Universe: From Big Bang to Planets and Life

Posted on Mar 15, 2025 in Physics

The Universe

It’s a huge vacuum in which billions of galaxies float. For each galaxy, there are thousands of stars, planets, and nebulae.
Some of them can be seen with the naked eye, and others can be seen with telescopes.
Formation of the observable cosmos: 75% hydrogen, 20% helium, and 5% the rest of the elements.

90% of the total matter in the universe is dark matter, whose composition and position are unknown because it cannot be seen or emit radiation.
Proof of existence: A few galaxies are close due to gravitational attraction caused by dark matter.

Bodies attract; the closer they are and the larger their mass, the greater the attraction.

According to the theory of general relativity, masses act on the space around them, deforming it.

There are concentrations of high-density material.
Its gravitational field is so large that even light cannot escape from it.
We know of its existence by radiation (especially X-rays) emitted by matter falling just before entering the black hole.
The more bodies fall, the larger the mass and gravitational attraction.
Sagittarius A*: Center of the Milky Way, mass of 3 million suns, point of no return: 7.7 million km.

(13.7 billion years ago)

Stage of inflation: the Big Bang. The supercompressed universe expanded, growing at enormous speed.
Formation of matter: The universe was composed of subatomic particles (electrons, quarks) bathed in vast amounts of energy: photons. After three minutes, upon cooling these particles down to a billion degrees, protons and neutrons were formed.
The first atoms: About 300,000 years after the Big Bang, hydrogen and helium atoms formed.
The Power of the Universe: The charged particles (protons and electrons) interfered with photons. When combined, light could travel freely through space. The universe became transparent, and cosmic radiation emerged.
The formation of stars and galaxies: 400 million years after the Big Bang, denser areas became centers of gravitational attraction. Material was collected, forming nebulae, planets, stars, and galaxies.

Dark energy could separate galaxies from each other to great distances. It could even disassemble atoms.

A supernova explodes.
The explosion generates a shock wave.
The wave is close to a nebula.
The wave compresses the nebula, causing it to collapse.
In the center of the nebula, particles are closer, so there are more collisions between them. The center of the nebula is heated. The hydrogen nuclei move at great speed and can merge, forming helium and releasing energy.

Require energy, carbon, liquid water, and an atmosphere.
The distance of the planet to the star is crucial.
Sufficient gravity on the planet is needed. If gravity is too small, it cannot retain the atmosphere.
A molten metallic core generates a magnetic field that protects against radiation.
A large satellite.
The existence of giant planets nearby, protecting other planets from possible impacts.
Within the Milky Way, away from the galactic center, where supernova explosions release a lot of radiation.

Outer planets: Jupiter, Saturn, Uranus, and Neptune are called giants and are formed by gases.
Inner planets: Mercury, Venus, Earth, and Mars are called terrestrial and are formed by solid material (rock and metal).