More summary of this Brian Greene book. Earlier: post 1.
3, Origins and Entropy: From Creation to Structure, p44
If the universe began with a big explosion, how has so much order, with complex structures, emerged? Because, consistent with the second law of thermodynamics, pockets of order can exist among wider disorder.
Greene sketches our understanding of the Big Bang: that some 14bya the entire universe was compressed into a nugget, which expanded. What ignited it? Repulsive gravity. Alan Guth, in the 1970s, realized that in some conditions a repulsive gravity could be produced, and this would result in a very fast “inflationary” period early in the history of the cosmos. One prediction of this theory was a “cosmic background radiation,” which turned out to be the cause of the static on old-fashioned TVs. Further, this inflation revealed aspects of quantum features that are usually confined to the microworld: tiny differences in temperature were, via inflation, became projected onto the universe at large, and since that been discovered, and mapped.
This inflation would have arisen from an extremely low entropy situation; such a situation would be very rare, but given an infinite universe, even something extremely rare would occur eventually by sheer chance.
This tiny piece of space stretched enormously, like a bubble, but was unstable, so it disintegrated, becoming particles, becoming slightly more or less dense in various regions. Some of which became stars and galaxies. Gravity, being so weak, is negligible except at astronomical scales, but its effect would cause some molecules to be pulled into a denser core; counter-intuitively, as heat flows out, the shell gets cooler and the core gets hotter — hot enough to trigger nuclear fusion. A star is born.
4, Information and Vitality: From Structure to Life, p67
What is the difference between life and nonlife? Once again, Greene describes the idea of nested stories. You can’t explain life through reductionism to fundamental particles. The questions we ask determine the stories that provide the most useful answers. Physics makes sense at different levels that make sense on their own. It’s equally important to synthesize them into a seamless narrative. Greene mentions analogous ideas from Ken Wilson (renormalization), Sean Carroll (poetic naturalism), Stephen Hawking and Leonard Mlodinow (model dependent realism), and E.O. Wilson (consilience).
The understanding of how the elements form came in stages. Only the first few (the lightest) elements formed just after the Big Bang (in predicted ratios that were verified decades later. Heavier ones: inside stars. But only the elements up to iron. The heavy elements were formed when a star collapses and explodes, or when neutron stars collide. [[ The second stage, at least, is what Carl Sagan meant when he said “we are made of star-stuff.” ]]
The sun is a third-generation star, based on the amount of heavy elements it contains. Detritus from its formation became planets. Earth’s first half billion years we call the Hadean period. Only 150my after its birth, Earth collided with Theia, obliterating the latter and forming the moon, among other effects, including Earth’s tilt.
We’re pretty sure liquid water is required for our kind of life. In the 1920s Newtonian ideas (e.g. that atoms were like tiny little solar systems) gave way to quantum reality, particles that exist only with degrees of probability. Math explained ‘levels’ of electrons’ probability clouds; one a tier was full a stable atom resulted: helium, neon, etc. [[ the noble gases ]] Other types barter with other atomic species, by sharing electrons, i.e. molecules. Thus water, H2O, is extremely stable. The shape of the water molecule enables it to dissolve nearly everything. E.e. salt. Making it crucial for life.
The Unity of Life, p86. The next observation: cells in virtually all lifeforms are indistinguishable. Presumably because they all evolved from a common source. This is telling. Further, all life has two qualities: information, and energy. The processes are identical in all life.
The Unity of Life’s Information, p87. Lifeforms tend to move, but so can some automated systems. Motion in life arises from an interplay of information and execution, sort of like software and hardware. Within cells, similar processes play out. Amino acids, proteins; DNA. The code for building proteins are the same in all life. In combinations of molecules constituting genes, p90.
The Unity of Life’s Energy, p90. A steam engine extracts energy from the environment, by burning coal or some other fuel. Animals extract energy food, plants from sunlight, and typically stores it in some way, and distributes it as needed. The extraction and distribution occurs in all life the same way. Another astonishing achievement by nature. The chemical burning is called a redox reaction; details p91. Electrons looking for a place to rest. Of all possible types of energy processes, life uses just one, 92b. Again, suggests a single origin to life, some four billion years ago.
Biology and Batteries, p93. Life uses biological batteries, in every cell. Details. Similar to how ordinary batteries work. Details. With comments about the trillions of ATP molecules involved every second in our bodies.
Summary, p95. The main point being these processes are universal across all life, suggesting they emerged from a common ancestor. Just as Einstein sought to unify nature’s forces.
Evolution Before Evolution, p96. The question of life’s origin involves several parts. Initially Darwinian evolution seemed simple and intuitive, almost self-evident. Overwhelming evidence supported it. Even though Darwin knew nothing of how descent took place (i.e. genes or DNA). Those were discovered by Watson and Crick, in 1953. Traits are modified through error. Such error rates are extremely small, , but systems evolved this way given the timescales involved—billions of years. Natural selection is innovation through trial and error.
The field continues to be refined. Yet the foundation is rock-solid. The Darwinian framework thus applies to other realms than life. Example of ‘molecular Darwinism.’
Toward the Origins of Life, p102. Attention on RNA came in the 1960s; both software and hardware, it solves and chicken and egg problem. Before there was life perhaps there were RNA molecules, which evolved into the first cells. Recall the 1950s experiment with gases and electric current. This is the ‘RNA World’ hypothesis. Other ideas have been proposed since then, such as life forming near volcanic vents deep in the sea.
The Physics of Information, p106. How do these molecules ‘know’ what to do? Or, how did they come to do what they do? It’s all physics. It’s an information based story. Nothing about life contradicts physical law. Life is physics orchestrated.
The energy driving life comes ultimately from the sun. And before that, gravity. “The nuclear force, in tandem with gravity, is a fount of life-giving low-entropy fuel.”
Knowledge has become increasingly specialized. Other ideas in play concern whether life might be unique, or common. Prigogine and ‘order out of chaos’. Benard cells. Example of a kid on a swing. Dissipative adaptation. All ideas in their early stages.
Next: how do we get from life to consciousness?
