When Uncle Joshua, a character in Peter De Vries’s 1959 novel, The Tents of Wickedness, says that nostalgia “ain’t what it used to be,” the line is played for humor: To those stuck in the past, nothing—not even memory itself—survives the test of time. And yet Uncle Joshua’s words have themselves aged pretty well (despite being widely misattributed to Yogi Berra): Technology, though ceaselessly striving toward the future, has continually revised how we view the past.

Nostalgia—generally defined as a sentimental longing for bygone times—underwent a particularly significant metamorphosis in 1888, when Kodak released the first commercially successful camera for amateurs. Ads soon positioned it as a necessary instrument for preserving recollections of children and family celebrations. According to Nancy Martha West, the author of Kodak and the Lens of Nostalgia, the camera “allowed people … to arrange their lives in such a way that painful or unpleasant aspects were systematically erased.”

Technology is poised to once again revolutionize the way we recall the past. Not so long ago, nostalgia’s triggers were mostly spontaneous: catching your prom’s slow-dance song on the radio, riffling through photo albums while you were home for the holidays. Today, thanks to our devices, we can experience nostalgia on demand. The Nostalgia Machine website plays songs from your “favorite music year”; another app, Sundial, replays the songs you were listening to exactly a year ago. The Timehop app and Facebook’s On This Day feature shower you with photos and social-media updates from a given date in history. The Museum of Endangered Sounds website plays the noises of discontinued products (the chime of a Bell phone, the chirping of a Eurosignal pager). Retro Site Ninja lets you revisit web pages from the ’90s.

This is just the beginning: While these apps and websites let us glimpse the past, other technologies could place us more squarely inside it. But although psychologists believe nostalgia is crucial for finding meaning in life and for combatting loneliness, we don’t yet know whether too much of it will have negative, even dystopian, effects. As technology gives us unprecedented access to our memories, might we yearn for the good old days when we forgot things?

1 | Breaking the 3-D Wall

In her 1977 essay collection, On Photography, Susan Sontag wrote that photos “actively promote nostalgia … by slicing out [a] moment and freezing it.” Because a photograph’s perspective is fixed, a viewer can’t move within it, and is unable to experience the captured space the way the photographer or her subject did. New technology, however, can turn old photos into 3-D graphics that provide the illusion of moving through space.

DeAgostini; SSPL / Getty; Sergio Schnitzler; Timquo / Shutterstock

Imagine the “bullet time” effect made famous by The Matrix—in which a scene’s action is either stopped or dramatically slowed down, while a camera seems to weave through the tableau at normal speed—applied to an old family photo, viewed on your laptop. Whereas The Matrix required 120 cameras to achieve its signature effect, a new approach known as 3-D camera mapping allows special-effects teams to inexpensively add dimensionality to 2-D photos. Recently, media designers like Miklós Falvay have used the approach to enhance archival images taken with a single still camera, giving viewers the impression that they are navigating spaces photographed years ago.

Artists have used other new techniques to project old photographs onto 3-D spaces. For its production of A 1940s Nutcracker, for example, the Neos Dance Theatre, in Mansfield, Ohio, used 3‑D‑graphics software to transform 1940s photos of Mansfield into virtual set pieces that dancers could interact with, creating the illusion that they were moving through old city streets. In this way, audience members who grew up in the ’40s were treated to the feeling of traveling through childhood landscapes.

Down the line, we may experience new forms of three-dimensional entertainment at home. Testing the appeal of holographic content, the BBC last year unveiled a rudimentary holographic TV, which used a variation on a Victorian theater technique—involving a transparent acrylic pyramid—to make footage of a beating heart and a dinosaur animation appear to float in midair. Although the BBC has no plans to bring such a TV to market, other companies are pursuing higher-tech commercial products, among them Samsung, which has patented a design for a TV that would broadcast laser-generated holographic images. When the technology is eventually perfected, people may watch home movies play out not on a screen but in the center of their living room.

2 | Reliving History

Even in 3-D, movies have a limited capacity for evoking real-life experiences. A viewer will never be able to choose his own perspective—to walk to another room, say, or to view a scene from the vantage point of a child rather than from that of a taller adult. Virtual-reality technology promises to give users a chance to do just that.

In a tantalizing example of how VR might be personalized in the future, Sarah Rothberg, an NYU researcher who specializes in virtual reality, has re-created her old house in “Memory Place: My House,” an Oculus Rift experience cum traveling art exhibit. Entering various rooms prompts the playing of home videos, filmed years before by Rothberg’s late father, whose early-onset Alzheimer’s disease inspired the project. After months of poring over old footage and photos, Rothberg was skeptical that the resulting experience would dislodge additional memories, but when she put on the Oculus Rift headset and walked across the virtual house’s parquet-floored hallway, something felt off: In the real house, a floorboard had been loose and rose at one end, though she had not thought about that fact in many years. As VR gear becomes cheaper, more of us might be able to re-create and then tour our own childhood homes—imagine an immersive, autobiographical version of Minecraft or The Sims.

3 | Backing Up Your Memories

Of course, to appreciate detailed replications of one’s past, one must have detailed memories of one’s past—and memory typically deteriorates with age. But experiments on other primates suggest that technological interventions may one day help us overcome this frailty. Theodore Berger, a biomedical engineer and neuroscientist at the University of Southern California, has developed a means of translating the neuron-firing pattern that the brain uses to code short-term memory into the pattern it uses to store long-term memory—a method he likens to translating “Spanish to French without being able to understand either language.” In some human trials, the translations have been found to be 90 percent accurate. Using this method, Berger’s team has created a mathematical model capable of recording the signals a rhesus monkey’s brain produces in response to stimuli, translating them, and feeding them back to the brain in order to facilitate long-term recall—even when the monkey has been drugged so as to inhibit the formation of lasting memories.

One day, we may even be able to create backups of our memories. In 2011, UC Berkeley researchers led by Jack Gallant, a cognitive neuroscientist, conducted an elaborate series of experiments that involved showing subjects video clips while taking fMRI scans of their brains, and then using a mathematical model to map how visual patterns translated into brain activity. After presenting a new clip to the subjects, the researchers used the resulting fMRI data to reverse engineer, from an archive of other footage, a video mashup that bore a striking resemblance to the clip the subjects had actually seen. Gallant believes that we could one day map brain activity triggered by a recalled memory and then reverse engineer a video of that memory.

For now, though, memory movies are a long way off. In a 2015 experiment, Gallant found that his model was three times more accurate at guessing the image a subject was looking at than at guessing one she was merely recalling. Another difficulty is that memories, especially nostalgic ones, shift over time. “What you recall is confabulated, made up,” Gallant told me. “Even if you can make a faithful reconstruction of a memory you decode from the brain, that memory is already wrong.”

Even if we had total recall, it might be best to avoid incessantly replaying memories, both for the sake of our psychological equilibrium and for the sake of our lives in the here and now. Ditto clicking from one nostalgia app to another. Clay Routledge, a psychology professor at North Dakota State University who wrote the leading textbook on nostalgia, says the emotion is typically healthy; in moderation, it can even lead you to seek out new experiences. But he cautions that “too much time focusing on the past could jeopardize your ability to engage in other opportunities that will form the basis for future nostalgic memories.” In other words, nostalgia really won’t be what it once was if, in the future, you have nothing to remember but the time you spent swiping through your phone, remembering.