Paradox of the Day
Fermi Paradox
Given the size and age of the universe, where is everybody? The galaxy should be teeming with civilizations, yet we see no evidence of any.
Why it's paradoxical
The apparent contradiction between the high probability of extraterrestrial civilizations (billions of stars, billions of years) and the total lack of contact or detection. Proposed solutions include the Great Filter, the Zoo Hypothesis, and the Dark Forest theory.