• # Bayes' theorem

Describes the probability of an event, based on prior knowledge of conditions that might be related to the event.
• # Law of conservation of mass

The Law of Conservation of Mass dates from Antoine Lavoisier's 1789 discovery that mass is neither created nor destroyed in chemical reactions. In other words, the mass of any one element at the beginning of a reaction will equal the mass of that element at the end of the reaction. If we account for all reactants and products in a chemical reaction, the total mass will be the same at any point in time in any closed system.
• # The voltaic pile

First battery.
With this invention Alessandro Volta proved that electricity could be generated chemically. Volta's invention eventually led to the development of the field of electrochemistry.
• # Galois' Theory

Galois Theory uncovers a relationship between the structure of groups and the structure of fields. It then uses this relationship to describe how the roots of a polynomial relate to one another.
• # The Germ theory

It states that microorganisms known as pathogens or "germs" can lead to disease. These small organisms, too small to be seen without magnification, invade humans, other animals, and other living hosts. Their growth and reproduction within their hosts can cause disease.
• # The theory of electromagnetism

The Scottish scientist and mathematician James Clerk Maxwell, brought the correlation between electricity and magnetism for the first time using Maxwell’s equations.
Electromagnetism is the phenomenon which deals with the interaction between an Electric field and a magnetic Field.
• # The Periodic table

Mendeleev was not the first to attempt to find order within the elements, but it is his attempt that was so successful that it now forms the basis of the modern periodic table.
The real genius of Mendeleev’s achievement was to leave gaps for undiscovered elements. He even predicted the properties of five of these elements and their compounds.

In one of the most well-known accidental discoveries in the history of physics, on an overcast day in March 1896, French physicist Henri Becquerel opened a drawer and discovered spontaneous radioactivity.
• # Lebesgue integration

Lebesgue integration is an alternative way of defining the integral in terms of measure theory that is used to integrate a much broader class of functions than the Riemann integral or even the Riemann-Stieltjes integral. The idea behind the Lebesgue integral is that instead of approximating the total area by dividing it into vertical strips, one approximates the total area by dividing it into horizontal strips.
• # Bohr Model

The Bohr model and all of its successors describe the properties of atomic electrons in terms of a set of allowed (possible) values. Atoms absorb or emit radiation only when the electrons abruptly jump between allowed, or stationary, states
• # Theory of general relativity

General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time or four-dimensional spacetime.
• # Milky way's sister

On December 30, 1924, astronomer Edwin P. Hubble announced his discovery of the spiral nebula Andromeda, proving for the first time that our own Milky Way was but one of many galaxies in the vast universe.