The Solar System: Four and a Half Billion Years of Cosmic Evolution
By Alexx Pacifici (amateur astronomer)
The solar system is the area of neighboring space that comprises the known planets, moons, asteroids, comets, and other interplanetary matter that orbit our parent star, the Sun. It is approximately 4.5 billion years old, around 3/10th the age of the universe and is approximately two light-years in diameter. This means that if you were traveling from one side of the solar system to the other at the speed of light (300,000 km/s), it would take two years to complete the journey. The Sun is the key component of this elegant system, and its origin, along with ours, lies deep within the inconceivable past before it was even born.
The main elements that constitute the majority of matter within our solar system are primarily hydrogen, helium, oxygen, carbon, iron and nitrogen. These are the most abundant elements in the universe. An element is simply a type of atom. The lightest atom in the universe is hydrogen, which consists of only one proton and one electron; these are sub-particles that make up atoms. The succeeding elements in the periodic table get progressively heavier because they have more protons, neutrons, and electrons.
Our story begins long ago with a star that is no more. Inside the heart of stars - that is, within their cores, the temperature is so great that they generate nuclear fusion. This is what distinguishes a star from a planet or comet. Nuclear fusion is the smashing and merging of lighter elements to form heavier ones. Stars are the only place to naturally manufacture heavy elements because of their immense heat, which causes the atoms to move sporadically and smash into each other and bind through a force called the "strong nuclear force."
The predecessor to our Sun, along with every other star, went through this process. Our sun's ancestor was a very massive star; these types of stars live transient lives and die fantastically. At the end of a massive star's life, once it finishes nuclear fusion, it violently blows apart back into its primordial state: interstellar gas also known as a molecular cloud. When our Sun's predecessor exploded not only did it send all the hydrogen and helium back into space, but also the newly formed heavy elements discussed above. These new heavy elements provided the basis for the fundamental structure of life as we know it, carbon being the main element. This was to be the birthplace of our Sun, and subsequently the solar system.
This chemically enriched cloud of gas eventually became too dense at its center and collapsed into a ball of plasma under the force of gravity. This ball of plasma began to heat up and generate nuclear fusion, which counteracted gravity and thus the infant Sun was born.
For the first few hundreds of millions of years, extra material orbiting the Sun would continuously smash into each other, accreting and coalescing to form a bigger and bigger clump of material. These were considered the proto-planets, which were made of these newly formed elements from the previous star. Within the inner solar system were the four, terrestrial planets: Mercury, Venus, Earth, and Mars. Within the outer solar system were the four gas giants: Jupiter, Saturn, Uranus, and Neptune. Pluto resides way beyond Neptune in an icy asteroid belt called the Kuiper Belt. Orbiting these planets were objects called natural satellites, or moons. Moons are smaller bodies that get captured by a planet's gravity. Between Mars and Jupiter lies the asteroid belt, which is the result of a planet that never coalesced. This is because the gravitational waves from the Sun and Jupiter always ripped the potential planet apart.
In the first few hundred million years, meteors were continuously smashing into the inner planets, including Earth, which provided for a very violent beginning resulting in loads of craters. Eventually, when the majority of matter coalesced, and the amount of meteors diminished, the planets cooled; and due to its position in the solar system, Earth was lucky enough to have a congenial environment for an abundance of liquid water - a vital player in the game of life. Water is made up of hydrogen and oxygen - oxygen having been created in the heart of the Sun's predecessor through nuclear fusion.
With the help of ultraviolet radiation from the young sun, with organic material coming to our planet from meteors, and with organic material already existing on the planet, the first life was formed - quite quickly, within the first seven hundred million years. Life is a complex process whereby organic material is capable of reproducing itself and whose genetic identity is embedded in a molecule called DNA. It took its first form as a bacterium. Bacteria reside deep in the ocean and feed off the hydrogen released from ocean vents. Throughout the succeeding generations mutations occurred, allowing for bacteria to extract hydrogen directly from the water molecule (H2O), allowing for freedom of mobility throughout the ocean.
Another form of bacteria soon followed called cyanobacteria. These bacteria were different from the initial bacteria, as they were capable of photosynthesizing. Photosynthesis is the process of using light energy from the sun to draw carbon and water from the environment to produce carbohydrates and excrete oxygen. All plants today do this. This is the reason for the presence of oxygen in our atmosphere. Oxygen is, quite literally, the waste product of cyanobacteria and plants.
For over two billion years, cyanobacteria were the most complex life forms on the planet; and they ruled the world. But during their subtle presence, they continued to release oxygen into the atmosphere, eventually creating the ozone layer (O3). The ozone layer blocked harmful ultraviolet rays from the sun and consequently allowed for life to take its first baby step onto land.
Life was relatively simple until 600 million years ago, when a geological event called the Cambrian Explosion took place. Here was when the emergence of land plants and very complex animals, like fish, insects, reptiles, dinosaurs, birds, mammals, and primates (which includes humans) appeared - each as unique yet fundamentally identical to the other. We are all cousins, and we are all stardust. All life has DNA and the atoms that make up the DNA molecule were synthesized in the heart of stars billions of years ago.
Humans branched off from the great apes and into the genus Australopithecus a little under four million years ago. This genus developed bipedalism, which enabled the arms and hands to be free. Then, 2.5 million years ago, the genus Homo emerged. Throughout human evolution the jaw shrunk and big brains were developed, enabling high-level consciousness and intelligence. Bipedalism catalyzed tool-making because of the two free hands, which themselves had opposable thumbs capable of grasping things. The larynx lowered enabling verbal language.
By about 150,000-200,000 years ago modern Homo sapiens appeared. Since then humans have created religion, science, art, agriculture, writing, material wealth, and civilization. Humans have mastered language, tool making, agriculture, astronomy, digital technology, and figuring things out. With an increase in the species's population, humans have become one of the very few species capable of altering the environment and future environment of an entire planet.
