In other words, the average period of life has increased steadily. This is due to the fact that we have taken great care of our bodies; have improved the conditions in which we live, and made them more sanitary; have learned to fight and check and eradicate diseases, which only a few years ago we could not prevent people dying of when they once contracted them, and we know from the records which we keep that actually people live longer on the average today than only a few years ago, and it is safe to say that they live longer now on the average than at any time in the world’s history. Is There a Reason for Everything? The world is so constructed that there must be a reason or cause for everything. There are so many forces in the world that man has not yet been able to locate the original cause of every one of them. Concerning other things, he sees the effects without having any knowledge of the forces which are their cause. Other things he has never even bothered to inquire about, but simply takes them for granted. But every force, which means, of course, everything in the world, must have had a beginning and therefore something or a combination of things must have caused it to begin, and the thing or things that caused it to be is the reason for its being. Every little while someone makes a discovery of some new force, and then we suddenly realize that this force has been in existence all the time although not known to man, and we discover through this the reason for many other things being as they are. The other thing or side of the question is also true. We cannot have a cause without an effect. You cannot do anything without causing something to happen and producing an effect on one or more other objects either animate or inanimate. You cannot move your hand without creating some disturbance in the air. When you make a noise, low or loud, you produce sound waves. When you burn a stick of wood, you create smoke, ashes and gases of various kinds. You change the whole nature of what was the piece of wood, and yet no particle of what made the stick of wood is ever destroyed or lost, but appears in some other thing in the air or on or in the earth. What Makes an Echo? An echo is caused when the waves of air which you create when you shout are thrown back again when they are stopped by something they encounter and are turned back without changing their shape. Any kind of a sound wave will make an echo in this way.