Halakhah sobre Êxodo 3:15

We find that the light of the sun and of all the stars is eternal, of itself it does not increase nor decrease. However, the light appears to increase or decrease depending on whether the object being viewed is far or near. Also, the light varies due to changes in the atmosphere at the beginning or the middle of the day. Only the moon has a renewal of its light.¹ Ibn Ezra believes that the sun, all planets and all stars, generate their own light, and only the moon reflects light of another body (the sun). Therefore, the Hebrew term for month, “hodesh,” can truly apply only to a lunar month.² In Hebrew, a month is called “hodesh,” which is derived from the root “hidesh” meaning “renew.” Since only the moon has a renewal of its light, “hodesh” can only refer to a lunar month. We examine when such a month begins.

This caused the Gaon (Rabbi Saadia) to err when he said that he saw the moment of a solar eclipse in Baghdad and it was not at the time of our calculated molad.⁵ A solar eclipse occurs when the moon blocks the sun’s light from reaching earth. This can only happen at a time of true conjunction. From this he concluded that the calculation of the Rabbis was not accurate. However, their calculation is the accurate one. The Gaon made four errors: The first is that he should have known about the long and short paths, as astronomers do. For there is no disagreement between conjunction for the Jews and conjunction for the Gentiles with regard to the mean orbit, which then allows one to calculate the true conjunction. The second error is that the molad is calculated relative to Jerusalem, and there is ⅔ of an hour difference in longitude between Jerusalem and Baghdad.⁶ Jerusalem is at a longitude of 35÷10ʹ E while Baghdad is at 44÷30ʹ E. The difference is 9÷20ʹ, almost ⅔ of an hour (⅔ ׳ 15÷ = 10÷). The third error is that he should have known the difference in appearance based on longitude, since an eclipse is one of appearance.⁷ In a solar eclipse the sun’s rays are blocked by the moon from reaching earth. However, the sun continues to shine and its intensity is in no way diminished. Those who are elsewhere in the universe will see the sun’s rays. “The sun may therefore be eclipsed to one observer while to another elsewhere it is visible as usual. Hence in computing an eclipse of the sun it is necessary to take into account the position of the observer on the earth” (Berry, p. 60). This is in contrast to a lunar eclipse where the moon is darkened and it is dark for everyone in the universe, no matter where that person stands. The fourth error is the difference in appearance based on latitude.