Solar irradiance spectrum at top of atmosphere.

The solar constant is the amount of incoming solar radiation per unit area, measured on the outer surface of Earth's atmosphere, in a plane perpendicular to the rays. It is measured by satellite to be roughly 1367 watts per square metre. Thus, for the whole Earth, with a cross-section of 125,000,000 km², the power is 170 petawatt. The solar constant is not quite constant; see solar variation. Spectrum of solar irradiance at top of Earths atmosphere. ... Spectrum of solar irradiance at top of Earths atmosphere. ... Solar irradiance spectrum at top of atmosphere. ... Earth, also known as the Earth, Terra, and (mostly in the 19th century) Tellus, is the third-closest planet to the Sun. ... The watt (symbol: W) is the SI derived unit for power. ... A square metre (US spelling: square meter) is by definition the area enclosed by a square with sides each 1 metre long. ... This page lists examples of the power in watts produced by various different sources of energy. ... It has been suggested that this article or section be merged with Solar variation theory. ...

The solar constant includes all types of solar radiation, not just the visible light. (See electromagnetic spectrum for more details) It is linked to the apparent magnitude of the Sun, −26.8, in that the solar constant and the magnitude of the sun are two methods of describing the apparent brightness of the Sun, though the magnitude only measures the visual output of the Sun. The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... The electromagnetic spectrum is the range of all possible electromagnetic radiation. ... The apparent magnitude (m) of a star, planet or other heavenly body is a measure of its apparent brightness; that is, the amount of light received from the object. ...

The angular diameter of Earth seen from the sun is ca. 1/11,000 radian, so the solid angle of Earth seen from the sun is ca. 1/140,000,000 steradian. Thus, the sun emits about 2 billion times the amount of radiation that is caught by Earth, or about 3.86×10²⁶ watt. The angular diameter of an object as seen from a given position is the diameter measured as an angle. ... In mathematics and physics, the radian is a unit of angle measure. ... A solid angle is the three dimensional analog of the ordinary angle. ... The steradian (ste from Greek stereos, solid) is the SI derived unit of solid angle, and the 3-dimensional equivalent of the radian. ...

The Solar Constant is relatively constant, but varies according to sunspot activity. It affects mainly long-term climates, rather than short-term weather. A sunspot is a region on the Suns surface (photosphere) that is marked by a lower temperature than its surroundings, and intense magnetic activity. ... Composite satellite image showing the progress of a hurricane weather system approaching the East Coast of the United States Weather comprises all the various phenomena that occur in the atmosphere of a planet. ...

See also

• Earth's energy budget
• Solar variation