What Happens If A Black Hole Hits Earth?

Centering on primordial black holes, the video presents them as a potential explanation for all 86% of dark matter, with asteroid-mass black holes surviving observational constraints. It dramatizes their effects: a Phobos-mass black hole would punch through Earth like a bullet, while even the smallest would send a magnitude-4 seismic wave across the planet and glow with the power of a hundred Hiroshimas. Because live detection is unlikely, the Moon’s cratered surface is framed as the best archive, and scientists can distinguish black-hole impacts from asteroid craters by their distinctive “line explosion” shapes and ejecta patterns. No such craters have been found, but the video stresses that a single hit would confirm primordial black holes, reveal their masses, and shed light on dark matter and the early universe. It then broadens into theoretical physics, using Occam's razor to explain that any replacement for general relativity, such as string-theory fuzzballs, must replicate its successes and could be tested via gravitational-wave signatures.

• ▶ 1:55 Primordial black holes could have formed from especially dense regions in the early universe, potentially explaining all 86% of dark matter.
• ▶ 2:27 Astronomers have ruled out most PBH masses as dark matter: heavier than ~10^19 kg would be seen via gravitational lensing, while lighter than ~a trillion kg would have evaporated via Hawking radiation, leaving an asteroid-mass window.
• ▶ 4:02 If dark matter is made of asteroid-mass black holes, there would be enormous numbers of them, with dozens to thousands possibly in the solar system right now—making close passes or even passages through Earth surprisingly frequent.
• ▶ 4:34 An asteroid-mass PBH impact would not destroy Earth; the planet would survive even if such impacts occurred.
• ▶ 5:14 A Phobos-mass PBH (about 10^16 kg) would have an event horizon the size of a hydrogen atom and would punch through Earth like a bullet, consuming only a few thousand tonnes of material.
• ▶ 7:05 Its Eddington limit would be very low, yet the tiny glowing plasma cloud would shine with the power of a hundred Hiroshimas every second, creating a shockwave like a brightest shooting star.
• ▶ 8:52 A black hole passing through Earth would generate a planet-wide seismic shockwave; even the smallest PBH would cause a magnitude 4 quake felt across the entire planet at once, distinct from any normal earthquake.
• ▶ 10:28 Since live detection is unlikely, the Moon is the best archive: with no atmosphere or tectonics, it preserves ancient impacts, and black hole craters can be distinguished from asteroid craters by their deeper "line explosion" shape and steeper ejecta blanket.
• ▶ 12:24 No paired entrance/exit craters or exotic high-pressure quartz have been found yet, but finding even one impact would confirm primordial black holes exist, reveal their masses, and could clarify dark matter and conditions at the birth of spacetime.
• ▶ 13:13 Host promotes a new Above the Noise episode on Space Tourism and Billionaires in Space, inviting comments and a link in the description.
• ▶ 13:38 Thanks all Patreon supporters, emphasizing how much their support means to the show.
• ▶ 13:42 Encourages viewers to click the bell icon to join the "early gang" and get notifications, helping the show grow at no cost.
• ▶ 14:44 Occam's razor is a guiding principle, not a rule: any new theory must reproduce general relativity where it works, so you can't discard a successful theory without a replacement that covers those successes.
• ▶ 16:34 Fuzzball complementarity preserves the equivalence principle: an infalling observer experiences normal freefall, while a distant observer sees them smeared over the fuzzball surface, linking to the holographic principle.
• ▶ 18:06 Fuzzballs may be string theory's most testable prediction: gravitational-wave ring-downs could last longer than for classical black holes, and upgraded instruments might detect quantum fluctuations near the event horizon.

• ▶ 0:00 Black Holes and Primordial Origins (0:00 - 4:23) - - Clears up black hole misconceptions and covers primordial black hole formation, dark-matter role, and the remaining asteroid-mass window.
• ▶ 4:23 When a Primordial Black Hole Hits Earth (4:23 - 8:42) - - Details a PBH striking Earth: passage through the planet, atmospheric entry, Eddington limit, and the Tunguska comparison.
• ▶ 8:42 Searching for Ancient Impacts (8:42 - 13:13) - - Discusses seismic detection, lunar crater records, predicted crater shapes, and the status of the search.
• ▶ 13:07 Show Announcements (13:07 - 14:10) - - Contains show announcements and requests for viewer support.
• ▶ 14:06 Comments and Fuzzball Physics (14:06 - 20:09) - - Addresses viewer comments on MOND and fuzzballs, fuzzball complementarity, testing methods, and visualizations.