As a microbiologist (by training), I’ve been delighted with the recent interest Physics Today has taken in reporting current findings in biology. This trend reflects the fact that high school students now are introduced to physics before chemistry. Biology comes last. Many years ago biology was taught first, then chemistry, then physics. Now we realize that a clear understanding of how living things work requires an understanding of the more “basic” sciences.
As an astrobiology buff, I was very happy to see the article “The Laws of Life” in the March 2017 issue of Physics Today. Author Charles S. Cockell defines astrobiology as we would expect—a study of life as it might exist anywhere, how it “…originated, evolved, and covered planetary surface[s].” Cockell emphasizes the huge variety that life has assumed on Earth and the simple fact that it must conform to the laws of physics. For survival purposes, an enormous number of efficient proteins are produced, but thermodynamics restricts how molecules are assembled and used.
Silicon is more reactive than carbon, hence it can’t form the stable, long-chains that carbon does. Long-chain exceptions are silicates, made with oxygen. However, natural silicates on Earth are found in rocks only as minerals, glasses and “amorphous structures.” On the other hand, carbon-based compounds are found throughout the galaxy—in clouds, meteorites, and protoplanetary disks. Some are simple, some aromatic. Others contain cyanide in useful, branched structures. Carbonaceous compounds may contain sugar, amino acids, nucleostases, and carboxylic acid. Recently, organic molecules have been found on Ceres. Ribose and glycine (parts of RNA and amino acid, respectively) have been found on comets. In contrast, silicon out in space is found only in minerals and glasses, as on Earth.
Here’s where physics takes its stand–the factor that makes carbon-life probably universal is the Pauli Exclusion Principle. The pairing of electrons in an element “determines an atom’s radius and reactivity.” It is hard to deny that “…life anywhere [will] tap into the energy available in electrons, relatively easily yanked away from atoms to do work.” Cockell concludes simply: “…life on Earth is unexceptional.”
Maybe. It’s certainly been hard to re-invent. We apparently have a lot to learn about the limits to, and the extraordinary complexity of, getting life started.
Author of The Archives of Varok
The View Beyond Earth (Book 1.)
The Webs of Varok (Book 2.)
Nautilus Silver Award 2013 YA
ForeWord IBPA finalist 2012 adult SF
The Alien Effect (Book 3.)
An Alien’s Quest (Book 4. Released Nov.21, 2016)
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