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Why did a Cold War experiment put needles in orbit?

In 1963, Project West Ford used a belt of tiny orbiting dipoles to scatter radio signals between ground stations. It was an attempt to create a dependable reflection path above Earth. The project’s own retrospective describes successful communication and the move toward active satellites.

5–7 min

Questions you could explore

  • How does a passive reflector differ from a satellite that receives and retransmits a signal?

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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

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

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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