What is another word for rare earth hypothesis?
Pronunciation: [ɹˈe͡əɹ ˈɜːθ ha͡ɪpˈɒθəsˌɪs] (IPA) 
The "rare earth hypothesis" is a scientific theory that suggests the conditions necessary for complex life to form are exceptionally difficult to find in the universe, making the emergence of intelligent life exceedingly rare. There are several synonyms for this hypothesis, including the "great filter," which posits that intelligent life is hindered by a significant hurdle that most civilizations are unable to overcome, the "Fermi paradox," which refers to the apparent contradiction between the high probability of extraterrestrial civilizations and the lack of evidence for their existence, and the "anthropic principle," which states that the laws of the universe are precisely tuned to allow for the emergence of complex life forms. Regardless of the wording used, these hypotheses all explore the possibility that the emergence of intelligent life in the universe is an exceptionally rare occurrence.
