It is warm in summer because at that season of the year the heat rays of the sun strike our part of the earth through less air. The blanket of air which surrounds the earth is very much in comparison as to thickness like the peeling of an orange and surrounds the earth in just the same way. If you stick a pin straight into an unpeeled orange you only have to stick it in a little way before you reach the juicy part of the orange, but if you stick the pin in at an angle the pin will travel a much longer ways through pure peeling before it strikes the juicy part. Now, then, in summer the rays of the sun come down to us straight through the peeling of air, and less of the heat is lost by contact with the air, and that makes it warmer in summer. The explanation also accounts for your next question. Why Is It Cold in Winter? In winter the heat rays of the sun strike at our part of the earth at the angle at which you stick the pin into the orange when you wish to make it travel through the most peeling. In winter the rays strike the earth at such an angle that a great deal of the heat is lost in travelling through the air, because they have to come through so much more of the air. Of course, the sun’s rays strike some part of the earth straight down through the peeling of air at all times, and at the equator this occurs all the year round, so it is always summer there, while at the North and South Poles the rays always strike the earth at the greatest possible angle, and it is always very cold winter there. In between, when it is neither hot nor cold, we have spring and fall, due to the fact that the rays come down at an angle, but not so great an angle. Why Have We Five Fingers on Each Hand and Five Toes on Each Foot?