Dry air is about 78% nitrogen and 21% oxygen. The third most common gas is not carbon dioxide but argon, an inert noble gas, at nearly 0.93%. CO₂ makes up only about 0.04%. Yet that tiny fraction plays a key role in the greenhouse effect because, unlike argon, it absorbs infrared radiation.
On 27 August 1883, the eruption of the Indonesian volcano Krakatoa was heard as far away as Rodrigues Island, nearly 4,800 km away. Its pressure wave was picked up by barometers worldwide and circled the globe several times. The tsunamis that followed killed more than 36,000 people.
The deepest known point in the ocean, Challenger Deep, lies roughly 10,900 m below the Pacific surface. Drop Everest in and its summit would still sit about 2 km underwater. Down there, the pressure is more than 1,000 times what you feel at sea level, roughly a tonne pressing on every square centimetre.