2001: A Space Odyssey

Three million years ago, a crystal slab appears on the savanna and teaches the man-ape Moon-Watcher to think in tools. In 1999, a dig on the Moon uncovers a black monolith, TMA-1, which fires a signal toward Japetus, a moon of Saturn. Discovery sets out with Bowman, Poole, three hibernating crew and the HAL 9000 computer, who is hiding the real goal. Torn between the truth and orders to lie, HAL kills Poole and opens the hatches. Bowman survives and shuts him down. Alone, he reaches Japetus, where the monolith opens like a gateway full of stars. He passes through a network of stations between the stars, becomes the Star-Child and returns to Earth, where he sets off an orbiting nuclear bomb harmlessly in space.

1. ChangeSaturn became Jupiter

   In the book, Discovery heads to Saturn and the second monolith sits on the moon Japetus. The film switched to Jupiter because the effects team couldn't build convincing Saturn rings.

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2. ChangeWho orders HAL shut down

   In the book, Mission Control orders the crew to disconnect HAL if he fails again. In the film, Bowman and Poole decide on their own, hidden in the pod, and HAL reads their lips.

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3. ChangeOpen hatches

   The book's HAL opens the hatches and vents the ship's air, and Bowman barely makes it. In the film, he cuts life support to the hibernating crew and locks Bowman out.

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4. ChangeThe bomb the movie dropped

   The book ends with the Star-Child setting off an orbiting nuclear weapon far from Earth. Kubrick cut the idea because it felt too close to the ending of Dr. Strangelove.

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