The Big Bang Model
According to the current scientific consensus, the universe hasn't always existed as we know it. Approximately 13.8 billion years ago, all matter, energy, space, and time itself were concentrated in an infinitely small, incredibly dense, and hot point known as a singularity.
From that point, the universe began to expand (and continues to do so), cooling down gradually. This drop in temperature allowed pure energy to transform into matter, laying the physical and chemical foundations for everything that exists in the cosmos.
Chronology of Cosmic Evolution
The process of cosmogenesis was not an instantaneous event; it occurred through very distinct phases in which the conditions of the universe changed radically.
The Planck Era (The Beginning)
13.8 billion years ago
Time zero of the universe. Temperatures and densities were so extreme that current laws of physics did not apply, and the four fundamental forces (gravity, electromagnetism, strong and weak nuclear forces) were unified into a single "superforce".
Cosmic Inflation
Fractions of a second later
Space experienced a hyper-accelerated expansion, growing exponentially in size in an almost imperceptible timeframe. This stretched out quantum irregularities and explains why the observable universe is so uniform on a large scale today.
Formation of basic matter
The first 3 minutes
As the cosmos cooled, quarks were able to bind stably to form the first protons and neutrons. Later, these particles joined to create the first simple atomic nuclei, made almost exclusively of hydrogen and helium.
Recombination (Let there be light)
380,000 years later
The universe finally cooled enough for freely roaming electrons to attach to atomic nuclei to form neutral atoms. Light, which until then was trapped bouncing around in a "fog" of charged particles, could travel freely. That first light is still traveling today and we detect it as the Cosmic Microwave Background.
The birth of stars and galaxies
100 - 400 million years later
The universe entered a dark age until massive clouds of hydrogen and helium gas began to collapse under their own gravity. The increase in pressure and temperature in the center of these clouds ignited the first nuclear fusion processes, giving birth to the first stars. These began to cluster together thanks to dark matter, forming the first galaxies.
Formation of the Solar System
4.6 billion years ago
From the remnants of older stars (which exploded as supernovae and scattered heavier elements through space), our Sun and the protoplanetary disk formed, eventually giving rise to Earth and the rest of our solar system.
The legacy of cosmogenesis: We are a direct biological consequence of this stellar evolution. The heavy elements in our bodies, like the carbon in our cells, the calcium in our bones, or the iron in our blood, were forged in the fiery core of ancient stars that exploded billions of years ago. We are, quite literally, "stardust".
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