Additionally, how do we get Vitamin D from a nuclear reaction? It doesn’t seem intuitive that a nuclear fusion reaction would suffice me with an important nutrient.
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The nuclear fusion reactions in the sun release light. Said light is absorbed by plant leaves and processed into energy by chlorophyll, and that energy is used to perform chemical reactions in the plant, most notably converting carbon dioxide and water into carbohydrates and oxygen gas.
Plants don’t get their energy from the sun, they just use sunlight as an ingredient in the chemical reaction they use to make sugars, which gives them energy.
Basically it’s like using heat to cook food, but with visible light instead of heat. When you cook, it’s not the heat that gives you energy, it’s the food.
The nuclear reaction doesn’t produce Vitamin D itself.
It’s that nuclear reaction keeps the Sun very hot. Very hot bodies radiate energy, which means they emit electromagnetic waves. Because we’re lucky enough that we have an atmosphere, most of the radiated energy is not lethal. For the most part we get (non lethal) ultraviolet, visible light and infrared.
All this gives plants their energy and triggers in humans the production of Vitamin D. In particular, Vitamin D needs UVB (Ultraviolet Type B), while photosynthesis relies on visible light from blue to red.
(*) When I say non lethal, I mean non-ionizing radiation. Excessive UV from sunlight can still cause skin cancer, but it doesn’t do that by forcing electrons to detach from atoms.
Because photons of light carry energy. They can be emitted when something is very hot. When the are absorbed they can bump electrons to higher states in their molecules.
This question and your other can be broken up into how the sun emits light and how life uses light. I think you’re more interested in the latter.
Different wavelengths of light have different properties. For those in a certain range, the human eye can register those as visible light, with a color. For those a little lower in energy (infrared) they are efficient at heating things up. Higher (ultraviolet) is higher energy.
Molecules in leaves or the skin are structured to use that energy for biological processes. Light gives a high energy electron as that is used to do stuff.
I’ll dig up some links.
https://education.nationalgeographic.org/resource/photosynthesis/ https://education.nationalgeographic.org/resource/sun/
The sun is basically a candle. A gigantic, round, nuclear candle.
It has a flame (all over), and it has a limited amount of fuel (it’s mass). In a few billion years, this candle will have burned up, and the flame will die out.
Like the flame of a candle, this produces a lot of energy in the form of radiation: you can feel the heat of a flame radiating from a distance. But this is a nuclear candle, so besides heat and visible light, it produces all kinds of radiation.
Because the sun is so big, it produces a massive amount of radiation. A part of this, is the sunshine that reaches the Earth.
Much of the more harmful radiation is filtered out by the Earth’s atmosphere and electromagnetic field. But as you know, nothing feels like sunlight 😉
This is the source of energy that fuels all life on the planet.
For example, food. Animals eat eachother or plants, but plants don’t eat other living things. Plants “eat” sunlight. All a plant needs to grow, is earth, water, and sunlight.
They use earth and water to grow, and they absorb sunlight to power that entire process.
In turn, animals eat those plants in order to live, and other animals eat them to live.
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