Show Notes
The topic for this episode comes straight out of our figurative backyard - The CN Tower! This iconic Canadian landmark was the world’s tallest building from its opening in 1976 right up until 2007 and today we find out how and why this concrete and steel behemoth was built.
Originally built and owned by CN Rail, the CN tower was initially built to house UHF and VHF transmitters as Toronto’s skyline became more crowed in the 1960s and existing TV and radio transmitters had become more and more obstructed. Construction began in 1973 at a cost of $63 million CAD at the time (the equivalent of $350 million CAD today), with a return on CN’s investment only 15 years later, just 4 years prior to ownership being transferred to Canada Lands in 1995.
John has a bit of an axe to grind about including the 104m of steel antenna in the height of the tower rather than capping the measurement with the 450m of concrete shaft, claiming that this is the equivalent of measuring a hat in a person’s height. However, most people’s hats aren’t responsible for providing television and radio signals for a major Canadian city for close to 5 decades so we should potentially make an exception. This enormous antenna was originally the primary purpose for building the tower but today while still operational it broadcasts just 16 channels with the broadcasting making up less than 1% of the tower’s revenue, as it is now primarily a tourist destination with more than 2 million visitors during a normal year.
Being constructed prior to computational modelling meant an enormous number of manual calculations, and designed drafted by hand with pens, ink and slide rules. With a capacity to withstand wind speeds of up to 418km per hour and earthquakes up to 8.5 on the Richter Scale, the CN tower made use of a number of impressive construction techniques such as pre- and post-tensioned cables and also contains copper cables running the entire height of the tower.
Declared one of the modern 7 wonders of the world by the American Society of Civil Engineers in 1995, the CN Tower is truly an icon of Canada and the city affectionately known as “the 6ix”, Toronto.
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Image Gallery
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What is Measured in Metric?
Civilization and the world around us, from the monuments that astound us to the mundane infrastructure that serve us, we rarely think about how it all came together. Welcome to Measured in Metric, where we dive into the stories of the builders, the visionaries, and the influencers that have shaped the world we live in.
