Venus rotates slower than it orbits

Venus takes 243 Earth days to complete a single rotation on its axis, but only 225 Earth days to orbit the Sun. You would celebrate your birthday more often than you would see a single sunset.

This isn't just a slow spin. Venus is the only planet in our solar system that rotates backward, or clockwise. If you stood on the surface, the sun would rise in the west and set in the east, assuming you could see through the thick sulfuric acid clouds.

Astronomers believe a massive celestial collision trillions of tons heavy likely smacked the planet billions of years ago. The impact was so violent it pushed the planet’s rotation into a grinding halt and forced it to start spinning the wrong way.

Because the planet rotates backward while it orbits forward, the time from one noon to the next—a solar day—takes about 117 Earth days. This means a Venusian year lasts less than two Venusian solar days.

The atmosphere is so heavy it behaves like a fluid, dragging against the planet's surface. This atmospheric friction actually exerts enough torque to keep the planet's rotation sluggish.

While Earth's atmosphere is a thin veil, the air on Venus is 90 times denser. Walking through it would feel like trekking through water 3,000 feet deep in the ocean.