eli5: Why are the sun rays harmful but not rays for artificial lights?
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Because the sun emitts UV-light, which is invisible for us. UV-light is ionizing and can therefore cause skin cancer.
Sun rays aren’t harmful in and of themselves. Just like everything in our lives, it’s moderation that is the key. Yes, excessive UVB from the sun causes sunburns, but you need a minimum amount of UVB every day in order to combine with a type of cholesterol in your body (there are multiple types) to produce Vitamin D, which fortifies bones.
As someone who suffered a really bad VitD deficiency, I can tell you, get your 15-20 minutes in the sun a day. Otherwise, months of not going out will lead to immense bone pain that will make you feel like your bones are dissolving, and it’s a pain and ache that is hard to describe.
Folate is also broken down by too much UV light, which folate is a key nutrient for DNA building and maintenance, leading to cancer if not in ample supply. This is why pregnant women should take a lot of folate if she is out in the sun a lot and should try to stay in the shade to keep it from breaking down, as the fetus is building a lot of DNA.
It’s all about moderation. Even O2, food, and water can all kill you in large enough doses.
Light from the sun is a wide spectrum of waves. Some of them are ionizing waves, this means the fotons have enough energy to knock off electrons, and this makes them harmful.
Artificial lights tend to be more specific in the wavelengths that they emit, because they are made by design. Therefore they don’t emit any ultraviolet or ionizing radiation as that light is wasted energy for the purpose of lighting up a room.
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