Changes

By the close of the 19th century, the study of physics was widely thought to be essentially complete, with the exception of only a few "loose ends"—minor unsolved problems to be dealt with. As a solution to the so-called ultraviolet catastrophe problem, which involved light emission from [[black body|hot, dark objects]], Max Planck proposed in 1900 that the sources of light could be represented by small individual oscillators.  Planck referred to the individual oscillators as ''quanta''.  In 1905, [[Albert Einstein]] published a heuristic explanation for the [[photoelectric effect]] problem:  light could be thought of as being composed of very small, discrete packets (quanta), as opposed to the classical representation of light as a collection of waves. By the end of the 1930s, [[quantum mechanics]]—the name given to the new theory that applied to matter and energy on atomic scales—was well-established.  Other physicists began applying the theory to more specific aspects of physics, resulting in quantum mechanical descriptions of electricity and magnetism, the [[weak force|weak]] and [[strong force|strong]] atomic forces, condensed matter physics, and many other areas.  

By the close of the 19th century, the study of physics was widely thought to be essentially complete, with the exception of only a few "loose ends"—minor unsolved problems to be dealt with. As a solution to the so-called ultraviolet catastrophe problem, which involved light emission from [[black body|hot, dark objects]], Max Planck proposed in 1900 that the sources of light could be represented by small individual oscillators.  Planck referred to the individual oscillators as ''quanta''.  In 1905, [[Albert Einstein]] published a heuristic explanation for the [[photoelectric effect]] problem:  light could be thought of as being composed of very small, discrete packets (quanta), as opposed to the classical representation of light as a collection of waves. By the end of the 1930s, [[quantum mechanics]]—the name given to the new theory that applied to matter and energy on atomic scales—was well-established.  Other physicists began applying the theory to more specific aspects of physics, resulting in quantum mechanical descriptions of electricity and magnetism, the [[weak force|weak]] and [[strong force|strong]] atomic forces, condensed matter physics, and many other areas.  

Also in the early 1900s, [[Poincare]] published his discovery of what became known as the [[special relativity]], which gave new insights on the relation between [[space]] and [[time]].  Others later extended the concept to non-inertial [[Inertial frame of reference|reference frames]], which resulted in the [[general relativity|general theory of relativity]], an improved description of [[gravity|gravitational]] interactions.

Also in the early 1900s, [[Henri Poincaré]] published his discovery of what became known as the [[special relativity]], which gave new insights on the relation between [[space]] and [[time]].  Others later extended the concept to non-inertial [[Inertial frame of reference|reference frames]], which resulted in the [[general relativity|general theory of relativity]], an improved description of [[gravity|gravitational]] interactions.

=== Contemporary Physics ===

=== Contemporary Physics ===