The price of 1 million lumen-hours since the Middle Ages. A lightbulb does that in ~600 hours, or about 2 months of daily usage. So multiply these prices by 6 to see how much it used to cost to use a lamp for one year. So many things we take for granted used to be such luxuries. pic.twitter.com/hEYmqVf6D5
— Tim Urban (@waitbutwhy) February 17, 2022