The biosphere is the thin living skin of the Earth — the places where animals, plants, and tiny living things can actually live. That is soil, forests, rivers, the surface of the sea, and the lower air, not the dead rock deep below or the empty space far above. It is a science-class and environment-news word, not something you say when you mean “outside.” Though actually people stretch it, and say “our biosphere” as if it simply meant “the environment” or “the planet.” The tidy idea is more precise: it is the living layer, where rock, water, and air meet life. An Austrian geologist, Eduard Suess, coined the German word Biosphäre in 1875; English borrowed it. There was also a famous sealed glass world called Biosphere 2, which makes some students think the word means a man-made dome. That was a name, not the meaning.