The Formation of Gaia and Luna
Four billion five hundred million years ago, the local solar system took shape in a remote region of one of the Milky Way’s spiral arms. As the galaxy spun, ever so slowly, a cloud of supernova gas was induced to spin by the passage of one of the galaxy’s spiral density waves. The motion of this particular force then contributed to the collapse of the cloud, which caused it to heat up.
Eventually, after coming together by a chance combination of phenomena based on a foundation of quantum uncertainty, the temperature within the natal system became hot enough to vaporize the dust particles in the enormous cloud. Then, as the gaseous structure swirled faster and faster, over a period of one hundred thousand years, it contracted under its own mass. This flattened the cloud out into an accretion disk with a huge bulge in the center.
In time, the centralized gravity compressed the burgeoning solar system enough to produce a late-generation star, incorporating the debris from generations of earlier stars, while the remaining gas flowed around it in orbit. Most of the gas flowed into and added mass to the emerging Sun, although the force from this prevented some of the gas from making the journey. Instead, it formed a rotating disk of various different elements around the star. This disk then radiated its energy away and gradually cooled off.
After a few hundred million years, the accretion disk finally cooled off enough for metals to condense out into tiny bits. Shortly thereafter, rock and even ice began to condense into minuscule pieces of matter. In the densest portions of the cloud, temperatures had dropped to less than ten degrees above absolute zero. At this point atoms combined into a number of different materials such as methane, ammonia, and formaldehyde.
All the while, molecules continued to collide into each other forming larger and larger masses as time went on. This continued until many of the celestial substances had joined together to form small boulders composed of a range of different materials. Then, once the larger masses grew enough to exhibit a nontrivial attraction their growth accelerated rapidly. At this point, their gravity gave them an edge over the smaller accumulations.
As a result, the largest astronomical objects became seedling planets, which quickly swept up all of the surrounding debris into their orbits. Then, at this stage of nebular evolution, the combination of rotation, magnetic fields, and heat all led to the development of energetic jets of material that shot out of the northern and southern poles of the solar system at velocities that gradually approached speeds upwards of hundreds of miles per second.
In the center of it all, the recently formed Sun grew into a large star that emitted infrared light. Although, within a million years of this, the gravitational attraction of the star caused it to shrink to its present size, and the added pressure caused by this collapse raised the star’s internal temperature high enough to trigger nuclear reactions in the core. As a result, the Sun stabilized and began to shine when the temperature within it reached about ten million degrees. This caused hydrogen to fuse into helium.
About a million years after the solar system cooled off, the Sun generated violent solar winds that blew huge amounts of volatile elements out into the expanding fabric of physical space for nearly ten million years. During this time, the growing planets gradually collided with each other, becoming more massive with each assault. The smaller of these remained close to the Sun, as their metallic and rocky bodies formed over tens of millions of years. This produced the seedlings of Mercury, Venus, Earth, and Mars.
Further out in space, the larger proto-planets pulled in the nebular gas that was forced towards them by the solar wind. Eventually, some of these became gas giants, like Jupiter and Saturn. As part of this, the density of matter in the original nebula dropped with distance beyond Jupiter, so the outer planets grew more slowly. By that point, dozens and dozens of different planets had become locked in orbit around the Sun and trillions of asteroids had come together to form the Oort cloud over three trillion miles from the central mass.
As the solar system continued to form, a planet named Thea, which was about four thousand miles in diameter, struck the early Earth with tremendous ferocity at many thousands of miles per hour. This tremendous collision, which was halfway between a glancing blow and a direct hit, severely disturbed the mantle of the Earth and completely destroyed the other celestial body in the process.
As a result of this, millions of tons of debris shot out into space, with a major portion moving into Earth’s orbit. Once there, the pieces of rock and metal coalesced after a phase of accretion and differentiation, to become the molten satellite that would eventually harden into the Moon. Meanwhile, other impacts tipped Uranus on its side and stripped Mercury of its crust. The rotations of the terrestrial planets, including Venus’s backward spin, were also set in motion by these astronomical collisions.
