What happens at a black hole's edge? It depends on your perspective

In a recent column, I wrote about black holes. A curious reader sent in a letter asking some interesting follow-up questions about topics that I didn’t really have time to delve into, more specifically about the relationship between matter and a black hole, as well as what happens at the centre of it all.

The easy answer to the second part is that we have no idea. End of column! More seriously, part of what makes black holes such interesting phenomena to study is that perspective really matters. We know that they are demarcated by a boundary known as…