Final answer:
It takes Earth 24 hours to complete one rotation around its axis, resulting in the alternation of day and night for various regions on the planet.
Step-by-step explanation:
The time it takes for Earth to rotate around its axis once is approximately 24 hours. This rotation results in the alternation of day and night on the planet as different regions are exposed to the sun throughout this period. While Earth rotates on its axis, it is also orbiting the sun over the course of a year, traveling at an impressive speed of approximately 110,000 kilometers per hour (or 66,000 miles per hour). However, the concept that the sun revolves around Earth every 24 hours is incorrect; it is actually Earth that rotates on its axis, creating the illusion of the sun moving across the sky.