- Death:- 18 April 1955 (aged 76)

- General relativity and special relativity
- Photoelectric Effect
- Mass Energy Equivalence
- Theory of Brownian Motion
- Einstein Field Equations
- Bose- Einstein Statistics
- Bose Einstein Condensate
- Unified Field Theory
- EPR Paaradax

1) General Relativity-

**General relativity**, or the **general theory of relativity**, is the geometric theory of gravitation published by Albert Einstein in 1916 and the current description of gravitation in modern physics. General relativity generalizes special relativity and Newton’s law of universal gravitation, providing a unified description of gravity as a geometric property of space and time, or spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present.Einstein’s theory has important astrophysical implications. For example, it implies the existence of black hole—regions of space in which space and time are distorted in such a way that nothing, not even light, can escape—as an end-state for massive stars. There is ample evidence that the intense radiation emitted by certain kinds of astronomical objects is due to black holes

2) Photoelectric Effect-

In the **photoelectric effect**, electrons are emitted from atoms when they absorb energy from light. Electrons emitted in this manner may be called *photoelectrons*.

In 1887, ^{Heinrich Hertz} discovered that electrodes illuminated with ultraviolet light create electric sparks more easily. In 1905 Albert Einstein published a paper that explained experimental data from the photoelectric effect as being the result of light energy being carried in discrete quantized packets. This discovery led to the quantum revolution. Einstein was awarded the Nobel Prize in 1921 for “his discovery of the law of the photoelectric effect”

The photoelectric effect requires photons with energies from a few electronvolts to over 1 MeV in high atomic number elements.

3) Mass Energy Equivalence -

In physics, **mass–energy equivalence** is the concept that the mass of an object or system is a measure of its energy content.

The equivalence is described by the famous equation:

where *E* is energy, *m* is mass, and *c* is the speed of light. Thus, this mass–energy relation states that the universal proportionality factor between equivalent amounts of energy and mass is equal to the speed of light squared.

4) Theory of Brownian Motion -

**Brownian motion** or **pedesis** is the random motion of particles suspended in a fluid (a liquid or a gas) resulting from their collision with the quick atoms or molecules in the gas or liquid. The term “Brownian motion” can also refer to the mathematical model used to describe such random movements, which is often called a particle theory.

This transportation phenomenon is named after the botanist Robert Brown. In 1827, while looking through a microscope at particles found in pollen grains in water, he noted that the particles moved through the water but was not able to determine the mechanisms that caused this motion. Atoms and molecules had long been theorized as the constituents of matter, and many decades later, Albert Einstein published a paper in 1905 that explained in precise detail how the motion that Brown had observed was a result of the pollen being moved by individual water molecules. This explanation of Brownian motion served as definitive confirmation that atoms and molecules actually exist, and was further verified experimentally by Jean Perrin in 1908. Perrin was awarded the Nobel Prize in Physics in 1926 “for his work on the discontinuous structure of matter”.

5) Einstein Field Equations -

he **Einstein field equations** (**EFE**) or **Einstein’s equations** are a set of 10 equations in Albert Einsteins general theory of relativity which describe the fundamental interactions of gravitation as a result of spacetime being curved by matter and energy. First published by Einstein in 1915 as a tensor equation, the EFE equate local spacetime curvature with the local energy and momentum within that spacetime.

Similar to the way that electromagnetic fields are determined using charges and currents via Maxwell’s equation, the EFE are used to determine the spacetime geometry resulting from the presence of mass-energy and linear momentum, that is, they determine the metric tensor of spacetime for a given arrangement of stress–energy in the spacetime.

6) Bose- Einstein Statistics -

In quantum statistics, **Bose–Einstein statistics** is one of two possible ways in which a collection of non-interacting indistinguishable particles may occupy a set of available discrete energy states, at thermodynamic equillibrium. The aggregation of particles in the same state, which is a characteristic of particles obeying Bose–Einstein statistics, accounts for the cohesive streaming of laser light and the frictionless creeping of superfluid helium. The theory of this behaviour was developed (1924–25) by Satyendra Nath Bose, who recognized that a collection of identical and indistinguishable particles can be distributed in this way. The idea was later adopted and extended by Albert Einstein in collaboration with Bose.

7) Unified Field Theory -

Since the 19th century, some physicists have attempted to develop a single theoretical framework that can account for the fundamental forces of nature – a unified field theory. **Classical unified field theories** are attempts to create a unified field theory based on classical physics. In particular, unification of gravitation and electromagnetism was actively pursued by several physicists and mathematicians in the years between World War I and World War II. This work spurred the purely mathematical development of differential geometry. Albert Einstein is the best known of the many physicists who attempted to develop a classical unified field theory.

8) EPR Paaradax -

The **EPR paradox** is an early and influential critique leveled against quantum mechanics. Albert Einstein and his colleagues Boris Podolsky and Nathan Rosen (known collectively as EPR) designed a thought experiment intended to reveal what they believed to be inadequacies of quantum mechanics. To that end, they hypothesized a consequence of quantum mechanics that its supporters had not noticed but looked unreasonable at the time.