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Tim Harford introduces inventions, ideas and innovations that have helped to create the modern economic world. Once too precious to use, light is now too cheap to notice.

Once too precious to use, now too cheap to notice - the significance of the lightbulb is profound. Imagine a hard week's work gathering and chopping wood, ten hours a day for six days. Those 60 hours of work would produce light equivalent to one modern bulb shining for just 54 minutes. The invention of tallow candles made life a little easier. If you spent a whole week making them - unpleasant work - you would have enough to burn one for two hours and twenty minutes every evening for a year. Every subsequent technology was expensive, and labour-intensive. And none produced a strong, steady light. Then, as Tim Harford explains, Thomas Edison came along with the lightbulb and changed everything, turning our economy into one where we can work whenever we want to.

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