Factual error: On board spaceship Discovery, the crew's living area is the spinning centrifuge, which spins about its axis to generate a gravity-like acceleration at its perimeter, the floor. When exiting the centrifuge a crewman climbs a ladder from the floor up to the hub, where there's a door leading to other parts. When Poole & Bowman climb this ladder, it's evident that they're under full body weight the whole way up. But in reality they'd get steadily lighter toward the hub. In fact, they'd be practically weightless within a few feet of it.
Factual error: In the title shot, the camera rises above the dark side of the moon, revealing the crescent of the Earth, which in turn reveals the full disc of the Sun. The Sun is surrounded by the pinpoint lights of distant stars, but there are virtually no stars visible on the darkened far left and far right sides of the screen. This is exactly opposite of how real-life astronauts describe the star scape: Astronauts say that no stars are visible when looking in the general direction of the Sun, and that stars only become visible to the human eye as you turn away from the Sun.
Answer: As author Arthur C. Clarke explained it, the first Monolith (the one seen at the beginning of the film and then buried on the Moon) was a space probe from an incomprehensibly more advanced alien intelligence that resided inside a star elsewhere in the cosmos. The Monolith's objective was to seek out lifeforms that had potential and "tweak" their neural evolution, causing them to evolve toward intelligence. In the case of Mankind on Earth, once the modification was made, the Monolith probe retreated to the Moon and waited 4 million years for Mankind to reach it. When Mankind reached the Moon, the Monolith sent a signal to the next phase of the experiment, which was another Monolith in orbit of Jupiter. When Mankind reached the Jupiter Monolith in a matter of months, the Monolith acted as an interdimensional portal to the other side of the universe, transporting the evolved human specimen to its creator (that resided within a star). The creator intelligence found the specimen (Dave Bowman) to be of acceptable quality and rapidly evolved him to the next level, a Star Child. The Star Child is a "godly" evolution of Mankind. The Star Child chooses to instantaneously return to its home planet (Earth), where it stops a nuclear war.
Charles Austin Miller