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.