(condensed from Ein Ayah, Shabbat 2:298)

Gemara: Rava said to his attendant: You, who do not know how to determine the times of the Rabbis, should light the Shabbat candles once the sun is at the top of the palm trees. What does one do on a cloudy day? In a city, see a rooster; in a field, see a raven, or see an adani (a plant that follows the sun, like a sunflower).

(condensed from Ein Ayah, Shabbat 2:298)

Ein Ayah: In all areas of life, the Creator prepared all “measures” that are needed for existence and for spiritual and material sustenance, according to the situation. When someone’s situation is elevated, he will merit more precise parameters with which to reach true matters of which he is in need.

One who lacks the intellectual ability to reach the depths of this level of truth still has broad access to more accessible ways of determining what he needs. These systems suffice, even though they are not as precise as those of the more talented. The most basic light of truth is open to see for all with eyes. This is the significance of the sign that Rava gave for those who do not know the exact halachic end of the day: when the sun is at the height of the top of the date trees, light the candles. “I did not speak the matter from the beginning in a concealed manner” (based on Yeshaya 48:16) – there is not a need for deep and complex calculations.