【英语听力】英语高级听力材料：Journey to the Edge of the Universe

Hello, my name is Ann Druyan. When Carl Sagan, Steven Soter and I wrote the Cosmos television series in the late 1970s, a lot of things were different. Back then, the United States and the Soviet Union held the whole planet in a perpetual hostage crisis called the Cold War. The wealth and scientific ingenuity of our civilization was being squandered on a runaway arms race. They employed more than half the world scientists and infested the earth with 50, 000 nuclear weapons.

So much has happened since then. The Cold War is history and science has made great strides. We've completed the spacecraft reconnaissance of the solar system, the preliminary mapping of the visible universe that

surrounds us. And we've charted the universe within: the Human genome. When Cosmos was first broadcast, there was no World Wide Web, and, it was a different world. What a tribute to Carl Sagan, a scientist who took many a punch for daring to speculate, that even after 20 of the most eventful years in the history of science, Cosmos requires few revisions and indeed is rich in prophecy.

Cosmos is both the history of the scientific enterprise and an attempt to convey the soaring spiritual high of its central revelation, our oneness with the universe. Now please enjoy Cosmos: The proud saga of HOW, through the searching of 40, 000 generations of our ancestors we have come to discover our coordinates in space and in time. And how, through the awesomely powerful method of science, we have been able to reconstruct the sweep of cosmic evolution and to find our own part in its great story.

The cosmos is all that is, or ever was, or ever will be. Our contemplations of the cosmos stir us. There is a tingling in the spine, a catch in the voice, a faint sensation as if a distinct memory of falling from a great height. We know we are approaching the grandest of mysteries.

The size and age of the cosmos are beyond ordinary human understanding. Lost somewhere between immensity and eternity is our

tiny planetary home----the Earth. For the first time, we have the power to decide the fate of our planet and ourselves. This is a time of great danger, but our species is young and curious and brave, it shows much promise. In the last few millennia we have made the most astonishing and unexpected discoveries about the cosmos and our place within it. I believe our future depends powerfully on how well we understand this cosmos in which we float like a mote of dust in the morning sky.

We're about to begin a journey through the cosmos. We'll encounter galaxies and suns and planets, life and consciousness, coming into being, evolving and perishing. Worlds of ice and stars of diamond, atoms as massive as suns, universes smaller than atoms. But it's also a story of our own planet, and the plants and animals that share it with us. And it's a story about us, how we achieved our present understanding of the cosmos, how the cosmos has shaped our evolution and our culture, and what our fate may be.

We wish to pursue the truth no matter where it leads, but to find the truth we need imagination and skepticism both. We will not be afraid to speculate, but we will be careful to distinguish speculation from fact. The Cosmos is full beyond measure of elegant troves, of exquisite interrelationships, of the awesome machinery of nature.

The surface of the Earth is the shore of the cosmic ocean. On this shore, we've learned most of what we know. Recently, we've waded a little way out, maybe ankle-deep, and the water seems inviting. Some part of our being knows this is where we came from. We long to return, and we can, because the cosmos is also within us. We're made of star stuff. We are a way for the cosmos to know itself. The journey for each of us begins here. We are going to explore the cosmos in a ship of the imagination, unfettered by ordinary limits on speed and size, drawn by the music of cosmic harmonies. It can take us anywhere in space and time. Perfect as a snowflake, organic as a dandelion seed, it will carry us to worlds of dreams, and worlds of facts. Come with me.

Before us is the cosmos on the grandest scale we know. We are far from the shores of Earth, in the uncharted reaches of the cosmic ocean, strewn like sea froth on the waves of space, our innumerable faint tendrils of light, some of them containing hundreds of billions of suns.

These are the galaxies, drifting endlessly in the great cosmic dark. In our ship of the imagination, we're halfway to the edge of the known universe.

In this, the first of our cosmic voyages, we begin to explore the universe revealed by science. Our course will eventually carry us to a far-off and

exotic world, but from the depths of space we can not detect even the cluster of galaxies in which our Milky Way is embedded, much less the Sun, or the Earth.

We're in the realm of the galaxies, eight billion light years from home. No matter where we travel, the patterns of nature are the same, as in the form of this spiral galaxy. The same laws of physics apply everywhere, throughout the cosmos. But we have just begun to understand these laws. The universe is rich in mystery.

Near the center of a cluster of galaxies, there's sometimes a rogue elliptical galaxy made of a trillion suns, which devours its neighbors. Perhaps this cyclone of stars is what astronomers on Earth call a quasar.

Our ordinary measures of distance fail us here in the realm of the galaxies. We need a much larger unit -- the light year. It measures how far light travels in a year, nearly ten trillion kilometers. It measures not time, but enormous distances.

In the Hercules Cluster, the individual galaxies are about 300, 000 light years apart. So light takes about 300, 000 years to go from one galaxy to another.

