Chapter 1: Understanding Earth's Chemistry

To grasp the narrative of our planet, one must first appreciate the essentials of chemistry. This marks the beginning of our exploration into the history of Earth.

Reflecting on my childhood, my LEGO collection was limited to what I inherited from my siblings, stored in an old cake tin. That was my entire LEGO universe—nothing more, nothing less. Just as I never acquired new pieces, the Earth reached a similar state 3.9 billion years ago. By that point, our planet had amassed all the fundamental components it would ever possess.

As a result, we transition into a new eon—the Archaean, a term derived from the Greek word for 'beginning.' For the past 4 billion years, it has been a cycle of recycling and reusing, which, fundamentally, embodies chemistry.

Apologies if my explanation seems overly simplistic; my formal chemistry education was lacking, and I need to clarify some concepts for myself. I hope I don't offend any experts with my basic interpretations.

At its core, the essential elements of matter are atoms—think of them as our LEGO bricks.

An atom is minuscule; for instance, a single human hair is composed of roughly a million atoms side by side. The structure of an atom consists of a nucleus, made of protons (and typically neutrons), enveloped by electrons. An atom's identity is determined by its number of protons: one proton signifies hydrogen, two protons indicate helium, six protons correspond to carbon, and so forth, leading us to the Periodic Table of Elements.

The simplest atoms are hydrogen and helium, both birthed during the Big Bang, alongside a slight amount of lithium. Currently, hydrogen constitutes about 73% of the visible universe's mass, followed closely by helium at 25%, leaving a mere 2% for all other elements. These additional elements were synthesized in stars or during supernovae/kilonovae events.

The Earth itself comprises approximately 33% iron, 31% oxygen, 19% silicon, 13% magnesium, along with traces of nickel, calcium, aluminium, and others.

Atoms can unite to form intricate structures known as molecules. For example, water (H2O) is a molecule comprising two hydrogen atoms and one oxygen atom. These molecules can be deconstructed back into their atomic constituents, although atoms themselves remain indivisible under typical circumstances—some can split in nuclear reactors, but that's a different discussion. Additionally, certain radioactive atoms can transform into different elements over time.

By 3.9 billion years ago, our collection of basic elements was complete. Everything that has emerged in the past 3.9 billion years has been crafted from the atoms formed during the Big Bang and the subsequent stellar events, which eventually made their way to Earth during the Hadean Eon. This is the entirety of our atomic legacy.

This piece is Part 8 in a series exploring Earth’s history, each focusing on a 100-million-year interval.

The first video, "The History of Earth's Atmosphere," delves into the evolution of our planet's atmosphere through the ages.

The second video, "GCSE Chemistry: Atmosphere, formation of Earth's early atmosphere," discusses the formation of Earth's atmosphere during its initial stages.

For further reading, check out Part 7: BOMBARDMENT or Part 9: LIFE. If you'd like to explore more articles, please consider following me.