Final answer:
The Earth makes one complete rotation on its axis at the equator in roughly 24 hours when you divide the circumference of the Earth at the equator (40,000 km) by its spin rate (1670 km/hr). This period of time, known as a sidereal day, is fundamental for the day and night cycle.
Step-by-step explanation:
The question asks how long it takes for the Earth to make one complete rotation on its axis at the equator, given that the Earth's circumference at the equator is about 40,000 kilometers and that it spins at a rate of about 1670 kilometers per hour. To find the time it takes for one complete rotation, we divide the circumference by the spin rate:
Time = Circumference / Spin rate
Time = 40,000 km / 1670 km/hr
Time ≈ 23.95 hours
However, since we know that a day is made up of exactly 24 hours by our timekeeping, this small discrepancy is due to rounding off the spin rate and circumference. As it stands, the Earth makes one complete rotation in approximately 24 hours, and this is known as a sidereal day, which is the time it takes for the Earth to rotate 360 degrees relative to distant stars. This concept is fundamental in understanding the cycle of day and night on our planet.