How Long Would It Take to Fall through a Tunnel from One Side of the Earth to the Other?

Let's say you could drill a hole through the Earth. Theoretically, how long would it take to jump into the hole, fall through the Earth, and come out the other side? This question has been a staple of introductory physics classes since the answer -- 42 minutes and 12 seconds -- was first calculated in 1966. In 2015, however, physicist Alexander Klotz of McGill University in Montreal came up with a slightly faster calculation.

In an article published in the March 2015 issue of the American Journal of Physics, Klotz made different assumptions about the effects of air resistance and gravitational pull in such a "gravity tunnel." He concluded that this mythical thrill ride would actually take 38 minutes and 11 seconds.

Of course, this mathematical quandary will never be settled with actual data. Drilling a hole through the Earth, which has a diameter of 7,918 miles (12,742 kilometers), would be an impossible task.

More about gravity tunnels:

  • Between 1970 and 1989, Soviet engineers dug the Kola Superdeep Borehole in an effort to penetrate the Earth's crust to the greatest possible depth. In those two decades, they drilled to a depth of 7.5 miles (12 kilometers), which is a mere 0.1% of the Earth's diameter.

  • Cartoon fans of a certain age will remember when Bugs Bunny dug such a hole and emerged in China. In fact, a hole dug from North America would end up in the Indian Ocean.

  • If you were able to dig a hole through the center of the Earth and jump in, by the time you got to the bottom, the Earth's gravitational pull would whip you back towards the start, slinging you back and forth like a pendulum.

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More Info: Physics Central

Discuss this Article

Post 4

Well, I submit that yes, you would start by being flung back and forth, but gradually that energy would abate and you would end up suspended, unmoving, in the center of the Earth.

Perhaps someone cleverer than I could calculate how quickly that would occur.

Post 3

@anon993472: Assuming gravity was where? The surface? You would have to believe that gravity was generated at the surface. Much rather the core would be much more a likely suspect and the ping pong effect. China would be nice, but gravity comes from within and it would be more of a "ping" and to much less of a "pong" as gravity does really rule the events of the day. Wile E Coyote, Genius

Post 2

Where can we find the calculations for this 38 minute answer?

Post 1

Well, if a hypothetical 'gravity tunnel,' such as is proposed in this scenario, were to "sling you back and forth like a pendulum" (which it, indeed, would), then the question of how long it would take to fall through the Earth becomes meaningless, making any physicist's calculations also meaningless.

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