The universe, as you’ve probably heard, is expanding. This has all sorts of cool implications but one of the most basic is that it screws around with your sense of geometry. It also messes with your concepts about distance. For instance, even though a) the most distant observations allow us to look about 14 billion years in the past, and b) those signals have been traveling toward us at the speed of light for the age of the universe, c) the sources are now way more than 14 billion light years away. And d) There’s at least 4 different ways to say how far the sources are away, all of them perfectly legit.
This week I’ll talk about how the expanding universe makes any description of travel directions problematical. The only problem is that I don’t have a good way of phrasing the question. Do you have any ideas? If so, please post them below.