During the late 1890s the creation of the quantum mechanics and Einstein’s Relativity beckoned a new age in physics: modern physics.  The terminology of modern physics refers to any branch of physics, such as nuclear physics or electromagnetism, which was developed in the early twentieth century or older branches that were greatly influenced by twentieth century physicists. In more simple terms, modern physics refers to any part of physics which incorporates quantum mechanics or Einstein’s Relativity. Modern physics often deals with two extremes: the extremely large or fast or the extremely small or slow. For example, part of modern physics deals with quantum effects which deals with distances comparable to atoms while other parts deal with the speed which light travels at. Before delving deeper into modern physics it is important to understand the two concepts that laid its foundation and the scientists who discovered them.

The first founding concept of modern physics was quantum mechanics or the quantum theory which was developed by the German scientist, Max Planck. The quantum theory explains the nature and behavior of matter and energy on the atomic and subatomic level. The theory assumes that electromagnetic energy is emitted from or absorbed by matter in discreet amounts or packets. This energy is directly proportional to the frequency of the electromagnetic radiation and the proportionality is provided by Planck’s constant or h. Due to the success of the quantum theory in explaining the features of the universe on such small scales it has many practical applications. For example the theory is used in electronics within devices such as the laser, microchip, microscope and magnetic resonance imaging (MRI).

The second founding concept of modern physics is Einstein’s Theory of Relativity. His theory encompasses two parts: general and special relativity. General relativity explains the laws of gravitation and its relation to other forces in nature while special relativity applies to the elementary particles and their interactions, describing all their physical characteristics except with the ones with gravity. Einstein’s theory revolutionized the former theory of mechanics which was created primarily by Isaac Newton. The theory introduced many concepts and greatly improved upon previous works, such as the science of elementary particles. On top of greatly improving the field of physics Einstein’s theory has many practical applications such as the GPS.

Einstein’s Theory of Relativity refers to elementary particles. These elementary particles or fundamental particles are particles whose substructures are unknown. They are occasionally also referred to as “the basic building blocks of matter.” Known elementary particles are divided up into two groups: the fermions and the bosons. The fermions are the matter and antimatter particles which include quarks, leptons, antiquarks, and antileptons. The bosons are known as force particles which mediate the interactions between fermions. Bosons include gauge bosons and the Higgs boson. Sometimes these elementary particles combine to create a composite particle. Several of these composite particles are very important such as the proton and neutron which are made of quarks.

Quarks are fundamental constituents of matter or elementary particles. They carry one of three color charges of the strong interaction and antiquarks similarly carry an anticolor. These color charged particles interact through a gluon exchange the same way that charged particles exchange particles in terms of a photon exchange. Gluons are also color charged, meaning that when they combine it results in an amplification when they are separated. Color charged particles may also combine to form color neutral composite particles which are referred to as hadrons. These hadrons are categorized by two groups: baryons and mesons. Baryons contain three quarks whereas mesons are made of one quark and one anti quark. Perhaps the most famous baryons are protons and neutrons.

Unlike the quark, a lepton does not undergo strong interactions. There are two main classes of leptons, those being charged leptons and neutral leptons. Charged leptons can combine with other particles to form composite particles such as atoms. On the other hand neutral leptons rarely interact with anything and are therefore rarely observed. There are several types of leptons such as electronic leptons, muonic leptons, and the tauonic leptons. Each has varying characteristics like electric charge, spin, and mass. Unlike quarks, leptons are subject to three fundamental interactions: gravitation, electromagnetism, and the weak interaction. For every lepton there is a corresponding antilepton that has an equal magnitude but opposite charges. The only possible exception to this is the neutral lepton which may be their own antiparticle.

A gauge boson acts as a force carrier, it carries any of the fundamental interactions. Elementary particles interact with one another through the exchange of gauge bosons. Gauge bosons are divided up into four groups: photons, W and Z, and gluons. Photons carry an electromagnetic force, W and Z bosons carry a weak interaction, and gluons carry a strong interaction. On the other hand a Higgs boson is an elementary particle that has no electric charge, spin, or color change. It is overall very unstable and decays into other particles almost immediately. The Higgs boson was created to justify the missing mass within the Higgs Field. The field exists everywhere in space and apparently contains only W and Z bosons which have no mass. Yet the field had a particle which had a mass, as a result they named this particle the Higgs boson and scientists have been attempting to discover it ever since. The Higgs Boson is often regarded as the “God Particle” due to its great importance to the field of theoretical and modern physics and because it is extremely elusive and difficult to find.

A gluon is an elementary particle which acts as the exchange particle for the strong force between quarks. They are responsible for being the bond between particles when they come together to form composite particles such as protons and neutrons. They carry the color charge of the quarks which they are bonded with, unlike photons which do not carry an electric charge even after bonding with other particles. As a result a gluon not only mediates the combination of particles but actually takes part in it seeing as since they carry a charge afterwards. Unlike quarks which only have three color charges, gluons have nine seeing as since they form a color combination, such as red-blue, but it overall depends on the colors of the quarks which they bond.

Overall the field of Modern Physics is revolutionizing the world around us. Although it began nearly a century ago it has made countless discoveries and led us to seek a greater understanding of the world. Additionally, the discoveries will not cease due to the continuity of research, such as the search for the Higgs boson, and devotion of physicists and other researchers to the field. New theories are replacing older ones and innovation will continue to occur. In the end this was all made possible due to the work and foundation laid by our predecessors and the founders of Modern Physics.



Krane, Kenneth S. Modern Physics. Hoboken, NJ: Wiley, 2012. Print.


“What Is the Higgs?” The New York Times. The New York Times, 07 Oct. 2013. Web. 03 May 2017.

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