When we look at an oak, a sequoia, or a balsa tree in the Amazon rainforest, we're looking at solidified carbon and oxygen. Trees do not obtain structural mass from the soil; it comes out of thin air. Plants are built almost entirely from atmospheric gases—living, complex architectures of carbon, oxygen and sunlight. No wonder that as children, we hug them, play and climb in them, or wander through their woods, hearing them sighing in the wind. Around 90% to 95% of a tree's dry weight is carbon and oxygen, pulled directly from atmospheric carbon dioxide. Most people assume trees draw their body from the earth, yet the soil volume beneath a canopy remains unchanged as a sapling matures into a giant. Roots do not consume dirt to build branches; large trees leave no gaping holes in the ground. Instead, the root network is a mechanical anchor to hold the heavy tree structure upright, while absorbing water and a tiny fraction of soil minerals—nitrogen, phosphorus, and potassium. These are their biological multivitamins, accounting for less than 5% of final dry mass. Through photosynthesis, sunlight breaks apart carbon dioxide and water molecules. The plant releases oxygen back into the atmosphere and chains the remaining carbon and oxygen into glucose molecules, forming complex structural polymers like cellulose and lignin. Across the globe, an estimated 3 trillion trees hold roughly 500 billion cubic meters of wood. Every forest on Earth is in reality solidified atmosphere—hundreds of billions of tons of air trapped, structured and given physical form by living plants. Mankind owes its survival to these friendly giants of the natural world.

Computer scientist Sara Hooker on underestimating difficulty:

SpaceX engineers spent several days inspecting Ship 40 in the waters off Christmas Island. They collected heatshield samples and gained vital insight into how the vehicle handled reentry with improvements now planned on future vehicles