The Midrash states that “there is a sheath around the sun” and explains this to be the meaning of the verse: “He has set up a tent for the sun” (Psalms 19:5). This sheath is mentioned in several places in the Sages’ writings, in which they imply that were it not for its existence, life on earth would suffer terribly and perhaps even perish.
Yet, as much as we can see the sun with the naked eye or through a filter, it clearly has no visible sheath or covering. On the other hand, the Sages beheld the same sun, yet firmly insisted that a sheath exists, because the Torah states that it is there. In this age of spacecraft and X-ray photography of the sun, do scientists have something to tell us on this subject?
Dr. N. Vidal, a senior astronomer at the Greenwich Observatory in England, Professor of Astronomy at Australia’s National University and a visiting professor at the Harvard-Smithsonian Center for Astrophysics at Harvard University, Massachusetts, explains:
“The sun is a giant ball of gas, whose outermost temperature is 6000 °C (10,832 °F). Gases at much higher temperatures flow beneath the surface. According to our estimates, the temperature continues to rise as we approach the center of the sun, where it reaches 15,000,000 °C! Today, we picture the center of the sun as a type of ‘nuclear reactor’ that releases vast quantities of heat, which make their way slowly outward. As it moves out, the strength of this heat diminishes until it reaches the surface layer, where it is ‘only’ 6000 °C. The extremely high temperatures within the sun cause gas storms of tremendous proportions, which form waves, which crash against the surface gases with unbelievable force. These outer layers themselves absorb the heat being radiated from within the sun, and restrain the shockwaves caused by these waves striking it. We call this outer layer, ‘the sheath.’
The heart of the sun. There, the temperatures are extremely high… In this area, there is the highest radiation of ultraviolet rays, X-rays, and gamma rays. If these rays were to reach the earth directly, they would incinerate the entire world. Area B is the outermost sheath that restrains these rays, as well as the shockwaves that burst out from the sun’s interior, and ‘softens’ them. This level is called the ‘photosphere,’ and its temperature is 6000 °C.”
Today we realize that just as the Earth has a surrounding atmosphere, which both provides oxygen for life and protects us from the dangerous cosmic radiation, so the sun has a sheath that protects the inhabitants on Earth. The Sages knew of this sheath’s existence from its source in the Torah. Furthermore, based upon the Midrash, they knew of its protective role, and the fact that Earth’s inhabitants could perish were the sheath to fail in its task.