When the ground is scorching, the air just above it is much hotter and less dense than the air higher up. Light rays coming from the sky are bent upwards there before reaching your eyes. Your brain reads that patch of sky at ground level as a pool of water. Proof that it is no hallucination: you can photograph a mirage.
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.