In “The Singularity Is Always Near,” an essay in The Technium, an online “book in progress,” author Kevin Kelly critiques arguments on exponential growth made in Ray Kurzweil’s book, The Singularity Is Near. Kurzweil responds.

Allow me to clarify the metaphor implied by the term “singularity.” The metaphor implicit in the term “singularity” as applied to future human history is not to a point of infinity, but rather to the event horizon surrounding a black hole. Densities are not infinite at the event horizon but merely large enough such that it is difficult to see past the event horizon from outside.

I say difficult rather than impossible because the Hawking radiation emitted from the event horizon is likely to be quantum entangled with events inside the black hole, so there may be ways of retrieving the information. This was the concession made recently by Hawking. However, without getting into the details of this controversy, it is fair to say that seeing past the event horizon is difficult (impossible from a classical physics perspective) because the gravity of the black hole is strong enough to prevent classical information from inside the black hole getting out.