The Archives
385 enduring inquiries, newest first. Browse by topic or explore chronologically.
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history6 min readHow Did Ancient China Build Its 1,800 km Grand Canal?
In five years, Sui China dug about 1,800 km of canals linking the Yangtze to the north. Here is how Emperor Yang's engineers actually built the Grand Canal.
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history8 min readHow Did Constantinople Store Water for a Million People?
At its peak Constantinople held about 500,000 people, served by the ancient world's longest aqueduct and the 80,000-cubic-metre Basilica Cistern.
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history7 min readHow Did Egyptians Drill Through Granite Without Steel?
The Egyptians drilled granite with hollow copper tubes and quartz sand, never steel. Here is how tubular drills and bow drills cut stone with abrasive grit.
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science7 min readHow Do Waterspouts Form and Why Do They Appear Over Water?
A waterspout is a spinning funnel of sea mist that grows from the sea surface upward, not downward. Here is how both types form and how they differ.
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history8 min readHow Egyptians Aimed the Great Pyramid at True North
The Great Pyramid faces true north within four arcminutes. A 2017 test showed an equinox shadow could do it — but a two-star method also dates the work.
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history8 min readHow the Maya Built Tikal's Pyramids Without Metal Tools
Tikal's Temple IV rose 65 metres without metal tools, the wheel or draft animals. The secret was limestone, burnt-lime mortar and corbelled vaults.
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geography7 min readWhat Is the Deepest Canyon on Earth? Yarlung Tsangpo
The Yarlung Tsangpo Grand Canyon in Tibet plunges up to 6,009 meters, the deepest canyon on land at three times the Grand Canyon. Why the number is disputed.
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geography8 min readWhat Is the Flattest Place on Earth? Salar de Uyuni
Salar de Uyuni in Bolivia varies less than one meter across 10,582 square kilometers: the flattest place on Earth, and a calibration target for satellites.
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geography7 min readWhat Is the Lowest Capital City on Earth? Baku, Azerbaijan
Baku, Azerbaijan sits 28 meters below sea level: the lowest capital city on Earth. Why the Caspian Sea sits so low, and what life is like there.
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geography7 min readWhat Is the Oldest Desert on Earth? It's the Namib
What is the oldest desert on Earth? The Namib of Namibia has been arid for 55 to 80 million years, at least eight times older than the Sahara.
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geography7 min readWhat Is the Saltiest Lake on Earth? It's Don Juan Pond
What is the saltiest lake on Earth? Don Juan Pond in Antarctica stays liquid at -50°C (-58°F) at over 40 percent salinity, saltier than the Dead Sea.
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geography8 min readWhat Is the Windiest Place on Earth? It's Cape Denison
What is the windiest place on Earth? Cape Denison, Antarctica, where katabatic winds average 71 km/h and once blew 143 km/h for 12 hours straight.
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science7 min readWhat Is a Brocken Spectre, the Giant Mountain Shadow?
What is a Brocken spectre? Your own shadow cast huge onto mountain fog, ringed by a rainbow glory. The physics and history of the giant mountain shadow.
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science6 min readWhat Is a Fog Bow, the White Rainbow With No Colors?
What is a fog bow? Fog droplets about 100 times smaller than raindrops smear sunlight into a white arc. The science of the white rainbow, and how to spot one.
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science6 min readWhat Is Virga, the Rain That Never Reaches the Ground?
What is virga? Precipitation that evaporates mid-air, fools weather radar and can precede microbursts. The science of the rain that never reaches the ground.
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geography7 min readWhy Do San Marino and Vatican City Survive Inside Italy?
Why are San Marino and Vatican City independent countries inside Italy? One survived 1,700 years of diplomacy; the other was born from a 1929 treaty.
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geography7 min readWhy Does Alaska Belong to America Instead of Canada?
Russia sold Alaska to America in 1867, but why is Alaska part of the United States instead of Canada? The answer involves a feared war with Britain.
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geography6 min readWhy Is Gibraltar Still British and Not Part of Spain?
Why is Gibraltar British when it sits on Spain's southern coast? A 1704 capture, the 1713 Treaty of Utrecht, and two referendums fully explain it.
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geography6 min readFrance's 730 km Border With Brazil: The Full Story
Why does France share a border with Brazil? Because French Guiana is part of France, its 730 km Amazon border is France's longest land border.
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geography7 min readWhy India and Bangladesh Traded 162 Enclaves in 2015
Why did India and Bangladesh swap enclaves? In 2015 they traded 162 enclaves at midnight, ending nearly 68 years of statelessness for about 51,000 people.
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geography8 min readWhy the Korean DMZ Is Earth's Most Fortified Border
Why is the Korean DMZ the most fortified border? It holds 2 million landmines and up to two million troops across a 250 km buffer drawn by the 1953 armistice.
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science5 min readWhat Are Mammatus Clouds, and Why Do They Hang From Storms?
Mammatus clouds are pouch-like lobes hanging from a storm's underside, made by sinking air. What they mean, how they form, and why they don't signal a tornado.
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science6 min readWhat Is a Circumhorizontal Arc, the So-Called Fire Rainbow?
A circumhorizontal arc is a band of spectral color made by ice crystals in high cirrus, not rain — and it only appears when the sun climbs past 58 degrees.
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geography6 min readWhat Is the Highest Capital City on Earth? La Paz, Bolivia
La Paz, Bolivia sits at 3,640 meters (11,942 feet), the highest capital city in the world. Why Bolivia has two capitals, and how the thin air shapes daily life.
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