The process
Some changes do not fit into a date: printing, steam, votes for women. They happen over centuries and in steps, and the order of those steps is what you can know without arguing about causes. Where the count starts is usually the surprise: paper is seven centuries older than Gutenberg, and the steam engine was pumping water sixty years before it moved a train.
Where this sits
- Comes after
- The line
Exercises from this rung
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Heredity, step by step.
Answer Mendel publishes his peas, Miescher isolates nuclein, The double helix is described, The human genome is finished
Why Mendel publishes his peas, 1866. Miescher isolates nuclein, 1869. The double helix is described, 1953. The human genome is finished, 2003. From the first step to the last, 137 years.
easierMeasuring the sky, step by step.
Answer Eratosthenes measures the Earth with a shadow, Copernicus puts the Sun at the centre, Galileo sees moons going round Jupiter, Bessel measures the distance to a star
Why Eratosthenes measures the Earth with a shadow, c. 240 BC. Copernicus puts the Sun at the centre, 1543. Galileo sees moons going round Jupiter, 1610. Bessel measures the distance to a star, 1838. From the first step to the last, 2077 years.
in betweenThe steam engine, step by step.
Answer Newcomen pumps mine water with steam, Watt patents the separate condenser, Trevithick puts an engine on rails, The first passenger railway opens
Why Newcomen pumps mine water with steam, 1712. Watt patents the separate condenser, 1769. Trevithick puts an engine on rails, 1804. The first passenger railway opens, 1825. From the first step to the last, 113 years.
harder