Anyone who's ever watched Star Trek has probably noticed one of the show's most influential, yet unheralded features: doors that open automatically on approach.
On the surface, this technological miracle would appear to be nothing more than a simple combination of portal and motion sensor, something we encounter every day in shopping malls and office towers. But the doors of Star Trek are much, much more; they are, in fact, sophisticated Artificial Intelligences that know when it's appropriate to open, and when they should stay firmly shut. They are, to coin a phrase, Context-Sensitive Doors.
A pair of CSDs in action.
Here, Captain Kirk charges from a turbolift equipped with CSDs. Kirk's rate of speed is commensurate with the crisis he's managing, but the smart doors have no trouble opening and closing in perfect time with his passage.
Context-sensitive doors offer a silent welcome to a distraught officer.
Meanwhile, Mister Spock must deal with an emotional crisis. Here, he emerges from a door, which quietly opens with the soft, comforting "swish" that is so identified with CSDs.
Mister Spock regains his composure - thanks in no small part to the bulwark provided by the CSDs.
Were these doors controlled via simple motion sensor, Spock's next action, pictured above, would be impossible: as soon as the first officer leaned back, the doors would open, and the stoic Vulcan would take a most undigified fall.
Even Vulcans get the blues, but a good set of doors at your back will bring the good times back.
But context-sensitive doors understand that sometimes, even Vulcans need emotional - and physical - support. Using state-of-the-art 23rd century sensors, the clever doors remain shut until Mr. Spock can regain control of his emotions.
CSDs (at right) are on the job on the Enterprise-D.
Context-sensitive doors remain in active service in the 24th century. Here, we see Geordi La Forge and Mister Worf respond to a distress call. The CSDs snap open with alacrity in response to the urgency of the situation.
As we see in the following sequence of photos, CSDs are often called upon to make snap judgements. When an intruder infiltrates the ship and starts throwing your crew around, should you remain open or closed? Here's one door's bold decision:
The CSD prepares to make a command decision.
The intruder, inhabiting the body of a Starfleet Admiral, prepares to throw Geordi through the doors. The doors have only a split-second to assess the situation.
The CSD stands firm.
The CSD makes its choice: remain closed. The doors can absorb some of the impact of Geordi's flight, reducing the chance that the officer will be injured. But it's a choice with serious implications for the CSD, as seen in the following sequence:
In this view from the corridor, we see the CSD bulging slightly from Geordi's impact.
An instant later, the impact drives the doors from their hinges - a noble but necessary sacrifice to spare a valuable officer from serious injury.
One of the doors thrusts itself beneath Geordi's rump, saving his ass - literally!
"Thank goodness for Context Sensitive Doors!" is the thought no doubt running through Lieutenant La Forge's mind.
Just another day of service for Starfleet's unrecognized heroes: the Context-Sensitive Doors.
The stated goal of the Enterprise's mission is to seek out new worlds and new civilizations, to boldly go where none have gone before. In short, they seek out the unknown. Well, as a 20th century explorer might have said, had he lived to see the wondrous days to come, "There are things known and things unknown, and in between are the context-sensitive doors."