Physics is the scientific study of matter and energy and how they interact with each other.
This energy can take the form of motion, light, electricity, radiation, gravity . . . just about anything, honestly. Physics deals with matter on scales ranging from sub-atomic particles (i.e. the particles that make up the atom and the particles that make up those particles) to stars and even entire galaxies.
How Physics Works
As an experimental science, physics utilizes the scientific law to formulate and
Test hypothesis that are based on observation of the natural world. The goal of physics is to use the results of these experiments to formulate scientific laws, usually expressed in the language of mathematics, which can then be used to predict other phenomena.
The Role of Physics in Science
In a broader sense, physics can be seen as the most fundamental of the natural sciences. Chemistry, for example, can be viewed as a complex application of physics, as it focuses on the interaction of energy and matter in chemical systems. We also know that biology is, at its heart, an application of chemical properties in living things, which means that it is also, ultimately, ruled by the physical laws.
Major Concepts in Physics
Because physics covers so much area, it is divided into several specific fields, such as electronics, quantum physics, astronomy, and biophysics.
Fields of Physics
Physics is a diverse area of study and in order to make sense of it scientists have been forced to focus their attention on one or two smaller areas of the discipline. This allows them to become experts in that narrow field, without getting bogged down in the sheer volume of knowledge that exists regarding the natural world.
Below is a list - by no comprehensive - of different disciplines of physics. The list will be updated with new additions and definitions as appropriate.
· Acoustics - the study of sound & sound waves
· Astronomy - the study of space
· Astrophysics - the study of the physical properties of objects in space
· Atomic physics - the study of atoms, specifically the electron properties of the atom
· Biophysics - the study of physics in living systems
· Chaos - the study of systems with strong sensitivity to initial conditions, so a slight change at the beginning quickly become major changes in the system
· Chemical physics - the study of physics in chemical systems
· Computational Physics - the application of numerical methods to solve physical problems for which a quantitative theory already exists
· Cosmology - the study of the universe as a whole, including its origins and evolution
· Low temperature physics - the study of physical properties in low temperature situations, far below the freezing point of water
· Crystallography - the study of crystals and crystalline structures
· Electromagnetism - the study of electrical and magnetic fields, which are two aspects of the same phenomenon
· Electronics - the study of the flow of electrons, generally in a circuit
· Fluid Dynamics / Fluid Mechanics - the study of the physical properties of "fluids," specifically defined in this case to be liquids and gases
· Geophysics - the study of the physical properties of the Earth
· High Energy Physics - the study of physics in extremely high energy systems, generally within particle physics
· High Pressure Physics - the study of physics in extremely high pressure systems, generally related to fluid dynamics
· Laser physics - the study of the physical properties of lasers
· Mathematical Physics - applying mathematically rigorous methods to solving problems within physics
· Mechanics - the study of the motion of bodies in a frame of reference
· Weather physics - the physics of the weather
· Molecular physics - the study of physical properties of molecules
· Nanotechnology - the science of building circuits and machines from single molecules and atoms
· Nuclear physics - the study of the physical properties of the atomic nucleus
· Optics - the study of the physical properties of light
· Particle physics - the study of fundamental particles and the forces of their interaction
· Plasma Physics - the study of matter in the plasma phase
· Quantum electrodynamics - the study of how electrons and photons interact at the quantum mechanical level
· Quantum physics - the study of science where the smallest discrete values, or quanta, of matter and energy become relevant
· Quantum optics - the application of quantum physics to light
· Quantum field theory - the application of quantum physics to fields, including the fundamental forces of universe
· Quantum gravity - the application of quantum physics to gravity and unification of gravity with the other fundamental particle interactions
· Relativity - the study of systems displaying the properties of Einstein's theory of relativity, which generally involves moving at speeds very close to the speed of light
· Statistical Mechanics - the study of large systems by statistically expanding the knowledge of smaller systems
· String theory - the study of the theory that all fundamental particles are vibrations of one-dimensional strings of energy, in a higher-dimensional universe
· Thermodynamics - the physics of heat
Major laws in Physics
Newton's Three Laws of Motion:
Sir Isaac Newton developed the three laws of motion which describe basic rules about how the motion of physical objects change. Newton was able to define the fundamental relationship between the acceleration of an object and the total forces acting upon it.
"Law" of Gravity:
Newton developed his "law of gravity" to explain the attractive force between a pair of masses. In the twentieth century, it became clear that this is not the whole story, as Einstein’s theory of general relativity has provided a more comprehensive explanation for the phenomenon of gravity. Still, Newton's law of gravity is an accurate low-energy approximation that works for most of the cases that you'll explore in physics.
Conservation of Mass-Energy:
The total energy in a closed or isolated system is constant, no matter what happens. Another law stated that the mass in an isolated system is constant. When Einstein discovered the relationship E=mc2 (in other words that mass was a manifestation of energy) the law was said to refer to the conservation of mass-energy. The total of both mass and energy is retained, although some may change forms. The ultimate example of this is a nuclear explosion, where mass transforms into energy.
Conservation of Momentum:
The total momentum in a closed or isolated system remains constant. An alternative of this is the law of conservation of angular momentum.
Laws of Thermodynamics:
The laws of thermodynamics are actually specific manifestations of the law of conservation of mass-energy as it relates to thermodynamic processes.
· The zeroth law of thermodynamics makes the notion of temperature possible.
· The first law of thermodynamics demonstrates the relationship between internal energy, added heat, and work within a system.
· The second law of thermodynamics relates to the natural flow of heat within a closed system.
· The third law of thermodynamics states that it is impossible to create a thermodynamic process which is perfectly efficient.
Electrostatic Laws:
Coulomb's law and Gauss's law are formulations of the relationship between electrically charged particles to create electrostatic force and electrostatic fields. The formulas, it turns out, parallel the laws of universal gravitation in structure. There also exist similar laws relating to magnetism and electromagnetism as a whole.
Invariance of the Speed of Light:
Einstein's major insight, which led him to the theory of relativity, was the realization that the speed of light in a vacuum is constant and is not measured differently for observers in different inertial frames of reference, unlike all other forms of motion. Some theoretical physicists have conjectured different variable speed of light (VSL) possibilities, but these are highly speculative. Most physicists believe that Einstein was right and the speed of light is constant.
Modern Physics & Physical Laws:
In the realm of relativity and quantum mechanics, scientists have found that these laws still apply, although their interpretation requires some refinement to be applied, resulting in fields such as quantum electronics and quantum gravity. Care should be taken in applying them in these situations.