Escaping from the Earth

The greatest high jumper in the world can lift himself no more than a few feet above the earth. With a balloon or a high-flying jet aircraft he can reach a height of several miles.

Only the rocket will enable us to reach the vast emptiness of space.

The pull of gravity depends upon size, or, more accurately, upon what is called mass. This is the amount of material in an object. The closer an object is to a large body like the earth, the greater is the earth's pull. If we get away from it, the strength of the pull weakens. The high jumper quickly falls back to earth. To get right away he would have to leap into space at a speed of seven miles per second. This is called the earth's escape velocity.

To launch a rocket into space at this speed demands enormous power, and material strong enough to withstand the tremendous strains and the heat produced by friction as the rocket rushes through the air.

There is an easier way of launching our rocket. We start with a rocket which need not escape completely from the earth. On top of it we place another smaller one and even a third. These can be fired in turn as the first one reaches the end of its flight and falls to earth.

As the rocket gets farther into space, the earth's atmosphere is left behind, and there is less resistance. The earth's gravity, too, grows weaker and in this way a high speed can be built up. At twenty-five thousand miles per hour our rocket will escape from the earth's pull and travel wherever it is steered.