Solar System and Earth’s Formation: A Comprehensive View
Copernicus and the Heliocentric Theory
Nicolaus Copernicus proposed that to explain the constitution of the universe, we must acknowledge that the Sun is the center of the world, a concept known as the Heliocentric Theory.
The Sun and the Milky Way
The Sun is one among the 100,000 million stars in our galaxy, the Milky Way. The solar system resides in one arm of the Milky Way, rotating at a speed of 760,000 Km/h. It takes 230 million years to complete one orbit, known as a galactic year.
Earth’s Age and Evolution
Until recently, it was believed that Earth was 6,000 years old. In reality, the Earth has a history of 4,560 million years. If we compress this time into one year, January 1 would correspond to the formation of Earth, and Homo sapiens would appear on December 31.
Darwin and the Origin of Species
Charles Darwin demonstrated in his work, “The Origin of Species,” that species change over time and share a common origin. So far, humans are the only known species capable of reflecting on our place in the universe and our origins.
Theories About the Solar System
A theory about the solar system must explain why:
- The Sun and all planets revolve in the same direction.
- The orbits of the planets are ellipses.
- The orbits of all planets are in the same plane (ecliptic).
- Interior planets are small and dense, unlike the outer planets.
- All heavenly bodies are rocky and have numerous impact craters.
Planetesimal Theory
The Planetesimal Theory posits that 4,800 million years ago, a nebula (a heap of dust and gas) underwent gravitational collapse. This collapse formed a large central mass and a rotating disk around it. The collision of particles in the central mass released a lot of heat, and hydrogen fusion began, forming the protosun. The dust and gas particles in the rotating disk grouped together, forming granules. The collisions and union of these planetesimals originated the primitive planets or protoplanets, clearing their orbital zones.
Panspermia Theory
Panspermia Theory is now considered a possible alternative. It suggests that an asteroid colliding with a planet could scatter debris to other planets. If the asteroid contained microorganisms, they could potentially survive the initial shock, interplanetary travel, and arrival on Earth.
Astronomical Units and Light Years
An astronomical unit (AU) is the average distance between Earth and the Sun, equivalent to 150 million km. A light-year is the distance light travels in one year. Light travels at 300,000 km/s and takes 8 minutes to reach Earth.
Stages of Earth’s Formation
The formation of Earth is divided into several stages:
- Formation of the terrestrial protoplanet: Within the nebular disk surrounding the protosun, the terrestrial protoplanet originated. The increase in its gravitational field attracted new planetesimals, primarily formed by iron and silicate, along with other volatile elements.
- Differentiation of densities: The early Earth was partially molten, and its components were distributed by density. Iron moved to the deeper areas, forming the Earth’s core, known as the nife.
- Surface cooling and formation of the oceans: The bombardment of planetesimals decreased as Earth cleared its orbit, and it began to cool. The lower surface temperature favored the condensation of water vapor, allowing water to occupy the lowest relief areas and form the oceans.
Hypotheses on the Origin of the Moon
There are several hypotheses for the origin of the Moon:
- Sister: The Moon formed simultaneously with Earth, following a parallel path. However, the Moon is 100 million years younger than Earth.
- Adopted: Earth and the Moon formed in parallel, but the Moon formed farther from the Sun and was later attracted by Earth’s gravitational field.
- Child: This is the most accepted theory. It states that in the early years of Earth, a terrestrial planet collided with it, producing a cloud of dust that grew and formed the Moon from the crust and mantle.
The Big Bang
The Big Bang is the moment when from “nothing,” the entire universe originated. Matter, initially a point of infinite density, “exploded,” causing the expansion of matter in all directions and creating what we know as our universe. Immediately after the “explosion,” particles of matter began to move rapidly away from each other. Theoretical physicists have reconstructed the chronology of events from 1/100 of a second after the Big Bang. The material released in all directions was composed of elementary particles: electrons, positrons, mesons, baryons, neutrinos, photons, and over 89 other known particles.
Miller’s Experiment
Miller’s Experiment involved a circuit with a bowl of boiling water, dragging components through ducts. In a glass, gases similar to those in the early atmosphere, as proposed by Oparin, were subjected to electric shocks. After a week, amino acids were formed.