What do we know about the structure, history, and evolution of the universe? Astronomer Phil Plait maps a timeline of the universe’s history and gives us an overview of the Big Bang, inflation and the cosmic microwave background – events that occurred between the initial phase of the cosmos to the rich variety of cosmic structures, ranging from stars and planets, to galaxies and galaxy clusters.
These are the first few minutes of the universe’s life, as explained by Plait:
When the universe got its start, it was unfathomably hot and dense. Even the basic forces we see today – gravity, electromagnetism, and the two nuclear forces responsible for holding atomic nuclei together, as well as letting them disintegrate in radioactive decay – were all squeezed together into one unified super force.
The universe expanded and cooled, the four forces went their separate ways, and the first basic subatomic particles were able to hold themselves together. This all happened in the very first second of the universe’s existence. Three minutes later, the universe cooled enough that the subatomic particles could start to stick together. For the next 17 minutes, the universe made atoms. For a few minutes the particles smashed together forming deuterium (an isotope of hydrogen), helium, and just a smattering of lithium. Then at T plus 20 minutes, the universe cooled enough that fusion stopped. When it did, there was three times as much hydrogen as helium in the universe.
For the complete understanding of universe, it helps to start at the beginning:
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