Likewise, where does that tree in your backyard come from? It is the product of carbon dioxide and water.
edit: The significance of this thought is when a child is asked where a tree or plant comes from, at least in the US, they inevitably answer the ground when the answer should be rain that falls from the sky and air. With the naive notion a tree comes from the ground we miss the obvious which is the ground doesn't sink when a tree grows from it.
One fun variant of this story is: A tree is made of CO2 from air, water and minerals from the ground, and sunlight. If that wood is burned in a campfire, you get back CO2 in air, and water as vapor, and minerals as ash, and (some of) the sunlight as redder light and heat.
A related common misconception is to forget that plants, like us and most life, burn carbohydrates to CO2. Rainforest trees for instance, are only net consumers of CO2 for a couple of hours around noon.
I'd like to see science education content that weaves stories like this into a coherent tapestry. A rough-quantitative tapestry. Enabling transferable understanding. But we're a long long way from that. If anyone knows of a community pushing in that direction, I'd love to hear of it.
Yet another angle on the same story: The oxygen that makes this cycle possible wasn’t always available on Earth. It was the cycle itself (specifically photosynthesis in microbes) that created our oxygen rich atmosphere. [1]
I’ve heard of Big History [2] as one effort to weave lessons into a coherent tapestry. Agreed that this is a great way to learn.
> Yet another angle [...] oxygen [...] wasn’t always available
Yes! For example, flammability scales with oxygen concentration, so at peak, wildfires could be continent-scale. And oxygen as toxic bio waste, which our own cells still struggle to handle safely, ties a bunch of stories together.
> Big History as one effort to weave lessons into a coherent tapestry
Just looking at its solar system intro[1], sigh. Creating content that is correct, accessible, and insightful, is hard. Really hard. And since it's not incentivized, it rarely happens. Introductions to the solar system are often so misleading, engendering so many misconceptions you would need to fight with later if you actually cared, that viewing them is arguably net-negative learning.
Coherence regrettably requires correctness. Else instead of a tapestry of understanding, one has a tangled mess of misconceptions. Having tapestry, connections, helps prune misconceptions, by making it easier to see that something isn't fitting. And by making it easier to explore and thereby spot them. But tapestry also seems more vulnerable to misconceptions. Mangle a bit of tangle and you still have tangle, but not so with tapestry. And misconceptions are pervasive in science education. So it seems both broader scope and better quality are needed. A daunting challenge.
>"People look at a tree and think it comes out of the
ground, that plants grow out of the ground, " he says, but "if you ask, where does the substance [of the tree] come from? You find out ... trees come out of the air!"
How did the farmer get his donkey out of the deep ditch? He filled it in with dirt. This is just Aesop's fable. But it falls into the same abstract thinking as where does fat go, C55H104O6+78O2 --> 55CO2+52H2O+energy[0], or what happens to a tree when it burns, CH4+4O2→CO2+H2O (plus heat!)[0]. We have a hard time seeing air (sic) as something tangible. Also, this inability to visualize abstract concepts leads to political points of view such as whether or not aerosol of breath contains disease or invisible gases causes global warming.
It’s really cool to observe, e.g. placing white stems of scallions in water and seeing green leaves materialize within days. The underlying biochemistry is fascinating too. [1]
edit: The significance of this thought is when a child is asked where a tree or plant comes from, at least in the US, they inevitably answer the ground when the answer should be rain that falls from the sky and air. With the naive notion a tree comes from the ground we miss the obvious which is the ground doesn't sink when a tree grows from it.