How does the presence of an atmosphere affect the length of day and night?
I am thinking by the rising and setting of the moon and sun.
Is this right?
Thank You.
Yes, you are right that the rising and setting of the moon and sun play a role in the length of day and night. However, the presence of Earth's atmosphere also has an impact on the duration of these periods.
To understand this, let's look at how the atmosphere affects the behavior of sunlight. When sunlight reaches Earth's atmosphere, it interacts with air molecules, scattering and bending its path. This scattering of light causes the sky to appear blue during the day.
During sunrise and sunset, however, the sunlight has to pass through a larger portion of the atmosphere, resulting in greater scattering and longer path lengths. As a result, the sunlight must travel a longer distance through the atmosphere, which leads to a prolonged period of twilight. Twilight is the period before sunrise and after sunset when the sky is neither fully dark nor fully lit.
The presence of an atmosphere doesn't directly affect the duration of day and night, but it does influence the length of twilight. Specifically, the atmosphere causes two types of twilight: civil twilight and nautical twilight.
Civil twilight is the period when there is still enough light for most outdoor activities without artificial lighting. It occurs before sunrise and after sunset when the sun is between 0° and 6° below the horizon. The exact duration of civil twilight depends on your latitude and time of the year, but it generally lasts around 30 to 60 minutes.
Nautical twilight is the period when it becomes difficult to distinguish the horizon at sea. It occurs when the sun is between 6° and 12° below the horizon. Nautical twilight generally lasts about an hour, providing additional time for activities that rely on lower light levels.
So, while the rising and setting of the moon and sun determine the start and end of day and night, the presence of Earth's atmosphere creates twilight, which prolongs the transition between daylight and darkness.