Squeeze the Earth into a black hole.
Any mass has an event-horizon size hiding inside it — the radius you'd need to compress it to. Crush the whole Earth down and it disappears inside a sphere just nine millimetres across.
shown at a fixed display size — not to scale between presets
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Mass M
M ∝ rs
10¹⁵ kg — a mountainlog scale10³⁷ kg — millions of Suns
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The Schwarzschild radius is the size any mass would need to be compressed to for its escape velocity to reach the speed of light — cross that boundary (the event horizon) and nothing, not even light, gets back out. This page uses the simplest case, the non-rotating (Schwarzschild) solution, not the more realistic rotating (Kerr) black holes real stars collapse into. The "real radius" comparison for masses between the labelled presets is a smooth interpolation, not a measured object — treat it as illustrative rather than a precise density model. Compressing ordinary matter down to its Schwarzschild radius isn't something any machine or chemistry can do; as far as we know, the only process that has ever actually done it is the gravitational collapse of a massive star's core after it runs out of fuel.