The huge void containing our Earth, the Sun that warms us, and the Moon and the stars that twinkle in the night sky, is known as the universe. But how big is it? You may think that the area from one end of the city you live in, to the other end, is very large. Some of you may have traveled from one end to the other of your country and you have seen how big it is. Some of you may even have traveled to far-off countries. But, do not forget… Even if you have gone all around the world, the distances involved are still nothing compared to the vastness of the universe. The space occupied by the Earth in the universe is no bigger than a grain of sand!