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→Modern Physics
==Modern Physics==
==Modern Physics==
Modern physics generally includes areas of study within physics that surfaced after 1900, the year in which [[Max Planck]] proposed a "quantum hypothesis" to explain the properties of light emitted by [[blackbody|hot, dark objects]]. The two major aspects of modern physics are
Modern physics generally includes areas of study within physics that surfaced after 1900, the year in which [[Max Planck]] proposed a "quantum hypothesis" to explain the properties of light emitted by [[black body|hot, dark objects]]. The two major aspects of modern physics are
*[[Relativity]], a form of mechanics that is applicable in very high-energy situations
*[[Relativity]], a form of mechanics that is applicable in very high-energy situations
===Further Development of Classical Physics===
===Further Development of Classical Physics===
Newtonian mechanics was expanded by several other scientists, notably [[Pierre-Simon Laplace]] and [[Joseph-Louis Lagrange]]. The motions of
Newtonian mechanics was expanded by several other scientists, notably [[Pierre-Simon Laplace]] and [[Joseph Louis Lagrange]]. The motions of
As Newton's laws became the dominant tool in physical science, they began to be applied to phenomena other than gravitational interactions. During the first half of the 19th century, several laws governing electricity and magnetism were discovered. In the mid-1860s, [[James Clerk Maxwell]] unified these individual laws into a single set of [[Maxwell's equations|equations]]. Maxwell was able to derive a [[wave equation]] from his new set of equations, and found that the speed of the waves predicted by the equation was close to the measured [[speed of light]]. [[Thomas Young]] had [[double-slit experiment|demonstrated]] in 1801 that light had wavelike properties, but Maxwell's result provided the new insight that light waves were oscillating electric and magnetic fields.
As Newton's laws became the dominant tool in physical science, they began to be applied to phenomena other than gravitational interactions. During the first half of the 19th century, several laws governing electricity and magnetism were discovered. In the mid-1860s, [[James Clerk Maxwell]] unified these individual laws into a single set of [[Maxwell's equations|equations]]. Maxwell was able to derive a [[wave equation]] from his new set of equations, and found that the speed of the waves predicted by the equation was close to the measured [[speed of light]]. [[Thomas Young]] had [[double-slit experiment|demonstrated]] in 1801 that light had wavelike properties, but Maxwell's result provided the new insight that light waves were oscillating electric and magnetic fields.
===The Modern Era===
===The Modern Era===
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 [[blackbody|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''. At the time, Planck did not regard his finding as revolutionary; he thought that he was merely "fudging" the mathematics to arrive at a better solution. However, in 1905, [[Albert Einstein]] published a solution to 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. The discoveries of Planck and Einstein ushered in an entirely new era in physics. 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''. At the time, Planck did not regard his finding as revolutionary; he thought that he was merely "fudging" the mathematics to arrive at a better solution. However, in 1905, [[Albert Einstein]] published a solution to 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. The discoveries of Planck and Einstein ushered in an entirely new era in physics. 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.
In another 1905 publication, Einstein announced his discovery of what became known as the [[special relativity|special theory of relativity]], which revolutionized the way physicists thought about [[space]] and [[time]]. Einstein later extended the concept to non-inertial [[reference frames]], which resulted in the [[general relativity|general theory of relativity]], an improved description of [[gravity|gravitational]] interactions, which was published in 1915.
In another 1905 publication, Einstein announced his discovery of what became known as the [[special relativity|special theory of relativity]], which revolutionized the way physicists thought about [[space]] and [[time]]. Einstein later extended the concept to non-inertial [[reference frames]], which resulted in the [[general relativity|general theory of relativity]], an improved description of [[gravity|gravitational]] interactions, which was published in 1915.
*Evidence suggests that the matter in the universe that humans can currently detect directly is only a fraction of the matter that actually exists. Attempts to discover the nature of the as-yet-undetectable [[dark matter]] are underway.
*Evidence suggests that the matter in the universe that humans can currently detect directly is only a fraction of the matter that actually exists. Attempts to discover the nature of the as-yet-undetectable [[dark matter]] are underway.
*The universe is known to be expanding at an accelerated rate. Such acceleration requires energy, but the form and source of this [[dark energy]] is not well-understood.
*The universe is known to be expanding at an accelerated rate. Such acceleration requires energy, but the form and source of this [[dark energy]] is not well-understood.
*Quantum mechanics has not yet successfully been applied to the gravitational interaction. At huge energy scales, where both quantum mechanics and general relativity are required to describe the system, the known laws of physics break down. Attempts to discover a quantum theory of gravity have led to [[superstring theory]] and [[m-theory]], but to date neither have permitted the design of a technologically feasible experiment to verify them.
*Quantum mechanics has not yet successfully been applied to the gravitational interaction. At huge energy scales, where both quantum mechanics and general relativity are required to describe the system, the known laws of physics break down. Attempts to discover a quantum theory of gravity have led to [[string theory]] and [[m-theory]], but to date neither have permitted the design of a technologically feasible experiment to verify them.
*General relativity predicts the existence of gravitational waves, but none have been conclusively detected. Due to the weakness of the gravitational interaction, extremely sensitive detectors are required. The [[LIGO]] project is an example of current efforts to detect such waves.
*General relativity predicts the existence of gravitational waves, but none have been conclusively detected. Due to the weakness of the gravitational interaction, extremely sensitive detectors are required. The [[LIGO]] project is an example of current efforts to detect such waves.