How Can You Tell if Light Is Red Shifted?

We measure the distance to these far away objects by seeing how the light from them has been shifted in frequency. Because things that are further away from us are moving away faster. So you can measure the red shift of an object and tell how fast it's moving away from us. And therefore you can tell how far away it is, and therefore you canTell how old it is,. The king right now is something with a red shift of 20, which means that it's a hundred and 80 million years after the big bang.