These are the world’s longest straight lines

Researchers use algorithms to find the longest straight-line distances on land and at sea

These are the world’s longest straight lines
Image: Chabukswar & Mukherjee
  • What links a small town in Portugal and a huge port city in China?
  • The answer may surprise even inhabitants of both places: the world's longest straight line over land
  • That line and its maritime equivalent were determined not by exploration but by calculation

What connects the Chinese port of Quanzhou with Sagres, a tiny parish in southern Portugal? No, it's not the New Silk Route, the Sino-European rail link inaugurated in 2017 (1). The answer is so arcane that it will surprise most inhabitants of either place: they are the extreme points of the world's longest straight line over land (2).

Following the course of that line would require directional rectitude of the highest degree. Travellers would have to forgo the relative comfort of well-worn roads and mountain passes and traverse daunting peaks and inhospitable deserts – not to mention innumerable private houses and public buildings.

Suggested route

Longest sailable straight line on Earth, as suggested by Reddit user kepleronlyknows.

Image: Reddit

They would cross 15 countries; skirting Madrid and Switzerland's alpine highlands; cutting off a corner of Austria and passing just north of Auschwitz in Poland; barely touching Ukraine and slicing through Belarus; travelling through Russia and Kazakhstan before hitting China and reaching the Formosa Strait; but not before dipping into Mongolia twice.

Because the globe is round and this map is not, the world's longest straight line over land – like all others long enough – looks like a bendy one on this image. For anyone walking the line, though, it would have been straight as a ruler, and, at the end of that trip, close to 20,000 miles long.

Threading the needle

Algorithmically correct: the world's longest sailable straight line goes from Pakistan to Kamchatka

Image: Chabukswar & Mukherjee

The world's longest straight line on land was calculated by researchers Rohan Chabukswar of the United Technologies Research Centre (UTRC) in Cork (Ireland) and Kushal Mukherjee at IBM's Research Laboratory in New Delhi (India).
In a paper published earlier this year (and last updated on 25 December), they set out their solution to the question of finding the world's longest straight lines over land and at sea. That question sounds simple enough, but isn't: "This is an optimisation problem, rendered chaotic by the presence of islands and lakes, and indeed the fractal nature of the coasts".

They were prompted by a map that had raised a lot of discussion since its first publication on Reddit in 2012. Posted by user kepleronlyknows, it purports to show the longest possible straight-line sailing route in the world: from Pakistan to Kamchatka, threading the needle twice – through the Mozambique Strait separating Madagascar from the African mainland, and via the Drake Passage between South America and Antarctica.

Walk this way

A long walk indeed, but a straight one: Portugal to China

Image: Chabukswar & Mukherjee

Commenters have since sought to prove or disprove the longest straight-line sea route, and the analogous route over land. Suggested but disproved longer routes include two nautical ones: from Norway to Antarctica – a valid route, but not in fact as long as the Pakistan to Kamchatka one; and from Québec to British Columbia, which turns out not to be a perfectly straight line.

One suggested longer overland route leads from from Wenling in China to Greenville in Liberia. But this line crosses the Dead Sea and if, as the authors say, that qualifies as a 'major body of water', it disqualifies the route as being entirely over land.

European leg

Strangely enough, the direction from Portugal to China is due northeast

Image: Google Earth

So Messrs. Chabukswar and Mukherjee decided to put the issue through a scientific wrangler. Instead of conducting an exhaustive search of all possible routes – more than 233 million great circles (3), as the authors suggest - they calculated the two paths using a so-called branch-and-bound algorithm.

They found that the original poster on Reddit was right: the longest sailable straight-line path does connect Pakistan to Kamchatka. To be precise, it links Sonmiani (25°17′ N, 66°40′ E), a coastal town (4) approximately 90 miles (145 km) northwest of Karachi, with an unnamed location in the Karaginsky District (58°37′ N, 162°14′ E), a virtually uninhabited part in the north of the Kamchatka peninsula. The path is almost 20,000 miles long (to be precise: 19,939.8 miles, or 32,090 km).

Asian leg

Steppe by steppe...

Image: Google Earth

The same algorithm was let loose on the dry-land variety of the straight-line question. Here, the answer links a point near Sagres (37°2′ N 8°55′ W) to a point in the south of the greater Quanzhou metro area (24◦33′ N, 118◦38′ E). The distance covered is much smaller than the longest straight line at sea: just short of 7,000 miles (6,984.8 miles, or 11,241 km).

The researchers formulate a few theoretical caveats to their result, and one practical one: "The problem was approached as a purely mathematical exercise. The authors do not recommend sailing or driving along the found paths".

