Universe and Its Origin

Study Notes

Universe is at least 13.8 billion years old; Solar System is 4.5-4.6 billion years old.
Comprises all space, time, matter, and energy.
4.6% baryonic matter: ordinary matter made of protons, electrons, neutrons forming atoms, planets, stars, and galaxies.
24% dark matter: invisible matter exerting gravitational forces but does not emit light, necessary for galaxy cohesion.
71% dark energy: a force causing the universe to expand, counteracting gravity.
Fundamental elements in the universe include Hydrogen, Helium, and Lithium.

Protostar: early stage of star formation from gravitational collapse of gases.
Thermonuclear reaction: fusion process in stars producing energy by fusing hydrogen into helium.
Main Sequence Stars: stars in a stable phase fusing hydrogen in their cores, balancing nuclear fusion's outward pressure with gravity.

Galaxy: Contains billions of stars, with diameters spanning 91 billion light years.

Ancient cultures presented various creation myths explaining the origin of the universe.
Steady State Model, Primordial Universe, Cyclical Universe, Ptolemaic Universe, and Einsteinian Universe were proposed theories preceding the Big Bang Theory.
Monotheistic religions attribute universe creation to a supreme being.

Widely accepted for explaining the universe’s expansion and origin.
Redshift: phenomenon where light from distant objects shifts to longer wavelengths, indicating they are moving away, contributing to the understanding of an expanding universe.
Cosmic Microwave Background (CMB): remnant radiation from the Big Bang, providing evidence for the universe's hot, dense initial state.

Initial conditions: all matter and energy existed in a hot, dense state around 13.8 billion years ago.
Rapid inflation occurred shortly after, leading to the formation of fundamental particles (quarks, hadrons, leptons).
Big Bang nucleosynthesis: formation of protons, neutrons, and light elements (hydrogen, helium, lithium) occurred roughly within 20 minutes post-Big Bang.
Universe cooled and transitioned to a matter-dominated period where photons decoupled from matter about 380,000 years later, leading to the release of CMB.
Over 100 million years, initial cloud formations led to the birth of stars and subsequently galaxies.
By 9.8 billion years after the Big Bang, dark energy began dominating the universe's dynamics, resulting in its accelerating expansion.
Formation of the Solar System occurred approximately 9.8 billion years post-Big Bang.