Five years ago, Redditor kepleronlyknows posted a thread on MapPorn revealing the longest straight-line water route on Earth. According to his investigation, the longest uninterrupted path that traverses our planet is a 20,000-mile boat ride connecting Pakistan to the Kamchatka Peninsula in Russia.
The Reddit user, an environmental law attorney from Georgia named Patrick Anderson, followed up with a YouTube video that traces the sailing journey in Google Earth, which you can watch below.
Anderson confessed he didn’t discover the ocean path but merely charted it on the map using coordinates he found on Wikipedia in an entry titled “Extreme points of Earth;” two scientists thought this was a neat discovery.
Physicist Rohan Chabukswar from the United Technologies Research Center Ireland in Cork City, Ireland, and engineer Kushal Mukherjee from IBM Research India in New Delhi set out to find if the route proposed by Anderson was correct.
It turns out the Redditor was entirely right. The two scientists did the math and confirmed Anderson’s claim in a paper published last week on the preprint server arXiv.
According to Science Magazine, the pair turned to data from the ETOPO1 Global Relief model of Earth’s surface constructed in 2008 by the National Oceanic and Atmospheric Administration. Then, the scientists applied an optimization algorithm known as “branch and bound” to calculate the longest straight-line path over the ocean.
As any cartographer will tell you, all straight-line paths along the globe follow a feature known as a great circle — an arc along one of the many largest imaginary circles that can be drawn around a sphere, MIT Technology Review explains. One such example is the Equator.
But the ETOPO1 Global Relief model is a global map with a 1.85-kilometer (around 1.14 miles) spatial resolution, which means it has more than 230 million possible great circles. Since each great circle in the model contains 21,600 points on either land or sea, this gives a total of five billion points to verify.
Chabukswar and Mukherjee’s algorithm significantly simplified the calculations and got the work done in 10 minutes. The results revealed that the longest straight-line journey by boat goes on for 32,089.7 kilometers (nearly 20,000 miles). The sailing route begins in Sonmiani, Pakistan, passes through the gap between Madagascar and continental Africa, continues between Antarctica and Tierra del Fuego in South America, and finally reaches north-northwest across the Pacific, eluding the Alaskan archipelago, until it comes to an end on the beaches of the Karaginsky District in Russian Kamchatka.
“This path is visually the same one as found by kepleronlyknows, thus proving his assertion,” the scientists said in a statement.
The pair also calculated the longest straight-line path on land uninterrupted by lakes or seas. Their algorithm needed 45 minutes to complete the calculations on a standard laptop and revealed the longest straight-line journey on land traverses more than 11,241.1 kilometers (almost 7,000 miles). The path goes across 15 countries, starting near Quanzhou in eastern China and waving through Mongolia, Kazakhstan, and Russia, until it finally reaches the town of Sagres in western Portugal.