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

 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 this image to look at the history of the universe how the most distant galaxies, seen as they were a long time ago, evolve and grow to the biggest systems that we see around us today. 
 
 
 
The image reveals something very intriguing about the beginning of our Milky Way. 
 
 
 
When we look at these early galaxies, they don't resemble the star cities that we see today. They are lumpy, they are irregular, they appear to be interacting with their neighbors, they’re physically very very small. So clearly the universe was very different in those early times. 
 
 
 
Twelve billion years ago, the universe was a much smaller place. It hadn’t expanded to the size / it is today. Our Milky Way would’ve been jostling for room. 
 
 
 
So it's very difficult for these early galaxies to establish themselves. These early galaxies are struggling to survive at this very early time. 
 
 
 
It was a case of survival of the fittest, the largest galaxies growing bigger by devouring the smallest. 
 
 
 
So it's tough for these early systems to form, but clearly they do, and they eventually merge with their neighbors and form the biggest systems that we see today. 
 
 
 
It was collisions in the early universe that created the beautiful spiral galaxy we live in today. But astronomers believe there is one final collision in store for the Milky Way, one which will change it foreve
  原文地址:http://www.tingroom.com/lesson/zrbaike/2011/260183.html