Coming to a sky near you: Comet SWAN at its best

Comet C/2020 F8 (SWAN), perhaps the brightest comet we will see this year, is at its best from now until mid-June. It should be visible in from the UK in the northwestern sky after sunset, close to the horizon.

A new law for metamaterials

Metamaterials, which are engineered to have properties not found in nature, have long been developed and studied because of their unique features and exciting applications. However, the physics behind their thermal emission ...

Solar energy tracker powers down after 17 years

After nearly two decades, the Sun has set for NASA's SOlar Radiation and Climate Experiment (SORCE), a mission that continued and advanced the agency's 40-year record of measuring solar irradiance and studying its influence ...

NASA selects new instrument to continue key climate record

NASA has selected a new space-based instrument as an innovative and cost-effective approach to maintaining the 40-year data record of the balance between the solar radiation entering Earth's atmosphere and the amount absorbed, ...

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Sunlight, in the broad sense, is the total spectrum of the electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the atmosphere, and the solar radiation is obvious as daylight when the Sun is above the horizon. Near the poles in summer, the days are longer and the nights are shorter or non-existent. In the winter at the poles the nights are longer and for some periods of time, sunlight may not occur at all. When the direct radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and heat. Radiant heat directly produced by the radiation of the sun is different from the increase in atmospheric temperature due to the radiative heating of the atmosphere by the sun's radiation. Sunlight may be recorded using a sunshine recorder, pyranometer or pyrheliometer. Sunlight takes about 8.3 minutes to reach the Earth. The World Meteorological Organization defines sunshine as direct irradiance from the Sun measured on the ground of at least 120 watts per square metre.

Direct sunlight has a luminous efficacy of about 93 lumens per watt of radiant flux, which includes infrared, visible, and ultra-violet light. Bright sunlight provides luminance of approximately 100,000 candela per square meter at the Earth's surface.

Sunlight is a key factor in photosynthesis, a process crucially important for life on Earth.

This text uses material from Wikipedia, licensed under CC BY-SA