If much of 20th-century art was an attempt to return to the primitive origins of art-making, those who chose light as their medium may have come closest. Long before humans learned to paint on cave walls or carve flutes and spearheads, they built fires and rolled boulders from the mouths of caves, allowing daylight to flood away darkness. And the subtle changes in light that they saw daily — from the flicker of a campfire to the first rays of sun escaping over the horizon — were full-blown aesthetic experiences. The same is true today. Light allows us not simply to see, but to become aware of ourselves as seers. It is a window onto the world, and into our consciousness.

Perhaps no artist of the past halfcentury has understood this better than James Turrell. For more than four decades, he has explored light, and its effect on viewers, in ambient spaces that approximate windows, skylights, and other apertures. Since the late 1970s, he has been transforming Roden Crater, a dormant volcano in the Painted Desert in Arizona, into a complex of tunnels, observatory-like “skyspaces,” and pools — a Minimalist pilgrimage site that recalls a pre-Columbian ruin.

The artist’s latest work at Pace Wildenstein is on a smaller scale, but at its best it also allows for an experience of the sublime. The pieces come in two types. Most impressive are five screenlike openings in the gallery wall that are filled with soft, gradually shifting colored light. Vaguely trippy, these works encourage external discovery: Go right up to wall and you’ll see that you can poke your head through; what seemed like a flat screen is in fact a window onto a cavity that houses a large glass volume filled with computer-programmed LED or neon lights. But the art’s primary impact is on internal experience. Titles like “Sojourn,” “As Imagined,” and “Stand Alone” read like invitations to a meditative journey. And the gallery provides benches for those who are prepared to embark. Because the gentle luminosity of the light is the sort associated with celestial events or the muted tones of dawn and dusk, rather than a blinding noontime blaze, you can look for as long as you want. As the colored forms slowly morph, you become conscious of yourself seeing. What you perceive is perception itself.

Also on view is a much less impressive group of holographs: flat black surfaces pierced by colored planes that seem either to jut forward into the space of the gallery or retreat into the wall. Smart but gimmicky, they do not hold your attention, let alone spur the imagination and open up dreamscapes. Unlike the glass pieces, they ask only that you look, not that you see.

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In the work of Walter de Maria, another artist associated with Minimalism and Earth art, light is not the primary medium, but it still plays an essential role. His “Lightning Field” (1977) is a spare man-made forest — a one mile-by-one kilometer grid of 400 lightning rods in a remote corner of New Mexico — that changes during the course of the day as the rising and setting sun sends shadows creeping along the ground. The piece’s otherworldly power can awaken the viewer to his own inner sublime.

The Gagosian Gallery is displaying two of Mr. de Maria’s installations from the 1980s. Metal rods are again the primary medium, but here they are horizontal, flat on the ground. The far more impressive of the two works, “A Computer Which Will Solve Every Problem in the World/3-12 Polygon,” fills the 21st Street space with rows of three, then four, then five, and so on up to 12, of these rods — 75 in total. (The companion piece at 24th Street extends the sequence from 13 through 15.) The work is at once a simple mathematical progression, an exploration of the essential quality of each number, and a lesson in turning a line into a curve.

All the rods are the same length, yet they differ in shape, having as many facets as the number they represent. The spacing between them also varies. And so as you circle though the gallery, the work seems to change constantly. The differently shaped rods reflect light at various angles. And because of the irregular spacing, certain perspectives offer perfectly straight lines while others present an array of sweeping curves. The genius of the work is that though the metal remains perfectly still, your perception of it is never static.

For all this brilliance, however, the work can also feel dated. “A Computer Which Will Solve Every Problem in the World” was made in the mid-1980s. As its ironic title suggests, it is a skeptical response to the increasingly powerful, new technology of the computer. Unlike Mr. Turrell’s new light art, which simultaneously gestures to a prehistoric past, a space-age future, and the computer-friendly world of today, Mr. de Maria’s installation is indelibly linked to a particular moment in time, now a generation old. His “computer” is not unlike those hulking early mainframes — an elegant giant of history that feels like a stranger in the present.

Turrell until April 28 (534 W. 25th St., between Tenth and Eleventh avenues, 212-929-7001);
De Maria until May 5 (522 W. 21st St., between Tenth and Eleventh avenues, 212-741-1717; and 555 W. 24th St., between Tenth and Eleventh avenues, 212-741-1111).