What If You Dug a Hole Through the Earth and Jumped In?
The short answer
About 38 minutes. If the hole had no air in it, you'd fall all the way through and stop exactly at the far end, 38 minutes after you jumped. The space station needs about 46 minutes just to get halfway around the planet. Then you'd fall back.
Gravity speeds you up all the way to the middle, where you pass through at about 9.9 km a second (about 22,000 mph). That's roughly 30 percent faster than the space station flies. Past the middle, the same pull slows you down, and you stop at the far end with no speed left.
Why 38 minutes, not 42
Many people learned 42 minutes. That number assumes the Earth has the same density all the way through. It doesn't. The planet is denser in the middle than near the surface, so the pull stays strong as you fall. It even grows, from 9.82 m/s² at the surface to 10.69 m/s² at the top of the core, about 2,900 km down. Only inside the core does it fade, to zero at the exact center.
Klotz worked it out in 2015: 38 minutes 11 seconds on the real Earth, 42 minutes 12 seconds on a uniform one. Our own calculation, from a standard model of Earth's interior, gets the same 38 minutes 11 seconds.
Why the real trip would end early
With no air and no friction, you'd swing back and forth forever. Rubbing on the walls takes a little off every trip, so each swing is shorter, until you stop in the middle.
Real air ends it much sooner. You'd reach your top falling speed within seconds, and the air lower in the shaft gets squeezed so thick under its own weight that you can't fall through it. You'd get no deeper than about 175 km, nowhere near the middle.
Then there's the heat. Near the inner core it's about 6,000 °C. The Sun's surface is about 5,500 °C (9,930 °F). Walls that hot give off 25,000 to 50,000 times the heat of full sunlight, and an empty shaft doesn't stop it. A real apple wouldn't bake. It would turn to vapor.
And the Earth spins. Unless the hole ran from pole to pole, the spin would push you into the wall early in the fall.
Where you'd come out
The film's hole starts at the Kola Superdeep Borehole in Russia, at 69.4°N, 30.6°E. Straight through the Earth from there is 69.4°S, 149.4°W: open Southern Ocean about 4,400 m deep, roughly 790 km north of the coast of West Antarctica. Around Antarctica, sea ice is largest in September and smallest in late February or early March.
Key numbers
| What | Number | Source |
|---|---|---|
| Time to fall through the real Earth, with no air and no spin | 38 min 11 s | Klotz 2015 |
| The same fall if Earth had the same density all the way through | 42 min 12 s | Klotz 2015 |
| Half an orbit of the space station | about 46.5 min | Our arithmetic from CelesTrak ISS orbital elements, 2026 |
| Speed of the space station | 7.66 km/s (about 17,100 mph) | Our arithmetic from CelesTrak ISS orbital elements, 2026 |
| Your speed passing the center of the Earth | about 9.9 km/s (about 22,000 mph) | Our arithmetic from Dziewonski and Anderson 1981 |
| Gravity at the surface, and at its peak at the top of the core, about 2,900 km down | 9.82 m/s² at the surface, 10.69 m/s² at the peak | Our arithmetic from Dziewonski and Anderson 1981 |
| Temperature at the inner core boundary | about 6,000 °C (6,230 K, give or take 500 K) | Anzellini et al. 2013 |
| Temperature of the Sun's surface | about 5,500 °C (9,930 °F) | IAU 2015 Resolution B3 |
| Heat given off by walls at 5,000 to 6,000 K | 25,000 to 50,000 times full sunlight | Our arithmetic from Anzellini et al. 2013 |
| Depth past which real air in the shaft is too dense to fall through | about 175 km | Concannon and Giordano 2016 |
| Ocean depth at the far end of a hole from Kola, 69.4°S, 149.4°W | about 4,400 m | GEBCO 2020 |
| Antarctic sea ice: largest and smallest | largest in September, smallest in late February or early March | NOAA Climate.gov, Antarctic sea ice extent |
What the film simplifies
- The film's hole has no air in it. With real air, you'd get no deeper than about 175 km and never reach the middle.
