M83 // Credit: ESO/IDA/Danish 1.5 m/R. Gendler, S. Guisard and C. Thöne
In the January Astronomy
, I published a short essay about the possible commonness of civilizations in the universe. That opened up a landslide of emails from interested readers, and I wanted to share a few of the comments with you here.
My story (on page 9) suggested that with approximately 400 billion stars in the Milky Way and at least 125 billion galaxies in the universe, there ought to be about 50,000 billion billion stars in the cosmos — an amazing number of possible places for civilizations to be lurking.
The comments were pretty supportive of lots of life out there, although some who wrote suggested that advanced life is extremely rare. “I’d say there’s an incredible number of habitable extrasolar planets in our galaxy,” wrote Evan Rothstein, “let alone the universe at large. . . . But then there is the problem of getting there.”
Robert Hazen wrote that he found the juxtaposition of my story and Bob Berman’s “It’s random” column (in which he discussed randomness as a big factor in the universe’s evolution) “truly thought-provoking.” Robert described the incredible number of stars and perhaps planets that must exist, but then cautioned that because so many unlikely events may have to occur to produce a civilization, then the odds may be very much against it. “After reading both pieces, I felt very alone!” he wrote.
Matthew Banks described the numbers game that we like to consider and then exclaimed, “Of course it’s not just probabilities that determine whether or not life arises near a particular star, but the question calls astrobiological daydreamers like me to return to what we know for certain: There is at least one planet in the universe with life, and beyond that, all is conjecture. Thanks for giving me something to ponder.”
I’ll continue sharing more of these in the coming days. I was truly inspired and amazed by the large outpouring of letters and emails over this topic, and I hope that you will feel free to write me about these kinds of ideas in the future — the wondrous things that bring us together as travelers on planet Earth.