While you might think it's the planet furthest from the Sun, Mercury is actually the fastest planet in our solar system.

Here's why:

* Orbital speed: Planets closer to the Sun have to move faster to stay in orbit. This is due to the Sun's strong gravitational pull.

* Mercury's orbit: Mercury is the closest planet to the Sun. Its average orbital speed is a whopping 47.87 kilometers per second (29.78 miles per second).

Let me know if you have any other space questions!