Star Trek: science on the edge.

Attention, Starfleet recruits! Get ready for Star Trek: Generations, the new movie opening in our galaxy this Thanksgiving. In this long-awaited, big-screen adventure, Enterprise Captain Jean-Luc Picard (bottom row, with crew, above) will meet his predecessor, Captain James T. Kirk (right), for the first time.

To pull off this spectacular feat, at least one of the captains will have to travel through time. After all, their tours of duty on the Enterprise take place some 120 years apart--and neither of them looks a day over, well, 60. Throughout the movie, they'll probably both be soaring through space faster than the speed of light.

Impossible? Absolutely, says former high school physics teacher Hal Coyle, an avid Trek fan.

But that's the beauty of science fiction. In a fictitious story, says Coyle, you can bend the laws of physics so "you can get from one place to another in hours or days, rather than in millions of years." Such an endless delay for viewers in the real world, says Coyle, "would make for a very dull movie."

SPEED LIMIT

If you don't believe that Star Trek bends the laws of physics, says Coyle, who has shown Trek clips in his physics classes, just look at the way the Enterprise moves. In one scene, Picard might say, "Number One! Set a course for Ultima Thuli at Warp 6." That's an order to get the ship moving at 6 x 6 x 6 x the speed of light--more than 200 billion kilometers per hour! About 10 seconds later, Commander William Riker confirms that the ship has reached that speed--and everyone's still standing around on the bridge as if nothing has happened.

What's wrong with this picture? Well, says Coyle, think about what it feels like to accelerate--change speed or direction--in a car. When you accelerate quickly from zero to 88km/hr, you get squished back into your seat. Turn a corner while traveling fast and you get "thrown" to the opposite side.

That squished-into-your-seat/flung-about feeling is a direct result of Newton's First Law of Motion. The law states that an object will stay at rest (or in motion at a constant speed in a straight line) unless acted on by an outside force. The force--from the car's engine and the seat pushing against you--is what overcomes your inertia, or resistance to a change in motion.

The faster you accelerate, the more force you need and feel. That's Newton's Second Law of Motion: Force (F) = Mass (m) x Acceleration (a). So imagine how squished you'd feel when accelerating from zero to 200 billion km/hr in just 10 seconds on the Enterprise.

"Everybody ought to be flattened and the ship torn apart before it could get anywhere near that speed," Coyle says. "There's no way you could build anything that could withstand that kind of acceleration."

REAL ACTION REACTION

For another example of Star Trek's creative break from the laws of physics, think about the last time you saw the Enterprise escape from an enemy Romulan spacecraft.

"Lieutenant Worf! Take evasive action," Captain Picard might holler. And the faithful Klingon would zig and zag the Enterprise out of danger.

In these scenes, it looks like the Enterprise is maneuvering like an airplane, says Coyle: "It banks, it turns, it looks like it's flying." But space is missing one vital ingredient planes need to fly: air. The curved surface of a plane's wings push against air to take off and change direction (see SW 3/25/94, p. 18).

"In space, you have nothing to push against," says Coyle. "For all practical purposes, space is completely empty." So the Enterprise, unlike an airplane, can't modify its motion by changing the way the atmosphere around it flows over its body.

Instead, a spacecraft must rely on a very basic application of Newton's Third Law of Motion: Every force has an equal and opposite reaction force. In other words, says Coyle, "if you want the Enterprise to go off to the left, you've got to create a thrust [or force] to the right."

A real-life spacecraft, like the space shuttle, creates force with propulsion jets, or thrusters, which explode gas out of the ship through nozzles. When a thruster forces gas out the back of the ship, for example, the escaping gas exerts a reaction force on the ship, pushing it forward.

For a spacecraft to move backward, forward, up, down, left, and right, it would need thrusters on all sides, says Coyle, including the top and bottom. But the only thrusters the Enterprise appears to have are those cylindrical "booms" on the back of the ship (see photo, p. 10).

"The only thing [those booms] appear to do is create a thrust toward the back--which would only move the ship forward," Coyle says. In the real world, where the Enterprise would have to obey the laws of physics, says Coyle, it would be lost in space--sailing endlessly "forward" with no turning back.

Good thing for Picard, Kirk, and the rest of the Enterprise crew that "the driving force behind Star Trek is entertainment, not science," Coyle says.

Still, he adds, if you do go to the new Trek movie this fall, keep your eyes open: It might be fun to see what science fact and fiction you can spot.