LearningJoy Explorers: Science Podcast for Kids
Nov 1, 2026 · 8 min · 8 segments
Where does a giant tree get all its weight if it doesn't eat the dirt? Join us as we unplug Shrivathsa's sky vacuum, meet the scientist who weighed a tree's soil for five years, discover how leaves…
He weighed dry soil in a big pot, planted a small willow tree in it, and gave it only water for five years.
What happened after five years? The tree gained about 75 kilograms, as much as a grown-up! Then he dried and weighed the soil again.
It had lost only about 50 grams, about two spoonfuls.
Whoa! So a tree is not made of dirt! Not at all! Van Helmont guessed the weight came from water.
He was half right.
The other half came from something invisible, the air.
Made of air? How can a tree eat thin air and turn it into hard wood? Under every leaf are thousands of tiny mouths called stomata.
They open to gulp carbon dioxide from the breeze.
Inside the leaf, sunlight powers photosynthesis.
The leaf joins carbon from the air with water from the roots to make sugar and lets out fresh oxygen for us to breathe.
Wait, and the tree uses that sugar to build wood? Wood, bark, leaves, and roots! In fact, about half of a dry tree trunk's weight is pure carbon that used to be floating in the sky.
No way! Let me tap this wooden
table.
I am
knocking on solid sky! You really are! Forests take in more carbon than they let out, so scientists call them a carbon sink, a safe storage place for carbon.
Every year, land plants soak up about a quarter of the extra carbon dioxide we add to the air.
How much carbon dioxide can one big tree soak up? One full-grown tree can take in about 22 kilograms of carbon dioxide every year.
That is about as heavy as a six-year-old child! Problem solved! Let's
He weighed dry soil in a big pot, planted a small willow tree in it, and gave it only water for five years.
What happened after five years? The tree gained about 75 kilograms, as much as a grown-up! Then he dried and weighed the soil again.
It had lost only about 50 grams, about two spoonfuls.
Whoa! So a tree is not made of dirt! Not at all! Van Helmont guessed the weight came from water.
He was half right.
The other half came from something invisible, the air.
Made of air? How can a tree eat thin air and turn it into hard wood? Under every leaf are thousands of tiny mouths called stomata.
They open to gulp carbon dioxide from the breeze.
Inside the leaf, sunlight powers photosynthesis.
The leaf joins carbon from the air with water from the roots to make sugar and lets out fresh oxygen for us to breathe.
Wait, and the tree uses that sugar to build wood? Wood, bark, leaves, and roots! In fact, about half of a dry tree trunk's weight is pure carbon that used to be floating in the sky.
No way! Let me tap this wooden
table.
I am
knocking on solid sky! You really are! Forests take in more carbon than they let out, so scientists call them a carbon sink, a safe storage place for carbon.
Every year, land plants soak up about a quarter of the extra carbon dioxide we add to the air.
How much carbon dioxide can one big tree soak up? One full-grown tree can take in about 22 kilograms of carbon dioxide every year.
That is about as heavy as a six-year-old child! Problem solved! Let's
The rest of this transcript — segmented and speaker-labeled, so you land on the exact moment something was said
Search every transcript — by keyword, by phrase, or by meaning, across every show Radar indexes
Trends — what is surging across podcasts, measured against its own baseline
Alerts — when a name you follow appears in a newly indexed episode
No account is needed to search Radar.
