Constellations don't move *in* the sky, they appear to move *across* the sky due to the Earth's rotation and revolution around the Sun. Here's a breakdown:

* Daily Motion: Due to Earth's rotation, constellations appear to move in a circle around the North Star (or South Celestial Pole in the Southern Hemisphere). This motion is about 15 degrees per hour.

* Monthly Motion: The Earth's revolution around the Sun causes constellations to appear to shift their positions in the sky over the course of a year. They move approximately 30 degrees per month.

Here's why:

* The Earth orbits the Sun in roughly 365 days.

* There are 360 degrees in a circle.

* So, the Earth moves about 1 degree per day in its orbit (360 degrees / 365 days).

* This means that constellations appear to shift about 30 degrees per month (1 degree per day * 30 days per month).

Important Note: This is a simplified explanation. The actual movement of constellations is slightly more complex due to the Earth's tilted axis and its elliptical orbit.