Some of the most fascinating questions science still lacks clear answers to lie at the intersections of traditional academic disciplines.

We aim to reveal how the laws of physics narrow the scope of evolutionary processes at all levels of life structure.

--- p.21

The phrase "equation of life" captures the growing ability to describe life at various levels of the hierarchy using physical processes and their mathematical representations.
Although I will present examples of equations throughout this book, I do not expect the reader to understand their nuances, details, or usage.
The reason I present the equations is to show that the physical principles underlying evolution can be expressed in such a concise mathematical form.

--- p.21

Even on a macroscopic scale, physics simultaneously explains and constrains the workings of biological systems.
Trying to figure out how large animals can swim through water often leads to questions like why fish don't have propellers.
What laws of physics make a flexible body a better solution for navigating the ocean and avoiding sharks than the human engineer's solution, a propeller? The behavior of fluids and the objects moving through them strictly constrains what organisms can evolve within them, and they also constrain the solutions organisms find to survive within these constraints.

--- p.24

What struck me after class was not how I could find biological examples of physical laws at work, but how thoroughly simple physical laws shape and select the features of life at every level of the hierarchy of life, from electrons to elephants.

--- p.25

No matter how we judge life, no matter what definition or concept we choose, all of these possibilities fit perfectly within the simple laws of physics.
In his fascinating 1944 book, What is Life?, the Nobel Prize-winning Austrian physicist Erwin Schrödinger defined life in physical terms: it has the characteristic of extracting “negative entropy” from its environment.
Although this definition is famous, it is unfortunate that it has little formal meaning in physics.
But he chose this phrase to capture the idea that life seems to be fighting against entropy (the tendency of energy and matter to diffuse and dissipate to achieve thermodynamic equilibrium).
Entropy is a fundamental property of matter and energy, encapsulated in the second law of thermodynamics, which states that things tend to achieve equilibrium.
In many cases, this quality is such that things become more disordered.
Schrödinger believed that the struggle against entropy was the essence of life.

--- pp.30~31

Rather than dwelling on the definition of life, this book focuses on the universality of what we call life—the reproducing and evolving substance.

--- p.33

If we believe that biological phenomena follow the laws of physics, we can expand our universal view of biology to ask fundamental questions like these:
If life exists beyond Earth, would it resemble life on Earth? Wouldn't the structure and form of alien life be similar to ours? At what level of organization would alien life resemble life on Earth? Are the elements selected in a ladybug's leg also selected in other galaxies? What about the molecules formed from atoms? Are the molecules that make and form ladybug legs the same in other galaxies? What about ladybugs themselves? Are there ladybugs in other galaxies?
Could there be a creature that resembles a ladybug? Could that ladybug be identical to an Earth ladybug at every level of its structure?
--- p.34

As early as 1894, in a Saturday Review article on extraterrestrial life, science fiction writer Herbert G.
WellsHerbert G.
Wells mentioned the idea that silicates (materials containing silicon, a component of rocks and minerals) might exhibit interesting chemical reactions at high temperatures.
〈People are struck by the bizarre imagery of a silicon-aluminum organism—how could it not be a silicon-aluminum man?—walking through a gaseous sulfur atmosphere on the shores of a sea of ​​liquid iron thousands of degrees hotter than a blast furnace.〉
--- p.35

Where Darwin and I differ is in the overall direction of his conclusions.
The claim that the world arose from something as mundane and simple as the law of gravity and blossomed into the infinite forms of biology is artistically fascinating, but scientifically misleading.
It is ironic that he chose gravity as the fundamental law of physics.
Because the law of gravity plays a huge role in shaping life on a large scale, from the proportions of animal sizes to the shapes of trees.
Gravity has been with us since the beginning of life's evolution, leaving a clear imprint on the form of all things.
The law of gravity governed the evolution of life as it emerged from the seas onto land, ensuring that life on Earth was not infinite but had limits.
The laws of physics are still shaping life forms today.
If you look at them one by one, they are infinite, but in a limited form.

--- p.139

One question here is how the first cell came into being.
What created this tiny box, allowing molecules to gather here and become self-replicating machines? Was this a random event in the history of life, or was it physically inevitable? To answer this question, we need to understand how these capsules are formed and what they are made of.

--- p.149

No scientist in his right mind would exclude silicon from the list of candidates for the foundation of life.
Even on Earth, where silicates make up 90 percent of the Earth's crust, silicon does not have to combine exclusively with oxygen in silicates.
Silicon carbide (SiC), a compound of silicon and carbon, occurs naturally.
Several silicides, such as SiN (silicon nitride), SiCN (silicon cyanide), and SiS (silicon sulfide), have been observed in the interstellar medium, showing that silicon can form unusual compounds on a cosmic scale.

--- pp.310~311