One of the points of discussion this year has to do with extremes of moonrises and moonsets that follow a different cycle than the annual extremes of sunrises and sunsets that we usually observe and admire at the Solar Calendar. For in-person sharing I had prepared printed sheets of the new FAQ #9 from the Solar Calendar FAQ page (https://gss.lawrencehallofscience.org/the-solar-calendar/).

Of note is the fact that in 2025 the Moon reached the overall extremes of moonrise and moonset positions in its 18.6 year cycle. 

You might be interested in more of the FAQs:

1. What do “solstice” and “equinox” mean?
2. Where is the sunset on the equinoxes, solstices, and at various times of year? 
(Solar Motion Demonstrator)
3. When is the exact time of solstice/equinox? When does the Sun set? 
4. What happens at noon at the Solar Calendar?
5. What celebrations happen around the times of solstices and equinoxes?
6. Is the winter solstice the day of latest sunrise and earliest sunset?
7. What causes the seasons? 
8. What is a sundial?
9. Do moonrises and moonsets behave the same as sunrises and sunsets?

Also of note is that there is in Ohio an ancient indigenous site, Hopewell Octagon Earthworks, that has an alignment with the northernmost rising of the Moon, as well as other alignments connected with Sun and Moon.

--Alan Gould

Solar Calendar Winter Solstice 

PS: Andrew Fraknoi posted on his website (https://www.fraknoi.com/astronomy/winter-solstice-arrives-on-sunday-dec-21/) and explanation about how the Earth got it's spin axis tilted, that might be the basis for yet another FAQ for the Solar Calendar FAQ page...

"You might ask why our planet has such dramatic changes in the length of the day and night?  If you’ll permit me to put it in informal language, it’s because the Earth is not orbiting the Sun with its head held high – it is leaning over as it goes around by about 23 degrees. So on one side of our orbit, we lean into the Sun – that’s the summer solstice.  On the other side of the Sun, we lean away from the Sun – that’s Sunday’s winter solstice.

"So why is the Earth leaning?  Venus and Jupiter are not; they do perfectly well going around the Sun with their rotation axis pointing straight up.  The answer lies in the ancient past.  Planet Earth got hit by a stray planet, very early in the violent history of the solar system, and like, many accident victims, couldn’t ever straighten out again. Back then, probably around 4 billion years ago, there were many more planets and mini-planets, formed from the great cloud of material around the Sun that gave rise to all the worlds of the solar system.  These “extra” planets had irregular orbits, and some fell into the Sun, while others collided or exchanged energy with more regular planets, changing their own orbits and the worlds they collided with.

"Our Earth got dealt a glancing blow by a sizeable world, a collision that may have changed the impactor’s orbit and sent it into the Sun or out of the solar system entirely. But, billions of years later, we are still stuck with a leaning planet and the seasons the tilt of our axis causes."