UpSwing Aerial’s Cara Zeisloft performs in Snow Birds at the Sawtooth Building this month.

Aerial dancers at UpSwing honor the longest night of the year.

Living in an artificially light-polluted environment as most of us do makes it difficult to get a sense of fall’s shortening days, except that, perhaps, our body rhythm tells us that it is 5 p.m., and the watch contradicts us: Nope, it’s already 6 p.m. Yet not all that long ago, before gas and electricity had become commonplace, shortening days affected everyone’s life. For one thing, candles were expensive, and oil lamps smoked. So, the arrival of the shortest day indeed became big deal: Time to party and anticipate the return of light.

In the Bay Area, many groups have found closer connections to Earth’s natural rhythms than the traditional holiday celebrations. One of them takes place every other year in that treasure venue for the arts, the Sawtooth Building in West Berkeley, home of Cherie Carson’s UpSwing Aerial Dance Company.

This is the seventh time that Carson has pulled out all the stops for her Solstice, which takes place—one evening only—on the day of the longest night, Dec. 21 this year.

Performing in Florida and Atlanta before moving in 2000 to the West Coast, where she studied with aerial pioneer Terry Sendgraff who in 2005 took over her studio, Carson has been fascinated for many years with performing in the air—on trapeze, tissu, slings, rope, and harness, and invented equipment. “It allows people to imagine the impossible,” she explained. “We can’t quite escape gravity, but aerial dance changes our perspective on it. It empowers the human spirit.” For similar reasons, she also choreographs shadow dances in which the dancers send the movements away from themselves.

Solstice starts in the dark and moves towards the light, culminating with Snow Birds—not the ones in Florida, but magical, mysterious, definitely airborne creatures. And since Solstice is a celebration, there will be a party. Of course.

Upswing Aerial Dance Company, Solstice, Dec. 21, 7 p.m., (no late seating), Studio 12, 252 Eighth St., Berkeley, $10-$25, UpSwingAerialDance.org/upcomingevents or at the door.