Are we alone? The most profound question humanity has ever asked.
With an estimated 100–200 billion galaxies and at least as many planets as stars in the Milky Way, the laws of probability alone suggest Earth is not unique. The Drake Equation reminds us that the number of communicating civilizations could range from 1 to millions — we simply don't know.
Three approaches: in situ (rovers, landers on Mars, Titan, Europa), remote sensing (atmospheric spectroscopy via JWST, ELTs), and SETI (searching for artificial radio/optical signals). The discovery of phosphine on Venus and organic molecules on Mars shows the search is accelerating.
"The universe is a pretty big place. If it's just us, seems like an awful waste of space."
— Carl Sagan