History of the Big Bang theory

[2] As a result, a variety of logical arguments for the universe having a finite past were developed by John Philoponus, Al-Kindi, Saadia Gaon, Al-Ghazali and Immanuel Kant, among others.

He described the birth of the universe in an explosion and the crystallization of matter to form stars and planets in a set of nested spheres around Earth.

Atoms spread evenly throughout space, until the repulsive force stops, and attraction appears as a reaction: then matter begins to clump together forming stars and star systems, while the material universe is drawn back together by gravity, finally collapsing and ending eventually returning to the Primordial Particle stage in order to begin the process of repulsion and attraction once again.

This part of Eureka describes a Newtonian evolving universe which shares a number of properties with relativistic models, and for this reason Poe anticipates some themes of modern cosmology.

Slipher used spectroscopy to investigate the rotation periods of planets, the composition of planetary atmospheres, and was the first to observe the radial velocities of galaxies.

Friedmann's 1924 papers included "Über die Möglichkeit einer Welt mit konstanter negativer Krümmung des Raumes" (About the possibility of a world with constant negative curvature) which was published by the Berlin Academy of Sciences on 7 January 1924.

In 1927, the Belgian physicist Georges Lemaitre proposed an expanding model for the universe to explain the observed redshifts of spiral nebulae, and calculated the Hubble law.

Also, the red shifts themselves were not constant, but varied in such manner as to lead to the conclusion that there was a definite relationship between amount of red-shift of nebulae, and their distance from observers.

It was actually Hoyle who coined the name of Lemaître's theory, referring to it as "this 'big bang' idea" during a radio broadcast on 28 March 1949, on BBC's Third Programme.

In the sixties, Stephen Hawking and others demonstrated that this idea was unworkable,[citation needed] and the singularity is an essential feature of the physics described by Einstein's gravity.

This led the majority of cosmologists to accept the notion that the universe as currently described by the physics of general relativity has a finite age.

Through the 1970s and 1980s, most cosmologists accepted the Big Bang, but several puzzles remained, including the non-discovery of anisotropies in the CMB, and occasional observations hinting at deviations from a black-body spectrum; thus the theory was not very strongly confirmed.

In 1990, measurements from the COBE satellite showed that the spectrum of the CMB matches a 2.725 K black-body to very high precision; deviations do not exceed 2 parts in 100000.

This showed that earlier claims of spectral deviations were incorrect, and essentially proved that the universe was hot and dense in the past, since no other known mechanism can produce a black-body to such high accuracy.

Further observations from COBE in 1992 discovered the very small anisotropies of the CMB on large scales, approximately as predicted from Big Bang models with dark matter.

In 2013 and 2015, ESA's Planck spacecraft released even more detailed images of the cosmic microwave background, showing consistency with the Lambda-CDM model to still higher precision.

According to the Big Bang model, the universe expanded from an extremely dense and hot state and continues to expand today. A common analogy explains that space itself is expanding, carrying galaxies with it, like spots on an inflating balloon. The graphic scheme above is an artist's concept illustrating the expansion of a portion of a flat universe.
Comparison of the predictions of the standard Big Bang model with experimental measurements. The power spectrum of the cosmic microwave background radiation anisotropy is plotted in terms of the angular scale (or multipole moment ) (top).