Giant Mirror

This jaw-dropping spherical mirror was loaned to us by friends at the Smithsonian Institution.

Designed to be part of a flight simulator, a small flaw (you can look, but you won’t find it) made it unusable for its intended purpose. And boy, are we glad, because this is probably our single most popular exhibit. Is it narcissism—or love of optics?

This mirror’s concave spherical shape focuses incoming light to a point—called the focal point—about 1.5 meters (5 feet) from its surface. Depending on where you stand relative to this focal point, you can give yourself a high five, watch a friend’s head shrink and explode, or enjoy a super-sharp view of distant objects. Walk slowly toward the mirror from beyond the focal point and you’ll see your own head seem to explode just as you pass through it.

As astounding as this mirror appears in person, the optical tricks it plays are not fundamentally different from those you can see in other concave spherical reflectors, such as a magnifying makeup mirror or even just the hollow side of a metal spoon. The main difference is its spectacular size—and a near-perfect smoothness that makes for exceptional clarity.

Can you come up with any new tricks? Let us know.

Like all concave mirrors, the Giant Mirror focuses incoming light (and sound) to a single point, called the focal point. (click image to enlarge)