Energy & Green Tech

Device generates light from the cold night sky

An inexpensive thermoelectric device harnesses the cold of space without active heat input, generating electricity that powers an LED at night, researchers report September 12 in the journal Joule.

Energy & Green Tech

Can solar power ever fully replace fossil fuels?

The 2019/20 Australian bushfire season, known as the black summer, changed how remote communities get electricity. But can we change the entire nation's energy use?

Energy & Green Tech

Renewables rescue stability as the grid loses spin

The high-altitude Atacama Desert of northern Chile is a surprising location for scientific insights: Its dry and dusty likeness to Mars makes it ideal for interplanetary testing, and distant worlds are particularly visible ...

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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