Theatrical folk are a superstitious lot. Wishing actors a broken leg (don't ever tell them "good luck"), avoiding whistling backstage (it used to confuse the stagehands), and being careful not to say Mac. . .—I mean, "The Scottish Play" (it's cursed, you know) are just a sampling of the multitude of time-honored theatre traditions. But the ghost light is one superstition that's also proven itself a modern theatre necessity.

A ghost light is a single bulb left burning whenever a theatre is dark. Some argue that its function is to chase away mischievous spirits; others insist it lights the way for the ghosts that are said to inhabit virtually every theatre, keeping them happy and contented. Either way, that light ensures that no one takes an accidental tumble off the stage.

"Mostly it's safety, just because they turn everything off at night," says Kim Russell, the stage manager for Legally Blonde. "You've got the edge of the stage leading to the orchestra pit, and if there weren't any lights and someone were to get in accidentally, it would be really easy to just walk off the edge of the stage and fall. It could be dangerous."

The New Amsterdam, another of Broadway's most haunted theatres, doesn't use a ghost light — at least, not a traditional one.

"We have a ghost, but we don't have a ghost light on the stage," says Dana Amendola, Disney Theatrical's VP of operations. "Because we are a different classification of building, we have to do more than just a ghost light. We have to pretty much leave the lights on."

According to Amendola, OSHA (Occupational Safety and Health Administration) requires some lights in the New Amsterdam remain on at all times, "so our ghost lights are actually up in the grid and shine down on the stage," according to Amendola. Even though it's lacking a lone bare bulb in the middle of the stage, the New Amsterdam Theatre still works hard to appease its resident ghost, former Ziegfeld showgirl Olive Thomas.

Photographs of Ms. Thomas hang at every entrance and exit to the theatre, and the cast and crew typically wish the late showgirl a good night when they leave by blowing her a kiss. "When she's been sighted, that's what she's done: blown a kiss to people that have seen her," says Amendola. He pauses before adding, "Usually people don't know who she is until they find out later on, and then they say, 'Oh my goodness!'"

It's not just on Broadway that the ghost light is important. There are theatre companies named after the ghost light in places such as Seattle, Iowa, Pennsylvania, Florida and Oklahoma City. Frank Rich, the formidable former New York Times theatre critic, revealed his sentimental and superstitious side when he titled his autobiography Ghost Light: A Memoir.

Even if after-hours lighting weren't required for safety purposes, superstitious thespians would probably still insist on keeping the ghost light burning. After all, the business of theatre is risky enough without an irate spirit or two in the wings.