WASHINGTON — When the sun sets in rural Africa, the world changes. Temperatures drop. New scents rise as street dust settles and cooking fires start. Markets empty, voices quiet down. Bodies and eyes that struggled all day with heat and glare relax and move toward sleep.


The most dramatic difference, though, is visual.


It comes when the stars appear; first a twilight sprinkling of them, then a tidal wave washing across the sky, covering and soaking it. At such a sight jangled daytime thoughts tend to give way to admiration, inquiry, meditation.


“African Cosmos: Stellar Arts” at the Smithsonian’s National Museum of African Art here, an exhibition packed with celestial bodies and patches of darkness sending forth light, invites comparable responses. Broadly it’s a show about the extent and persistence of cosmological consciousness in art, old and new, from the African continent. It’s also a bold demonstration of a more specific reality: In Africa art and science, including astronomy, have always intersected.


Organized by Christine Mullen Kreamer, the museum’s deputy director and chief curator, the exhibition opens, scientifically enough, with a reference to an instrument of exacting measurement: a circle of upright stones at Nabta Playa in Southern Egypt that functions as the world’s oldest known astronomical device.


Some 7,000 years after being built, at least a millennium earlier than Stonehenge, the grouping still accurately clocks sunrise and sunset and points to some of the sky’s brightest stars: Sirius, Arcturus and those in Orion’s belt. A bit later Sirius was worshiped by sky-scanning Egyptians as the force that engineered the annual flooding of the Nile. But Sirius was just one in an extended family of deities, all embodiments of natural elements: air, water, earth, stars. Despite spats and betrayals, they kept the cosmic machinery ticking. And approached with deferential prayers and gifts, they issued passes to the afterlife.


A lithe, gilded mummy cover in the show, made for a woman who worked as a temple singer, carries a hieroglyphic inscription in which the owner implores the sky goddess to please, please raise her up, in death, among the stars.


From Egypt the show takes a leap across the Sahara, to what is now Mali, in West Africa. The first stop, via a wall text, is Timbuktu, a city renowned for its manuscript libraries filled with, among many other things, astronomical treatises. In these books science was usually at the service of religion: the calculation of lunar phases and stellar coordinates was crucial to Muslim worship. In the 17th century, when Christian Europe was rejecting a Sun-centered concept of the universe, astronomical books in Islamic Africa were getting the cosmic story right. (The museum had planned to include manuscripts from a library in Timbuktu in this show, but as recent political turmoil there worsened, the loans became impossible.)


The Mali journey mapped by the show continues further to the Bandiagara region of cliffs and scrub brush settled by Dogon peoples, who trace their origins to a creator-spirit descended from the sky. An important feature of Dogon theology centers on a deity identified with the star Sirius and a companion star, Sirius B, invisible to the unaided eye. Although the second star was recorded for the first time by Western observers only in the 19th century, the Dogon suggest that their awareness of it goes far back into antiquity.


Recently art historians have expressed doubts, proposing that the Dogon came to know of the star only a few decades ago through contact with anthropologists. By conventional Western standards the debate must stay unresolved because, like many other sub-Saharan cultures, the Dogon have no written histories, meaning they have no retrievable, verifiable past, no authentic history at all.


Is this so? Western culture has implicit faith in the written or printed word. Ideas, including history, become real — graspable and authoritative — only when written. By contrast, much African history is based on oral traditions, passed down generationally in poetry and song, or encapsulated in visual forms like sculptures, paintings, weavings, beadwork, architecture, bodily scarification patterns and performances.


Entire cosmologies, who knows how old, are built into, and dramatized in, Dogon masquerades, through masks, like those in the show, some towering into the sky, others designed to scrape the ground. A fairly simple-looking Dogon stool — two horizontal wood disks, with carved figures standing on one and holding up the other — is a diagram of a layered universe, and an image repeated, and an idea reinforced, in many other forms. A remarkable female figure in the show has a miniature version of this cosmic image for a head, as if the vision of it had consumed and transformed her every thought.