Q. When does the sun shine vertically on the Equator ?
Answer: Twice a year
Notes: When the Sun is vertically above the equator, the day is of equal length all over Earth. This happens twice a year, and these are the “equinoxes” in March and in September. Between the two tropic zones, which includes the equator, the Sun is directly overhead twice per year. Outside the tropic zones, whether to the south or north, the Sun is never directly overhead.