Understanding Nisf Al Lail and its Application during Persisting Twilight
Everyone loves dimming lights. Dimming lights allow a person to set the brightness of a lamp exactly to one’s requirements: Very bright, normal, slightly dim, dim, or very dim. The final setting is when you hear the click sound and the light turns off. In this article, I want to take the concept of persisting twilight and explain it using the example of a dimming light.
A Normal Switch and the Night Sky
For about 10 months of the year, the example of the dimming switch is perfect in understanding the illuminance of the sky. Shortly before sunrise, the illuminance is very dim, and this gets brighter and brighter during the day. After the sun reaches its maximum point, the illuminance starts to dim again, until sunset and then continues to dim until “click” there is no more light in the sky.
When does the night sky go “click”?
Most scholars are of the opinion that there is no illuminance after the sun descends 18 degrees below the horizon.
A Faulty Switch and Abnormal Conditions
A perfectly working dimming switch is wonderful to use. You can turn it on and off and set the illuminance as you please, a faulty one makes life a little difficult.
Locations above 48 degrees latitude have periods of time (in the summer months) where the sun does not go below 18 degrees (the switch does not go “click”!). Understand this by thinking of a dimming switch that can get brighter and dimmer but never turn off. In some locations, this period when true night does not occur can last for one day and others for months on end. This is known as persisting twilight.
When does Fajr time start?
لأن الفجر عندهم اسم للبياض المنتشر في الأفق موافقا للحديث الصحيح كما مر بلا تقييد بسبق ظلام
In Raddul Muhtar ‘ala al Durr Al Mukhtar, a definition of Fajr is mentioned that is inclusive of the problematic scenario locations above 48 degrees latitude face.
“Fajr according to the scholars of the Madhab (Ahnaf) is the name given to the white which spreads in the horizon, [this is] in accordance with the authentic ahadith. There is no condition of the whiteness having been preceded by darkness.”
From this text, Fajr time starts on the appearance of the white that spreads (contrary to the illuminance which appears temporarily and then fades – this is Subh Kadhib). This is true even for those days when the illuminance from the previous night did not completely disappear. There is a point at night when the illuminance stops dimming and starts spreading. This occurs all year round, during persistent twilight, or otherwise. This is when Fajr starts throughout the year without exception.
When does the illuminance start to spread?
During the year (non-persisting twilight days), lights start to spread when the sun reaches 18 degrees below the horizon. During persisting twilight, the light starts to spread when it stops diminishing.
If Fajr exists, should we use approximation methods?
Approximation methods such as nearest day, nearest place and other calculation methods can only be justified if we agree that the definition of Fajr is not found. According to the definition of the jurists, the definition of Fajr is found, and therefore it cannot be permissible to use any approximation method in place of the actual time of Fajr.
When does the definition of Fajr occur during persisting twilight?
The diminishing of light and its illumination during the day and night is symmetrical. From sunset, the night becomes darker and darker until half the night has passed and then for the remaining half of the night, the sky gets brighter and brighter. This means that the definition of Fajr is found at half night. This is the time when it is permissible to perform your Fajr Salah and this is when your fasting begins.
The calculation of half-night is the same as that of istiwa’ (commonly known as Zawal time), it is based on the raw times of sunset and sunrise and not the adjusted times.
11th Shawwal 1441
A detailed article with further references is available here