Q: Twilight is the light visible above the horizon when the sun is below the horizon. It is civil twilight when the sun is 6º below the horizon; X twilight when 12º below; and astronomical twilight when 18º below. Name X.
A: Nautical twilight
Q: At astronomical twilight in the evening, Y becomes visible in the sky, and at astronomical twilight in the morning, Y becomes invisible. What is Y?
A: The faintest star visible to the naked eye
Q: An asura in Hindu mythology was slain by one of the avatars of Lord Vishnu at twilight because he had a boon that he couldn’t be slain at day or night. Name the asura.
A: Hiranyakashipu
Q: When the sun is setting behind you, the shadow that earth’s atmosphere casts will be in front of you, near the horizon. At civil twilight, this shadow has a faint pink border. It is sunlight diffracted in earth’s atmosphere. What is this pink belt called?
A: Belt of Venus
Q: During X (in Q1), the sunlight remaining in earth’s atmosphere has a deep blue shade – the result of ozone molecules absorbing light of other frequencies. The absorption is weak, so its effects are pronounced when light has to travel longer through the atmosphere, which happens at twilight. What effect is the absorption called?
A: Chappuis effect
Q: The red fox (Vulpes vulpes), seen here in the U.S. on March 21, 2018, is most active at twilight. What is the adjective that describes such animals?
A: Crepuscular
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