I often get asked what an "expanding universe" really means.
It's confusing, and for very good reasons. So, if you are perplexed by this, don't feel bad. We all are, although cosmologists — physicists that work on the properties of the universe — have figured out ways to make sense of it. In what follows, I'll try to explain how to picture this.
In the next few weeks, we will address other bizarre cosmic questions, such as the meaning of the Big Bang and the future and material composition of the universe.