In 1974, Drake tried a new approach, one that spoke instead of listening, by transmitting a carefully crafted message from the Arecibo Radio Telescope in Puerto Rico, the world's largest. The three minute signal was directed toward stars in globular cluster M13 with hopes that someone or something would intercept it sometime in the distant future. A much longer three-hour message to other carefully selected stars was subsequently transmitted in 2001 from a radio telescope in the Ukraine. Of course, if anyone is around when our 1974 message arrives at a hypothetical planet orbiting a star in M13, their response will not return here until fifty thousand years have transpired.
Since 1974, we've attached golden greeting cards to planetary recognizance spacecraft that fulfilled their primary missions then departed our solar neighborhood on an inter-stellar journey. But, it will take thousands of years before these vehicles reach the distance of the nearest star and they aren't even headed in that direction. Over the past decade, an explosion of planetary discoveries have been made but, so far, only a handful may have environments hospitable for microbial life or anything else we might consider intelligent.
While I'd be among the first to celebrate the discovery of life beyond Earth, so far there's no shred of evidence, no cryptic faint radio signals, no response to our outbound messages, no fragments of crashed alien spacecraft, no incontrovertible evidence embedded in meteorites nor any other proof that suggests we aren't the sole inhabitants of a Universe vast and grand beyond our most unbridled imaginings.
Instead, life may be far more rare than many hope or expect. Therefore, we may be more lucky than most of us suspect.
Here's few points to consider.
From a really big picture perspective, we live in a Galaxy whose central supermassive black hole remains in quiescence while those in many neighboring star systems spew radiation at lethal levels sufficient to snuff out life throughout much of their (assumed) planetary systems. Our solar system orbits the Milky Way's center between two spiral arms where conditions are relatively quiet, giving time for life to establish and evolve without interruption- all those fascinating phenomena filling our deep space images are safely located far in the distance where they can't harm us.
Closer to home, our host star has been stable and predictable throughout most of its existance while Earth's goldilocks' orbital distance permits the presence of liquid water and a breathable atmosphere. The orbit of our oversized Moon supports repeatable seasons and slow changing climates by stabilizing oscillations in our planet's rotation thus allowing life to gain an evolutionary foot hold and flourish. The gravittional influence of Jupiter helps make collisions with mass-extinction sized asteroids and comets extremely rare events for our world and Earth's still molten core projects an invisible shield that protects our world from solar winds and our star's deadly flares whereas Mars' cold core, for instance, allowed its atmosphere to be more or less blown away.
Moreover, over billions of evolutionary years, our biological lineage survived countless random mutations that led to the rise our species. Similarly, each of our family histories are filled with incalculable numbers of fortuitous events. Consider the disasters both natural and other wise, diseases, floods, famines, droughts, conflicts, social upheavals and injustices that had to be endured, overcome or avoided by our ancestors. Also, factor the matings whose gynecological resolutions fetilized each of our family trees and eventually resulted in the birth of you and me.
Finally, and my list so far has been far from exhaustive, since the Universe is mostly comprised of (essentially) empty space, our planet is far from a typical place. That makes the odds preventing the atoms in our bodies from being gathered here astronomically staggering!
Similar circumstances, no less daunting, would also comprise the collective histories of life on another planet. But this should not infer a personal frustration with continuing the search for extra-terrestrial life nor does it suggest the belief we're alone in the Cosmos.
Quite the contrary, we are not alone. We have each other and, for me, that's a limitless oportunity for hope.