Environmental Physics describes the application of broad science of physics (the study of the fundamental laws of nature pertaining to matter, energy, motion, and force) to environmental questions. Some aspect of physics is important in nearly every environmental issue, though few environment problems are solvable through just the application of physics.
While physics in most often brought to bear on environmental issues through its application by scientists trained in other fields such as chemistry, engineering, and geology, a growing number of physicists are applying their knowledge and skills to environmental issues and are recognized a community of environmental physicists.
Disciplines related to environmental physics
Normally, environmental isues are tackled by combining the environmental components of various sciences into an integrated and holistic scientific approach is often termed "environmental science." Environmental physics can been viewed a fundamental part of environmental science.
Environmental science includes (the following are a sampling and not comprehensive):  disciplinary and interdisciplinary natural sciences such as: atmospheric sciences, many branches of chemistry, biology, botany, climatology, ecology, hydrology, geography, geology, geophysics, acoustics, limnology, ornithology, marine biology, oceanography, soil science, toxicology;  social sciences such as anthropology, economics, demography, environmental ethics, environmnetal history, environmental law, and public policy; and  a recognition of numerous forms of engineering; and  a recognition of relevant non-sciences like politics.
The purpose of this article is to outline in general terms a few of aspects of physics that are relevent to the study of the environment and some of the environmental issues to which they are applied. Follow the key word links in this article to learn more about both the physics and the environmental issues.
Areas of Physics
Mechanics is one of the oldest branches of physics and addresses how physical objects respond to forces - their motions and acceleration. The basic laws of mechanics include three first articulated by Issac Newton (1643-1727). Extending the application of Newton's Three Laws with a understanding of the conservation of momentum and energy, particularly through mathematical formulations developed by Joseph-Louis Lagrange (1736-1813) and William Rowan Hamilton (1805 – 1865) dominated much of physics for two hundred years, and are taught and used in practically every branch of science and engineering today.
Classical mechanics explain and describing how the earth orbits the sun and its orientation gives rise to the seasons; how the moon orbits the earth and causes tides, how apples fall from trees and raindrops from the sky; how birds fly and fish swim; how mountains rise and landslides occur; the trajectory of satellites observing the earth's environment and a host of other phenomena.
At the beginning of the twentieth century, it began to be apparent that various phenomena could not properly be explained by classical mechanics; phenomena dealing with radiation, atomic and subatomic particles, and speeds approaching that of light. This led to an expansion of mechanics by physicists such as Albert Einstein (1879-1955) (relativity), Erwin Schrödinger (1887-1961) who reformulated the work of Hamilton for the new Quantum Mechanics and numerous others . Quantum mechanics and classical mechanics are not contradictory, rather classical mechanics is quantum mechanics applied to most day-to-day situations experienced by human beings. Given the added complexity of quantum mechanics, the mathematical formulations of classical mechanics are still used in most situations.
Quantum mechanics does have very important and pervasive applications such as transistor which lie at the heart of computers and practically all electronic devices. Quantum mechanics also explains how subatomic changes give rise to radiation, radioactivity, nuclear fission (bombs and power plants), nuclear fusion (a hoped-for source of clean energy), solar energy (the conversion of solar radiation into electricity), and many other things.
Thermodynamics is the study of energy, its conservation, its movement (heat) between bodies and forms (e.g., thermal, chemical, gravitational, electrical, radiation, etc.), and its manifestations on the properties of things (e.g., the temperature, pressure, and volume of a gas). Several "laws of thermodynamics" were formulated in the nineteenth century which allowed the understanding of many systems ranging from simple matter (solids, liquids and gases) to chemical processes to mechanical engines. Thermodynamics is central to understanding earth's atmosphere, climate and climate change, and weather (including wind, rain, clouds, snow, hurricanes and monsoons, El Nino and La Nina and much more); ocean currents and much else in oceanography; chemical processes, including how pollution forms and moves in air and [[Water Pollution|water]; biological systems; energy systems of all kinds including energy production, storage, transmission, use, and conservation; the formation of rocks and other aspects of geology; and even some forms of economics such as ecological economics.
Electromagnetism is the study of electricity and magnetism and their related phenomena. The earth's magnetic field has been a subject of fascination since the discovery that its influence on magnetized iron could be used in compasses to aid navigation in China sometime before 1100 AD. Locating the earth magnetic poles became an important goals of exploration in the frozen regions of the Arctic and Antarctic. The first attainment of the north and south magnetic poles in in 1831 and 1909 respectively were major events. Serious study of electrical phenomena did not occur until the eighteen century, but accelerated rapidly and was soon recognized as being very closely related to magnetism. In the mid-nineteenth century, James Clerk Maxwell (1831 – 1879) unified the two fields in a set of four equations that revealed that light was actually the propagation of electromagnetic "waves" through space. Thus, Maxwell unified three fields of physics, electricity, magnetism, and optics. Further, visible light was discovered to be but one small part of a vast spectrum of electromagnetic radiation that included radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. Einstein's study of electromagnetism led to his formulation of relativity and recognition of discrete units ("quanta") of radiation called 'photons".
Electromagnetism underlies a wide range of environmental phenomena, including: solar radiation (the energy source for life of earth and its climate), the nothern and southern lights, lightening, chemical bonding, and radiation in the earth's environment.
