How is the Universe bigger than its age?

We know that the Universe has been around for 13.8 billion years, but we also know we can see for 46 billion light-years. How is this possible?

“Nature decrees that we do not exceed the speed of light. All other impossibilities are optional.” -Robert Brault

One of the most remarkable discoveries of the 20th Century came from studying the great spiral nebulae littered throughout the night sky.

Image credit: Ken Crawford at Rancho Del Sol Observatory, via RC Optical Systems at http://gallery.rcopticalsystems.com/gallery/ngc7331_stephans.html.

It was quickly discovered that not only were these objects galaxies very much like our own Milky Way, many thousands of light-years in size apiece, but the vast majority of them were moving away from us. What was even more exciting is that the farther away — on average — these galaxies were, the faster they appeared to be receding. It took only a few years for both the mechanism and the law governing this phenomenon to be uncovered.

Image credit: the Astrophysics Research Institute at Liverpool John Moores University.