How big is the universe?

0										1 metre (100m)

We would make slow progress if we were to measure the universe a metre at a time. We can explore further, faster, if we allow each step to magnify tenfold - what scientists call an order of magnitude. All objects measuring between 1 and 10 metres long fall into one order of magnitude, which is our first step. The next step of our walk across the universe measures those things that are between 10 and 100 metres long, and so on.

So, first, visualise a metre. Picture something about 1 metre long. Common items include a golf club, a baseball bat, or a guitar...