You can try the first discovery and the 3D controls now. Stella unlocks every stage.
Where did the 74 kg a potted willow gained in five years come from? Descend nine orders of magnitude, through the leaf, the stomata, the chloroplast, the thylakoid membrane and Rubisco, and follow carbon from the air into the body of a tree.
In the 1600s Jan Baptist van Helmont filled a pot with 200 pounds (about 91 kg) of dried soil and planted a willow sapling weighing 2.3 kg. He gave it nothing but rainwater. Five years later the willow weighed 76.7 kg. It had gained 74 kg, yet when he dried and weighed the soil again, only about 57 g was missing. He concluded that the tree was made of water. He was half right. The other half of the answer was somewhere he could not see. On this journey you become a single carbon atom drifting in the air, and go looking for it.
Van Helmont’s willow experiment: Jan Baptist van .
Move the five years forward and compare the needle on the willow’s scale with the one on the soil’s scale.
Of the 74 kg, 57 g came from the soil. So where did the rest come from? The answer waits at the end of the journey, back at this willow.
You can try the first discovery and the 3D controls now. Stella unlocks every stage.
