Nautical Twilight is best described as:

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Multiple Choice

Nautical Twilight is best described as:

Twilight is defined by how far the Sun sits below the horizon, which determines how much light is left at dawn and dusk. Nautical twilight occurs when the center of the Sun is between about 6 and 12 degrees below the horizon. In this window there’s enough light for some sea tasks—horizon lines are still visible and navigation by stars is practical—but it isn’t full daylight. The description in the choice captures that idea by tying nautical twilight to the Sun’s center being 12 degrees below the horizon at the start (in the morning) and at the end (in the evening). This marks the boundary between nautical twilight and the darker astronomical twilight in the morning and civil twilight in the evening, and it correctly conveys the “incomplete darkness” character of this period. The other descriptions don’t fit: complete darkness is night (astronomical twilight or darker); the Sun above the horizon means daylight; and referencing the upper limb of the Sun being 12 degrees above horizon isn’t how twilight phases are defined.

Twilight is defined by how far the Sun sits below the horizon, which determines how much light is left at dawn and dusk. Nautical twilight occurs when the center of the Sun is between about 6 and 12 degrees below the horizon. In this window there’s enough light for some sea tasks—horizon lines are still visible and navigation by stars is practical—but it isn’t full daylight.

The description in the choice captures that idea by tying nautical twilight to the Sun’s center being 12 degrees below the horizon at the start (in the morning) and at the end (in the evening). This marks the boundary between nautical twilight and the darker astronomical twilight in the morning and civil twilight in the evening, and it correctly conveys the “incomplete darkness” character of this period.

The other descriptions don’t fit: complete darkness is night (astronomical twilight or darker); the Sun above the horizon means daylight; and referencing the upper limb of the Sun being 12 degrees above horizon isn’t how twilight phases are defined.

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