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# Solar constant

The solar constant is a flux density measuring mean solar electromagnetic radiation (solar irradiance) per unit area. [1]

## Angular diameter

The angular diameter, angular size, apparent diameter, or apparent size is an angular measurement describing how large a sphere or circle appears from a given point of view.

## Apparent magnitude

The apparent magnitude of a celestial object is a number that is a measure of its brightness as seen by an observer on Earth.

## Astronomical unit

The astronomical unit (symbol: au, ua, or AU) is a unit of length, roughly the distance from Earth to the Sun.

## Atmosphere of Earth

The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earth's gravity.

## Charles Greeley Abbot

Charles Greeley Abbot (May 31, 1872 – December 17, 1973) was an American astrophysicist and the fifth secretary of the Smithsonian Institution, serving from 1928 until 1944.

## Claude Pouillet

Claude Servais Mathias Pouillet (16 February 1790 &ndash; 14 June 1868) was a French physicist and a professor of physics at the Sorbonne and member of the French Academy of Sciences (elected 1837).

## Committee on Data for Science and Technology

The Committee on Data for Science and Technology (CODATA) was established in 1966 as an interdisciplinary committee of the International Council for Science.

## Cross section (geometry)

In geometry and science, a cross section is the non-empty intersection of a solid body in three-dimensional space with a plane, or the analog in higher-dimensional spaces.

## Earth

Earth is the third planet from the Sun and the only astronomical object known to harbor life.

In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space-time, carrying electromagnetic radiant energy.

## Electromagnetic spectrum

The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.

The faint young Sun paradox or faint young Sun problem describes the apparent contradiction between observations of liquid water early in Earth's history and the astrophysical expectation that the Sun's output would be only 70 percent as intense during that epoch as it is during the modern epoch.

## Flux

Flux describes the quantity which passes through a surface or substance.

## Formation and evolution of the Solar System

The formation and evolution of the Solar System began 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud.

## Inverse-square law

The inverse-square law, in physics, is any physical law stating that a specified physical quantity or intensity is inversely proportional to the square of the distance from the source of that physical quantity.

## Jules Violle

Jules Louis Gabriel Violle (16 November 1841, Langres, Haute-Marne – 12 September 1923, Fixin, Bourgogne-Franche-Comté) was a French physicist and inventor.

## Kilo-

Kilo is a decimal unit prefix in the metric system denoting multiplication by one thousand (103).

## Langley (unit)

The langley (Ly) is a unit of heat transmission, especially used to express the rate of solar radiation (or insolation) received by the earth.

## Latitude

In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earth's surface.

## Light

Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum.

## List of articles related to the Sun

Articles related to the Sun include.

## List of solar cycles

The following is a list of solar cycles (sometimes called sunspot cycles), tracked since 1755 following the original numbering proposed by Rudolf Wolf in the mid-19th centuryKane, R.P. (2002).

## Mont Blanc

Mont Blanc (Monte Bianco), meaning "White Mountain", is the highest mountain in the Alps and the highest in Europe west of Russia's Caucasus peaks.

## Mount Whitney

Mount Whitney is the tallest mountain in California, as well as the highest summit in the contiguous United States and the Sierra Nevada—with an elevation of.

## Orbital eccentricity

The orbital eccentricity of an astronomical object is a parameter that determines the amount by which its orbit around another body deviates from a perfect circle.

## Perihelion and aphelion

The perihelion of any orbit of a celestial body about the Sun is the point where the body comes nearest to the Sun.

## Physical constant

A physical constant, sometimes fundamental physical constant or universal constant, is a physical quantity that is generally believed to be both universal in nature and have constant value in time.

## Planck constant

The Planck constant (denoted, also called Planck's constant) is a physical constant that is the quantum of action, central in quantum mechanics.

## Pyrheliometer

A pyrheliometer is an instrument for measurement of direct beam solar irradiance.

The radian (SI symbol rad) is the SI unit for measuring angles, and is the standard unit of angular measure used in many areas of mathematics.

Radiation pressure is the pressure exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field.

## Samuel Pierpont Langley

Samuel Pierpont Langley (August 22, 1834 &ndash; February 27, 1906) was an American astronomer, physicist, inventor of the bolometer and aviation pioneer.

## Solar cycle

The solar cycle or solar magnetic activity cycle is the nearly periodic 11-year change in the Sun's activity (including changes in the levels of solar radiation and ejection of solar material) and appearance (changes in the number and size of sunspots, flares, and other manifestations).

Solar irradiance is the power per unit area received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument.

## Solar Radiation and Climate Experiment

The Solar Radiation and Climate Experiment (SORCE) is a NASA-sponsored satellite mission that measures incoming X-ray, ultraviolet, visible, near-infrared, and total solar radiation.

## Solar wind

The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona.

## Solid angle

In geometry, a solid angle (symbol) is a measure of the amount of the field of view from some particular point that a given object covers.

## Speed of light

The speed of light in vacuum, commonly denoted, is a universal physical constant important in many areas of physics.

## Stellar evolution

Stellar evolution is the process by which a star changes over the course of time.

No description.

## Sun

The Sun is the star at the center of the Solar System.

## Sunlight

Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light.

## Sunspot

Sunspots are temporary phenomena on the Sun's photosphere that appear as spots darker than the surrounding areas.

## Surface area

The surface area of a solid object is a measure of the total area that the surface of the object occupies.

## Watt

The watt (symbol: W) is a unit of power.

## References

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