To explore it, we'll take a journey to the very edge of the universe.

 

We're leaving the galaxy altogether, on a journey that will take us across billions of light years of space and billions of years of time.

 

What are the great things about telescopes is they are time machines. Because light travels at a finite speed, when we look at distant objects, we see them as they were when the light left them.

 

As astronomers look back over billions of years, they see a universe teeming with galaxies. But the extraordinary thing is that galaxies are not scattered randomly through space. They cluster along delicate filaments, forming a vast cosmic web. So what gives the universe this intricate structure, and what does it have to do with the birth of galaxies themselves, the answer is shrouded in darkness. Look back far enough, and gradually all the galaxies disappear.

 

We've reached a mysterious period of time 12 and a half billion years ago.

 

There is this time period that we can't see because nothing is formed yet. It’s this epoch that’s called the dark ages.

 

 

 

During the dark ages, the universe was a very different place from the one we live in today. Back then, it was filled with dense clouds of hydrogen gas, like the gas that obscures the stars in the Milky Way today, these clouds block what might lie within.