Life is not a miracle, but a natural [inevitable] consequence of the laws of physics and chemistry — Anonymous
Summary: The inevitability of formation of stars, such as our Sun, and planets, including Earth, is rooted in basic principles of physics and the ever-present randomness in the universe. The question of how life originated on Earth, and whether its emergence is also an inevitability, is a question worth pondering over. What follows looks into the factors that may have contributed to the origin of biology and why its emergence is an inevitability.
The Inevitability of the Formation of Stars and Planets
The inevitability of formation of stars and planets can be understood through the basic physical principles and ever-present randomness. The universe is composed of vast amounts of gas and dust, which, under the influence of gravity, coalesce to form stars. Our Sun, for instance, was born from a collapsing cloud of gas and dust approximately 4.6 billion years ago. This process is not unique to our solar system but is a common occurrence throughout the cosmos.
The collapse of the gas cloud into the formation of stars also results in the formation of planets. Small initial motions within the cloud translate into rotation as the cloud contracts due to the conservation of angular momentum. The rotating disk of material that forms around the growing protostar becomes the birthplace of planets.
The Role of Sun in the Formation of Complex Molecules
The primordial Earth was rich in carbon, nitrogen, hydrogen, oxygen, sulfur, and phosphorus — key elements that make up our biology (the biology we are familiar with, although, other kind of biology based on different chemical composition of self-replicating molecules could also exist). These elements provided the raw materials necessary for forming simple molecules, also referred to as monomers.
The presence of a star, like the Sun, in a planetary system is crucial for providing the energy necessary for chemical reactions that could lead to the formation of complex molecules. In the case of our solar system, the Sun’s energy, particularly in the form of ultraviolet (UV) light, played a significant role in driving photochemical reactions that broke molecular bonds and helped form new compounds. Additionally, atmospheric lightning (ultimately also driven by the Sun) provided bursts of energy, leading to the possibility of creating complex organic molecules. The monomers, fed by the Sun’s energy, linked together to form longer molecules called polymers that subsequently became the building blocks of biology.
The possibility of this mechanism was demonstrated in the famous Miller-Urey experiment, where a mixture of gases was exposed to electrical sparks, resulting in the formation of amino acids (monomers), which are essential for biology.
Polymerization and Building Blocks of Biology
Polymerization is the process by which monomers chemically bond to form larger, chain-like, or networked structures called polymers. This process is essential for the formation of complex molecules like proteins that are the basis for biology. Without polymerization, the assembly of complex structures necessary for life would not have been possible.
Autocatalysis and Self-Replication
The basis for the possible inevitability for the emergence of biology is the development of self-replicating molecules. A fundamental property of biology, after all, is some form of self-replication (or reproduction).
At some point in the chemical evolution leading to life, and as an outcome of incessant outcome of trials, certain molecules developed the ability to catalyze their own replication. This phenomenon is known as autocatalysis. In an autocatalytic system, a molecule (A) can interact with other molecules (X and Y) that are present in the environment to produce two copies of itself (2A). This self-replicating capability is a fundamental characteristic of biology.
One example of autocatalysis in prebiotic chemistry is the role of certain RNA molecules, known as ribozymes. Ribozymes (molecule A) can catalyze their own replication by assembling new RNA strands from free nucleotides (adenine [A], uracil [U], guanine [G], and cytosine [C]) (the X and Ys in the ambient environment). The original RNA strand acts as a template, with free-floating nucleotides in the environment aligning along the RNA sequence via complementary base pairing. Once the complementary strand is formed, it separates to become another, but identical, molecule (A becoming 2A).
It appears that moving from the emergence of polymers to self-replicating molecules is a significant leap, involving a highly improbable event. However, the low probability of occurrence is mitigated by the large number of trials of different chemical reactions taking place. The process is also aided by the concept of ergodicity according to which, while a small number of molecules may take an inordinately long time to explore a vast number of combinations, a large number of molecules can achieve the same results over a shorter time span.
Inevitability or Lucky Accident?
The emergence of self-replicating molecules and, by extension, biology itself raises the question: Was it an inevitability or a lucky accident? One can argue that given the right conditions and raw materials, the formation of self-replicating molecules is an inevitable consequence. The presence of key elements, energy sources, and suitable environmental conditions would have created self-replicating molecules allowing biology to emerge.
However, the lack of evidence for biology elsewhere in the universe, so far, suggests that the emergence of self-replicating molecules might have been a rare and fortuitous event. While we have identified exoplanets with conditions like those of early Earth, we have yet to find definitive evidence of life beyond our planet. This scarcity of evidence supports the notion that the origin of life may have involved a series of highly improbable events. However, given the possibility of billions of planets, it might just be a matter of time before we discover nascent or advanced forms of biology.
Summary
The formation of stars and planets, including the Sun and Earth, is rooted in fundamental physical principles and the inherent randomness of the universe. Simultaneously, given the limited amount of energy available on the Earth’s surface, the mechanism of natural selection is an inevitability. The missing link is the inevitable emergence of self-replicating molecules. Once that occurs, the domino effect of inevitabilities can provide a basis for the emergence of biology and eventually, us.
If this were to happen, an explanation for our consciousness, which can reflect on and question its own origin, would not necessitate a reason or an intelligent designer. Instead, one only needs to build upon the inevitable outcomes of a few basic physical laws and simple facts. In the simplicity and elegance of this explanation lies an explanation of our existence. In there lies our connection with the rest that is out there.
Ciao, and thanks for reading.
Notes:
Biology: Replication is a fundamental aspect of biology, referring to the process by which organisms create copies of themselves, ensuring the continuity of life.
Drakes Law: Drake’s Law, also known as the Drake Equation, is a probabilistic formula used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy. It was formulated by Dr. Frank Drake in 1961. The equation considers several factors that contribute to the development of intelligent life, including the rate of star formation, the fraction of stars with planetary systems, the number of planets that could potentially support life, and more
Ergodicity: If you take enough time, you’ll experience everything the system has to offer; A single molecules’ long-term experience is the same as what you’d get by looking at a whole group of molecules at one moment in time.
Organic Molecules: Organic molecules are built around carbon atoms, which can form strong, stable bonds with other elements, especially hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), and sulfur (S).
Prebiotic Chemistry: the study of the chemical processes that preceded the appearance of biology. Prebiotic chemistry explores how simple organic molecules, given the right conditions, could evolve into more complex structures capable of self-replication and metabolism.
Proteins: Proteins are made up of repeating units called amino acids (monomers). Inside the cells the synthesis of proteins is encoded in genes. Proteins are responsible for supporting a wide variety of biological functions.
UV Light: Ultraviolet (UV) light is a highly energetic form of radiation emitted by the Sun. It has the potential to disrupt chemical bonds due to its high energy levels.
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