Question

question 2a: how long does it take the moon to go through all its phases once? question 2b: what do you think the original meaning of the word \month\ was? question 2c: how would a calendar based on the moon differ from our present calendar?

Explanation:

Question 2a: The Moon takes approximately 29.5 days to go through all its phases once. This is known as a synodic month.
Question 2b: The word "month" likely has its origin related to the Moon's cycle. Historically, time - keeping was often based on the lunar cycle, so "month" originally referred to the period of the Moon's phases.
Question 2c: A lunar - based calendar has months that are based on the Moon's phases, typically about 29.5 days long. Our present - day Gregorian calendar is a solar calendar. Lunar calendars can have shorter months and may not align well with the solar year, leading to differences in the number of days in a year and the timing of seasons compared to the solar - based Gregorian calendar.

Answer:

Question 2a: Approximately 29.5 days
Question 2b: Related to the Moon's cycle
Question 2c: Lunar - based calendars have months based on Moon's phases (about 29.5 days long), may not align with solar year as well as the Gregorian calendar.