How do black holes destroy information and why is that a problem?
> The important thing is that all evolution equations that we know of are time-reversible.<p>I've heard this before, but it's so surprising to me, when one of the simplest mathematical operations - addition - is not reversible. e.g. if <i>a+b=4</i>, you can't infer the values of <i>a</i> and <i>b</i> (beyond their linear relationship). This non-injectivity is a kind of summarising, with less information, where more than one state maps to one.<p>So "evolution equations" (reality) are not like addition; state changes never summarise.