if you want capture more than 55% of the world’s population in a circle With a radius of 4,000 km, which city would you place at the epicenter? That’s what Reddit user Ken Myers was asked in 2013. In a matter of days, he calculated that the Valeriepieris Circle (from the account name on the platform), a circular region on a two-dimensional map centered in the South China Sea and with a radius of about 4,000 km, contains more than half the world. population.

More people lived within this one-sixth of the world than outside. But this representation left another interesting question open: “Where is the smallest circle that can be drawn on our planet? at least half of the population Then, in 2015, Danny Quah of the London School of Economics analyzed the circle in more detail under its title. The smallest human community in the world.

Acknowledging that the Valeriepieris circle was not actually a circle (it was drawn on a two-dimensional map instead of a sphere) and was based on outdated data, cartographer Alasdair Rae researched and discovered what is now named after the cartographer Alasdair Rae. Yuxi Circle, the world’s most densely populated region. Rae surrounded nearly 1,500 cities around the world. Find out how many people live within a radius of 4,000 km, just like the original Valeriepieris circle. He based his calculations on WorldPop data from 2020.

Of the 1,500 flats calculated for Rae, 148 contained populations of 4 billion or more. He has found specimens in Asia, including China, Myanmar (Mandalay), Laos (Vientiane), Bangladesh (Chattogram), India (Agartala), Bhutan (Thimpu) and Vietnam (Hanoi). But above all, Yuxi, a city in China’s Yunnan province4,320 million: It has the largest population in a radius of 4,000 km.

That is, the circle covers more than 55% of the world’s population, although it includes desolate areas such as the Taklamakan desert, the Tibetan plateau, Mongolia, and southern Siberia. There is more than one Yuxi in China, but it is in Yunnan province on the map and has a population of around 2.5 million. Frankly, when you draw a simple 4,000 km buffer, you always get a lot of sea, so he tried to see what kind of ellipse he could draw around Yuxi, which still contains over half the world’s population.

Densely populated areas around the world

Rae’s search for densely populated groups also revealed remarkable circles beyond Asia. It surrounded cities such as Cairo, Paris, and Mexico City. Traveling around Hanoi yields a population of 4.27 billion (54% of the world’s population). There is a population of 2.29 billion people around Cairo. This circle reaches most of Europe and still includes populated parts of India, Pakistan and Africa.

comparatively, Wandering around Paris you get a population of 1,190 million. This Eurocentric circle includes large bodies of water and sparsely populated islands such as Iceland and Greenland.

Across the Atlantic, you get a population of 730 million as you wander around Mexico City. Because America’s total population is concentrated in only three countries, the USA, Mexico, and Brazil (not included in this circle), it is significantly smaller than in other circles.

note: Note that white lines on flat maps are equidistant circles, but will only appear as circles when drawn on a sphere.

Placing countries above others

After her research, Rae still wanted more. And he started thinking, “What if someone made a tool like True Size Of and then combined it with NASA’s SEDAC Population Estimation Service?” So it occurred to him to take the form of a country, superimpose in another part of the world and get the population in it. He made a small attempt with the lower 48 US states, moved south and geodesically scaled them, and then calculated the population in them while placing them above China and India.

It has also done this by horizontally inverting the United States, as its west coast fits quite well with China’s east coast.

Valeriepieris Circle

It is worth noting that the environment of Valeriepieris inspired other people to look at population density in different ways. In 2015, Danny Quah of the London School of Economics took a closer look at Valeriepieris’ surroundings and was inspired to find the smallest circle in which more people lived than outside. He determined that a circle with a radius of 3,300 km is centered. near Mong Khet, MyanmarIt was “the densest group of people in the world”.

He developed an algorithm to answer this question. With the help of Ken Teoh, a Wharton School student, he demonstrated that Ken Myers’ estimate was very similar to his own. Of course populations in different parts of our planet change over time, but using population data on Earth’s surface at 100 km resolution in 2015, the smallest circle of our planet The rim containing most of the world was the rim located near Mong Khet, Myanmar, with a great rim distance of 3300 km.

Maps: Alasdair Rae | Danny Quah | Ken Myers