Final answer:
UFO sightings are often attributed to natural phenomena or human activity rather than extraterrestrial visitors, as there's a lack of credible evidence for the latter, despite popular representation in media and conspiracy theories. The skepticism among astronomers is based on factors such as the non-reporting by amateur astronomers and the absence of physical evidence.
Step-by-step explanation:
An explanation of UFO sightings with a great deal of scope includes considerations of natural phenomena, human activity, and hoaxes. Astronomers and skeptics often cite the vast distances and energy required for interstellar travel as reasons to doubt the extraterrestrial hypothesis for UFO sightings. Additionally, many UFO reports are resolved as IFOs (identified flying objects) upon further investigation. Natural explanations such as bright planets, ball lightning, and meteors, along with man-made ones like secret military craft, are often found to be the real causes behind these sightings. Moreover, the fact that amateur astronomers, who frequently observe the night sky, tend not to report UFOs, as well as the lacking of physical evidence of non-terrestrial origin, lead to further skepticism about the extraterrestrial origin of UFOs.
Media representations often sensationalize the idea of UFOs as alien spacecraft, possibly due to the intrigue and profit such stories can generate. While dark matter is widely accepted in the scientific community despite not being directly observed, UFOs as evidence of extraterrestrial life are not, primarily due to the lack of credible evidence and the availability of more plausible explanations for UFO sightings. The widespread public interest in conspiracy theories and the commercial benefits they offer further complicate the matter and add to the confluence of beliefs and skepticism surrounding the phenomenon of UFO sightings.