In a paper entitled "On the General Molecular Theory of Heat" written in 1904, Einstein put forth a derivation for the entropy (disorder or chaos) of a system, and the second law of thermodynamics (entropy in a system will increase or stay the same). More importantly, this paper also presented new ways for unpacking Boltzmann's constant (k), a number that is used to determine a quantity of energy generated by the random motion of molecules in a system.
Two years later in a paper whose title is way too long to type here, Einstein peered yet again into that fundamental Boltzmann's constant. He resolved that in a thermodynamic system, equilibrium gives way to "irregular fluctuations" that can be interpreted using Boltzmann's constant. At the end of that paper, he suggests a method to amplify voltages using electrically-connected metal plates.
In 1907, Einstein theorized a solid that met two criteria: the first is that all the atoms that make up the solid would move independently of every other; and the second, that every atom is oscillating (moving back and forth) at the same rate. The tough part is to get these atoms to move independently of each other, but Einstein was confident quantum mechanics would be able to solve this problem.
In a 1905 paper titled "Concerning an Heuristic Point of View Toward the Emission and Transformation of Light," Einstein put forward his notion that light was not a constant stream of illumination, but made up of "a finite number of energy quanta," or bundles, which have spatial boundaries.
In the same paper, Einstein basically outlined his theory on the photoelectric effect after noticing quanta of light were being absorbed, and some bounced off metals. The physicist then came up with a mathematical representation to describe the nature of the photoelectric effect.
In another 1905 paper, Einstein was able to derive an equation for Brownian Motion ”” random but ongoing motion of small particles in a fluid system ”” after introducing a coefficient that related the motion of a spherical particle. Though other derivations were available, Einstein's was especially important because it allowed for a definitive measurement of Avogadro's number, a constant that shows there are the same number of molecules in a quantity of gas regardless of what gas it is.
7. Einstein Weighs in on Rotational Brownian Motion
In a 1906 paper, Einstein went one step further and did important work into rotational Brownian motion, or rotational diffusion. This was important, as it was commonly believed that the short trips made by tiny particles were sharp, though the contrasting notion is that they, too, make sweeping, albeit small, cyclical motions.
Also known as the Planck-Einstein relation, the Einstein relation states that a photon's energy is equal to its frequency, using Planck's constant. This was major groundwork for Einstein's ultimate demonstration of the photoelectric effect.
In 1908 Einstein came up with a totally new way to measure slight electric charges, less than .00000001 volts. Using an auxiliary "induction machine," Einstein showed that you could use outside instruments to increase the precision of the measuring device, and thereby get accurate readings of minute energies.
In a seminal lecture before the Gesellschaft Deutscher Naturforscher in 1909, Einstein expounded on his theory of light's quantized nature. Essentially what Einstein was trying to get across was the idea that light was made up of a number of points, surrounded by a field that bore similar attributes to those points. This married the oscillating (wave) theory of light with the quantum (particle) theory.
In a paper concerning "The Theory of Opalescence..." published in 1910, Einstein made a monumental connection between critical opalescence (what happens at the exact point during a liquid's transition into a gas) and the scattering of electromagnetic radiation. He deduced that you could quantitatively measure both and relate them to each other.
In a paper published in 1912, Einstein put down in writing the Stark-Einstein law which relates thermodynamics to chemical reactions. The law states that for every of quantum of electromagnetic radiation that gets absorbed by a system, exactly one molecule of that substance is affected.
In a 1915 paper co-authored by W. J. de Haas, Einstein came up with a relation between three major phenomena: "magnetism, angular momentum, and" particle spin. In his only experimental work carried out, Einstein and de Haas showed that the motion of a charged and spinning particle outside a cylinder will force an electric current down a wire inside the cylinder.
In 1916, Einstein effectively predicted the future, putting down his theoretical ideas on stimulated emission ”” the principle behind lasers. Stimulated emission, in a nutshell, is the use of shooting a photon at an excited electron, after which it will emit energy in the form of a photon and jump down to a lower energy state.
The Einstein-Brillouin-Keller method was actually coined by Ian Percival in 1973, though it references and uses Einstein's ideas on quantization from a 1917 paper. The method came much in handy when older models of quantization proved insufficient for dealing with especially chaotic systems, whereas Einstein's methodologies could be used instead.