The Lake Wobegon Effect

Where “all the children are above average.” From the intro by Garrison Keillor to the News from Lake Wobegon on the radio show A Prairie Home Companion. Also known as illusory superiority. From the popular studies where, for example, 80% of people think they are above average drivers, when asked to estimate the % of chores done in the household it adds up to more than 100%, and we overestimate our input to project work and it’s impact on its success. For the best treatment I’ve read, and references, see Thinking Fast and Slow by Dan Kahneman.

Published 13 Dec 2014

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Buoyancy

John Muir quote illustration with a Sierra Nevada lake and distant mountains with a mountain chickadee bird on a branch in the foreground and the quote "As soon as we take one thing by itself, we find it hitched to everything else in the universe."

Hitched to everything else in the universe

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Parallax

Red volcano gray volcano - a red volcano's effusive eruption has lava flowing down its slope while a gray volcano's explosive eruption shoots ash into the air

Red volcano, grey volcano

Lake-effect snow

It’s always been mind-boggling to me how some of the largest and heaviest things we build on Earth are ships that float on water. Cruise ships are like floating towns, some able to accommodate over 5,000 people. How can it be that these gigantic, impossibly heavy objects made of steel can float on water? The key is displacement and realising the considerable weight that the water already supports. In a lake or ocean, each drop of water is supported by the water around it. 1m³ of fresh water weighs 1 metric tonne, which is 1,000 kg. If a ship displaces 1m³ of water, the buoyant force of the surrounding water supports 1 tonne of the ship’s weight. Therefore, a ship weighing 50,000 tonnes will just float if it displaces 50,000m³ of water. Sea water contains salt, which makes it denser than freshwater. As the denser water supports a greater weight, a ship will float slightly higher in salt water than in fresh. The International Load Line, previously called the Plimsoll line, shows how deep a boat sits in the water. To realise the immense power of water, you can try submerging a biscuit tin in a bath. It’ll put up quite a fight. Also see: Plimsoll line Watch out for barnacles Sonic boom Iceberg orientation Siphon…It’s always been mind-boggling to me how some of the largest and heaviest things we build on Earth are ships that float on water. Cruise ships are like floating towns, some able to accommodate over 5,000 people. How can it be that these gigantic, impossibly heavy objects made of steel can float on water? The key is displacement and realising the considerable weight that the water already supports. In a lake or ocean, each drop of water is supported by the water around it. 1m³ of fresh water weighs 1 metric tonne, which is 1,000 kg. If a ship displaces 1m³ of water, the buoyant force of the surrounding water supports 1 tonne of the ship’s weight. Therefore, a ship weighing 50,000 tonnes will just float if it displaces 50,000m³ of water. Sea water contains salt, which makes it denser than freshwater. As the denser water supports a greater weight, a ship will float slightly higher in salt water than in fresh. The International Load Line, previously called the Plimsoll line, shows how deep a boat sits in the water. To realise the immense power of water, you can try submerging a biscuit tin in a bath. It’ll put up quite a fight. Also see: Plimsoll line Watch out for barnacles Sonic boom Iceberg orientation Siphon

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