Paul Drude proposed the first theoretical model for a classical electron moving through a metallic solid.

In the realm of science fiction, there have occasionally been forms of life proposed that, while often highly speculative and unsupported by rigorous theoretical examination, are nevertheless interesting and in some cases even plausible.

His theory of peripatric speciation ( a more precise form of allopatric speciation which he advanced ), based on his work on birds, is still considered a leading mode of speciation, and was the theoretical underpinning for the theory of punctuated equilibrium, proposed by Niles Eldredge and Stephen Jay Gould.

Furthermore, Haeckel even proposed theoretical life-forms to accommodate certain stages in embryogenesis.

In a 1995 review of Rushton's Race, Evolution and Behavior, anthropologist and population geneticist Henry Harpending expressed doubt as to whether all of Rushton's data fit the r / K model he proposed, but nonetheless praised the book for its proposing of a theoretical model that makes testable predictions about differences between human groups.

Many theoretical search techniques for detecting Kaluza-Klein Resonances have been proposed using the mass couplings of such resonances with the top quark, however until the LHC reaches full operational power observation of such resonances are unlikely.

In 1917, Albert Einstein established the theoretical foundations for the laser and the maser in the paper Zur Quantentheorie der Strahlung ( On the Quantum Theory of Radiation ); via a re-derivation of Max Planck ’ s law of radiation, conceptually based upon probability coefficients ( Einstein coefficients ) for the absorption, spontaneous emission, and stimulated emission of electromagnetic radiation ; in 1928, Rudolf W. Ladenburg confirmed the existences of the phenomena of stimulated emission and negative absorption ; in 1939, Valentin A. Fabrikant predicted the use of stimulated emission to amplify “ short ” waves ; in 1947, Willis E. Lamb and R. C. Retherford found apparent stimulated emission in hydrogen spectra and effected the first demonstration of stimulated emission ; in 1950, Alfred Kastler ( Nobel Prize for Physics 1966 ) proposed the method of optical pumping, experimentally confirmed, two years later, by Brossel, Kastler, and Winter.

In 1958, Bell Labs filed a patent application for their proposed optical maser ; and Schawlow and Townes submitted a manuscript of their theoretical calculations to the Physical Review, published that year in Volume 112, Issue No. 6.

In fact, the theoretical physicist, J. M. Ziman, proposed that science is public knowledge and thus includes mathematics.

Norbert Wiener proposed the first set theoretical definition of the ordered pair in 1914:

This theory proposed that there are certain theoretical and conceptual opposites, often arranged in a hierarchy, which human logic has given to text.

One of the oldest and most commonly used formulations is the " transformation theory " proposed by the late Cambridge theoretical physicist Paul Dirac, which unifies and generalizes the two earliest formulations of quantum mechanics-matrix mechanics ( invented by Werner Heisenberg ) and wave mechanics ( invented by Erwin Schrödinger ).

The experiment as described is a purely theoretical one, and the machine proposed is not known to have been constructed.

Many candidate theories of everything have been proposed by theoretical physicists during the twentieth century, but none have been confirmed experimentally.

The American theoretical physicist John Archibald Wheeler coined the term wormhole in 1957 ; however, in 1921, the German mathematician Hermann Weyl already had proposed the wormhole theory, in connection with mass analysis of electromagnetic field energy.

The Bussard ramjet is a theoretical method of spacecraft propulsion proposed in 1960 by the physicist Robert W. Bussard, popularized by Poul Andersons novel Tau Zero, Larry Niven in his Known Space series of books, Vernor Vinge in his Zones of Thought series, and referred to by Carl Sagan in the television series and book Cosmos.

A further form of geosynchronous orbit is proposed for the theoretical space elevator, in which one end of the structure is tethered to the ground, maintaining a longer orbital period than by gravity alone if under tension.

John von Neumann immediately saw the significance of this insight, and in March 1947, proposed to Robert Richtmyer, leader of the theoretical division, a statistical approach to the problem of neutron diffusion in fissionable material.

A framework called comparative institutional analysis is proposed to deal with the game theoretical structural understanding of the variety of social norms.

