History of the Big Bang theory

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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.
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The history of the Big Bang theory began with the

Hubble's Law
of the expansion of the universe provided foundational support for the theory.

Philosophy and medieval temporal finitism

In

view of creation.[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.[3]

English theologian Robert Grosseteste explored the nature of matter and the cosmos in his 1225 treatise De Luce (On Light). 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. De Luce is the first attempt to describe the heavens and Earth using a single set of physical laws.[4]

In 1610, Johannes Kepler used the dark night sky to argue for a finite universe. Seventy-seven years later, Isaac Newton described large-scale motion throughout the universe.

The description of a universe that expanded and contracted in a cyclic manner was first put forward in a poem published in 1791 by Erasmus Darwin. Edgar Allan Poe presented a similar cyclic system in his 1848 essay titled Eureka: A Prose Poem; it is obviously not a scientific work, but Poe, while starting from metaphysical principles, tried to explain the universe using contemporary physical and mental knowledge. Ignored by the scientific community and often misunderstood by literary critics, its scientific implications have been reevaluated in recent times.

According to Poe, the initial state of matter was a single "Primordial Particle". "Divine Volition", manifesting itself as a repulsive force, fragmented the Primordial Particle into atoms. 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.[5]

Early 20th century scientific developments

Observationally, in the 1910s,

Vesto Slipher and later, Carl Wilhelm Wirtz, determined that most spiral nebulae (now correctly called spiral galaxies) were receding from Earth. 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. Wirtz observed a systematic redshift of nebulae, which was difficult to interpret in terms of a cosmology in which the universe is filled more or less uniformly with stars and nebulae. They weren't aware of the cosmological implications, nor that the supposed nebulae were actually galaxies outside our own Milky Way.[6]

Also in that decade,

Friedmann–Lemaitre–Robertson–Walker
universe.

In 1927, the

De Sitter
, and independently derived Friedmann's equations for an expanding universe. 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.

In 1929,

Milton Humason formulated the empirical Redshift Distance Law of galaxies, nowadays known as Hubble's law, which, once the Redshift is interpreted as a measure of recession speed, is consistent with the solutions of Einstein's General Relativity Equations for a homogeneous, isotropic expanding universe. The law states that the greater the distance between any two galaxies, the greater their relative speed of separation. In 1929, Edwin Hubble discovered that most of the universe was expanding and moving away from everything else. If everything is moving away from everything else, then it should be thought that everything was once closer together. The logical conclusion is that at some point, all matter started from a single point a few millimetres across before exploding outward. It was so hot that it consisted of only raw energy for hundreds of thousands of years before the matter could form. Whatever happened had to unleash an unfathomable force, since the universe is still expanding billions of years later. The theory he devised to explain what he found is called the Big Bang theory.[citation needed
]

In 1931, Lemaître proposed in his "hypothèse de l'atome primitif" (hypothesis of the primeval atom) that the universe began with the "explosion" of the "primeval

cosmic microwave background radiation, the remnant radiation of a dense and hot phase in the early universe.[8]

Big Bang theory vs. Steady State theory

Hubble's Law had suggested that the universe was expanding, contradicting the

steady state" cosmological model, intended this to be pejorative, but Hoyle explicitly denied this and said it was just a striking image meant to highlight the difference between the two models.[9]
Hoyle repeated the term in further broadcasts in early 1950, as part of a series of five lectures entitled The Nature of The Universe. The text of each lecture was published in
The Listener a week after the broadcast, the first time that the term "big bang" appeared in print.[10] As evidence in favour of the Big Bang model mounted, and the consensus became widespread, Hoyle himself, albeit somewhat reluctantly, admitted to it by formulating a new cosmological model that other scientists later referred to as the "Steady Bang".[11]

1950 to 1990s

multipole moment
) (top).

From around 1950 to 1965, the support for these theories was evenly divided, with a slight imbalance arising from the fact that the Big Bang theory could explain both the formation and the observed abundances of

oscillating universe. 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. However, due to a lack of a theory of quantum gravity
, there is no way to say whether the singularity is an actual origin point for the universe, or whether the physical processes that govern the regime cause the universe to be effectively eternal in character.

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.

1990 onwards

Huge advances in Big Bang cosmology were made in the 1990s and the early 21st century, as a result of major advances in

WMAP
.

In 1990, measurements from the

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. From then on, models of non-standard cosmology
without some form of Big Bang became very rare in the mainstream astronomy journals.

In 1998, measurements of distant supernovae indicated that the expansion of the universe is accelerating, and this was supported by other observations including ground-based CMB observations and large galaxy red-shift surveys. In 1999–2000, the Boomerang and Maxima balloon-borne CMB observations showed that the geometry of the universe is close to flat, then in 2001 the

2dFGRS
galaxy red-shift survey estimated the mean matter density around 25–30 percent of critical density.

From 2001 to 2010,

clusters of galaxies
.

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.

Much of the current work in cosmology includes understanding how galaxies form in the context of the Big Bang, understanding what happened in the earliest times after the Big Bang, and reconciling observations with the basic theory. Cosmologists continue to calculate many of the parameters of the Big Bang to a new level of precision, and carry out more detailed observations which are hoped to provide clues to the nature of

General Relativity
on cosmic scales.

See also

References

  1. ^ "Big bang theory is introduced – 1927". A Science Odyssey. WGBH. Retrieved 13 September 2023.
  2. JSTOR 3622478
    .
  3. doi:10.1093/bjps/30.2.165
    .
  4. PMID 24627918
    .
  5. Bibcode:1994QJRAS..35..177C
    .
  6. ^ "Big Bang: The Accidental Proof | Science Illustrated". Retrieved 4 July 2020.
  7. S2CID 120551579
    . (English translation in: Gen. Rel. Grav. 31 (1999), 2001–2008.)
  8. ^ "Georges Lemaître, Father of the Big Bang". American Museum of Natural History. Archived from the original on 17 January 2013.
  9. ^ Mitton, S. (2005). Fred Hoyle: A Life in Science.
    Aurum Press
    . p. 127.
  10. ^ The book in question can [no longer] be downloaded here: [1]
  11. ^ Rees, M., Just Six Minutes, Orion Books, London (2003), p. 76

Further reading
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