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How did John Snow investigate whether drinking water spread cholera?

A map of deaths raises a question; it does not answer every part of it. Snow also investigated people near the Broad Street pump who used different water supplies, including a workhouse and a brewery. Their circumstances helped him examine an explanation that proximity alone could not settle.

3–7 min

Questions you could explore

  • Why are nearby people who did not use the pump especially informative?
  • What alternative explanation would the comparisons need to address?

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Why does a radiocarbon date need a second kind of clock?

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History

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A deep object is not necessarily the oldest thing at an archaeological site. A later pit can cut through earlier ground, leaving a sequence that has to be reconstructed from relationships between layers.

12–15 min

Reading a buried timeline

History12–15 minA deep object is not necessarily the oldest thing at an archaeological site. A later pit can cut through earlier ground, leaving a sequence that has to be reconstructed from relationships between layers.

History

When Britain’s railways needed a shared clock

A timetable becomes awkward when the clocks at its two ends disagree. In nineteenth-century Britain, railway journeys helped turn local time into a shared coordination problem, while the telegraph helped distribute an answer.

8–10 min

When Britain’s railways needed a shared clock

History8–10 minA timetable becomes awkward when the clocks at its two ends disagree. In nineteenth-century Britain, railway journeys helped turn local time into a shared coordination problem, while the telegraph helped distribute an answer.

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