Regardless, during its formation, the early Earth went through a phase of differentiation in which the chemical composition became layered. Over the course of a few hundred million years, the energy released by radioactive decay gradually heated the already molten Earth, melting some of its main constituents. This molecular mixture consisted of mainly iron and silicates, with small amounts of other elements.
Most of the metal that was brought to the planet in chondrite materials during the accretion process melted, and being heavier than other elements sank to the center. As a result of this process, the silicates were forced to the surface as the iron traveled down for years on end. When the iron finally reached the center of the Earth, nearly four thousand miles down, it began to accumulate, forming a solid core surrounded by molten metal.
The motion of the molten metal within the outer planetary core, along with the effect caused by the overall planetary rotation, then created a magnetic field. As the conducting fluid moved through the existing magnetic field, electric currents were induced, creating a second distribution of magnetic forces. This second magnetic field then reinforced the original magnetic field, and a self-sustaining system was formed.
As the Archean Eon unfolded, the solid outermost portion of the Earth gradually formed as the planet cooled. At that time, this external crust, known as the lithosphere, was rich in the element silicon with lesser amounts of aluminum, iron, magnesium, calcium, potassium, and sodium. As such, that particular layer of the planet was composed of large, rigid slabs called tectonic plates, consisting of the African, North American, South American, Eurasian, Australian, Antarctic, and Pacific plates, along with several minor structures, as well.
As these geological formations emerged, the weak nuclear force continued to produce the radioactive decay that served to heat the planet’s core, thus allowing the interior to deform and flow. This heat was carried toward the surface of the planet by slow, solid-state convection which meant that the twenty mile thick rigid slabs were moved along the broiling magma beneath them. As part of this, many of the deep fractures in the Earth’s crust served as conduits for materials to rise up from the mantle, yielding much of the planet’s mineral wealth.
Four billion two hundred million years ago, the Earth’s atmosphere was enriched in noble gases such as argon and neon, but these were quickly swept away by the solar winds. These elements were eventually replaced by other molecular structures. As part of this, the planet belched out massive clouds of greenhouse gases from its interior.
In addition to this, many light elements were ejected from volcanoes leading to an atmosphere that included carbon dioxide, nitrogen, and water vapor, but no oxygen. Then, depressions in the Earth’s crust acted as natural basins in which captured meteorite water, which was slowly rising from the interior of the planet, came together to form a massive worldwide ocean. Although, since the atmosphere was dominated by carbon dioxide the water-soaked planet was a drab green color rather than the familiar blue of modern times.
All of this activity set the hydrologic cycle in motion. Water began to be stored in glaciers, polar ice caps, and oceans. Then, heat from the Sun evaporated the water from the Earth’s surface and the water condensed out into clouds. This fell back to the Earth, as rain and snow, then it ran back into storage and began the cycle all over again. Along with this, plumes of exceptionally hot material rose from deep within the Earth’s mantle.
These columns were relatively stationary within the Earth, while the tectonic plates moved above them. So, as the volcanic rock rose up from those plumes it created tiny landmasses on the surface of the water. Then, as the plates moved, islands formed in new regions and as these proto-continents underwent metamorphism, clay and mud formed.
Soon, the land began to fuse together to form larger, more stable islands. In addition to this, landmasses also began to grow when pieces of crust were scraped off as plates descended under the proto-continents, all of which were no more than three hundred miles in diameter. As a result, these structures were short-lived since their constituent rocks were destroyed by the earliest geological forces. Nonetheless, within two hundred million years of the Earth’s formation, the planet was more or less completely covered with land and water.
Along with this, the newly formed Moon gradually served to slow the planet’s rotation to its present speed, ultimately creating the twenty-four-hour day and setting the stage for seasonal change throughout the year. The presence of this satellite world also generated enormous waves as it moved through the Earth’s orbit. So, the resulting tides churned up the seas, mixing an array of minerals and nutrients in countless different ways. Ultimately, this helped to create the primordial soup from which life would inevitably emerge, thereby setting the stage for everything to come…