Contrapose Dance and Quicksilver Dance go Dancing in the Streets at 3 p.m. Saturday at Union Square Plaza 90 Union Square, Somerville. Free.

Two troupes take part in this day of free public performance:

Contrapose Dance, under the artistic direction of Courtney Peix, presents sections of a work called HoverDive – a collaboration with scientist Larry Pratt, musician Amber Vistein and costume designer Jennifer Varekamp that incorporates fluid dynamics, chaos and entropy from Pratt’s oceanographic research.

Quicksilver Dance, with the artistic direction and choreography of Mariah Steele and original music composed by Ryan Edwards, presents “The Constant Effort of Beginning,” about the cycle of ecological life; “Caesar and Cleopatra,” imagining how the historical figures’ relationship grew into romance and an equal partnership; and “On the Threshold of Memory,” investigating the line between knowing and not knowing, sensing and perceiving, and visualizing and remembering.

Information is here.

Gender-swapped “Trouble With Tribbles” at 8 p.m. Saturday at Unity Somerville, 6 William St., just off College Avenue near Davis Square, Somerville. Free, but a $5 donation would be appreciated.

This is a faithful reproduction of the classic “Star Trek” episode from December 1967, except that the Post-Meridian Radio Players have swapped Capt. Jane T. Kirk (Karen Sarao) for James T. Kirk, Ms. Spock (Adria Kyne) for Mr. Spock and Lt. Uhura (Michael Lewis) for, well, Lt. Uhura, and so on.

The Players, founded in 2005, perform shows Golden Age of Radio-style, with actors
in front of microphones and live sound effects performed on stage. This time they’re tackling a TV episode in which “a dispute over control of a planet brings the starship USS Enterprise to a space station where the crew must deal with Klingons, edgy Federation officials and a previously unknown species of small, unbearably cute, voraciously hungry and rapidly multiplying furry creatures.” Information is here.

Secret Gardens of Cambridge Tour from 10 a.m. to 4 p.m. Sunday. Tickets are $25.

This biennial, self-guided garden tour takes you for a stroll through an eye-catching array of back yards, side yards, front yards and even an open field of lupines across four Cambridge neighborhoods. More than 20 privately owned gardens will be open to ticket holders, with nine new from previous years, providing an opportunity to explore the city, discover spaces, encounter new ideas and designs and learn gardening tips.

“Secret Gardens” is sponsored by the Friends of Cambridge Public Library and is the single biggest fundraiser for the library. Tickets are at all branches of the Cambridge Public Library as well as at Bonny’s Garden Center, Brattle Florist, Dickson Bros. Hardware, Mahoney’s Brighton, Nomad, Pemberton Farms, Porter Square Books and Rodney’s Books. Information is here.

First Anniversary of Don’t Make Art, Just Make Something! Dinner, Art + Music event from noon to 4 p.m. at The Democracy Center, 45 Mount Auburn St., Harvard Square. Pay what you will.

Hosted by the Miranda’s Hearth arts community, these Dinner, Art + Music events are dedicated to “building community through creativity.” There will be art projects, an informal jam session, people to meet and food, so visitors should bring food to contribute to the potluck, art supplies, musical instruments, friends and themselves!

Aisling will give her talk from TEDxSomerville at 1 p.m. Union Press will set up a pull-a-print table and sell letterpress posters, and members of the Hearth and Boston Art Critique group plan a Guerrilla Art Show. Artists with a piece to show are invited to bring it and add it to the show.

The group, named after artist, entrepreneur, and teacher Miranda Aisling, wants to build a community art hotel in which everything from the furniture to the quilts to the soap is made by members of the community and visitors can buy what they use during their stay, buy something similar in the gallery or take a class to learn how to make it. Until there is a location, the core 15-member group holds events throughout the area.

“Don’t Make Art, Just Make Something” is Aisling’s book about getting started – intended to help people reframe the way they think about approaching projects and ideas. Sunday’s event serves as the official release of its Sketchbook Edition, and there will be T-shirts and bumper stickers available to mark it.

Information is here.

Reading by Members of the Boston Chapter of the National Writers’ Union at 2 p.m. Sunday at The Center for Arts at the Armory, 191 Highland Ave., Somerville. Free.

Local members of the National Writers’ Union will read original work form various genres, including fiction, memoir, poetry and creative nonfiction and some stuff that is simply undefinable. Food and drink will be available. “Come to listen, shmooze, eat, browse, buy books and be inspired,” organizers say. Information is here.