探索频道英语听力 Cosmos 宇宙的边疆08

In this, our first cosmic voyage we have just begun the reconnaissance of Mars and all those other planets and stars and galaxies. In voyages to come, we will explore them more fully. But now we travel the few remaining light minutes to a blue and cloudy world, third from the sun. The end of our long journey is the world where we began. Our travels allow us to see the Earth anew as if we came from somewhere else. There are a hundred billion galaxies and a billion trillion stars. Why should this modest planet be the only inhabited world? To me, it seems far more likely that the cosmos is brimming over with life and intelligence. But so far, every living thing, every conscious being, every civilization we know anything about lived there - on Earth.

Beneath these clouds, the drama of the human species has been unfolded. We have at last come home.

Welcome to the planet Earth, a place with blue nitrogen skies, oceans of liquid water, cool forests, soft meadows, a world positively rippling with life. In the cosmic perspective, it is, for the moment, unique. The only world in which we know with certainty that the matter of the cosmos has become alive and aware. There must be many such worlds scattered through space, but our search for them begins here with the accumulated wisdom of the men and women of our species acquired at great cost over a million years.

There was once a time when our little planet seemed immense when it was the only world we could explore. Its true size was first worked out in a simple and ingenious way by a man who lived here in Egypt in the third century B.C.

This tower may have been a communications tower, part of a network running along the North African coast by which signal bonfires were used to communicate messages of state. It also may have been used as a lighthouse, a navigational beacon for sailing ships out there in the Mediterranean sea.