Student Discovers How Long It Really Takes to Fall through the Eart

Zain Haidar
Published: March 30,2015




 
Uh oh, physics teachers. It might be time to rewrite your textbooks.
It's been taught for decades that it would take 42 minutes to fall through the Earth, assuming you had the resources to build a tunnel long enough and avoid incineration at the core.
Alexander Klotz, a graduate student at McGill University in Canada, has found that widely accepted number is off by nearly 4 minutes.
(MORE: Earth's Inner Core has its Own Inner Core) 
Klotz's calculation, published in the March issue of the American Journal of Physics (AJP), doesn't have massive implications for science, but it says something about the nature of common knowledge.
"This is the kind of paper we love," AJP editor David Jackson told Science Magazine.
The problem is brought up in intro physics classes because it helps students understand Newton's law of gravity, and as Science Magazine points out, it features a "common but very important type of cyclical motion."
On top of those valid reasons, we've all wondered about digging a tunnel through the Earth and jumping through to the other side.
Here's how Klotz cut the time down:
Normally the Earth-Tunnel-Fall assumes that the Earth has a uniform density throughout for the sake of simplicity. Because the Earth is composed of several different layers, however, density increases as you approach the core and lessens on the return trip, which affects how gravity acts on moving bodies.
Using the Preliminary Reference Earth Model, Klotz figured out how mass is distributed throughout the interior of the Earth, and with that number, arrived at a time of 38 minutes and 11 seconds for a complete subterranean trip.
So, if you're planning on a voyage through the Earth, prepare for some serious heat and a shorter journey.
MORE: Earth at Night