The Nile, at about 6,650 km, is often listed as the world's longest river, just ahead of the Amazon at around 6,400 km. But some studies, picking a different Andean source for the Amazon, credit it with nearly 7,000 km. It all depends on choosing the most distant source and where the mouth begins, two points that are surprisingly hard to pin down.
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.