What with its capacity to engage past, present and future nearly simultaneously, our mind is the most sophisticated time-travel equipment out there. Is there any hope to approximate such advanced operations outside the brain?

Artists try. Just a few weeks back, at the Hirshhorn, Arte Povera artist Michelangelo Pistoletto delivered an hour-long lecture on attempts at layering the past and present in his mirror paintings, where painted figures from an indeterminate past mingle with our own reflection. They're valiant efforts, certainly, but not without awkwardness.

New York City artist Shimon Attie enlists a slide projector in a similar campaign to fuse past with present. In events that last a few nights or a few weeks, Attie projects old photographs onto public spaces -- facades and city sidewalks, mostly -- to create a visual image of memories that usually live only in the mind. After a decade of effort, he has produced a strong crop of installations and documentary photographs.

Like memory, the images Attie projects are there and not there. His specters last only as long as the bulb is screwed in and the electricity flows. When Attie grapples with the Holocaust's ghosts in contemporary Europe, as he often does, his works serve as reminders of a receding past. At Numark, "Sites Unseen" collects photographs from six of the artist's projects, most executed in Europe. They plant bygone times squarely in the present.

Attie's career-launching work, "Writing on the Wall," is represented by six pictures here. After graduating from art school in 1991 (he'd abandoned a career in psychology and was in his thirties at the time), Attie headed to the rapidly gentrifying Jewish quarter of the former East Berlin. There, he felt the presence of long-dead Jews who once walked the neighborhood's streets and lived in its houses. He found archival pictures shot there in the '20s and '30s and projected the pictures onto the buildings they'd been taken in front of. If a building had been razed, he made do with its neighbor. For a night or two, as he trained pictures on forlorn facades, the past alighted on the present: Old men stood outside their former homes; kids sat on street corners as they used to.

Attie's methods may sound as didactic as a schoolteacher's, but the resulting images are complex. His wide-angle shots often include neighboring construction pits where dirt piles and scaffolding signal gentrification. The ghosts of Past, Present and Future mill about in the same frame.

As art objects, the photographs are luscious. Shooting with slow shutter speeds, allowing for color saturation in the photograph that is deeper than what is apparent on the street, Attie milks rich blue from a streetlight, hot pink from a curtain and rich amber from sodium lights. Six pictures from the series anchor his Numark show and confirm Attie's creative strength.

Attie paid for the Berlin project with his own savings, but commissions soon rolled in. He's since worked in Copenhagen, Amsterdam and elsewhere in Germany on public art projects referring both to the Holocaust and to contemporary refugee and immigration issues. The bright light of his illuminations makes people take notice and register, however subtly, his protests. Attie's work holds all of us -- you, me, political institutions -- accountable.

The strength of Attie's interventions is sometimes lost in his photographs, though. His project in Copenhagen, where he submerged light boxes illuminating archival and contemporary photos of Jews and modern-day immigrants in the Borsgraven Canal, must have been a dramatic sight. But the photographs of those water-blurred pictures, three of which hang at Numark, fail to convey that power.

Likewise, Attie's "Brick by Brick" installation in Cologne, where he projected furnishings of the type confiscated from Jews onto a former Nazi warehouse, was likely chilling at the time. But the resulting photo of lamps and chairs hovering on brick piers serves only to show you had to be there.

Attie's most successful photographic project since "Writing on the Wall" was his collaboration with New York City arts group Creative Time for "Between Dreams and History." For this piece, he interviewed 75 longtime Lower East Side residents -- the block he investigated was rich with Chinese, Dominicans and Jews -- asking them to share dreams they'd had about the neighborhood, their nighttime prayers or their favorite nursery rhyme.

For nearly a month, blue lasers traced selected phrases across the facades of those buildings his interviewees lived in. Sometimes poetic, sometimes banal, the words ran over the bright awnings for Lee's Sportswear and Alterations to Go, as if dissecting collective memory into so many individual recollections.

The Lower East Side project happened just four years ago, but already the landscape Attie captured has changed. As hipsters invade at a steady clip, the storefronts in the area are juggled. H.H. Hardware, of 95 Rivington in Attie's picture, has since secured new digs down the street.

Even more has changed in Berlin, where many of the dilapidated buildings Attie shot a decade ago have been sacrificed for stylish, modern housing and storefronts. The moment they're executed, Attie's projects become historical documents themselves, freezing a moment in the cycle of growth and change that maintains any city's vitality.

The backhoes will come. New buildings will go up. The future, like new experiences and the memories they generate, pushes out the past. But memory persists, haunting not our city streets but our imaginations.

Shimon Attie: Sites Unseen at Numark Gallery, 406 Seventh St. NW, Tuesday-Saturday 11 a.m.-6 p.m., 202-628-3810, through Dec. 21.

"Joachimstrasse 11a, Berlin": Shimon Attie projects pictures of places from an irretrievable past onto their present-day facades.Attie's "Mulack- strasse 37, Berlin," left, from his "Writing on the Wall" series, and, from New York, "Laser Writing Out Latino Senior's Nighttime Prayer."