The story of the sun, moon, and stars . in is nowpretty well given up. The apparent blackness of aspot-nucleus does not prove actual blackness or ab-sence of heat. A piece of white-hot iron, held upagainst the sun, looks black; and it may be merelythe contrast of the glowing photosphere which makesthe nucleus seem so dark. It is even believed thatthe blackest parts may be the most intensely hotof all. Another proposed explanation was of dark cloudsfloating in the suns atmosphere. There, again, arefound difficulties, particularly in the fact that, as thespots move across the sun, the changes wh
The story of the sun, moon, and stars . in is nowpretty well given up. The apparent blackness of aspot-nucleus does not prove actual blackness or ab-sence of heat. A piece of white-hot iron, held upagainst the sun, looks black; and it may be merelythe contrast of the glowing photosphere which makesthe nucleus seem so dark. It is even believed thatthe blackest parts may be the most intensely hotof all. Another proposed explanation was of dark cloudsfloating in the suns atmosphere. There, again, arefound difficulties, particularly in the fact that, as thespots move across the sun, the changes which regu-larly take place in their appearance make it prettyclear that their shape is not flat, but hollow and cave-like. The changes here spoken of are seemingchanges of shape, caused by change of position. MORE ABOUT THE SUN. 135 There are also real changes constantly taking the spots often keep their general outlineslong enough to be watched across the face of the sun,and even to be known again after spending nearly a. A TYPICAL SUN-SPOT. fortnight hidden on the other side, still they are farfrom being fixed in form. The alterations are at times not only very great,but very rapid. Sometimes in a single hour of watch-ing, an astronomer can see marked movement going 136 STORY OF THE SUN, MOON, AND STARS. on—as you or I might in an hour observe movementsslowly taking place in a high layer of clouds. Formovement to show at all in one hour, at so immensea distance, proves that the actual rate of motion mustbe very great. The first great fact which was got from the studyof these spots was this, that this great sun is verymuch like our own earth, in so far as it rotates on anaxis in exactly the same way that our earth does. Notonly do the spots change their position on the face ofthe sun, in consequence of the suns rotation on itsaxis, but they change very much from day to day, andeven from hour to hour; so that we have evidence notonly that the sun is rotating lik
Size: 1466px × 1704px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookidstor, booksubjectastronomy
