Final answer:
The subject of this question is Physics, specifically the feasibility of contact with aliens. Astronomers are skeptical of claims about UFOs being spaceships from extraterrestrial civilizations due to the immense energy expense and lack of contact with our governments or leaders.
Step-by-step explanation:
The subject of this question is Physics. The behavior and study of objects and forces in the universe can provide insights into the feasibility of contact with aliens. One reason astronomers are skeptical of claims about UFOs being spaceships from extraterrestrial civilizations is the tremendous distance and energy expense involved in interstellar travel. In addition, the lack of systematic contact with our governments or leaders further diminishes the credibility of these claims.