The 1968 cult classic horror movie "Night of the Living Dead," filmed near Evans City, was based on a purported fallen satellite that released radiation, causing the unburied dead to come back to life.

A similar result isn't anticipated when a NASA spacecraft - Deep Impact - launched Wednesday at Cape Canaveral, Fla., slams into Comet Tempel 1 on July 4 at a rendezvous point 80 million miles from Earth. But speculation on whether the impact, which scientists hope will carve out a crater in Comet Tempel 1 that could swallow the Roman Coliseum, will in any way alter the course of the comet is the kind of "fallout" from which movie ideas are born.

With a launch window only one second long, there wasn't much margin of error for the mission, which carries a $330 million price tag.

It is an exciting undertaking on NASA's part because it has the potential to provide scientists with some long-sought-after chemical clues to the origins of the sun and planets. It isn't very often that the nation's space program has an "easily accessible" comet for such a mission.

According to the cover story of the March 24, 1997, Newsweek magazine, "Most of their days, comets float anonymously in a halo called the Oort Cloud, a backwoods of space way past Pluto. But once in a while, gravitational jolts from passing stars send a comet hurtling from the kingdom of ice into a trip around the sun. It may be a permanent orbit or, if the comet is going fast enough, it may escape the solar system altogether."

The United States was treated to quite a show in March and April 1997 when Comet Hale-Bopp made its once-in-4,200-years visit to Earth's evening sky. Its closest point to Earth was 122 million miles.

But the unpredictable nature of comets was evident in 1973 when the much-hyped Comet Kohoutek proved to be a disappointment for night-sky watchers and astronomers - professional and amateur - followed in 1986 by a disappointing visit of Halley's comet, which reappears about every 76 years.

For at least some people on this planet, the July 4 collision - the relative speed of the two objects at the moment of impact will be 23,000 mph - will create a flash that might be visible in the dark sky by the naked eye. It will be an Independence Day "fireworks" display like none before it.

The force of the collision will be equivalent to 4½ tons of TNT, NASA says.

Two objectives are at the heart of the Deep Impact mission. Besides the collision goal, the craft is carrying the most powerful telescope ever sent into deep space. The telescope will remain with the main craft when the impactor springs free on the day before the collision.

The telescope will "watch" the collision from what scientists hope will be a safe distance - 300 miles.

Other NASA space telescopes like the Hubble also will observe the collision, along with ground observatories.

It also will be an exciting moment for amateur astronomers.

Not much is known about Comet Tempel 1 besides it being an icy, rocky body about nine miles long and three miles wide. The crater resulting from the collision is expected to be two to 14 stories deep and possibly 300 feet in diameter, the length of the playing area of a football field.

What will be the result of the collision? No one can be absolutely sure at this time - scientists don't expect the comet to turn as a result of the impact and head toward Earth - but earthlings can feel at least some sense of comfort that scientists, even now, are confident that, with a little notice, they could go to a war footing and knock an intruder out of the sky.

There already are at least two programs in the United States that watch for asteroids, those small planets with orbits usually between those of Mars and Jupiter. Some scientists would like to see options for blowing up asteroids tested, which presumably could be adapted to an anti-comet initiative. This mission might provide invaluable data toward that goal.

For those who think such initiatives are unnecessary, because of the huge distances between objects in space, it is appropriate to note that scientists believe 65 million years ago a five-mile-wide object hit the Yucatan Peninsula, wiping out the dinosaurs. And, in 1908, a 200-foot rock blew up over Siberia, flattening thousands of square miles of forest.

Scientists believe that a meteorite a half-mile wide could deposit enough debris into the atmosphere to block out the sun, plunging Earth into a years-long night.

The July 4 "meeting" in space isn't expected to do anything like that but, considering that comets have always fascinated the earthbound, the coming event is destined to be something special in terms of arousing interest. From an economic standpoint, there could be ocean cruises or long collision weekends (July 4 will be a Monday this year) at hotels beyond the bright lights of metropolitan areas.

The impending collision also could bring predictions of doom, as the arrival of comets always has done down through the ages.

But the prospect of the unburied dead coming back to life need not be a worry - in Evans City or anywhere else.

Well, probably not.