WASHINGTON — No one knows the components of dark matter, the mystery of Mona Lisa’s smile or precisely how long it will take Kim Kardashian to lose the 50 pounds she gained during her pregnancy.

Amid this vast ocean of bewilderment, however, a small group of volunteers managed to expand the well of shared human knowledge last week by joining a daylong group editing session sponsored by Wikipedia and the Smithsonian Institution’s American Art Museum in Washington. The gathering — called an edit-athon — was the latest collaboration between the online encyclopedia and cathedrals of culture like the Smithsonian to expand and improve Wikipedia entries, which are subject to the vagaries of volunteer contributions. At the same time, the Smithsonian is able to better publicize what’s in its extensive collections.

“Wikipedia is driven by this desire to share knowledge freely with the world, and that is in sync with our mission,” said Sara Snyder, webmaster at the Archives of American Art, a Smithsonian research center that held an editing session in March to beef up the digital encyclopedia’s entries on female artists.

These amateur-professional collaborations began in 2010 as the brainchild of Liam Wyatt, a former bartender, fire twirler, podcaster and vice president of Wikimedia Australia, during an unpaid five-week stint as Wikipedian in residence at the British Museum. The following year, the Archives of American Art appointed its own Wikipedian in residence and organized an edit-athon, enlisting local volunteers to create new articles using the archives’ resources. Other institutions, including the New York Public Library, the Children’s Museum of Indianapolis and the Picasso Museum in Barcelona have joined what has been called the GLAM-Wiki initiative. (GLAM stands for galleries, libraries, archives and museums.)