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Could an ancient industrial civilization leave evidence in rocks?

Imagine looking for traces of industry millions of years after its buildings disappeared. The Silurian hypothesis is a thought experiment about which signals might survive in rocks and which natural events could imitate them. It is not a discovery of an earlier industrial civilization.

5–7 min

Questions you could explore

  • What combination of traces would be harder for one natural event to explain?
  • How could geological processes erase or imitate possible evidence of a much older industry?

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The same Sun can light a blue afternoon and a red evening

Earth and weather3–5 minSunlight takes a different route through the atmosphere near the horizon than overhead. Which colors scatter along that route helps explain a blue afternoon and a red sunset.

Earth and weather

How can lines on a map show a steep hill?

A flat map can warn you that a route climbs sharply before you ever see the hill. Contour lines join places of equal height, and their spacing adds information about how quickly the ground rises.

2–3 min

How can lines on a map show a steep hill?

Earth and weather2–3 minA flat map can warn you that a route climbs sharply before you ever see the hill. Contour lines join places of equal height, and their spacing adds information about how quickly the ground rises.

Earth and weather

How can an earthquake alert arrive before strong shaking?

An earthquake alert can beat the strongest shaking to a distant location even though the earthquake has already started. Detection and communication can travel ahead of the damaging waves, but nearby places may receive little or no warning.

4–5 min

How can an earthquake alert arrive before strong shaking?

Earth and weather4–5 minAn earthquake alert can beat the strongest shaking to a distant location even though the earthquake has already started. Detection and communication can travel ahead of the damaging waves, but nearby places may receive little or no warning.

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