Throughout most of the universe, chemistry as we know it barely ever happens.
Almost the entire universe is dark, cold, and empty space, far from the heat and light of stars or geothermal activity. Molecules lie frozen on asteroids or suspended in gas clouds, too cold and far away from each other to interact.
On the stars that speckle the universe, temperatures are so hot that almost all connections between molecules are broken down as soon as they form. Stars are extremely energetic but as a consequence are made up of relatively simple stuff.
Surrounding many stars are planets and moons, making up just a tiny fragment of the universe’s mass.
Chemistry is the study of atoms, molecules, and how they interact with each other, and it’s here in this fraction of a fraction of the universe that temperatures can be right for molecules to combine and create chemical interactions as we know them.
In our own solar system, many of the planets and moons have their own chemistry, from the hydrocarbon oceans of Titan, the largest moon of Saturn, to Mercury, the closest planet to the Sun, which is scorched by heat and solar winds. These planets lie in the balance between temperatures that are too hot or too cold, and too much pressure or not enough.
When conditions are just right on these planets and moons, gasses, liquids, and solids interact, combining and recombining in a near infinite number of forms.
The Earth is a haven for complex chemistry. On the Earth we sit underneath an ocean of gas that rolls above our heads, on solid ground that is bordered on every side by liquid oceans.
The different states are important, as they maximise the complexity of chemical interactions that can happen.
Liquid evaporate, rain down, and flow across the solid Earth, carving valleys and canyons which mix tons of sediments and dissolved chemicals.
The ebb and flow of the gas in the atmosphere creates our weather. Carried within it are aromas and scents, which swirl past us every second of the day.
The interaction of these forces move molecules across the surface of the Earth, alternately forming complex molecules and breaking them back down. It’s a utopia for complex chemistry.
Eventually, this environment led to one of the most interesting phenomena in the universe.
After millions of years of these complex interactions, a very unique molecule formed: A molecule that could replicate itself, which became the ancestor of all life on Earth.
It is in large part because of the conditions that allowed complex chemistry that life formed on Earth, and apparently not on other planets of the solar system (as far as we know).