- The apple comes out of the core baked and steaming. Walls that hot would really turn him to vapor, even in a shaft with no air.
- The film ignores Earth's spin. Kola isn't at a pole, so the spin would push the apple into the wall.
- The far end of a real hole is the seabed, about 4,400 m under the Southern Ocean. The film draws the shaft running up through the water so the apple can pop out at the sea ice.
- Rocket stands in for the space station. He flies at its speed, but his 46 minutes leaves out the climb to orbit and the trip back down.
- Gravity is drawn as a character having a picnic in the middle of the Earth. At the exact center, the pull from every side cancels out to zero, and that is where the apple ends up resting.
At a glance
Runtime 1 minute 3 seconds · Topics: Gravity, Earth's interior, Orbits · Captions on YouTube · Full script below
Test yourself
Why does the fall take about 38 minutes on the real Earth but 42 minutes on an Earth with the same density all the way through?
Answer
The real Earth is denser in the middle than near the surface, so gravity stays strong, and even grows, as you fall toward the core. You pick up speed sooner and finish the trip faster.
Where on the way down is the pull of gravity strongest, and where is it zero?
Answer
It is strongest at the top of the core, about 2,900 km down, at 10.69 m/s². It is zero at the exact center, where the pull from every side cancels out.
With no air and no friction, why does the apple stop exactly at the far end, not fly out of the hole?
Answer
Gravity speeds him up on the way to the middle and slows him by the same amount on the way out. So he rises to exactly the height he started from, with no speed left.
The script
Host: What if you dug a hole through the Earth and jumped in?
Rocket: Race you to the other side, Grandpa!
Host: Rocket flies around the planet as fast as the space station.
Host: The apple just falls.
Gravity: My apple! Come here!
Host: Gravity pulls him faster and faster
Host: and through the middle he goes faster than the space station!
Host: It's as hot as the surface of the Sun down there
Gravity: No! Come back!
Host: Now Gravity is pulling him back so he slows down
Host: and stops right at the other end
Host: 38 minutes
Rocket: 46 minutes! New record! Wait What
Host: An apple with no engine just beat a rocket
Host: With no air in the hole he'd fall back And forth Forever
Gravity: Hi! Bye! Hi! Bye!
Host: But every bump on the walls slows him a little more until he stops in the middle
Gravity: Mine!
Rocket: Best of three!
Gravity: Both mine!
Host: No air in the hole so nothing slows him down
Host: About 22,000 miles an hour
Host: In the sea ice off Antarctica
Sources
- A fall through the real Earth with no air takes 38 min 11 s; a uniform Earth gives 42 min 12 s.Klotz 2015
- With air in the tunnel a faller reaches top speed almost at once, and the squeezed air prohibits travel past about 175 km down; with friction on the walls the faller halts at the center; the paper repeats 38 min 11 s against 42 min 12 s.Concannon and Giordano 2016
- The density model of Earth's interior (PREM) behind our calculation of gravity inside the Earth and the speed at the center.Dziewonski and Anderson 1981
- The space station's orbit (elements of November 7, 2026): half an orbit takes about 46.5 min, at about 7.66 km/s.CelesTrak ISS orbital elements, 2026
- The space station circles Earth about every 90 minutes at about five miles per second.NASA Space Station Facts and Figures
- The temperature at the inner core boundary is about 6,230 K, give or take 500 K (about 6,000 °C).Anzellini et al. 2013
- The Sun's surface temperature is 5,772 K (about 5,500 °C).IAU 2015 Resolution B3
- Friction on the walls would shorten each swing until you stopped at the center.Science News Explores
- Earth's spin would soon push a falling object into the walls of the tunnel unless it ran from pole to pole.Alaska Science Forum, The Cannon Ball Express
- The ocean is about 4,400 m deep at 69.4°S, 149.4°W, the point straight through the Earth from Kola.GEBCO 2020
- Antarctic sea ice is largest in September and smallest in late February or early March.NOAA Climate.gov, Antarctic sea ice extent