Searching for Extraterrestrial Life

I'm reading a book about the possibility of life as we know it (or maybe as we don't know it) on other planets in our solar system and on extrasolar worlds, THE SECRET LIFE OF THE UNIVERSE, by astrobiologist Nathalie A. Cabrol. The author, director of the Carl Sagan Center at the SETI Institute, has worked on multiple unmanned space exploration programs. Reflections on her own experiences in that field lend a lively, personal touch to her in-depth analysis of the subject. Published in 2023, the book contains information about discoveries nearly as up to date as a reader could hope for. This book could serve as a valuable resource for science-fiction writers.

After two introductory chapters about Earth and the origins of living organisms here, she lays out the basic conditions for life as we know it -- mainly a temperature range where liquid water exists, the presence of certain vital elements, and particular levels of gravity and atmospheric pressure. Ideal geological and meteorological conditions also contribute to the probability that life could develop and survive.

Detailed analyses of Venus and Mars explore whether living creatures, if only on the microbial level, could exist there. Other possilities are some of Jupiter's moons and Titan, a moon of Saturn, since organic molecules and liquid water have been discovered on them. More surprisingly, Cabrol proposes possible environments for organic evolution on dwarf planets and even Mercury and our moon. Later chapters plunge into more speculative discussions of life that might exist on planets of other stars. She delves into the Drake equation (how statistically likely are extrasolar biospheres, intelligence, and civilizations?) and the Fermi Paradox (if other advanced civilizations exist in the universe, where is everybody?). Of course, the problem with determining the likelihood of some of the factors involved is that we have a sample of only one, our own world. There's a chapter on the active search for life throughout the galaxy, especially the SETI project. The author also considers the broad question of the definition of life and whether artificial intelligence could qualify.

The book's endnotes direct the reader to the resources the author drew upon. Her treatment of the various topics is so extensive and deep, however, even sometimes getting rather technical with discussions of organic and inorganic chemistry, that anyone wanting to use this work as background for creating alien lifeforms would hardly need to look elsewhere.

Margaret L. Carter

Please explore love among the monsters at Carter's Crypt.

Cosmic Times and Distances

This video compresses the total history of the universe and Earth into a single monologue of less than twenty minutes:

History of the Entire World

The summary is heavily weighted toward human history, of course. If the timing of events were in proper proportion, the existence of life on this planet would take up only a tiny interval at the end, and humanity probably wouldn't even be mentioned on that scale. It's quite entertaining if you can tolerate its being peppered with repetitions of two words that used to be classified as "unprintable." My first thought, after watching the podcast, was how infinitesimally short, on a cosmic scale, the history of our civilization is.

Here's a visualization of planetary sizes and distances compared to the Sun if the radius of the solar system equaled the length of a football field:

NASA Solar System Scale

The Sun would be about the diameter of a dime. The four inner planets—Mercury, Venus, Earth, Mars—are the size of grains of sand, and Earth sits on the two-yard line. Even Jupiter has a diameter equal to only the thickness (not the diameter) of a quarter. By the time we get to Pluto, we're on the 79-yard line. It boggles the mind to consider how much of our solar system consists of empty space. Imagine how empty actual interstellar space is!

In one of his late writings, Mark Twain compares the time span of life on Earth to the Eiffel Tower. On that scale, human history would correspond to the layer of paint on the very top. Twain says something like, "Maybe it's obvious that the whole tower was built for the sake of that little skin of paint on the top, but I have my doubts."

As a believer in a Creator, I do believe that the universe was made for humanity. BUT—it was made for all the other creatures in existence, too. C. S. Lewis writes somewhere that each of us can truthfully say the entire world was made for us, as long as we remember that every other being can truthfully make the same claim. "All is done for each." As he puts it in the "great dance" scene of his novel PERELANDRA, "There seems no center because it is all center." Which harmonizes with the astronomical observation that no matter where we stand in our expanding universe, space seems to be moving away from us uniformly in all directions, because no matter what our position, from our viewpoint we're at the center.

In that respect, we'll probably have something fundamentally in common with any other intelligent entities we may meet.

Margaret L. Carter

Carter's Crypt