A day on Venus is longer than its year because the planet rotates extraordinarily slowly. Venus takes about 243 Earth days to complete one rotation on its axis, but only about 225 Earth days to orbit the Sun. In other words, Venus finishes its journey around the Sun before it finishes turning around once. Scientists believe this slow rotation may have been caused by massive collisions early in the planet's history or by atmospheric tides produced by its incredibly dense atmosphere, which is about 90 times the pressure of Earth's. These forces gradually altered its spin over billions of years. Adding to its oddity, Venus rotates in the opposite direction of most planets in the Solar System. If you stood on its surface, the Sun would rise in the west and set in the east. MLA Source: Carroll, Michael, and William Sheehan. Venus Revealed: A New Look Below the Clouds of Our Mysterious Twin Planet. Cambridge University Press, 2009. Want more interesting content like this ? Follow gravit...