Nature
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# These Are The Longest Straight Lines You Can Sail And Drive On Earth

What’s the longest straight line you can drive or sail on Earth? It sounds like a weird question, and it is. But thankfully, someone has worked out the answer. Thank god!

In a paper published on arXiv, researchers Rohan Chabukswar and Kushal Mukherjee from United Technologies Research Center in Ireland and IBM Research India attempted to work this out. They also took a look at the longest distance you can sail in a straight line, too.

They were inspired by a Reddit post in 2012, when user kepleronlyknows showed that the longest straight line on Earth that could be sailed – without hitting land – went from Pakistan to eastern Russia. As Earth is a sphere the line appears curved, like an orbit.

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Coming to a scientific conclusion on this, however, was a bit tricky. They note that both islands and lakes make calculating either longest line difficult, as does the sheer number of possible routes.

At first they considered using trial and error to find an answer, looking at each possible “great circle”. These are the possible routes that can be taken with, for example, the equator being a great circle. The only problem is, well, there were 233 million circles each 1.8 kilometers (1.1 miles) wide.

So instead they settled on an algorithm, called a branch-and-bound algorithm, to find solutions. This looked at subsets of circles, and then narrowed them down to find the best one, with the result turning up in a mere 10 minutes, notes Science Magazine.

And the result? Well, the straightest line you can sail on Earth is indeed from Pakistan to Russia, as the Reddit post suggested. Starting in Balochistan, Pakistan, and “threading the needle” between Africa and Madagascar, and Antarctica and South America, you end up in Kamchatka Krai, Russia – a total of 32,089.7 kilometers (19,939.6 miles).

The longest drivable route is quite a bit shorter, coming in at 11,241.1 kilometers (6,984.9 miles). It runs from Quanzhou in China through Mongolia, Russia, and Europe, and ends near Sagres, Portugal. It incorporates a total of 15 countries.

Of course, available roads might make this a bit tricky, but as the crow flies it’s dead straight. You could probably drive it non-stop in almost a week, while walking non-stop would take you a good three months.

So, there you have it. If you want to sail in a really long straight line, then Pakistan to Russia is probably your best bet. And if you want to drive in a straight line, well, there’s a route for you to try and follow.

“The problem was approached as a purely mathematical exercise,” the researchers noted in their paper. “The authors do not recommend sailing or driving along the found paths.”

[H/T: Science Magazine]

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• sail,

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• drive,

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