The CN Tower was built with a helicopter lifting its antenna and was the world's tallest freestanding structure

science & techWikipedia1973–1976 · Toronto, Canada

The CN Tower was built with a helicopter lifting its antenna and was the world's tallest freestanding structure

the gist

The CN Tower began as a 1968 plan by Canadian National Railway for a broadcast platform, because skyscrapers were blocking signals and microwave links. Construction began in February 1973, and a slipform platform climbed the core at about 6 metres a day as concrete was poured. The tower became the world's tallest freestanding structure on 31 March 1975. A Sikorsky S-64 Skycrane helicopter lifted the antenna in 36 sections, saving months of construction time, and the tower opened on 26 June 1976.

how it works

A slipform is a platform on hydraulic jacks that climbs as concrete is poured and sets, so the core rises continuously. Plumb bobs hung from the platform allowed workers to check that the tower stayed vertical.

so what

The tower's height came from a practical problem: new buildings were blocking broadcast signals, so the solution was to rise above them. It also shows how a helicopter could replace a crane, and its engineering was done while the project's surrounding development was still being planned.

the bigger pattern

Tall towers were often built to solve communications problems, as Toronto's skyscrapers did. The same logic led other cities to build broadcast towers above their urban clutter.

fun fact

A stuntman named Dar Robinson jumped off the CN Tower in 1979 for a film scene.

Hampi was once one of the world's largest cities, until its Vijayanagara capital was destroyed in 1565

the gist

Hampi is a UNESCO World Heritage Site in Karnataka, India, with more than 1,600 surviving remains spread over 4,100 hectares. It was the capital of the Vijayanagara Empire from 1336 to 1565. Travellers from Persia and Portugal described it as a prosperous, wealthy and grand city with temples, markets and farms along the Tungabhadra River. By 1500 it was estimated to be the world's second-largest city after Beijing, and probably India's richest at the time. In 1565 a coalition of Muslim sultanates defeated the Vijayanagara Empire, its capital was conquered and destroyed, and the city was left in ruins. Hampi remains a religious centre, with the active Virupaksha Temple at its heart.

how it works

The city was built around a fortified core with temples, markets and water structures along the river, supplied by an extensive network of roads and waterworks. When the empire fell, the city was not rebuilt, so its stone monuments were left standing.

so what

Hampi shows how quickly a great city can vanish after a military defeat, and how a ruined capital can remain sacred. Its ruins give historians a view of medieval South Asia that few other sites can match.

fun fact

The name Hampi comes from Pampa, an old name for the Tungabhadra River.

From Wikipedia, the free encyclopedia · text CC BY-SA 4.0

Image: Wikimedia Commons

source: Wikipedia ↗

2 min

politicsshortCNA2:01

False allegations about Singapore’s hand in Indonesia’s markets and a made-up meeting

from CNA

CNA Verify has found close to 400 posts pushing falsehoods tying Singapore to Indonesia’s stock market rout and to a secret meeting that never took place. Together, they drew nearly 12 million views, and some were circulated by accounts that appeared to be working in concert, across multiple social media platforms.

Here’s how the disinformation campaign targeting Singapore was uncovered.

on YouTube: CNA ↗