Two decades after his death, we still haven’t found any extraterrestrial life — and Sagan, who always hoped for such discovery, probably would be surprised by that. SETI has detected no persuasive evidence of distant intelligence. The subject of a book Sagan co-authored, “Intelligent Life in the Universe,” remains speculative half a century later. The hard evidence didn’t materialize in his lifetime and hasn’t yet surfaced in ours, although there have been tantalizing signs, hints, possibilities. That’s not good enough. Science sets high standards, and Sagan liked to say that extraordinary claims require extraordinary evidence.
But look what has been discovered since he left us. Then, only a handful of stars were known to have planets. Now we know that planets are everywhere, that they’re a common feature of star formation and that Earth-sized planets exist in great abundance. When Sagan died, the age of the universe was still uncertain. We now know it is 13.82 billion years old. (Cosmology is getting so precise we will probably learn at some point that the universe began on a Thursday.) We now know that the universe is accelerating in its expansion due to “dark energy.” We now know that Einstein was right when he predicted the existence of gravitational waves. (But did we ever really doubt him?)
What would Sagan be most excited about? Maybe this new era of gene editing. What’s going to happen with CRISPR? What kind of world are we creating? The world still needs people who can explain stuff — and so it misses Carl Sagan.