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Reading a buried timeline

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

Questions you could explore

  • How does a cut through a layer reveal relative order?
  • What can a sequence establish without giving calendar dates?

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

History4–5 minA radiocarbon measurement does not translate directly into one calendar year. The amount of radiocarbon in the atmosphere has varied, so dating relies on comparison with material whose age is already known.

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.

History

How did reusable type change the making of a page?

In Gutenberg's Mainz workshop in the 1450s, separate pieces of metal type could form a page and be used again. Printing repeated text, but hand finishing still helped make individual Bibles differ.

12–15 min

How did reusable type change the making of a page?

History12–15 minIn Gutenberg's Mainz workshop in the 1450s, separate pieces of metal type could form a page and be used again. Printing repeated text, but hand finishing still helped make individual Bibles differ.

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