In the movie "Armageddon," astronomers spot an asteroid that will hit the Earth in a matter of days. The asteroid is the size of Texas and the impact will cause total annihilation of life on Earth (or at least the people on it). A crew of astronauts and oil drillers must land on the asteroid, drill 800 feet into it, implant a nuclear bomb, liftoff from the asteroid and detonate the bomb. The explosion will fracture the asteroid and send the pieces on either side of the Earth in a near miss that will save humanity. This rousing action-adventure story has little scientific basis.
In the movie, when they land on the asteroid, the astronauts have special thrusters on their spacesuits to help them walk normally in the low gravity environment. Okay, fair enough. But inside the spacecraft that lands on the asteroid, the unsuited crewmembers walk around just as normally. Gravity works the same whether they are inside or outside of the spacecraft.
In Armageddon, the asteroid is the size of Texas; most asteroids are only several kilometers wide (astronomers would spot an asteroid the size of Texas well before it was a few days away from Earth). In the movie, the asteroid is a rough surface with razor-sharp crags and huge canyons. Actual photos of the asteroid Eros from the NEAR spacecraft show the surface to be relatively smooth, albeit cratered.
A similar movie, "Deep Impact," was released at the same time as "Armageddon." The story line was similar, but it involved a comet instead of an asteroid. "Deep Impact" was less of an action-adventure film and handled the human side of what would happen in the event of such an impact. We know that such impacts have happened over the history of Earth and the solar system and even witnessed the impact of comet Shoemaker-Levy 9 into Jupiter (see How Comets Work).
We'll look at how sci-fi has made mistakes with antimatter, gravity and black holes next.