Final answer:
The question 'Where are they?' is called the Fermi Paradox, which refers to the contradiction between the high probability of extraterrestrial life and the lack of evidence or contact with intelligent civilizations. The Copernican principle suggests that intelligent life may be common, but the Fermi Paradox arises from the absence of contact.
Step-by-step explanation:
The question, 'Where are they?', is called the Fermi Paradox. The Fermi Paradox refers to the apparent contradiction between the high probability of extraterrestrial life based on the vastness of the universe, and the lack of evidence or contact with intelligent civilizations.
The Copernican principle suggests that intelligent life may be common in the universe, and organic life around older stars may have had more time to develop advanced technology. However, despite these possibilities, we have yet to make contact with any other intelligent civilizations, leading to the Fermi Paradox.