Unveiling the Universe: From Big Bang to Galaxies
The Universe: Composition
Visible Matter:
- Normal (0.4%): Stars, planets, and intergalactic hot gas
- Normal non-luminous (3.6%): Black holes and intergalactic gas
Invisible Components:
- Dark Matter (21%): Unknown composition, inferred from mass measurements.
- Dark Energy (75%): Unknown nature, responsible for the accelerating expansion of the universe.
The Origin of the Universe: The Big Bang
All matter was concentrated in a small area and underwent a massive explosion (the Big Bang). Matter was propelled outwards in all directions, and in regions of higher density, the first stars began to form.
Confirmation of the Big Bang: Cosmic Microwave Background Radiation
In 1965, microwave radiation was detected coming from all points in space. This radiation is interpreted as the afterglow of the Big Bang.
The Echo of the Big Bang
The COBE satellite detected temperature variations in the microwave background radiation, providing further confirmation of the Big Bang theory.
Evolution of the Universe
In the initial moments after the Big Bang, the universe was extremely hot, leading to the formation of photons, quarks, and electrons, which then formed protons and neutrons.
After 10-6 seconds, protons and neutrons collided, producing energy. After 100 seconds, protons and neutrons combined to form simple atoms like helium, and photons became bound.
Approximately 1.1013 seconds after the explosion, the temperature cooled to 3000K. Photons lost energy, and electrons could be captured by atomic nuclei, leading to the formation of the first atoms. Eventually, photons separated, creating light.
200 million years later, the first galaxies formed, followed by the first stars 400 million years after the Big Bang.
Theories: Future of the Universe
- Open Universe: The universe will continue to expand indefinitely.
- Closed Universe: The universe will eventually contract, leading to a “Big Crunch,” potentially followed by another Big Bang.
Structure of the Universe
The universe is composed of galaxies and nebulae.
Nebulae
Nebulae are clusters of cosmic dust and hydrogen gas.
Galaxies
A galaxy is a collection of stars and dust held together by gravitational attraction. Our galaxy, the Milky Way, is approximately 200 billion years old and spans about 100,000 light-years. There are an estimated 100 billion galaxies in the universe, including elliptical, spiral, and irregular types.
Stars
Stars are celestial bodies that emit energy in the form of light and heat. They form in dense regions where gas and dust are compressed.
Formation of Chemical Elements
The formation of heavier chemical elements occurs in two phases:
1st Phase
Inside stars, hydrogen is successively fused into heavier elements, up to lead, through nuclear fusion.
2nd Phase
During explosive events like supernovae, heavier elements beyond lead are formed. When a star dies, this material becomes part of the interstellar gas and can contribute to the formation of new stars and planets.
Solar System
The Solar System consists of the Sun, planets, asteroids, and satellites. Planets orbit the Sun due to gravitational attraction. The planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune, along with plutoide planets.
The Earth
The Earth formed from interstellar matter and dust that began to collect and collide, forming larger bodies. This mass heated up as more material impacted it, eventually melting.
The materials within the Earth arranged themselves according to density, with the densest materials (the core) sinking to the center and the lighter materials (the crust) forming the outer layer.
Crust
The crust varies in thickness from 5 to 10 km under the oceans to up to 80 km under continents.
Mantle
The mantle is approximately 2900 km thick, with temperatures ranging from 1000 to 3300 °C. It is divided into the upper mantle (670 km) and the lower mantle (2230 km). A semi-liquid portion exists within the mantle.
Core
The core extends from 2900 km to 6400 km and is very dense and highly compressed. It has a very high temperature and is primarily composed of iron.
Tectonic Plates
The lithosphere, the outer layer of the Earth, is fragmented into tectonic plates. Convection currents within the mantle cause these plates to move, leading to collisions. These collisions can result in the formation of mountain ranges, earthquakes, tsunamis, and volcanoes.