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- https://phys.libretexts.org/Bookshelves/Astronomy__Cosmology/Astronomy_1e_(OpenStax)/28%3A_The_Evolution_and_Distribution_of_Galaxies/28.03%3A_The_Distribution_of_Galaxies_in_SpaceCounts of galaxies in various directions establish that the universe on the large scale is homogeneous and isotropic (the same everywhere and the same in all directions, apart from evolutionary change...Counts of galaxies in various directions establish that the universe on the large scale is homogeneous and isotropic (the same everywhere and the same in all directions, apart from evolutionary changes with time). The sameness of the universe everywhere is referred to as the cosmological principle. Galaxies are grouped together in clusters. The Milky Way Galaxy is a member of the Local Group, which contains at least 54 member galaxies.
- https://phys.libretexts.org/Bookshelves/University_Physics/University_Physics_(OpenStax)/University_Physics_III_-_Optics_and_Modern_Physics_(OpenStax)/11%3A_Particle_Physics_and_Cosmology/11.07%3A_The_Big_BangThe universe is expanding like a balloon—every point is receding from every other point. Distant galaxies move away from us at a velocity proportional to its distance. This rate is measured to be appr...The universe is expanding like a balloon—every point is receding from every other point. Distant galaxies move away from us at a velocity proportional to its distance. This rate is measured to be approximately 70 km/s/Mpc. Thus, the farther galaxies are from us, the greater their speeds. These “recessional velocities” can be measure using the Doppler shift of light. According to current cosmological models, the universe began with the Big Bang approximately 13.7 billion years ago.
- https://phys.libretexts.org/Courses/Grossmont_College/ASTR_110%3A_Astronomy_(Fitzgerald)/13%3A_Galaxies/13.17%3A_The_Distribution_of_Galaxies_in_SpaceCounts of galaxies in various directions establish that the universe on the large scale is homogeneous and isotropic (the same everywhere and the same in all directions, apart from evolutionary change...Counts of galaxies in various directions establish that the universe on the large scale is homogeneous and isotropic (the same everywhere and the same in all directions, apart from evolutionary changes with time). The sameness of the universe everywhere is referred to as the cosmological principle. Galaxies are grouped together in clusters. The Milky Way Galaxy is a member of the Local Group, which contains at least 54 member galaxies.
- https://phys.libretexts.org/Courses/Skidmore_College/Introduction_to_General_Relativity/07%3A_Cosmology/7.01%3A_Modeling_the_UniverseMetrics come about by first proposing a matter/energy distribution and then solving the Einstein Field Equations. E.g., to get the metric of a star or black hole we can think of the universe as contai...Metrics come about by first proposing a matter/energy distribution and then solving the Einstein Field Equations. E.g., to get the metric of a star or black hole we can think of the universe as containing a single point mass with spherical symmetry and by imposing this constraint, we solve the equations to get the Schwarzschild metric. However, what if we want to determine a metric for the universe as a whole? What does the distribution of matter look like? What constraints can we impose?
