What If the Moon Was 400 km Above Earth? (I Simulated It)

Put the Moon where the space station flies and it would fill 109 degrees of sky. It would also be torn apart before it finished one orbit. I worked out where the Roche limit is, then simulated a cloud of loose rock to see how much of the Moon survives at different distances. 0:00 The question 0:26 The rules 0:47 What you would see 1:12 The tides 1:48 The tipping point (Roche limit) 2:21 The simulation 2:53 The verdict 3:16 Saturn's rings 3:30 The real Moon is drifting away 3:51 The answer HOW THIS WAS MADE Setup: the Moon's surface is 400 km above Earth's surface, so its centre is 8,508 km from Earth's centre. (A Moon centred 400 km up is impossible: it would sit inside the Earth.) Sky size: angular radius = asin(Moon radius / distance from the observer) = 54.4 degrees, so about 109 degrees across and about 42% of the visible sky. Orbit: circular, tidally locked. Period 129 minutes, speed 6.8 km/s. Tides: stretching acceleration at the surface = 2 G M_Earth R_Moon / d^3. At 8,508 km it is 2.25 m/s2, against the Moon's own surface gravity of 1.62 m/s2. At the real distance it is about 1/66,000 of surface gravity. The ratio of tidal strength at 8,508 km versus 384,400 km is about 92,000. Roche limit for loose rock: where stretch equals surface gravity, 9,490 km from the centre (about 3,000 km above the ground). The flowing-liquid limit is quoted at about 18,400 km (rigid and fluid Roche limits, e.g. the standard 2.44 R (rho_planet / rho_moon)^(1/3) form). Simulation: 1,257 test particles on the Moon's disc, 2-D, tidally locked start, Earth and Moon gravity, RK4 integration for two orbits at 20,000, 15,000, 12,000 and 8,508 km. Percent shown is the share within 3 Moon radii of the Moon's centre at the end. At 8,508 km about 48% of particles dip inside Earth's radius and the rest go to wide orbits. It is a toy model: no collisions, no rock strength, no 3-D. Recession: about 3.8 cm per year, measured by lunar laser ranging off the retroreflectors left by the Apollo missions. Edouard Roche (1820-1883), French astronomer, worked out the limit in the 1840s-1850s. Every visual is drawn in code. The Moon and Earth textures are generated, not photographs. No stock footage and no AI-generated video. Narration is a synthetic voice (ElevenLabs). Meridian Lab asks one question per video and answers it by running the numbers.