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The rule of 7

The Rule of 7 illustration: two people walk together along the street, bombarded by imagery of apples; on posters, on the front page of newspapers, by a large promotional 3-D apple perched atop a news-stand. By the end of the scene, their conversation about whether they are hungry has turned to one specifically about buying an apple to eat.

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The rule of 7 is an idea in marketing that it can take hearing a message 7 times before we might take action.

Apparently the rule is from early movie marketing and while I don't know if I'd rely on the number it certainly seems a sensible idea to keep in mind that you can't expect people to take action the first time they hear your message — if you're trying to get people to try something new be it buying food, downloading your app, watching a movie, or a choosing an electric car, it takes a while and repeated exposure before you can expect it to pay off.

I can't remember where I heard it, but some advice I keep in mind when communicating is that by the time you're tired of saying it, others are just starting to hear it. It's not a bad thing to repeat your main message.

I learned about the Rule of 7 from the recent book Human Powered by Trenton Moss.

When putting an apple in the adverts on this sketch I was reminded that so often it's the things in the supermarket that are most healthy for us that don't get anyone shouting about them at all.

Published 7 Nov 2021

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Keep exploring

What is the potato radius example explained: showing a bumpy potato-like asteroid at the centre of an expanding circle and how it becomes rounder and more planet like as it gets larger

The Potato Radius: When Asteroids Turn Spherical

Braille reading and writing system: the letters of the alphabet in english braille showing how it's constructed from 6 dots

Pillars of hope, steel starter bars or starter rods stick out of a house so that in the future it's easier to add an extra storey

Pillars of hope

The upward spiral from Stephen Covey illustration: showing a spiral growing from the bottom with Learn Commit Do repeating as it rises and someone reading a map, packing their gear and heading off determinedly on a trip illustrating each step

The Upward Spiral

The coastline paradox: a map of the UK dividing up the coastline with ever smaller rulers shows how the coastline length dramatically increases

The coastline paradox

The Stroop test

Asteroids are often considered irregular, lumpy, potato-shaped rocks, while planets seem smooth and spherical. The “potato radius” is the fascinating threshold where this transformation begins—a concept that illustrates how gravity shapes celestial bodies. What is the Potato Radius? When a space rock’s radius (the distance from its centre to its edge) grows to around 200–300 kilometres, its own gravity becomes powerful enough to reshape it. At this size, gravity pulls the rock’s mass inward toward its centre, overcoming its irregular structure and creating a more spherical shape. Think of it like compressing a crumpled ball of paper into something rounder and smoother. Rocks smaller than this threshold retain their irregular, asteroid-like shapes, while larger bodies transition into planet-like spheres due to self-gravity. This natural process highlights the profound role gravity plays in shaping the universe. Potatoes as Asteroids in The Empire Strikes Back Our image of asteroids is so closely linked to potatoes that they have even served as asteroid doubles in movies. In a brilliant example of creative special effects, The Empire Strikes Back used potatoes as some of the asteroids in the famous scene where the Millennium Falcon flies through an asteroid field. Related Ideas The potato radius and other remarkable natural phenomena feature in Professor Brian Cox in the BBC series Forces of Nature. Also see: Not sure about Asteroids, meteors and meteorites? Solar System Sizes The Goldilocks Zone What causes the seasons? What is a blue moon? Phases of the moon The potato radius features, along with many other fun, spacey-sketches in my book Big Ideas Little Pictures…Asteroids are often considered irregular, lumpy, potato-shaped rocks, while planets seem smooth and spherical. The “potato radius” is the fascinating threshold where this transformation begins—a concept that illustrates how gravity shapes celestial bodies. What is the Potato Radius? When a space rock’s radius (the distance from its centre to its edge) grows to around 200–300 kilometres, its own gravity becomes powerful enough to reshape it. At this size, gravity pulls the rock’s mass inward toward its centre, overcoming its irregular structure and creating a more spherical shape. Think of it like compressing a crumpled ball of paper into something rounder and smoother. Rocks smaller than this threshold retain their irregular, asteroid-like shapes, while larger bodies transition into planet-like spheres due to self-gravity. This natural process highlights the profound role gravity plays in shaping the universe. Potatoes as Asteroids in The Empire Strikes Back Our image of asteroids is so closely linked to potatoes that they have even served as asteroid doubles in movies. In a brilliant example of creative special effects, The Empire Strikes Back used potatoes as some of the asteroids in the famous scene where the Millennium Falcon flies through an asteroid field. Related Ideas The potato radius and other remarkable natural phenomena feature in Professor Brian Cox in the BBC series Forces of Nature. Also see: Not sure about Asteroids, meteors and meteorites? Solar System Sizes The Goldilocks Zone What causes the seasons? What is a blue moon? Phases of the moon The potato radius features, along with many other fun, spacey-sketches in my book Big Ideas Little Pictures

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