Like stars, and planets and people, galaxies are born, live and die. They may all experience a tumultuous adolescence. During their first hundred million years, their cores may explode, seen in radio light, great jets of energy pour out and echo across the cosmos. Worlds near the core or along the jets would be incinerated. I wonder how many planets ……

(I wonder) how many planets and how many civilizations might be destroyed.

In the Pegasus Cluster there is a ring galaxy, the wreckage left from the collision of two galaxies, a splash in the cosmic pond. Individual galaxies may explode and collide and their constituent stars may blow up as well. In this supernova explosion a single star outshines the rest of its galaxy. We are approaching what astronomers on Earth call the Local Group.

3 million light years across, it contains some twenty galaxies. It's a sparse and rather typical chain of islands in the immense cosmic ocean. We are now only two million light years from home. On the maps of space, this galaxy is called M31, the great galaxy Andromeda. It's a vast storm of stars and gas and dust. As we pass over it, we see one of its small satellite galaxies. Clusters of galaxies and the stars of individual galaxies are all held together by gravity.

Surrounding M31 are hundreds of globular star clusters. We are approaching one of them. Each cluster orbits the massive centre of the galaxy, some contain up to a million separate stars. Every globular cluster is like a swarm of bees bound by gravity -- every bee, a sun. From the Pegasus Cluster, our voyage's taken us 200 million light years to the Local Group dominated by two great spiral galaxies.

Beyond M31 is another very similar galaxy, its spiral arms slowly turning once every quarter billion years. This is our own Milky Way seen from the outside.This is the home galaxy of the human species.

In the obscure backwaters of the Carina-Cygnus spiral arm, we humans have evolved the consciousness and some measure of understanding. Concentrated in its brilliant core and strewn along its spiral arms are four hundred billion suns. It takes light a hundred thousand years to travel from one end of the galaxy to the other. Within this galaxy are stars, worlds and it may be an enormous diversity of living things and intelligent beings and space faring civilizations.

Scattered among the stars of the Milky Way are supernova remnants, each one the remains of a colossal stellar explosion. These filaments of glowing gas are the outer layers of a star which has recently destroyed

itself. The gas is unraveling, returning star stuff back into space. And at its heart are the remains of the original star, a dense shrunken stellar fragment called a pulsar - a natural lighthouse blinking and hissing, a sun that spins twice each second. Pulsars keep such perfect time that the first one discovered was thought to be a sign of extraterrestrial intelligence, perhaps a navigational beacon for great ships that travel across the light years and between the stars. There may be such intelligences and such starships, but pulsars are not their signature. Instead, they are the doleful reminders that nothing lasts forever, that stars also die.

We continue to plummet, falling thousands of light years towards the plane of the galaxy. This is the Milky Way - our galaxy seen edge-on, billions of nuclear furnaces converting matter into starlight. Some stars are flimsy as a soap bubble; others are a hundred trillion times denser than lead; the hottest stars are destined to die young; but red giants are mostly elderly. Such stars are unlikely to have inhabited planets. But yellow dwarf stars, like the sun, are middle-aged, and they are far more common. These stars may have planetary systems, and on such planets for the first time in our cosmic voyage we encounter rare forms of matter - ice and rock, air and liquid water.

Close to this yellow star is a small warm cloudy world with continents

and oceans. These conditions permit an even more precious form of matter to arise: Life. But this is not the earth; intelligent beings have evolved and reworked this planetary surface in a massive engineering enterprise. In the Milky Way galaxy, there may be many worlds on which matter has grown to consciousness. I wonder, are they very different from us? What do they look like? What are their politics, technology, music, religion? Or do they have patterns of culture we can't begin to imagine? Are they also a danger to themselves?

Among the many glowing clouds of interstellar gas is one called the Orion Nebula, only 1500 light years from Earth.

These three bright stars are seen by earthlings as the belt in the familiar constellation of Orion, the Hunter.

The nebula appears from Earth as a patch of light, the middle star in Orion's sword. But it is not a star, it is another thing entirely, a cloud that veils one of nature's secret places.

This is a stellar nursery, a place where stars are born. They condense by gravity from gas and dust until their temperatures become so high that they begin to shine. Such clouds mark the births of stars as others bear witness to their deaths.

And after stars condense in the hidden interiors of interstellar clouds, what happens to them? The Pleiades are a loose cluster of young stars only 50 million years old. These fledgling stars are just being let out into the galaxy. Still surrounded by wisps of nebulosity, the gas and dust from which they formed.

There are clouds that hang like inkblots between the stars. They are made of fine rocky dust, organic matter and ice. Inside, a few stars begin to turn on, nearby worlds of ice evaporate and form long comet-like tails driven back by the stellar winds.

Black clouds, light years across, drift between the stars. They are filled with organic molecules. The building blocks of life are everywhere. They are easily made. On how many worlds have such complex molecules assembled themselves into patterns we would call "alive"?

Most stars belong to systems of two or three or many suns, bound together by gravity. Each system is isolated from its neighbors by the light years. We are approaching a single ordinary yellow dwarf star surrounded by a system of nine plan ets, dozens ……

……dozens of moons, thousands of asteroids and billions of