Episode guide
Oxygen: Where Does It Come From?
Every breath you take was made by something green, and much of it came from the sea. This episode traces one gulp of air backward to the leaves and the plankton that built it.
The science, gently
- Plants, algae, and tiny ocean plankton make oxygen using sunlight, water, and air.
- Around half of Earth's oxygen comes from phytoplankton, drifting in the sea where no one sees them.
- The oxygen in tonight's breath may have been made thousands of miles away.
Wonder together
- Who do you think made the breath you just took, a tree or the sea?
- If air is invisible, how do we know it is there?
- What would you say to a plankton if you could thank it?
Tonight's calm-down
Put a hand on your belly and take one slow gift of a breath. In for four, out for six. Somewhere an ocean made that air for you, and it will keep making more while you sleep.