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# Cosmology Cheatsheet ## Basic Concepts - Cosmology: The study of the universe on its largest scales. - Universe: Everything that exists, including all matter and energy. - Big Bang Theory: The prevailing theory of the origin and evolution of the universe. - Dark Matter: Matter that does not interact with light and cannot be detected directly, but can be inferred from its gravitational effects on visible matter. - Dark Energy: A hypothetical form of energy that is thought to permeate all of space and accelerate the expansion of the universe. ## History of the Universe - Planck Epoch: The earliest known period of the universe, which lasted from the beginning of time to 10^-43 seconds. - Grand Unification Epoch: A period of the universe's history, from 10^-43 seconds to 10^-36 seconds, when the strong, weak, and electromagnetic forces were unified. - Inflationary Epoch: A brief period of exponential expansion of the universe, occurring at around 10^-36 seconds after the Big Bang. - Electroweak Epoch: A period from 10^-36 seconds to 10^-12 seconds after the Big Bang, when the strong and electroweak forces separated. - Particle Era: The period from 10^-12 seconds to 380,000 years after the Big Bang, when particles combined to form atoms. - Era of Nucleosynthesis: The time period from 3 to 20 minutes after the Big Bang, when light elements were formed. - Era of Recombination: The period about 380,000 years after the Big Bang, when atoms formed and the universe became transparent to radiation. - Cosmic Microwave Background: Radiation left over from the Big Bang, which fills the entire universe and is observed as a faint glow in the microwave region of the electromagnetic spectrum. - Era of Galaxies: The period from about 400 million years after the Big Bang to the present, during which galaxies formed and evolved. ## Theories and Models - Lambda-CDM Model: The most widely accepted model of the universe, which includes dark matter and dark energy. - Inflationary Cosmology: A theory that proposes the universe underwent a brief period of exponential expansion at the beginning of time. - Multiverse Theory: The idea that there may be multiple universes, each with different physical laws and constants. - String Theory: A theoretical framework that attempts to unify all the forces of nature and explain the fundamental nature of matter and energy. ## Observations and Measurements - Redshift: The phenomenon in which light from distant objects is shifted towards longer wavelengths, indicating that the object is moving away from us. - Cosmic Distance Ladder: A series of methods used to measure distances to celestial objects, including parallax, standard candles, and redshift. - Hubble's Law: The observation that the farther away a galaxy is, the faster it appears to be moving away from us. - Cosmic Microwave Background Radiation: Radiation left over from the Big Bang, which provides a snapshot of the universe about 380,000 years after the Big Bang. ## Key Figures - Edwin Hubble: American astronomer who first observed and described the expansion of the universe. - Georges Lemaître: Belgian physicist and astronomer who proposed the Big Bang Theory. - Stephen Hawking: British physicist who made significant contributions to our understanding of black holes, the Big Bang, and the origin of the universe. ## Resources for Cosmology ### Websites - [NASA: Cosmology](https://www.nasa.gov/mission_pages/cosmology/index.html) - [European Space Agency: Cosmology](https://www.cosmos.esa.int/web/cosmology) - [Cosmos: The SAO Encyclopedia of Astronomy](https://www.cfa.harvard.edu/cosmos/) - [Cosmology at the Perimeter Institute](https://perimeterinstitute.ca/research/research-areas/cosmology) - [American Astronomical Society: Cosmology](https://aas.org/cosmology-astroparticle-physics) ### Journals - [Physical Review D](https://journals.aps.org/prd/) - [Astrophysical Journal](https://iopscience.iop.org/journal/0004-637X) - [Monthly Notices of the Royal Astronomical Society](https://academic.oup.com/mnras) ### Books - *Cosmology* by Steven Weinberg - *The Early Universe* by Edward Kolb and Michael Turner - *Cosmology for the Curious* by Delia Perlov and Alex Vilenkin - *An Introduction to Modern Cosmology* by Andrew Liddle - *The Large Scale Structure of Space-Time* by Stephen Hawking and George Ellis