The Biblical account relates that Isaiah the prophet was sent to Hezekiah to inform him that he would die from his illness. Hezekiah prayed for healing, and Isaiah had not left the palace when he was sent back to the king with a different message: The Lord would heal him and give him another 15 years of life. A sign was to confirm the healing. The shadow could move forward or backward on an outdoor stairway. Hezekiah chose for the shadow to move backward (2 Kings 20:10).
On March 5 in 702 B.C.E., the 16th year before Hezekiah’s death, a prominent solar eclipse appeared over the Middle East (according to NASA). Its path crossed the Arabian Peninsula, and the obscuration of the sun over Israel was more than 60 percent.
If a stairway had been engulfed in darkness and then restored to daylight, the shadow would have appeared to retreat. A shadow wave, produced by an eclipse, may also have given the appearance of a shadow retreating.
The Akeidas Yitzchak explains that solar eclipse really refers to the death of the righteous, the lights of our community who are extinguished. Yesod Olam goes in the other direction. He understands the four reasons for a solar eclipse as allegories for the movement of the moon. For example, the two brothers who die refer to the sun and the moon who both lose their light, so to speak, during a solar eclipse. Rema offers a different allegorical interpretation, connecting the four reasons to the movements of the astrological signs relating to a solar eclipse. - TorahMusings.com
The Mishnah Berurah rules that it is forbidden to tell another person that a rainbow is visible, because this violates the prohibition of slander
Since it appears as a sign of human sin, it might be suggested that דבה it would also be forbidden to announce the time of a future solar eclipse. However, unlike a rainbow, a solar eclipse may be entirely predicted, and on the basis of this, R. Avigdor Nebenzahl (b. 1935) ruled that it is permitted to publicize the dates and times of a future eclipse.
ידוע הכלל אשר אין לחדש ברכה שלא הוזכרה בש"ס )ב"י או"ח סמ"ו(. וי"ל הטעם דאין מברכין ע"ז מפני שהוא סימן לפורעניות הבאה )סוכה כט, א(. ואדרבה צריכה תפלה לבטלה וצעקה ולא ברכה.
There is a well-established principle that it is forbidden to institute a blessing that is not mentioned in the Talmud. And some say that the reason that no blessing was instituted is because the eclipse is a bad omen. To the contrary, it is important to pray for the omen to be annulled, and to cry out without a bracha.
- R' Menachem Mendel Schneerson, 1957
Our Rabbis instituted blessings over acts of creation and powerful natural events, like lightning and thunder and so on. However, they did not do so for a lunar or solar eclipse. And if only today we could institute a blessing when we are aware that an eclipse is indeed an incredible natural event. But we cannot, for a person is forbidden to make up a blessing. If a person still wants to make some form of a blessing, he should recite the verses “And David blessed...blessed are you, G-d, the L-rd of our father Israel, who performs acts of creation.”
- R. Chaim Dovid HaLevi, Av Beis Din of Tel Aviv and Yaffo
A person who has undergone ritual immersion (tevilah) in the day because of contact with a ritually impure source is required to wait until sunset before he is considered to have left his state of tumah, ritual impurity. R. Avigdor Nebenzahl wrote that a total solar eclipse does not bring to an end the period of tumah, even though the sky is dark enough to see the stars. Instead, sunset is required.20 He derived this ruling from the verse (Lev. 22:7): ובא השמש וטהר — “the sun will come and he will become pure.” According to R. Nebenzahl, the sun is required to set in its normal fashion in order for the impurity to be lifted, a condition that does not occur in a solar eclipse. - Hakirah.org
Maharal (Be’er Ha-Golah, ch. 6, p. 106) explains that the Gemara is offering reasons why God established nature in such a way that there would be solar eclipses. If people did not sin, we would merit eternal light. However, because God knew people would sin, He created the world in such a way that solar eclipses would happen. - TorahMusings.com
Some authorities believe that the Gemara is not talking about solar eclipses. Rav Yonasan Eybeschutz (Ye’aros Devash 2:10) suggests that the Gemara is referring to sunspots. While solar eclipses can be predicted, sunspots cannot and are caused by sin. Rav Yehosef Schwartz (Divrei Yosef 1:9) suggests that the Gemara is discussing unexpected atmospheric phenomena. He says that on 28 Iyar 1838 in Jerusalem at 4pm, the sun turned dark red for about an hour. Everyone was amazed by the sight. Over the next three months, Jerusalem experienced a terrible plague with many deaths. Rav Schwartz says that this was an example of the Talmudic phenomenon. - TorahMusings.com
“And they have been created, as Moses tells us, not only that they might send light upon the earth, but also that they might display signs of future events. For either by their risings, or their settings, or their eclipses, or again by their appearances and occultations, or by the other variations observable in their motions, men oftentimes conjecture what is about to happen, the productiveness or unproductiveness of the crops, the birth or loss of their cattle, fine weather or cloudy weather, calm and violent storms of wind, floods in the rivers or droughts, a tranquil state of the sea and heavy waves, unusual changes in the seasons of the year when either the summer is cold like winter, or the winter warm, or when the spring assumes the temperature of autumn or the autumn that of spring. And before now some men have conjecturally predicted disturbances and commotions of the earth from the revolutions of the heavenly bodies, and innumerable other events which have turned out most exactly true: so that it is a most veracious saying that “the stars were created to act as signs, and moreover to mark the seasons.” And by the word seasons the divisions of the year are here intended. And why may not this be reasonably affirmed? For what other idea of opportunity can there be except that it is the time for success? And the seasons bring everything to perfection and set everything right; giving perfection to the sowing and planting of fruits, and to the birth and growth of animals.”
(Creation 1.58–59 PHILO-E)