Hourwiz Explains · video notes

A hole through the Earth: our full simulation

From the Hourwiz video “Jump into this hole.” · Checked Oct 15, 2026

Watch on YouTube (opens in a new tab)

In the video we built the planet in code and dropped you in. Here's the full simulation: how the model works, every number it gave, where you'd come out, and the files, so you can check our work.

The thought experiment

A magic tunnel straight through the center: no air, no heat, and we ignore Earth's spin. You step in at rest and fall. Physicist Alexander Klotz (2015) puts the spin's effect at “about four seconds over a forty minute trip”, and Earth's slightly squashed shape at about ten seconds.

• You're weightless the whole way down, because you're in free fall, the same reason astronauts float (NASA).
• Gravity itself is zero only at the center, where the planet pulls equally from every side. Both of our models give exactly 0 there.

Our method

Our model. Two Node scripts we wrote, no outside libraries, run on Oct 15, 2026 with Node v24.21.0. Every input is a published value listed in the sources below.

• Two Earths. Model 1 is the textbook Earth: the same density all the way through, radius 6,371 km, GM = 398,600 km³/s² (NASA). Model 2 is the real, layered Earth: the density of the Preliminary Reference Earth Model (PREM, Dziewonski & Anderson, 1981), built from seismic data, region by region (12 regions), with G = 6.67430 × 10⁻¹¹ m³ kg⁻¹ s⁻² (NIST).
• The fall. Gravity at each depth comes from the mass below you. We stepped the motion with the RK4 method at dt = 0.01 s, from rest at the surface to the stop on the far side, and logged the state every 5 seconds.
• Pressure. We added up the weight of the rock above each depth (dP/dr = −ρg) on the PREM densities.

How we checked the model

• Our PREM densities match the IRIS PREM table at 21 of 21 test points.
• Our PREM Earth weighs 5.97318 × 10²⁴ kg; NASA lists 5.9722 × 10²⁴ kg (ratio 1.00016).
• On the textbook Earth, the step-by-step run equals the exact formula, π√(R/g): 42 min 10.4 s.
• A constant-gravity run gives 37 min 58.2 s; Klotz gives 38 min 0 s. With g = 9.81 m/s² instead of our 9.82, the same formula gives 37 min 59.4 s.
• You stop 0.000 km from the far surface in both models: no energy is lost or gained.

The results: two Earths

Our model. Times are from the moment you jump. Speeds in mph, from our run; the crust here is PREM's global average, 24.4 km.

Our model: the real Earth gets you through 3 min 59.8 s faster (9.5%), with a top speed of about 22,200 mph instead of 17,700.

• Why the real Earth is faster. Most of Earth's mass is packed into its dense core: rock near the center is about 13 tonnes per cubic meter (PREM: 13.09 g/cm³), against 2.6–2.9 in the crust. At the top of the core the density jumps from 5.57 g/cm³ (mantle) to 9.90 g/cm³ (core). So as you fall, gravity first gets stronger.
• Peak gravity: 1.088 g (10.689 m/s²) at the top of the core, 2,891 km down, in our model. Klotz: gravity rises below the surface, “reaching a maximum of about 1.09 g”. Then it drops to zero at the center.
• We agree with the peer-reviewed number. Klotz (2015): “PREM: 38 minutes 11 seconds; constant gravity: 38 minutes 0 seconds; uniform density: 42 minutes 12 seconds.” Our runs: 38 min 10.7 s and 42 min 10.4 s (with his g = 9.81, the textbook formula gives 42 min 11.7 s).
• The textbook fall is half an orbit. Klotz: “The period of oscillation and the peak velocity are the same for a circular orbit at Earth's surface.” A ground-skimming orbit takes 84 min 21 s (our math), so the fall through is half of that.
• For scale: the space station moves at 17,500 mph (NASA). On the textbook Earth you pass the center about as fast; on the real Earth, faster.

Bonus: New York to Los Angeles, no engine

A straight tunnel between the two cities (3,873 km long, 302 km down at its deepest) takes 42 min 10.4 s on the textbook Earth and 41 min 50.6 s on the real one, topping out near 5,400–5,500 mph (our model). Klotz: “42 minutes for short trips and 38 minutes for long trips”.

Heat and pressure on the way down

Our model (pressure). Our tunnel ignores heat; these are the conditions the tunnel walls would face.

• A real-world check: lab experiments reported by the ESRF (2013) put the inner-core boundary at “330 GPa (3.3 million atmospheres)”, within 0.3% of our 329.1 GPa.
• The heat: the same study estimates “around 5500 K at the inner core boundary”, about 9,440 °F (our conversion). The Sun's surface is about 5,772 K, about 9,930 °F (NASA). So near the center it's nearly as hot as the surface of the Sun.

The deepest hole ever dug, to scale

• The Kola Superdeep Borehole, Russia: 12,262 m (40,230 ft), about 7.6 miles straight down. Drilling started in May 1970. The hole is only about 9 inches (23 cm) wide.
• Why it stopped: at the bottom it was about 180 °C, over 350 °F (356 °F), about twice the roughly 100 °C (212 °F) the drillers expected. Drilling stopped in 1992; after the Soviet Union collapsed, the money ran out too.
• Still the deepest hole straight down. Some curved oil wells are longer, but none goes deeper below the surface.
• And no, nobody recorded screams down there: Skeptoid traced that clip and calls it a hoax.

Our math. Kola's 12.262 km divided by Earth's 6,371 km radius (NASA) is 0.19%.

Kola is about 0.2% of the way to the center (0.1% of the way through). The full trip is about 7,918 miles (USGS).

