Final answer:
Correct option: a) 1
The Moon completes approximately 13 orbits around Earth in one year, based on its sidereal period of 27.3 days.
Step-by-step explanation:
To determine the number of orbits the Moon completes around Earth in one year, we can use the known orbital period of the Moon.
The Moon's sidereal period, the time it takes to complete one orbit relative to the stars, is approximately 27.3 days. Because there are about 365 days in a year, we can calculate the number of orbits by dividing the number of days in a year by the length of the Moon's period.
- 365 days/year ÷ 27.3 days/orbit
- ≈ 13.37 orbits/year
This calculation shows that it's not precisely 12 or 13 orbits because of the fraction, but it's close to 13 orbits in a year. So, when rounding to the nearest whole number, we can say that the Moon completes approximately 13 orbits around Earth in one year.
It's worth noting that this is based on the sidereal month rather than the synodic month which is approximately 29.5 days and is the period from one new moon to the next.
A synodic month is longer because it has to account for the Earth's movement around the Sun in addition to the Moon's orbit around Earth.