Health

Do you need more vitamin D in the winter?

Vitamin D is a nutrient your body needs to keep your bones healthy and strong. It also has properties that support your immune system and neuromuscular health.

Oncology & Cancer

Q&A: Tips for cancer patients to stay safe in the summer

I have diabetes and high blood pressure. I take medication but have committed to a healthier lifestyle, including daily walks outside, swimming and other outdoor activities with my family. Recently, I was diagnosed with breast ...

Diseases, Conditions, Syndromes

Tick season is starting sooner, and they are showing up in new places

As tick season gets into full swing, we spoke with two experts who study them to learn about the latest in tick research and how to stay protected. Emily Struckhoff is a vector-borne disease program specialist with Penn State ...

Oncology & Cancer

Skin cancer survivors: How to stay safe in the sunshine

For many people, playing and relaxing in the sun is fun. But for skin cancer survivors, the sun can be a source of fear and anxiety. That's because sun exposure is one of the most significant risk factors for developing skin ...

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Sunlight

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