High Energy Physics
High energy physics is the study of the constituent particles that make up atoms (electrons, protons, neutrons), their subcomponents (quarks), others numerous other particles as well as the interactions between them (mediated by yet more particles). This area is typically studied in a few ways such as by accelerating particles to high speeds and smashing them together; or by studying high particles moving through space and colliding with the earth; or by observing certain phenomena in outer space. In all cases, the particles are fast moving and thus "high energy." This field has led to an understanding of the fundamental forces in nature: gravity, electromagnetism, strong and weak forces (electromagnetism and the weak force unify at very high energies) and the efforts to create a "unified field theory" that sees all forces of nature as manifestations of a single force or "field."
High energy physics has less application to environmental issues that other areas of physics, but it does provide the understanding behind radiative decay and issues related to radioactive waste; nuclear fission and contemporary forms of nuclear power as well as the promise of "clean energy" from nuclear fusion. Moreover, high energy physics has been the driving force for many advances in computing and sensors that have found application in environmental issues.
Matter: solids, liquids, gases
The manifestations of mechanics, thermodynamics, and electromagnetism in different materials in different conditions gives rise to a vast number of phenomena that are studied by physicists.
A longitudinal wave or vibration (displacement) are ways of describing sound. When uniform, the state of a fluid's pressure is equilibrium; in the presence of sound, the tiniest volume of any given substance begins to move, manifesting the vibration. The motion of molecules produce a fluctuation in air density and pressure. When the pressure rises on the wave it is called compression; for example, each time the cone of speaker moves outward, it produces compression. Vice versa when it decreases, it is termed called dilation. The sound that humans hear ranges from 20 to 20,000 Hertz (Hz). Sound frequencies below 20 Hz cannot be heard by humans, such as those produced by earthquakes. Waves above 20,000 Hz (ultrasonic) are heard by numerous animal species such as dogs and dolphins, but not humans. Unwanted or intrusive sound is termed Noise pollution.
Applications of Physics to some major Environmental Issues
When one thinks about the problems with our environment many think of the social issues and combat it on a social level. In the realm of environmental science, chemistry is the first discipline that comes to mind. But one must not omit the physical aspects and how the applications of physics are also very important. From energy conservation issues in the development of energy saving materials to the challenge of disposal and storage of waste the physical sciences are intrinsically involved in these challenges.
Physics of Climate and Air Pollution
Motion of the atmosphere and oceans are studied to analyze the Earth's climate and the constituents of the atmosphere. Major physical processes involved are: atmospheric and ocean circulation; albedo effects at the earth's surface; thermal stratification of water and atmosphere; ultraviolet capture by the ozone layer; greenhouse gas storage and efflux from soil, water and organic matter; and gas dynamics of pollutant movement in the atmosphere. Some chemical phenomenon are intrinsically linked with physical processes, especially where air pollutants are reactive and in the case of carbon storage, where some processes in soil and water involve chemical transformation as well as absorption, absorption and storage. In analyzing these phenomena, environmental physicists develop complex mathematical models to study these interrelated effects.
Physics and Energy
Law of Conservation of energy which also stands as the first law of thermodynamics is the concept that energy can change it's form but cannot be created nor destroyed. An example of the change is the work in a light bulb when heat energy is converted into light energy.
Fission is named after the process of cell division in biology. Discovered by German radio chemists Otto Hahn in and Nuclear Chemist Fritz Strassmann in 1938. Fission is created when neutron atoms are caught by a Uranium nucleus creating a compound nucleus in an excited state(Oscillating) then ultimately splitting by electric repulsion being stronger than the atomic force . Otto Hahn's former colleague, Lise Meitner led to the conclusion that energy is released during this process of atoms splitting. To vision large-scale use of the energy released the greatest example is the atomic bomb. Like a set of dominoes one fission event triggers another each neutron that's released creates two more neutrons after every fission reaction, so that the process spreads throughout the nuclear fuel. The fact that more neutrons are produced in fission than are consumed also gave the possibility of creating the chain reaction to produce energy for the everyday consumer in nuclear reactors. Such a reaction can be either rapid (as in an atomic bomb) or controlled (as in a reactor). Following Albert Einstein's E=mc2 (energy equals mass multiplied by the acceleration of light squared) equation that the loss of mass resulting from the splitting process must have been converted into energy in the form of kinetic energy that could in turn be converted into heat. Essentialy the masses of these fragments of atoms are less than the original mass. This '"lost'" mass that has been calculated to be about less than 1% percent of the original mass is converted into energy according to Einstein's equation.
Nuclear Energy II - Fusion
Fusion begins with a fission reaction but fusion differs from fission in how it gets its power. When two light nuclei fuse to form a greater nucleus. But before two nuclei come together they must rise above the Coulomb repulsion barrier which is created by their electrostatic energy. A clear example of fusion would be the sun the heat from the sun is the result of a fusion reaction. To produce a fusion reaction three things are needed high particle density, very high temperature and last a lengthy confinement time. With a high particle density the collision rate of the particles will naturally be increased which in turn increases the reaction rate. The temperature necessary must be greater than 10 Kelvin in order for the particles to overcome their electrical repulsion. Once the particles come together at the necessary temperature they must stay together long enough for the reaction to take place.