There is hope, however, for whoever had their heart set on long straight-line travels. Here are a few of the world's longest straight-line roads (5):

1. Highway 10 (Saudi Arabia): 159 miles (256 km)

There is little remarkable about either Haradh or Al Batha, two dusty towns in Saudi Arabia's Rub-al-Khali desert, or the featureless distance between them. Except that almost that entire stretch is traversed by a dead-straight road. Leaving the oil town of Haradh in the interior of the country, Saudi Highway 10 heads due east in a curveless line for 159 miles (256 km), bending slightly before entering Al Batha, near the Gulf coast and the Saudi border with the United Arab Emirates. That makes Highway 10 the longest straight stretch of road in the world.

2. US-54 (United States): 108 miles (173 km)

In its entirety, US Route 54 runs from Griggsville, Illinois to El Paso, Texas, covering 1,197 miles (2,115 km). For 108 miles, from Liberal, Kansas to Dalhart, Texas, US-54 runs in a virtually straight line (passing through Oklahoma as well). There are a few slight kinks in over the course of 54's 'straight' trajectory, though.

3. Eyre Highway, Australia (90 miles, 145.6 km)

The entire Eyre Highway is 1,030 miles (1,660 km) long, linking Norseman in Western Australia to Port Augusta in South Australia across the deserted Nullarbor Plain. It is part of Highway 1 that connects Perth to Adelaide, and the only 'sealed' road between both states. Between Balladonia and Caiguna, the road is completely straight for 90 miles – the longest stretch of straight road in Australia, commonly known as '90 Mile Straight'.

Longest Straight Line Paths on Water or Land on the Earth, the paper by Rohan Chabukswar and Kushal Mukherjee, can be accessed here at

Strange Maps #954

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(1) A 7,500-mile (12,000-km) China Railway cargo service from Yiwu, calling on Hamburg, London and Madrid. The service could become part of China's wider Belt and Road Initiative: a massive infrastructure project connecting Chinese manufacturing to its markets in Europe and elsewhere.

(2) Perhaps the 1,000-odd inhabitants of Sagres, the westernmost point on the European road network, will be less surprised. Sagres also is a terminus of the longest (non-straight) driveable distance between two points on earth. The other one is Khasan, a Russian city on the North Korean border, and the eastern terminus of that country's road network. The route connecting both places is 8,726 miles (14,043 km) long.

(3) A great circle or orthodrome is the largest circle that can be drawn on a spherical object.

(4) Sonmiani is also notable as the northernmost point of the Arabian Sea, a seaside resort for Karachiites and a launch site for the Pakistani space agency.

(5) Most so-called straight roads have slight curves, hence the many differing lists.

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Are we really addicted to technology?

Fear that new technologies are addictive isn't a modern phenomenon.

Credit: Rodion Kutsaev via Unsplash
Technology & Innovation

This article was originally published on our sister site, Freethink, which has partnered with the Build for Tomorrow podcast to go inside new episodes each month. Subscribe here to learn more about the crazy, curious things from history that shaped us, and how we can shape the future.

In many ways, technology has made our lives better. Through smartphones, apps, and social media platforms we can now work more efficiently and connect in ways that would have been unimaginable just decades ago.

But as we've grown to rely on technology for a lot of our professional and personal needs, most of us are asking tough questions about the role technology plays in our own lives. Are we becoming too dependent on technology to the point that it's actually harming us?

In the latest episode of Build for Tomorrow, host and Entrepreneur Editor-in-Chief Jason Feifer takes on the thorny question: is technology addictive?

Popularizing medical language

What makes something addictive rather than just engaging? It's a meaningful distinction because if technology is addictive, the next question could be: are the creators of popular digital technologies, like smartphones and social media apps, intentionally creating things that are addictive? If so, should they be held responsible?

To answer those questions, we've first got to agree on a definition of "addiction." As it turns out, that's not quite as easy as it sounds.

If we don't have a good definition of what we're talking about, then we can't properly help people.


"Over the past few decades, a lot of effort has gone into destigmatizing conversations about mental health, which of course is a very good thing," Feifer explains. It also means that medical language has entered into our vernacular —we're now more comfortable using clinical words outside of a specific diagnosis.

"We've all got that one friend who says, 'Oh, I'm a little bit OCD' or that friend who says, 'Oh, this is my big PTSD moment,'" Liam Satchell, a lecturer in psychology at the University of Winchester and guest on the podcast, says. He's concerned about how the word "addiction" gets tossed around by people with no background in mental health. An increased concern surrounding "tech addiction" isn't actually being driven by concern among psychiatric professionals, he says.

"These sorts of concerns about things like internet use or social media use haven't come from the psychiatric community as much," Satchell says. "They've come from people who are interested in technology first."

The casual use of medical language can lead to confusion about what is actually a mental health concern. We need a reliable standard for recognizing, discussing, and ultimately treating psychological conditions.

"If we don't have a good definition of what we're talking about, then we can't properly help people," Satchell says. That's why, according to Satchell, the psychiatric definition of addiction being based around experiencing distress or significant family, social, or occupational disruption needs to be included in any definition of addiction we may use.

Too much reading causes... heat rashes?

