Back to topics

How did unopened photographic film record a nuclear-age clue?

Photographic film can record an unwanted trace without a camera taking a picture. In a 1949 paper, Kodak researcher J. H. Webb described fogging associated with contaminated packaging made in 1945. His investigation followed the clue from film to cardboard and then to a proposed origin, separating what was measured from the historical explanation.

3–7 min

Questions you could explore

  • What additional observations turn an unexpected mark into evidence about its cause?

Start reading

Ready to try your ideas aloud?

Your topic carries over. Record up to 2½ minutes, depending on your plan.

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.

How did unopened photographic film record a nuclear-age clue? | Speech Topic | speaking.app