• On a 12-inch globe, Kola would be 0.3 mm deep (our math).
• At Kola's average pace over its roughly two decades of drilling, digging to the center would take about 10,000 years, and all the way through about 20,000. Our estimate: a straight-line extrapolation. Real drilling slows down with depth, so this is a floor, not a forecast.

Where you'd come out

Our calculation · Natural Earth data. The point straight through the center, the antipode, is at the same latitude in the other hemisphere and 180° of longitude away (USGS). We tested each point against Natural Earth's 1:10m country outlines (public domain). “Nearest land” is the nearest outline point, so it slightly over-estimates the distance. City coordinates are approximate city centers.

• All 10 big cities in the lower 48 come out in open ocean, hundreds of miles from land. The USGS says the same: “For the continental United States and Alaska, the antipode location will be somewhere in the Indian Ocean.”
• The “remote French islands” are the French Southern and Antarctic Lands: small islands in the southern Indian Ocean, including Amsterdam, Saint-Paul, Kerguelen and Crozet. Denver's nearest is in the Île Saint-Paul and Île Amsterdam group.
• Hawaii is the exception: USGS: “you will end up in Botswana, a country in Africa with no active volcanoes.” Our Honolulu point agrees.
• So can you dig a hole to China? Not from any US city we checked. China's other side is southern South America: from Beijing you'd come out in Argentina. Big Think's Frank Jacobs: “There's almost no overlap in North America”. The ocean covers about 71% of Earth's surface (NOAA), so most tunnels end in water.

Left out on purpose. Our script flags any landing point within about 50 km of a coast or border. We only list points we're sure of; the rest stay off this page until we've checked them on a map.

Download our model's output

Plain-text files from the runs above. Open the CSVs in any spreadsheet.

• Fall summary (.csv, 3 KB): time, speed and gravity at each depth, for the textbook Earth, the real Earth and the constant-gravity check, plus the New York to LA tunnel.
• Full fall trace (.csv, 46 KB): depth, speed and gravity every 5 seconds of the fall, all three models.
• Pressure by layer (.csv, 1 KB): our PREM pressure from the surface to the center.
• Dig scale (.csv, 1 KB): each depth as a share of the radius, on the football field and on a 12-inch globe, plus the Kola-pace estimate.
• Antipodes (.csv, 2 KB): the 14 start points above, where each comes out and the nearest land.
• The fall model's run log (.txt, 8 KB): the script's own printout, with the self-checks.

Edited for the web. In the run log we removed our internal source-row tags and one place name; the numbers are unchanged. The antipode file has only the rows on this page.

Images in the video

• Earth: NASA Earth Observatory (Blue Marble Next Generation); clouds: NASA Goddard
• Inside the Earth: U.S. Geological Survey, This Dynamic Earth
• Map data: Natural Earth

Everything else, including the tunnel, the drill rig and the to-scale graphics, is drawn in code by Hourwiz.

Sources

Every fact on this page comes from these pages, opened on Oct 15, 2026. Things change: check the live page before you rely on it.

1. A. R. Klotz, “The Gravity Tunnel in a Non-Uniform Earth”, Am. J. Phys. 83, 231 (2015) Fall times, 1.09 g, orbit match, spin effect. Full text: ar5iv
2. NASA NSSDC, Earth fact sheet Radius 6,371 km, GM, mass, mean density.
3. NASA NSSDC, Sun fact sheet Effective temperature 5,772 K.
4. IRIS EMC, PREM (Dziewonski & Anderson, 1981) The layered Earth model.
5. PREM_1s table (CDS mirror of the IRIS file) Layer depths and densities; our 21-point check.
6. NIST CODATA 2022, Newtonian constant of gravitation
7. NIST, standard atmosphere 1 atm = 101,325 Pa.
8. NIST, unit conversions Exact foot and mile.
9. NASA, what is microgravity? (grades 5–8) Free fall; the station's 17,500 mph.
10. ESRF, “The Earth's centre is 1000 degrees hotter than previously thought” (2013) 330 GPa and about 5,500 K at the inner-core boundary.
11. USGS, This Dynamic Earth: inside the Earth Crust about 5 km under oceans, about 30 km under continents.
12. EarthDate, Kola Superdeep 40,230 ft (7.62 mi), May 1970, 9 inches wide, 180 °C vs 100 °C expected.
13. BBC Future, “The deepest hole we have ever dug” (May 6, 2019) Stopped in 1992; the heat; no money after the Soviet collapse.
14. Guinness World Records, deepest penetration into the Earth's crust
15. Wikipedia, Kola Superdeep Borehole Longer curved wells; still the deepest below the surface.
16. Skeptoid #307, Brian Dunning (Apr 24, 2012) The recording is a hoax.
17. Guinness World Records, deepest mine Nearly 4 km down.
18. NOAA Ocean Service, ocean depth Challenger Deep about 10,935 m (35,876 ft).
19. NFL rulebook (2024) 100 yards goal line to goal line.
20. USGS Yellowstone Volcano Observatory, volcanism on the other side of the world (Mar 30, 2026) Antipodes; 12,742 km (7,918 mi); US in the Indian Ocean; Hawaii to Botswana.
21. Big Think, Frank Jacobs, Strange Maps on antipodes (Jul 23, 2010) Almost no overlap in North America; China and South America.
22. Atlas Obscura, Frank Jacobs, on tunnels through the Earth (Apr 19, 2024)
23. NOAA Ocean Service, sea surface temperature facts The ocean covers 71% of Earth's surface.
24. Natural Earth, terms of use Public domain. Data: natural-earth-vector

Our model is a thought experiment: a frictionless tunnel with no air, no heat and no spin, rounded as shown. NASA, USGS, NOAA, ESRF and the authors cited didn't make, review or endorse this page or the video.

No sponsor and no affiliate links on this page. Vendors are named so you can check them yourself, not as recommendations.

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