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Related subjects: Physics; Portals; Science

The Physics Portal

A stylized depiction of a Lithium atom.

Physics (Greek: physis – φύσις meaning "nature") is a natural science that involves the study of the fundamentals that govern the universe, dimensions, and energy or matter. This has led to the discovery and understanding of the laws and principles which govern the physical universe - as perceived by earthlings. More broadly, Physics is the general analysis of nature, conducted in order to understand how the world and universe behave. One tool which helps with this general analysis is the study of the elementary constituents of the universe and their interactions.

Physics is one of the oldest academic disciplines, perhaps the oldest through its inclusion of astronomy. Evidence exists that the earliest civilizations dating back to beyond 3000 BCE, such as the Sumerians, Ancient Egyptians, and the Indus Valley Civilization, all had a predictive knowledge and a very basic understanding of the motions of the Sun, Moon, and stars. Although originally part of other physical sciences and mathematics, Physics emerged to become a unique modern science during the Scientific Revolution of the 16th century.

Physics is both significant and influential, in part because advances in its understanding have often translated into new technologies, but also because new ideas in physics often resonate with other sciences, mathematics, and philosophy. For example, advances in the understanding of electromagnetism or nuclear physics led directly to the development of new products which have dramatically transformed modern-day society (e.g., television, computers, domestic appliances, atomic power, and nuclear weapons); advances in thermodynamics led to the development of motorized transport; and advances in mechanics inspired the development of calculus.

Physics also has philosophical implications. It can be historically traced back to ancient Greek philosophy. From Thales' first attempt to characterize matter, to Democritus' deduction that matter ought to reduce to an invariant state, the Ptolemaic astronomy of a crystalline firmament, and Aristotle's book Physics, different Greek philosophers advanced their own theories of nature. Well into the 18th century, physics was known as " Natural philosophy". By the 19th century physics was realized as a positive science and a distinct discipline separate from philosophy and the other sciences. Physics, as with the rest of science, relies on philosophy of science to give an adequate description of the scientific method.

Selected article

Sirius B, bottom left, is a white dwarf star.

A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. As white dwarfs have mass comparable to the Sun's and their volume is comparable to the Earth's, they are very dense. Their faint luminosity comes from the emission of stored heat. They comprise roughly 6% of all known stars in the solar neighbourhood The unusual faintness of white dwarfs was first recognized in 1910 by Henry Norris Russell, Edward Charles Pickering and Williamina Fleming, and the name white dwarf was coined by Willem Luyten in 1922. White dwarves continue to lose energy and fade, becoming Black dwarfs...

Selected picture

Image credit: NASA, J.Warren & J.Hughes et al. , Rutgers

A false colour image of Tycho's Supernova Remnant, of Tycho's Supernova of 1572.

Did you know...

Mock mirage of the setting sun
  • ...the mirage of astronomical objects is an optical phenomenon, which produces distorted or multiple images of astronomical objects such as the Sun, the Moon, the planets, bright stars and very bright comets
  • ...that your watch would be at a different time orbiting a black hole than it would be on earth?
  • ...that Aristotle's ideas of physics held that because an object could not move without an immediate source of energy, arrows created a vacuum behind them that pushed them through the air.
  • ...that nuclear fusion reactions are probably occurring at or above the sun's photosphere; it is a process called solar surface fusion.
  • ...that, in the Large Hadron Collider, protons move at 99.9999991% of the speed of light when accelerated to the energy of 7 TeV?
  • ...that the submarine telescope ANTARES, intended to detect neutrinos, may also be used to observe bioluminescent plankton and fish?
Artist's depiction of the WMAP satellite measuring the Cosmic Microwave Background Radiation to help scientists understand the Big Bang
  • ...that lasers can be used to separate two isotopes very efficiently?
  • ...that neutron stars are so dense that a teaspoonful (5 mL) would have ten times the mass of all human world population?
  • ...that every year, the Moon moves 3.82 cm away from Earth?
  • ...that gold leaf is about 500 atoms thick?
  • ...that if we travel at the speed of light it would take us no time at all to cross the universe according to our watches?
  • ...that Neptune was discovered by its gravitational pull on Uranus?

Physics topics

Classical physics traditionally includes the fields of mechanics, optics, electricity, magnetism, acoustics and thermodynamics. The term Modern physics is normally used for fields which rely heavily on quantum theory, including quantum mechanics, atomic physics, nuclear physics, particle physics and condensed matter physics. General and special relativity are usually considered to be part of modern physics as well.

Fundamental Concepts Classical Physics Modern Physics Cross Discipline Topics
Space Classical Mechanics Special Relativity and General Relativity Mathematical Physics
Time Electromagnetism Quantum Mechanics Astronomy
Matter States of Matter Quantum Field Theory Chemical Physics
Energy Thermodynamics Quantum Gravity Materials Science
Electromagnetism Solid Mechanics Condensed Matter Physics Geophysics
Strong interaction Fluid Mechanics Atomic Physics Biophysics
Weak interaction Acoustics Nuclear Physics Nanotechnology
Gravitational Field Optics Particle Physics  
Entropy   Plasma Physics  

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