Where Do Trees Get Their Mass?
Why Hacker News recommends it
HN uses it as the go-to demonstration of how unintuitive mass conservation is, especially in weight loss and burning threads.
What it is
Veritasium asks people where a tree's mass comes from, then explains that most of a dry tree's mass originates from carbon dioxide in the air. It combines street interviews with a short explanation of photosynthesis.
Recommended by 3 HN commenters across 3 different months, 2015 to 2021.
What Hacker News said
Strong rec lathiat · 2021-04 · on “Where does a candle go when it burns?”
"Where do trees get their mass?" - [this video] This was highly enlightening the first time I watched it :)
Recommends lkbm · 2015-04 · on “When You Lose Weight, Where Does It Go?”
There's a nice Veritasium episode wherein he asks people on the street where a tree's mass comes from: [this video] (This isn't just one of those "let's laugh at how dumb people on the street are" videos; it's done explicitly as a learning exercise. His PhD looked at how addressing misconceptions and going from there to correct explanations works much better than simply providing explanations: [LINK] ) I thought of it upon seeing the first chart in the BMJ article.)
Recommends JshWright · 2017-11 · on “When somebody loses weight, where does the fat go?”
An interesting corollary to this is "Where do trees get their mass?" Veritasium has a fun video demonstrating how unintuitive this is: [this video]
Cites MarcScott · 2015-04 · on “When You Lose Weight, Where Does It Go?”
And the reverse biochemical process is equally misunderstood. I used to teach high school Science and everyone thought a tree's mass came from the soil. [this video]