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Big Bang cosmology is the prevailing scientific theory explaining the origin and evolution of the universe, suggesting it began from an extremely hot and dense singularity approximately 13.8 billion years ago and has been expanding ever since. This model is supported by multiple lines of evidence, including cosmic microwave background radiation, the abundance of light elements, and the redshift of galaxies indicating an expanding universe.
The cosmic microwave background (CMB) is the thermal radiation left over from the Big Bang, providing a snapshot of the infant universe approximately 380,000 years after its birth. It serves as a critical piece of evidence for the Big Bang theory and offers insights into the early universe's conditions, composition, and large-scale structure.
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Redshift is the phenomenon where light or other electromagnetic radiation from an object is increased in wavelength, or shifted to the red end of the spectrum, as the object moves away from the observer. It is a crucial observational evidence for the expansion of the universe and supports the Big Bang theory.
Hubble's Law states that the velocity at which a galaxy recedes from an observer is directly proportional to its distance from the observer, implying that the universe is expanding. This relationship is fundamental to cosmology and provides evidence for the Big Bang theory, as it suggests that galaxies were once closer together in the past.
Nucleosynthesis is the cosmic process by which new atomic nuclei are created, primarily occurring in stars through nuclear fusion and during explosive events like supernovae. This process is responsible for the formation of most elements in the universe beyond hydrogen and helium, shaping the chemical composition of the cosmos.
The Inflationary Universe theory posits that the universe underwent an exponential expansion in the first tiny fraction of a second after the Big Bang, solving several cosmological puzzles such as the horizon and flatness problems. This rapid expansion set the initial conditions for the large-scale structure of the cosmos we observe today.
The expansion of the universe refers to the observation that galaxies and other cosmic structures are moving away from each other, suggesting that the universe has been growing since the Big Bang. This phenomenon is supported by the redshift of light from distant galaxies and is a fundamental aspect of modern cosmology, indicating that space itself is stretching over time.
Dark matter is a form of matter that does not emit, absorb, or reflect light, making it invisible and detectable only through its gravitational effects on visible matter. It is believed to constitute approximately 27% of the universe, influencing the structure and evolution of galaxies and galaxy clusters.
Dark energy is a mysterious form of energy that is hypothesized to be responsible for the accelerated expansion of the universe, accounting for approximately 68% of the total energy content of the cosmos. Its nature remains one of the biggest unsolved problems in physics, with various theories suggesting it could be a property of space itself or a new dynamic field.
General relativity, formulated by Albert Einstein, is a theory of gravitation that describes gravity as the warping of spacetime by mass and energy, rather than as a force acting at a distance. It fundamentally changed our understanding of the universe, predicting phenomena such as the bending of light around massive objects and the existence of black holes.
The cosmological constant, denoted by the Greek letter Lambda (Λ), is a term introduced by Einstein in his field equations of General Relativity that represents a constant energy density filling space homogeneously. It is associated with the energy of the vacuum and is a crucial component in the Lambda-CDM model, which describes the accelerated expansion of the universe due to dark energy.
The cosmological constant, denoted by the Greek letter Lambda (Λ), was introduced by Albert Einstein in his equations of General Relativity to allow for a static universe, but it is now understood as a measure of the energy density of empty space, or dark energy, that is driving the accelerated expansion of the universe. This constant plays a crucial role in the current Lambda Cold Dark Matter (ΛCDM) model, which is the standard model of Big Bang cosmology.
Sphaleron processes are non-perturbative effects in the Standard Model of particle physics that play a crucial role in the violation of baryon and lepton numbers, potentially explaining the matter-antimatter asymmetry in the universe. These processes are significant at high temperatures, such as those present shortly after the Big Bang, and involve transitions between different vacua of the electroweak theory.
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