Are Aliens Real? Defining Life, Habitable Worlds, and the Drake Equation
To the point
Kevin Knuth notes that defining life matters and that life may hinge on liquid water, so scientists look for habitable-zone worlds, but the Drake Equation yields uncertain estimates of intelligent civilizations, there is no confirmed evidence of aliens or Earthly visitation, and even with credible data only a fraction of galactic civilizations might travel between stars.
