Pseudoscience/Big Bang Theory
Big Bang Theory
The Big Bang is a theory that describe a universe that expanded from an initial state of high density and temperature. The notion of an expanding universe was first originated by physicist Alexander Friedmann in 1922 with the mathematical derivation of the Friedmann equations.
The Friedmann equations start with the assumptions that the universe is spatially homogeneous and isotropic on scales larger than the order of 100 Megaparsecs.
Independent of Friedmann's work, the Big Bang was first proposed in 1931 by Roman Catholic priest, physicist and Jesuit Georges Lemaître. Lemaître suggested the universe emerged from a "primeval atom".
Various cosmological models of the Big Bang explain the evolution of the observable universe from the earliest theorized periods through its subsequent large-scale form. These models offer a explanation for a broad range of observed phenomena, including the abundance of light elements, the cosmic microwave background (CMB) radiation, and large-scale structure.
The uniformity of the universe, known as the flatness problem, is explained through cosmic inflation: a sudden and very rapid expansion of space during the earliest moments.
This model met the required compatibility with the Hubble–Lemaître theory in that the farther away a galaxy is, the faster it is moving away from Earth, thus was not disregarded and remains a popular theory.
Extrapolating the theory of a "cosmic expansion" backward in time using the known laws of physics, the models describe an increasingly concentrated cosmos preceded by a singularity in which space and time lose meaning (typically named "the Big Bang singularity"). Physics lacks a widely accepted theory of quantum gravity that can model the earliest conditions of the Big Bang.
CMB reinforced the Big Bang theory
In 1964 the CMB was discovered, which convinced many cosmologists that the competing steady-state/Non-expanding model of cosmic evolution was falsified.
The Big Bang models conveniently predict a uniform background radiation (which would also be the case in a steady-state/Non-expanding model). The Big Bang model states that this uniform radiation was caused by high temperatures and densities in the distant past.
Estimates of the theorized expansion rate of the "universe" place the Big Bang singularity at an estimated 13.78 billion years ago.
According to the Big Bang model, after its initial "expansion", the universe cooled sufficiently to allow the "formation" of subatomic particles, and later atoms. The unequal abundances of matter and antimatter that allowed this to occur is an unexplained effect known as baryon asymmetry. These primordial elements—mostly hydrogen, with some helium and lithium—later coalesced through gravity, forming early stars and galaxies.
Astronomers theorize the universe has "gravitational effects" of an unknown "dark matter" surrounding the galaxies. The Big Bang models and various observations indicate that this excess gravitational potential is not created by baryonic matter, such as normal atoms.
Theories involving redshifts of supernovae indicate that the expansion of the universe is accelerating, forming an unexplained phenomenon known as dark energy.
The Big Bang theory depends on two major assumptions:
- the universality of known physical laws - The universality of physical laws is one of the underlying principles of the theory of relativity.
- the cosmological principle - a notion that states that on large scales the universe is homogeneous and isotropic—appearing the same in all directions regardless of location.