Waterbury evening Democrat., 1907-10-10
Difference Between the Star Day
 and the Sun Day.
IT IS GREATEST IN WINTER.
Why the Difference Occurs and How It May Be observed-oddIy Enough the Shortest Day In the Year Is Really the Longest Day In Time.

Really the Longest Day In Time.
 How long, after all, is day? The geographies say that 1t is the time re. quired for the earth to turn once on its axis, that 1t measures twenty-four hours by the clock and that a fraction more than 365 of them are to be found in year.
 It is good plan when one reads anything in a book to test it when he can for himself. We want to see just how long it takes the earth to turn over once. Let us take any one of the fixed stars that chances to be in line with some convenient point and, watch in hand, notice the precise mo- ment at which the star touches, let us say, particular tree, branch or stee- pie on the horizon line. If on the next evening we stand at precisely the same spot and sight the same star again in line with the same point as before, then we shall know that the earth has turned on its axis just once.
 Curiously enough, however, we shall discover, if this is done carefully, that, in spite of what the books say, it does not require twenty-four hours for the earth to turn over once About four minutes before the day is up, by the clock, the earth has revolved once and brought the star back to it's old posi- tion in the sky Really, then, the earth turns on its axis once in twenty-three hours, fifty-six minutes and four sec onds and, as one can easily reckon, makes, something more than 366 revo- lutions in year.
 But human beings are not so much interested in the stars as in the sun. We really don't care much how long 1t takes the earth to turn over and bring a star back again to the same point in the sky or how many times in a year star seems to go by. We set our clocks and reckon our year. by the turning of the earth under the sun, and because the earth not only turns under the sun, but also goes round it, it takes about four minutes longer to bring the sun up to its old place in the sky than to bring back star. This comes about simply enough. Suppose one is in a room looking out the win dow at tree. If he turns round once exactly he will find himself looking straight at the tree again, but if he tried the same thing when he was on a moving train he would find that while he was making the turn the tree had fallen behind. He would then, ac- cording to the way he twirled, have to turn little more or a little less to bring the tree straight before his nose.
 Therefore 1t is not quite true that & day is the time required for the earth to turn once on its axis. 1t really is this time plus the four minutes or so required for 1t to turn and look back at the sun. The time required for this extra turn is not the same at all times in the year. One can easily see in the case of the moving train that the fast CT the cars were moving or the nearer the track the tree stood the more the latter would seem to shift its position. Since the earth is some 100000 miles nearer the sun in winter than in sum- mer, and since also the nearer the sun it is the faster it travels, the difference between star day and sun day is greatest fin winter.
 Oddly enough, it happens that Dec. %, which has the least daylight of any day in the year and is therefore commonly said to be the shortest ot all days, is really the longest. It does, as Ii matter of fact, run almost half a minute over twenty-four hours, while the true shortest day, which comes on Sept. r, falls short by about the same time.
 So we really have three different days" There is the star day. which is the time during which the earth turns over once. This. because the earth spins steadily, is always the same length, fwenty-three hours. fifty six minutes, four and nine-hundredths seconds, and there are 366 of them in a year. Then there is the ordinary le- gal day, which is the time required for a proper clock to get round twice. This Is just twenty-four hours. Be- sides these. there is the sun day. its time told by the sundlal. which, talk ing short with long, averages twenty four hours, but is never found to be exactly the same length for two days in succession.
 There is a string of long days in the winter, followed by a series of short ones in the spring. In the summer the sun days get long again. though not quite so long as in the winter. Tn the autumn come :he shortest days of all. Only occasionally are clock day and sun day of the same length. Only four times a year do clock noon by the clock hands and sun noon by the sundiaI occur at the same moment. while. because the long and short sun days are found in sets, they Oftentimes may be more than fifteen minutes apart.
 The vast majority of the people reckon their time by the sun. But time for civilized men is time by the clock. The days are all tEenty-four hours long. and no matter where the sun is it is noon for us when the clock strikes 12 Nevertheless. astronomers often go by star time. get in an extra day in each year and have their noon fall at all times of the day or night E I. Brewster in ChicagO RecOud-Her- aId