Final answer:
Mercury has traditionally been a hard planet to observe and study due to its proximity to the Sun, short orbital period and high speed, and harsh environment.
Step-by-step explanation:
Mercury has traditionally been a hard planet to observe and study for several reasons:
- Proximity to the Sun: Mercury is the closest planet to the Sun, which makes it difficult to observe because it is always seen against bright twilight skies and never moves very far from the Sun in the sky.
- Short orbital period and high speed: Mercury has the shortest period of revolution around the Sun, only 88 days, and the highest average orbital speed of any planet. Its rapid movement makes it challenging to track and study.
- Harsh environment: Mercury experiences extreme temperature variations, ranging from scorching hot during the day to freezing cold at night. Its lack of atmosphere also leads to an inhospitable environment for building an astronomical observatory.