What If You Dug a Hole to the Center of the Earth? (Hour by Hour)

Nobody has dug deeper than about 12 kilometers. The center of the Earth is 6,371 kilometers down. Otto is going to try to get there, and the fall takes minutes, not hours. Depth by depth, on a clock: a mine where people work in 66 °C rock, the record hole where the rock started behaving like plastic, the legend of the "well to hell" and where it really comes from, the moment the rock ends and the metal begins, the center, and the three cheats that make the famous "42 minutes" possible. This is a thought experiment, NOT a plan. The hole Otto needs can't exist, it wouldn't stay open, and nothing we can build would survive the trip. Where the science is thin or disputed, we say so. Chapters 0:00 The hole that can't exist 0:40 0 to 4 km: what people can still dig 1:26 12,262 m: Kola, the end of human digging 2:27 The "well to hell" legend and the three cheats 3:26 Free fall: crust and mantle 5:17 Liquid outer core, solid inner core 6:40 The center 7:54 The way out: the 42 minutes, and where it breaks 8:25 The cheats: air, friction and rotation 9:02 The honest summary: how little we have touched What's estimated, and what's disputed • The fall times and speeds (1 km at 14 s, 10 km at 45 s, 100 km at 2 min 24 s, 1,000 km at 7 min 36 s, 2,890 km at 13 min 18 s, the center at 21 min 6 s, 7.9 km/s) are OUR OWN CALCULATION from a simple model: uniform Earth, no air, no friction. The real Earth is denser inside, so treat them as estimates, not measurements. • "42 minutes" is the uniform-density model. With the real density profile, a 2015 paper in the American Journal of Physics (Klotz) gets about 38 minutes. • Kola's depth (12,262 m, 1989) is well documented. The temperature at the bottom (about 180 °C, against about 100 °C expected) and the rock behaving like plastic and closing the hole come from popular accounts of the project, not from the original reports. Sources also disagree on when the project closed, so we give only "in the nineties". • Mponeng's figures (about 4 km, rock at 66 °C, air below 30 °C) come from an encyclopedia article. Which mine is the deepest today is not settled in our sources. • Temperatures are in degrees Celsius. Kelvin appears only where a source gives it: the base of the mantle is about 4,200 K (about 3,900 °C), and the inner core is estimated at roughly 5,400 to 6,230 K (about 5,100 to 6,000 °C), with an uncertainty of about 500 degrees. Nobody has measured it. • "As hot as the Sun" is only "the same order": the Sun's visible surface is about 5,500 °C. The two are similar, not equal. • Gravity rising about 9% near the bottom of the mantle comes from one popular write-up of the standard Earth model. We could not open the table. • With air in the tunnel, Otto does not cross: a 2016 preprint (Concannon & Giordano), which we read through Science News, models about 1.8 years to reach the center. It is a preprint, not a peer-reviewed result. Without air but with friction, he ends up stopped at the center. • The Coriolis point (only a pole-to-pole tunnel avoids the wall) comes from popular science essays, with no number. • The "well to hell" in Siberia is a legend: the screams were a sound effect from a 1972 horror film, and the story spread through Finnish newspapers in 1989. We cite the encyclopedia account; we did not open the Snopes article itself. • The core is known from earthquake waves, lab experiments and calculation. Nobody has been there. Sources • Structure of the Earth (radius, layers). https://en.wikipedia.org/wiki/Structu... • Kola Superdeep Borehole. https://en.wikipedia.org/wiki/Kola_Su... • Mponeng Gold Mine. https://en.wikipedia.org/wiki/Mponeng... • Gravity train (free fall through the Earth). https://en.wikipedia.org/wiki/Gravity... • Klotz (2015), "The Gravity Tunnel in a Non-Uniform Earth", abstract. https://arxiv.org/abs/1308.1342 • Concannon & Giordano (2016), "Gravity tunnel drag", preprint, via Science News. https://www.sciencenews.org/article/f... • Earth's inner core (Lehmann, outer core, pressure). https://en.wikipedia.org/wiki/Earth%2... • Anzellini et al. (2013), melting of iron, ESRF summary. https://www.esrf.fr/home/UsersAndScie... • Earth's mantle. https://en.wikipedia.org/wiki/Earth%2... • Geothermal gradient. https://en.wikipedia.org/wiki/Geother... • Well to Hell (legend). https://en.wikipedia.org/wiki/Well_to... • The Sun's photosphere (about 5,772 K). https://en.wikipedia.org/wiki/Photosp... Secondary sources quoted in the video • EarthDate, on Kola. https://www.earthdate.org/episodes/ko... • Damn Interesting, on Kola. https://www.damninteresting.com/the-d... • Oikofuge, "Falling through the Earth" (gravity inside, Coriolis). https://oikofuge.com/falling-through-...