Where Physics and Biology Intersect

Life and the Second Law of Thermodynamics

Life is orderly, contrasting the second law of thermodynamics, which states that systems naturally become more disordered over time. A few examples of the second law are that sandcastles erode, leaves scatter, perfume evaporates, a cup of coffee and the universe cool. Despite this law, living organisms maintain order, resisting this natural trend. However, once an organism dies, the once living body follows the law’s inevitable path towards disorder. Until then, life maintains its order. We benefit from this and may even contribute to the stability of our existence by building structures, organizing society, etc.

A simplified statement of the second law of thermodynamics is that entropy, a measure of disorder, will not decrease in an isolated system that is not receiving external energy. This raises some questions about life and life’s order: What makes life possible? How did it start? How has complexity evolved? Does life exist elsewhere? Does the second law pertain to cosmic phenomena like the universe’s geometry and galactic attraction centers? This essay explores some of these questions.

The Origin of the Universe

The origin of the universe is a subject of scientific inquiry and speculation. Ancient scholars posited that light existed first (“… darkness was upon the face of the deep, … and then there was light…”); a notion echoed in modern science’s “Big Bang” theory. This theory suggests that the universe originated from an immense explosion, resulting in the creation of light and matter. There is ongoing scientific debate about whether time itself began with the Big Bang or pre-existed this event.

Evidence for the Big Bang includes the cosmic microwave background radiation, detectable even today, which was first identified by Penzias and Wilson in their seminal 1965 paper. Their discovery significantly contributed to our understanding of the universe’s origins and earned them the Nobel Prize in 1978.

Preceding the discovery of the microwave background radiation, Edwin Hubble observed that galaxies, though moving somewhat randomly, are drifting away from one another. If one reverses this movement in time, then the universe would have originated from a large explosion in a small volume.

After the Big Bang, matter formed into rotating galaxies with stars made of compressed hydrogen. At the center of most galaxies are dense mass attraction centers called Black Holes, where gravity is so strong that no light can escape. Stars emit light through a thermonuclear reaction known as fusion, which occurs when hydrogen is strongly compressed by gravity — though not as strongly as in Black Holes. For more comment, see https://ronaldabercrombie.blog/2023/12/17/vi-brief-outline-for-general-relativity/post .

Stars have a life cycle on a cosmic time scale, far beyond human experience. Stars create atoms that are more complex than hydrogen, and this more complex matter is the stuff that forms planets, like Earth, which orbit their star. Earth’s elements, formed in earlier stars, may be logically organized as in the Periodic Table, and these elements combine into molecules, making up our planet’s substance.  

As this essay concerns biophysics, we must discuss life on Earth. The question remains: how did it originate? Part of the challenge in understanding the origin of life is its complexity and diversity today. Natural selection has increased life’s complexity over time. Initially, it must have been much simpler.

Life requires three main criteria: 1.) a protective barrier from the outside world, 2.) controlled exchanges of solutes and energy across this barrier, and 3.) an ability to reproduce. It seems unlikely for these to arise simultaneously, but they are all essential for life.

Membrane barriers in a water environment could form from amphipathic molecules like phospholipids… potentially a first step. However, the introduction and role of genetic material (reproduction) and/or the first molecules managing solute and energy exchanges across a membrane barrier remain unanswered questions. Perhaps, genetic material initially served both functions.

Alternatively, primordial molecules made of amino acids from outer space may have possessed an unknown ability to replicate…. providing life its start.

Biochemists may someday design simple, self-replicating proteins that transport nutrients, or genetic material capable of also supporting transport. However, such molecules would have required a protective membrane barrier. This may be hypothesized as having occurred in early tidal pools on a planet with a mild climate.

It is possible that primitive life forms emerged multiple times in the universe or more than once on Earth over its three to four billion years, often failing to reproduce. Eventually, a viable cell succeeded, leading to the beginning of life here. Fragile new life forms arising on Earth today would not be expected to compete with the evolved robust organisms already existing. Any newer event would likely be short-lived and overcome by competition.

Scientific speculation requires experimental verification to be of any practical use of course. Although much of this is speculative, future experiments could test hypotheses. For example, AI (artificial intelligence) might assist in designing RNA-like or protein-like molecules that support both transport and reproduction, thus helping to advance our understanding life’s origins.

The Big-Bang created universe does not guarantee life. Yet, it seems odd that there has been no firm evidence of life elsewhere, despite extensive efforts to find it. However, it would be arrogant for us to think that in this universe of great immensity, we are unique, being alone in having life.

On Earth, evolved humans have certainly had an impact. We have demonstrated abilities such as building industrial machines and computers, cultural institutions, showing empathy for others, and transferring our knowledge. Yet, we also seek dominance, sometime vilify others, ignore our harmful impact, and are indifferent to harm we may cause the planet and other creatures. Some of these “human” traits have remained in modern times despite having questionable use for civilization’s future.

Today, one hears concerns about artificial intelligence, but historical patterns of human behavior have shown not only the beneficial but also the very deeply troubling tendencies of human intelligence as is evidenced by examining the history of civilization. Human intelligence, like artificial intelligence, has its troubling side.

Final comment. The events leading to the origin of our universe and the life within seem improbable, making our existence on Earth appear to be the result of surprising, random, and for us fortunate, events many eons ago and even more recently along our individual ancestral line. As our existence seems improbable, gratitude and humility may be most appropriate for us now.