Twilight phenomenon

High school (ages 12+)
Environment & Earth

Name:

Date:

Step 1 · Read the article

Open the article and read it at the level above. Then answer the questions below in your own words.

https://smallwhale.org/articles/twilight-phenomenon

1. How deep is Twilight phenomenon?
2. What is the primary scattering mechanism?
3. What is the ecological transition?
4. What are the three stages of twilight and how far below the horizon is the sun in each stage?
5. Why do sailors need nautical twilight?

Write what each word means, using the article.

Do not copy the article. Write two things you learned, the way you would explain them to a friend.

Answers below are taken from the article’s stored facts, so they match what the student read.

1. How deep is Twilight phenomenon?Civil (0-6°), Nautical (6-12°), Astronomical (12-18°) below the horizon
2. What is the primary scattering mechanism?Rayleigh scattering of sunlight by atmospheric molecules
3. What is the ecological transition?Facilitates behavioral shifts for diurnal and nocturnal species
4. What are the three stages of twilight and how far below the horizon is the sun in each stage?Civil twilight is when the sun is 0 to 6 degrees below the horizon. Nautical twilight is when the sun is 6 to 12 degrees below. Astronomical twilight is when the sun is 12 to 18 degrees below.
5. Why do sailors need nautical twilight?During nautical twilight the horizon is still visible, but people need artificial lights for most tasks. This helps sailors see the sea and the horizon to stay on course.

Rayleigh Scattering: The scattering of light by particles much smaller than the wavelength of the light.
Atmospheric Optics: The study of how atmospheric conditions affect the path and appearance of light.
Circadian Rhythms: The natural, internal processes that regulate the sleep-wake cycle and other daily rhythms.
Diurnal Organisms: Animals that are primarily active during daylight hours.