Untold ages ago, the sun was a spinning, burning mass of matter far larger than it is now, and spinning very niuch faster.It was not yet formed into a compact centre of heat and light then. As it spun at a very high speed, a se- ries of fragments detached themselves from it, which became the planets.' Our earth is one of these planets. The flam- ing mass that was the material of the earth broke in turn into two masses, a larger, the earth itself, and a smaller, which is now the dead, still moon.
Astronomers give us good reasons for supposing that sun and earth and moon and all that system were then spin- ning at a speed much greater than the speed at which they are moving today, and that at first our earth was a flaming thing on which no life could live.' They make us believe that the sun, white-hot though it is, is now much cooler than it was, and that it spins more slowly now than it did, and that it continues to cool and slow down.They also show that the rate at which the earth spins becomes smaller and continues to become smaller - that is to say, that our day is growing longer and longer, and that the heat at the centre of the earth goes down slowly. There was a time when the day was not a half or not a third of what it is today; when a flaming hot sun, much greater than it is now, must have moved visibly - if there had been an eye to see it - fromits rise to its setting across the skies. There will he a time when the day will be as long as a year is now, and the cooling sun, without its beams, will hang motionless in the sky.
