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The Einstein–de Sitter universe is a model of the universe proposed by Albert Einstein and Willem de Sitter in 1932. [1] On first learning of Edwin Hubble's discovery of a linear relation between the redshift of the galaxies and their distance, [2] Einstein set the cosmological constant to zero in the Friedmann equations, resulting in a model of the expanding universe known as the Friedmann ...
If the universe has higher density, , then it is called "spatially closed": in this simple approximation the universe would eventually contract. On the other hand, if has higher lower density, ρ ≤ ρ c {\displaystyle \rho \leq \rho _{c}} , then it is called "spatially open" and expands forever.
The portion of the universe that can be seen by humans is approximately 93 billion light-years in diameter at present, but the total size of the universe is not known. [3] Some of the earliest cosmological models of the universe were developed by ancient Greek and Indian philosophers and were geocentric, placing Earth at the center.
The model is a braneworld theory developed while trying to solve the hierarchy problem of the Standard Model.It involves a finite five-dimensional bulk that is extremely warped and contains two branes: the Planckbrane (where gravity is a relatively strong force; also called "Gravitybrane") and the Tevbrane (our home with the Standard Model particles; also called "Weakbrane").
The fractal dimension of a homogeneous 3D object would be 3, and 2 for a homogeneous surface, whilst the fractal dimension for a fractal surface is between 2 and 3. The universe has been observed to be homogeneous and isotropic (i.e. is smoothly distributed) at very large scales, as is expected in a standard Big Bang or Friedmann-Lemaître ...
The radius of a sphere lives in the third dimension: it is not part of the 2 dimensional surface. However, the value of this radius affects distances measure on the two dimensional surface. Similarly the cosmological scale factor is not a distance in our 3 dimensional space, but its value affects the measurement of distances.
[6] [7] [8] The current version of The Scale of the Universe 2 uses Pixi.js instead of Flash, ported by Matthew Martori. [6] The Scale of the Universe was featured on NASA's Astronomy Picture of the Day on October 7, 2018. [9] In 2020, animation studio Kurzgesagt released the app Universe in a Nutshell, which took inspiration from The Scale of ...
Starobinsky inflation gives a prediction for primordial observables, e.g., the spectral tilt and the tensor-scalar ratio : ,, [11] where is the number of e-foldings since the horizon crossing.