What is a hologram? Is it an illusion or is it real, an image or an object?

Well, both.

If you ask the curators at the MIT Museum, they’ll write “a hologram is not an image of an object, but a device that records and replays the light wave front from an object or scene.” Yet at the same time, “Holography is a way of using laser light to make a single recording of the way an object looks from many different positions.” The conflicting definitions are a reflection of the dual nature of holograms: they are both what we see (a projection) and the creator of what we see (a re-creation of one object manipulated through a different one). Although holograms today are ubiquitous and easily identifiable—on the backs of our bank and credit cards, on the baseball cards and stickers we collected as kids, or on museum walls—discovering and defining what they mean, or are, is still a murky endeavor.

It might help to understand a hologram through our experiences. Besides the attributes of an object, such as shape, size and texture, our perception of that item depends in part on our own memories. We rely on our recollections to make sense of what we see. An object is not just its material properties, but a mix of those physical features combined with the feelings and reactions we have from having seen similar-looking objects.

So, for me, a hologram of a train arriving to the station, when viewed from different angles, looks uncannily like the Princeton Junction station train arriving from the north, heading toward Trenton, and reminding me of my undergraduate trips outside of Princeton University. And since a hologram projects different images depending on where you look at it, the images literally carry a multi-faceted set of perspectives (in my example, how fast I would have to run to catch the train before it left the station!). But the question is, which perspective is correct? Which is the most real?

We know that our memories deviate imperfectly from the reality of the moment, and can be warped in the process of being formed. From a purely physics perspective, a hologram is essentially a phony as well, an imperfect replication of light waves focusing at a certain distance away from the object, recreating its properties for the viewer yet still looking decidedly off. A hologram represents what it’s modeled after only at the object’s surface. Put your hand in front of the projection, at the edge of the wave front, and the true nature of a hologram becomes transparent. As you reach out to grasp the object, the image disappears, collapsing to two dimensions on the palm of your hand.

The MIT Museum’s hologram description continues, “A hologram’s beauty and mystery are the products of universal laws of physics.” We may understand those laws, and the principles behind the formation of a holographic image, but its mysterious nature remains elusive.