Final answer:
Mercury will go through 3 periods of retrograde during 2021.
Step-by-step explanation:
Mercury will go through 3 periods of retrograde during 2021.
All planets, including Mercury, can exhibit temporary retrograde motion, which is the apparent backward motion of a planet in its orbit as observed from the Earth. This occurs when the planets move in relation to the background stars, and it is caused by the difference in orbital speeds between Earth and the other planets.
Mercury, being an inner planet, experiences retrograde motion more frequently compared to outer planets. In 2021, Mercury will have 3 retrograde periods: from January 30th to February 21st, from May 29th to June 22nd, and from September 27th to October 18th.