Five years ago, a user on the r/MapPorn subreddit posted a map that allegedly illustrates the longest straight path on Earth without hitting land. The route begins in southern Pakistan and ends at northeastern Russia.

Now, two researchers have finally proven if that route is indeed the longest straight path on Earth.

The Longest Straight Path On Sea

The original post sparked huge debates online, with the bulk of naysayers wanting to be sure that it was truly the longest path available without encountering land. At the same time, a similar question arose for land — what was the longest straight path without hitting water?

Thanks to Rohan Chabukswar of the United Technologies Research Center in Ireland, and Kushal Mukherjee of IBM Research in India, we finally have an answer. They have successfully developed an algorithm that calculates the longest straight route on land and on sea.

Traveling Straight

The most obvious solution is to calculate every possible straight line that runs around the planet, but that would take a very long time considering there are more than 5 trillion points to consider. So, Chabukswar and Mukherjee found a better way. They created an algorithm that uses a technique called branch and bound, which works by treating possible solutions as branches on a tree.

Rather than going through every possible solution, the algorithm checks one branch after another. This technique, known as branching, is essentially similar to brute-forcing all possible solutions, but the second part of the technique, called bounding, makes the task easier.

Under each branch is a subset of possible solutions, out of which comes the most optimal one. The algorithm tries to pick out a property of the subsets that depends on how close the other solutions are to the optimal one. This goes on until all branches are tested, and then we end up with the optimal solution.

As it turns out, the original post on Reddit was right on the money.

"This path is visually the same one as found by kepleronlyknows, thus proving his assertion," said Chabukswar and Mukherjee.

"[T]he path [originates] in Sonmiani, Las Bela, Balochistan, Pakistan, threading the needle between Africa and Madagascar, between Antarctica and Tierra del Fuego in South America, and ending in Karaginsky District, Kamchatka Krai, Russia." It spans 32,089.7 kilometers — or about 19,940 miles.

Meanwhile, the longest path on land stars in Jinjiang, Fujian, in China, and ends at Portugal. The route, at 11,241.1 kilometers long — or about 6,985 miles — passes through 15 countries.

"[T]he path [originates] near Jinjiang, Quanzhou, Fujian, China, weaving through China and Mongolia for a bit, passing though Kazakhstan and Russia to further weave through Belarus and Ukraine, and passing through Poland, Czech Republic, Germany, Austria, Liechtenstein, Switzerland, France, and Spain, to end near Sagres, Portugal, traversing a total of 15 countries."

Travelers, you know what to do.