ciple and the Conclusions Drawn from It“, published in 1907, in which he addressed how the rule of special relativity might also apply to acceleration.
In short, he argued that free fall is really inertial motion; and for the observer, the rules of special relativity must apply. This argument is also known as the Equivalence Principle, which states that gravitational mass is identical to inertial mass. In the same article, Einstein also predicted the phenomenon of gravitational time dilation – where two observers situated at varying distances from a gravitating mass perceive a difference in the amount of time between two events.
In 1911, Einstein published “On the Influence of Gravitation on the Propagation of Light“, which expanded on the 1907 article. In this article, he predicted that a box containing a clock that was accelerating upwards would experience time faster than one that was sitting still within an unchanging gravitational field. He concludes that the rates of clocks depend on their position in a gravitational field, and that the difference in rate is proportional to the gravitational potential to first approximation.
In the same article, he predicted that the deflection of light would depend upon the mass of the body involved. This proved to be especially influential, because for the first time, he had offered a testable proposition. In 1919, German astronomer Erwin Finlay-Freundlich urged scientists around the world to test this theory by measuring the deflection of light during the solar eclipse of May 1929.
Einstein’s prediction was confirmed by Sir Arthur Eddington, who’s observations were announced shortly thereafter. On Nov. 7th, 1919, the The Times published the results under the headline: “Revolution in Science – New Theory of the Universe – Newtonian Ideas Overthrown”. General Relativity has since developed into an essential tool in modern astrophysics. It provides the foundation for the current understanding of black holes, regions of space where gravitational attraction is so strong that not even light can escape.
Modern Quantum Theory:
Einstein also helped advance the theory of quantum mechanics. Throughout the 1910s, this science was expanding in scope to cover many different systems. Einstein contributed to these developments by advancing the theory of quanta to light and used it to account for various thermodynamic effects that contradicted classical mechanics.
In his 1905 paper, “On a Heuristic Point of View Concerning the Production and Transformation of Light“, he postulated that light itself consists of localized particles (i.e. quanta). This theory would be rejected by his contemporaries – including Neils Bohr and Max Planck – but would be proven by 1919 with experiments that measured the photoelectric effect.
He expanded on this further in his 1908 paper, “The Development of our Views on the Composition and Essence of Radiation“, where he showed that Max Planck’s energy quanta must have well-defined momenta and act in some respects as independent, point-like particles.This paper introduced the photon concept and inspired the notion of wave–particle duality (i.e. light behaving as both a particle and a wave) in quantum mechanics.
In his 1907 paper, “Planck’s Theory of Radiation and the Theory of Specific Heat“, Einstein proposed a model of matter where each atom in a lattice structure is an independent harmonic oscillator – existing in equally spaced, quantized states. He proposed this theory because it was a particularly clear demonstration that quantum mechanics could solve the specific heat problem in classical mechanics.
In 1917, Einstein published an article titled, “On the Quantum Theory of Radiation” that proposed the possibility of stimulated emission, the physical process that makes possible microwave amplification and the laser. This paper was enormously influential in the later development of quantum mechanics, because it was the first paper to show that the statistics of atomic transitions had simple laws.
This work would go on to inspire Erwin Schrödinger’s 1926 article, “Qu