英语听力：自然百科 穿越银河系的旅行 Through Milky Way—23

But dark matter does more than simply holds galaxy like ours together. Astronomers think it binds the Milky Way into an extraordinary structure along with billions of other galaxies. To explore it, we'll take a journey to the very edge of the univers

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—24

Its extremely frustrating because this region, this time period holds within it, in some sense, the rose headstone of / galaxy formation. But there are clues as to what was happening inside those dense hydrogen clouds. Look back even further in time

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—25

What happens is that, first the dark matter forms the structure, the ordinary matter then follows the dark matter. The ordinary matter is hydrogen and helium at this stage. And the hydrogen and helium fall/ to the center of the dark matter halos that

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—26

So what we are looking at is a region about 200 million light years across which is actually just a small part of our really big simulation that we call Bolshoi which is Russian for big. Everything that you see here is actually completely invisible.

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—27

But our time traveling isnt yet over. There is still the question of how the first galaxies kindled the very first stars. We are on a journey visiting the Dark Ages, a time over 12.5 billion years ago. The sight is spectacular. The sky is ablaze with

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—28

The first stars in our Milky Way were fearsome high-octane stars, burning their hydrogen fuel at tremendous rates, rushing through their life cycle. They like the rockslides. They live fast and die young. They run out of their fuel very quickly and e

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—35

You know, the indications there are a lot of those stars have planets, maybe have them built since planets you know, being like kittens, you know, just dig one, you get a couple. They are probably on the order of the million and million planets out t

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—34

One type of giant planet orbits very close to its star, we call them hot Jupiters because these Jupiter-like planets are so close that they are blowtorched by the intense heat from the star. The other sort of planet we have found is also bizarre. Wev

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—33

Venus is closer to the Sun, Mars is farther from the Sun. And there is a zone in between, the blazing hot furnace Venus, the frigid Mars. That zone in between we call a habitable zone and the earth lies smack in that thing where water would be in liq

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—32

A new galaxy is formed where, instead of the discs that the original galaxies have, where all the stars are going around more or less on a plane. Instead the stars are going every which way just like the elliptical galaxies that we see. And so we are

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—30

We've transported the earth 3 billion years into the future. The sky is dominated by a massive galaxy called Andromeda. The view looks peaceful enough. But whats about to happen is one of the greatest calamities in the universe. The clues lie in thes

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—29

And every faint smudge of light you are looking at is a galaxy. For Richard Ellis, it's a galactic treasure trove. So much like an archaeologist/, we piece together history by digging into deeper and deeper layers. So a cosmologist like myself, uses

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—31

Our galaxy is rushing toward the great galaxy Andromeda, they are rushing toward each other. And they are going to encounter each other in a couple billion years. Abraham and his colleagues decide to try to simulate this clash of the Titans. This was

英语听力：自然百科 野性俄罗斯之西伯利亚 Siberia—18

They wont be strong enough to challenge for females until they are five years old. Til that day, they will regularly hone their sparring skills. They will stay with the group until they mature. During the long winter chill, Lake Baikal transforms fro

英语听力：自然百科 澳大利亚大堡礁 Great Barrier Reef—5

shows it really quite well. In order to bring back a piece of this mystery, his team of divers will be risking their lives. Diving problems, you got currents, tides, waves. We havent been here before. We haven't been this deep, though. One of those c

英语听力：自然百科 澳大利亚大堡礁 Great Barrier Reef—4

Inside the flesh of these tiny animals are microscopic plants called algae, but these aren't parasites. None of this would be here without them. Wachenfeld: When the algae photosynthesize, they take energy from sunlight and carbon dioxide, then make

英语听力：自然百科 澳大利亚大堡礁 Great Barrier Reef—3

As a polyp grows, it puts up a wall of limestone around itself. And then it multiplies. Each polyp can produce thousands of offspring, which all work together to build a living fortress-- a coral reef. After just a few years, a single piece of coral

英语听力：自然百科 澳大利亚大堡礁 Great Barrier Reef—2

Where every plant and animal helps sustain the whole.The waste from parrot fish cements the reef. Stinging anemones provide a haven to the vulnerable. Even killers play their part, preventing a population explosion that would destroy this fragile eco

英语听力：自然百科 澳大利亚大堡礁 Great Barrier Reef—1

Where the forces of nature meet? In a hidden world, a tropical miracle. At this moment, evolution is building a living colossus, a giant built by nature's tiniest creature, a model of reincarnation, a survivor born from disasterthe Great Barrier Reef

英语听力：自然百科 野性俄罗斯之西伯利亚 Siberia—17

Three thousand five hundred meters up in the Sayan Mountains near the Russian-Mongolian border, Siberian ibex search for food. They scratch a living from the meager grasses on the sunnier south facing slopes. But some have a different sort of appetit