Eli5: What is the difference between natural and artificial light; and why can some plants thrive on artificial light?
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Natural light is the term given to direct or indirect sunlight. Artificial lights are light that come from other sources. (if you want to be stricter about it, artificial light is light that comes from man made sources).
Light is light. What characterizes light is the frequency spectrum and the intensity within that spectrum. This as interpreted by our eyes and brains as color. It is entirely possible for artificial light to match natural light. However it is uncommon.
Sun light is very intense – don’t ever look directly at the sun. Replicating it would be quite energy intensive and wasteful. Most artificial lights are much less intense than the sun and our eyes do fairly well even in less intense light.
Plants have evolved and adapted to their particular ecosystem. Most fully grown trees are adapted to handle (and sometimes require) natural direct sunlight. Some plants have evolved to require less than the full sun intensity. Generally speaking these would be plants that grow in the shade of other plants and trees. These kind of plants will also do fairly well under artificial lights which are typically less intense than direct sunlight.
Other factors also come into play. Sun light also heats up stuff very quickly. Some plants are not adapted to handle increased temperatures and will not thrive under the hot direct sun. So it isn’t simply about natural or artificial lights.
Natural light is light produced by natural sources :
sunlight and all it’s variants, e.g, direct sunlight , cloudy sunlight
moonlight (actually sunlight reflected off the moon)
starlight, similar to sunlight , because the sun is essentially a star
twilight or dawn light
auora borealis , aurora australis
glow worms , bioluminescent algae underwater , fire-flies
radio-active glow, (e.g., uranium)
lightning bolts
fire light (fires created by lightning)
— — — — — — —
Artificial light (not made by nature ) is light made by humans, often in a factory :
streetlights , car headlamps , torches , building and domestic lamps (incandescent , fluorescent , LCD , LEDs ) ,
television screens , computer screens , phone screens ,
photo flash units ,
cigarette light / cigarlight / matchstick flame , stove or oven flames .
Natural light is just another word for sunlight, artificial light is produced by lamps. Light is light, though. It’s all photons. The intensity and wavelength (roughly, the color) may vary, but other than that there is no difference.
Plants are pretty adaptable organisms able to use a wide variety of wavelengths in the color spectrum (you can see [here](https://cdn.kastatic.org/ka-perseus-images/27c5e928745dbde12550494315ec70253091eee5.png)…the higher the white lines, the more easily that light color can be used. Plants don’t use much in the yellow-green, but use a lot of violet, blue, and red.
Natural light has plenty of wavelengths in these colors, and so do most artificial lights. As long as artificial light meets the needs of the plants, it’s no different than natural light for them.
However, artificial light won’t grow all plants. Probably the _main_ reason for this is that it’s often too dim. Even bright indoor lighting is vastly dimmer than sunlight. Our eyes just don’t really notice this because they are very good at adjusting to different light levels. But outdoors can easily be ten to one hundred times brighter than an ordinary indoor room. Many plants need bright light and can’t survive on 1/10th or 1/100th the light level they are adapted to.
Natural light comes from things that get very hot, like the sun. That light has energy distributed over a range of different wavelengths that usually include all the visible wavelengths, some ultraviolet and some infrared.
The wavelengths of artificial light depend on the source of the light. An incandescent lightbulb will give you a similar spectrum to the Sun, because all it’s doing is getting hot enough to emit light.
Fluorescent lights emit very specific wavelengths only, which is why colors look weird under them. They put in enough wavelengths to fool your brain into thinking that they’re white, but they’re not really. A television also produces only three colors, and can make you think you’re seeing white.
LEDs also produce only specific wavelengths, based on the energy levels in the diode. They combine several of them to look white, and in fact it was a very big deal when they finally figured out how to make blue ones.
Plants are nature’s solar panels. They have specific molecules that are able to absorb specific amounts of energy that correspond to specific wavelengths of light, because the wavelength of light is its energy. If the light you shine on a plant doesn’t contain enough of the wavelengths it’s good at absorbing, the plant can’t get enough energy.
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