Erwin Schrödinger, an Austrian physicist and Nobel Prize laureate, explored fundamental questions about life in his influential 1944 book, “What Is Life?”. Renowned for his work in quantum theory, including the development of the wave equation which earned him the Nobel Prize in Physics in 1933, Schrödinger sought to understand how physical and chemical processes within living organisms could be explained by the laws of physics. This was a pioneering approach, as biology at the time was largely separate from the physical sciences. He questioned how life manages to maintain its highly ordered state despite the natural tendency towards disorder observed in the physical world. His work was published nearly a decade before James Watson and Francis Crick elucidated the double helix structure of DNA.
Life’s Battle Against Entropy
The Second Law of Thermodynamics states that in any closed system, disorder, or entropy, naturally tends to increase over time. Systems generally move towards a state of maximum disorganization and equilibrium. For instance, ink spreads in water, and a hot object cools, illustrating this progression towards increased disorder. Living organisms, however, present an apparent challenge to this law by maintaining and even increasing their internal order and complexity.
Schrödinger proposed that living systems achieve this by “drawing order from their environment.” He suggested that organisms “feed on negative entropy,” or what is more accurately termed free energy, from their surroundings. This concept explains how organisms resist decay into thermodynamic equilibrium.
Organisms consume energy and nutrients to sustain their complex structures and processes. Through metabolic activities, they take in highly ordered substances and break them down, releasing less ordered byproducts and heat into their environment. This process effectively exports entropy to the surroundings, allowing the organism to maintain its internal low-entropy state. Living systems are considered open systems, meaning they exchange matter and energy with their environment, which allows them to avoid the universal increase in entropy seen in isolated systems.
The Blueprint of Heredity
Schrödinger also theorized about the physical nature of hereditary material, anticipating the structure and function of DNA. He proposed that genetic information must be stored in a molecule he termed an “aperiodic crystal.” Unlike a traditional crystal with a repeating, predictable molecular pattern, an “aperiodic crystal” would possess a complex, non-repeating arrangement of atoms. This unique structure would allow it to encode a vast amount of diverse information within a relatively small number of atoms.
Schrödinger hypothesized that this “code-script” held the instructions for an organism’s development and function. He suggested that such a molecule could be stable enough to persist through generations while also being capable of undergoing subtle, infrequent changes, which correspond to mutations. These changes would drive biological evolution, explaining how species adapt and diversify over time.
He recognized that the stability of molecules, unlike larger chaotic systems, could be explained by quantum mechanics, even at room temperature. This provided a physical basis for how a genetic molecule could maintain its integrity while also allowing for the necessary variations that drive evolution. His idea of an “aperiodic crystal” provided a conceptual framework for hereditary material that was later validated by the discovery of DNA’s double helix structure, which stores genetic information.
Schrödinger’s Enduring Influence
Schrödinger’s “What Is Life?” significantly influenced the scientific community, particularly among physicists who then turned their attention to biological questions. The book inspired a new generation of researchers and helped bridge the gap between physics and biology, fostering an interdisciplinary approach to understanding life’s fundamental processes and leading to the emergence of molecular biology.
Notably, the book directly influenced James Watson and Francis Crick, who both credited Schrödinger’s ideas as a source of inspiration for their pursuit of the structure of DNA. Crick, a physicist by training, was motivated by the book to transition into biology, joining the Cavendish Laboratory in Cambridge to study protein structures. Watson, too, was convinced by the book that genes were molecules and that their structure needed to be discovered, leading him to focus on DNA.
Although some of Schrödinger’s specific proposals were speculative at the time, his conceptual framework guided subsequent research. His foresight regarding the nature of genetic information and the thermodynamic principles governing living systems were largely confirmed by later discoveries. The book’s lasting legacy lies in its role as a catalyst, shifting scientific thought towards exploring biological phenomena through the lens of physics and chemistry.