17 - The cosmic box

Summary

I could be bounded in a nutshell and count myself king of infinite space, were it not that I have bad dreams.

William Shakespeare (1564–1616), Hamlet

THE UNIVERSE IN A NUTSHELL

Reflecting walls

We look out in space and back in time and the things seen at large distances are similar to things that existed in this part of the universe long ago. The scenery billions of light years away, as we see it, is the same as the scenery here billions of years ago. With a time machine that could travel back into the past we would have less need of large telescopes that strain to reach the limits of the observable universe.

This argument prompts the following thought. Things are very much the same everywhere at the same time, why not then confine our attention to a single region, concentrate on its history and ignore the rest of the universe? The history of what happens in this single region is the same as the history of what happens everywhere.

But this argument has an apparent drawback. Any chosen sample region is influenced by other regions near and far, how then can we afford to ignore the affect of these other regions? Light, for instance, travels great distances and influences what happens in the sample region. If we are to pay undivided attention to a single region, ignoring all other regions, we must in some way allow for their influence.