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- https://phys.libretexts.org/Bookshelves/College_Physics/College_Physics_1e_(OpenStax)/34%3A_Frontiers_of_Physics/34.04%3A_Dark_Matter_and_ClosureThe motion of stars in galaxies and the motion of galaxies in clusters imply that there is about 10 fold more mass as in the luminous objects we can see. The indirectly observed non-luminous matter is...The motion of stars in galaxies and the motion of galaxies in clusters imply that there is about 10 fold more mass as in the luminous objects we can see. The indirectly observed non-luminous matter is called dark matter. Why is dark matter a problem? For one thing, we do not know what it is. It may well be 90% of all matter in the universe, yet there is a possibility that it is of a completely unknown form -- a stunning discovery if verified. Dark matter has implications for particle physics.
- https://phys.libretexts.org/Courses/Skidmore_College/Introduction_to_General_Relativity/02%3A_Schwarzschild_Geometry/2.01%3A_Non-Euclidean_GeometryA space in which the rules of Euclidean space don't apply is called non-Euclidean. The reason for bringing this up is because our modern understanding of gravity is that particles subject to gravity e...A space in which the rules of Euclidean space don't apply is called non-Euclidean. The reason for bringing this up is because our modern understanding of gravity is that particles subject to gravity exhibit curved motion not because there is a force acting on them but because spacetime is non-Euclidean.
- https://phys.libretexts.org/Bookshelves/Astronomy__Cosmology/Astronomy_1e_(OpenStax)/29%3A_The_Big_Bang/29.01%3A_The_Age_of_the_UniverseCosmology is the study of the organization and evolution of the universe. The universe is expanding, and this is one of the key observational starting points for modern cosmological theories. Modern o...Cosmology is the study of the organization and evolution of the universe. The universe is expanding, and this is one of the key observational starting points for modern cosmological theories. Modern observations show that the rate of expansion has not been constant throughout the life of the universe. Initially, when galaxies were close together, the effects of gravity were stronger than the effects of dark energy, and the expansion rate gradually slowed.
- https://phys.libretexts.org/Bookshelves/Astronomy__Cosmology/Astronomy_2e_(OpenStax)/29%3A_The_Big_Bang/29.02%3A_The_Age_of_the_UniverseCosmology is the study of the organization and evolution of the universe. The universe is expanding, and this is one of the key observational starting points for modern cosmological theories. Modern o...Cosmology is the study of the organization and evolution of the universe. The universe is expanding, and this is one of the key observational starting points for modern cosmological theories. Modern observations show that the rate of expansion has not been constant throughout the life of the universe. Initially, when galaxies were close together, the effects of gravity were stronger than the effects of dark energy, and the expansion rate gradually slowed.
- https://phys.libretexts.org/Learning_Objects/A_Physics_Formulary/Physics/03%3A_RelativityGeneral and special relativity starting from the Lorentz transform to Black holes
- https://phys.libretexts.org/Bookshelves/Relativity/General_Relativity_(Crowell)/08%3A_Sources/8.01%3A_Sources_in_General_Relativity_(Part_1)The Schrödinger equation and Maxwell’s equations treat spacetime as a stage on which particles and fields act out their roles. General relativity, however, is essentially a theory of spacetime itself....The Schrödinger equation and Maxwell’s equations treat spacetime as a stage on which particles and fields act out their roles. General relativity, however, is essentially a theory of spacetime itself. The role played by atoms or rays of light is so peripheral that by the time Einstein had derived an approximate version of the Schwarzschild metric, and used it to find the precession of Mercury’s perihelion, he still had only vague ideas of how light and matter would fit into the picture.
- https://phys.libretexts.org/Bookshelves/Modern_Physics/Book%3A_Spiral_Modern_Physics_(D'Alessandris)/8%3A_Misc_-_Semiconductors_and_Cosmology/8.2%3A_Modeling_the_Universe_(Project)Cosmology is the scientific study, and the associated mathematical models, of the universe as a whole. Amazingly, using only a few basic scientific principles one can construct a quantitative model of...Cosmology is the scientific study, and the associated mathematical models, of the universe as a whole. Amazingly, using only a few basic scientific principles one can construct a quantitative model of the universe that agrees surprisingly well with observational data. This model not only is in agreement with current observations, but makes clear predictions for the age of the universe and its future fate.
- https://phys.libretexts.org/Bookshelves/Relativity/General_Relativity_(Crowell)/02%3A_Geometry_of_Flat_Spacetime/2.06%3A_The_Light_ConeIn Newtonian physics, causal relationships fell into two classes: (1) could potentially cause any event that lay in its future or (2) could have been caused by any event in its past. In a Lorentz spa...In Newtonian physics, causal relationships fell into two classes: (1) could potentially cause any event that lay in its future or (2) could have been caused by any event in its past. In a Lorentz spacetime, there is a third class of events that are too far away from in space, and too close in time, to allow any cause and effect relationship, since causality’s maximum velocity is c . The boundary of this set is formed by the lines with slope ±1 on a (t,x) plot. This is referred to as the light
- https://phys.libretexts.org/Courses/Grossmont_College/ASTR_110%3A_Astronomy_(Fitzgerald)/14%3A_The_Big_Bang/14.01%3A_The_Age_of_the_UniverseCosmology is the study of the organization and evolution of the universe. The universe is expanding, and this is one of the key observational starting points for modern cosmological theories. Modern o...Cosmology is the study of the organization and evolution of the universe. The universe is expanding, and this is one of the key observational starting points for modern cosmological theories. Modern observations show that the rate of expansion has not been constant throughout the life of the universe. Initially, when galaxies were close together, the effects of gravity were stronger than the effects of dark energy, and the expansion rate gradually slowed.
- https://phys.libretexts.org/Bookshelves/Astronomy__Cosmology/Big_Ideas_in_Cosmology_(Coble_et_al.)/17%3A_Dark_Energy_and_the_Fate_of_the_Universe/17.02%3A_Candidates_for_Dark_EnergyInstead, they suggest, the entire idea is due to an illusion caused by the fact that we reside in a region of the Universe with slightly lower than typical density, a condition that could mimic the ef...Instead, they suggest, the entire idea is due to an illusion caused by the fact that we reside in a region of the Universe with slightly lower than typical density, a condition that could mimic the effects of acceleration on the supernova data that provided the primary evidence of the acceleration in the first place.
- https://phys.libretexts.org/Courses/Georgia_State_University/GSU-TM-Introductory_Physics_II_(1112)/zz%3A_Back_Matter/10%3A_13.1%3A_Appendix_J-_Physics_Formulas_(Wevers)/1.03%3A_RelativityGeneral and special relativity starting from the Lorentz transform to Black holes