Many candidate theories of everything have been proposed by theoretical physicists during the twentieth century, but none have been confirmed experimentally.

Hundreds of theoretical models were proposed to explain these bursts in the years following their discovery, such as collisions between comets and neutron stars.

Additional classes beyond this two-tiered system have been proposed on both observational and theoretical grounds.

A proof theoretical abduction method for first order classical logic based on the sequent calculus and a dual one, based on semantic tableaux ( analytic tableaux ) have been proposed ( Cialdea Mayer & Pirri 1993 ).

The working principle of a yupana is unknown, but in 2001 an explanation of the mathematical basis of these instruments was proposed by Italian mathematician Nicolino De Pasquale.

Alternatively, a Greek derivation from " manless, without husbands " ( a-privative and a derivation of * man-also found in Slavic muzh ) has been proposed, an explanation deemed " unlikely " by Hjalmar Frisk.

One of the most frequent speculations is that the entire book ( excepting 9: 4-20 ) was originally written in Aramaic, with portions translated into Hebrew, possibly to increase acceptance-many Aramaisms in the Hebrew text find proposed explanation by the hypothesis of an inexact initial translation into Hebrew.

Georg Wissowa proposed the explanation that it might be because the first slaves of the Romans must have been Latins of the neighbouring tribes.

The most widely accepted explanation for these phenomena is that dark matter exists and that it is most likely composed of heavy particles that interact only through gravity and possibly the weak force ; however, alternate explanations have been proposed, and there is not yet sufficient experimental evidence to determine which is correct.

Pauling first proposed the concept of electronegativity in 1932 as an explanation of the fact that the covalent bond between two different atoms ( A – B ) is stronger than would be expected by taking the average of the strengths of the A – A and B – B bonds.

Mises had earlier applied the concept of marginal utility to the value of money in his Theory of Money and Credit ( 1912 ), in which he also proposed an explanation for " industrial fluctuations " based on the ideas of the old British Currency School and of Swedish economist Knut Wicksell.

Mingroni has proposed heterosis ( hybrid vigor associated with historical reductions of the levels of inbreeding ) as an alternative explanation of the Flynn effect as it pertains to increases of g.

Thus like many of Cassidy's derivations, this proposed explanation appears quite improbable.

Besides, Brorsen had already proposed the correct explanation for the gegenschein ( interplanetary dust reflections ).

In 20th century an alternative explanation, called " friction heating " was proposed, whereby friction of the material was causing the ice layer melting.

The COX-3 pathway was believed to fill some of this gap but recent findings make it appear unlikely that it plays any significant role in humans and alternative explanation models are proposed.

A commonly proposed alternative explanation is that the universe is not transparent, and the light from distant stars is blocked by intermediate dark stars or absorbed by dust or gas, so that there is a bound on the distance from which light can reach the observer.

The psychical investigator Guy William Lambert proposed a geophysical explanation for poltergeist activity which results from the activity of underground water and other factors.

One proposed explanation of the existence of the recency effect in a continual distractor condition, and the disappearance of it in an end-only distractor task is the influence of contextual and distinctive processes.

Some parapsychologists still proposed that telepathy may have a physical explanation.

An explanation on the neural level of the decline of working memory and other cognitive functions in old age has been proposed by West.

* Le Sage's theory of gravitation ( 1784 ) also called LeSage gravity, proposed by Georges-Louis Le Sage, based on a fluid-based explanation where a light gas fills the entire universe.

Severe sexual, physical, or psychological trauma in childhood has been proposed as an explanation for its development ; awareness, memories and emotions of harmful actions or events caused by the trauma are removed from consciousness, and alternate personalities or subpersonalities form with differing memories, emotions and behavior.

The second theory proposed by London and Palen is based on a sociocultural explanation of gentrification.

The later theory of light by Isaac Newton in his Opticks proposed a different explanation for reflection, refraction and interference of light assuming the existence of light particles.

Hamilton decided to launch a measured and extensive defense and explanation of the proposed Constitution as a response to the opponents of ratification, addressing the people of the state of New York.

Published rates vary between trials, the proposed explanation being differences in study methods and reporting of prevalence rather than incidence values.