What is Persistent Twilight? A Very Brief Explanation
As the sun sets below the horizon, the sky turns a deep red colour. This colouring is because the Sun’s rays can still reach the sky above it. After a while, the Sun will descend further, by a certain angle, below the horizon until none of its rays will be able to reach the sky. It is at this point we get complete darkness.
In northern parts of the world, the Sun does not descend by an angle sufficiently below the horizon for the sky to turn completely dark. The Sun’s rays will continue to reach and illuminate the sky for the whole night. It is this phenomenon that is termed Persistent Twilight. This can be seen in this online video: (Please click here for video redirect – note how the faint yellow light continues to persist)
How does this affect prayer times?
The time for Isha salah begins when the sky has gone dark due to the sun descending the horizon by a certain angle. As we can see from the definition above, Isha time can not technically begin as visible twilight still remains in the sky.
Are there any other prayer times that are affected?
Yes, the starting time of Fajr. This is because Fajr time begins when, in the darkness of night, a white line rises parallel to the horizon. When persistent twilight occurs and the sky does not go dark, the white line will never appear as the horizon is already illuminated.
So there is no Fajr time either?
There is no visible start time, but there is a finish time. That is, when the sun itself begins to become visible on the horizon.
So when do we pray Isha and Fajr?
Scholars have studied this case in depth and have provided many options based on a Prophetic Hadith on this specific issue. The three that are most commonly used are:
1 . The One Seventh Rule: Isha time starts after one seventh of the night has passed. Fajr time starts with the last seventh of the night.
2. Aqrabul Bilad: In a county where there is no persistent twilight, the the times of Isha and Fajr as a percentage of the length of the night are found. These percentages are then used in areas of persistent twilight.
3. Tanseef al-Layl: The time between sunset and sunrise is halved, with Isha used for the first half, and Fajr for the second.
4. Aqrabul Ayyam: Fixing the time to the last occurrence of the Fajr or Isha angle.
By angle, we mean the angle of the Suns declination as it descends below the horizon of the viewer. For an in-depth explanation as well as the various angles in use today giving us a major difference in our Fajr and Suhur times, please await the upcoming article entitled “Fajr: Shedding Light on The Dawn”, Insha’Allah.