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

Sunlight 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.

3–5 min

Questions you could explore

  • Why are some wavelengths scattered more strongly?
  • What changes when sunlight reaches us from near the horizon?

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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.

Why does a compass not always point toward true north?

Earth and weather3–5 minA compass needle responds to the magnetic field around it, not directly to the geographic North Pole. The difference between magnetic and true north changes with location and time.

The same Sun can light a blue afternoon and a red evening | Speech Topic | speaking.app