But as Feifer points out in his podcast, both popularizing medical language and the fear that new technologies are addictive aren't totally modern phenomena.

Take, for instance, the concept of "reading mania."

In the 18th Century, an author named J. G. Heinzmann claimed that people who read too many novels could experience something called "reading mania." This condition, Heinzmann explained, could cause many symptoms, including: "weakening of the eyes, heat rashes, gout, arthritis, hemorrhoids, asthma, apoplexy, pulmonary disease, indigestion, blocking of the bowels, nervous disorder, migraines, epilepsy, hypochondria, and melancholy."

"That is all very specific! But really, even the term 'reading mania' is medical," Feifer says.

"Manic episodes are not a joke, folks. But this didn't stop people a century later from applying the same term to wristwatches."

Indeed, an 1889 piece in the Newcastle Weekly Courant declared: "The watch mania, as it is called, is certainly excessive; indeed it becomes rabid."

Similar concerns have echoed throughout history about the radio, telephone, TV, and video games.

"It may sound comical in our modern context, but back then, when those new technologies were the latest distraction, they were probably really engaging. People spent too much time doing them," Feifer says. "And what can we say about that now, having seen it play out over and over and over again? We can say it's common. It's a common behavior. Doesn't mean it's the healthiest one. It's just not a medical problem."

Few today would argue that novels are in-and-of-themselves addictive — regardless of how voraciously you may have consumed your last favorite novel. So, what happened? Were these things ever addictive — and if not, what was happening in these moments of concern?

People are complicated, our relationship with new technology is complicated, and addiction is complicated — and our efforts to simplify very complex things, and make generalizations across broad portions of the population, can lead to real harm.


There's a risk of pathologizing normal behavior, says Joel Billieux, professor of clinical psychology and psychological assessment at the University of Lausanne in Switzerland, and guest on the podcast. He's on a mission to understand how we can suss out what is truly addictive behavior versus what is normal behavior that we're calling addictive.

For Billieux and other professionals, this isn't just a rhetorical game. He uses the example of gaming addiction, which has come under increased scrutiny over the past half-decade. The language used around the subject of gaming addiction will determine how behaviors of potential patients are analyzed — and ultimately what treatment is recommended.

"For a lot of people you can realize that the gaming is actually a coping (mechanism for) social anxiety or trauma or depression," says Billieux.

"Those cases, of course, you will not necessarily target gaming per se. You will target what caused depression. And then as a result, If you succeed, gaming will diminish."

In some instances, a person might legitimately be addicted to gaming or technology, and require the corresponding treatment — but that treatment might be the wrong answer for another person.

"None of this is to discount that for some people, technology is a factor in a mental health problem," says Feifer.

"I am also not discounting that individual people can use technology such as smartphones or social media to a degree where it has a genuine negative impact on their lives. But the point here to understand is that people are complicated, our relationship with new technology is complicated, and addiction is complicated — and our efforts to simplify very complex things, and make generalizations across broad portions of the population, can lead to real harm."

Behavioral addiction is a notoriously complex thing for professionals to diagnose — even more so since the latest edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), the book professionals use to classify mental disorders, introduced a new idea about addiction in 2013.

"The DSM-5 grouped substance addiction with gambling addiction — this is the first time that substance addiction was directly categorized with any kind of behavioral addiction," Feifer says.

"And then, the DSM-5 went a tiny bit further — and proposed that other potentially addictive behaviors require further study."

This might not sound like that big of a deal to laypeople, but its effect was massive in medicine.

"Researchers started launching studies — not to see if a behavior like social media use can be addictive, but rather, to start with the assumption that social media use is addictive, and then to see how many people have the addiction," says Feifer.

Learned helplessness

The assumption that a lot of us are addicted to technology may itself be harming us by undermining our autonomy and belief that we have agency to create change in our own lives. That's what Nir Eyal, author of the books Hooked and Indistractable, calls 'learned helplessness.'

"The price of living in a world with so many good things in it is that sometimes we have to learn these new skills, these new behaviors to moderate our use," Eyal says. "One surefire way to not do anything is to believe you are powerless. That's what learned helplessness is all about."

So if it's not an addiction that most of us are experiencing when we check our phones 90 times a day or are wondering about what our followers are saying on Twitter — then what is it?

"A choice, a willful choice, and perhaps some people would not agree or would criticize your choices. But I think we cannot consider that as something that is pathological in the clinical sense," says Billieux.

Of course, for some people technology can be addictive.

"If something is genuinely interfering with your social or occupational life, and you have no ability to control it, then please seek help," says Feifer.

But for the vast majority of people, thinking about our use of technology as a choice — albeit not always a healthy one — can be the first step to overcoming unwanted habits.

For more, be sure to check out the Build for Tomorrow episode here.

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According to the latest version of the Inglehart-Welzel World Cultural Map, Belgium and the United States are now each other's closest neighbors in terms of cultural values.

Credit: World Values Survey, public domain.
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