Turtles All The Way Down

I was attending a conference, and the speaker used the phrase "turtles all the way down". This is a bit obscure, so I'll explain. Apparently, someone, perhaps an atheist, perhaps someone believing in evolution, or some such was talking about the Earth being round.

This woman proclaimed that the Earth was not round, but was carried on a turtle's back (that's digging to some old mythology). The speaker, being clever, (it's alleged to be mathematician, Bertrand Russell) asked the woman "Ah, but what does the turtle stand on?". She said "Very clever, young man. But I have an answer! It's turtles all the way down!"

Despite this odd explanation, it's seen as a kind of infinite recursion/regression.

Of course, you could read Wikipedia (which I consulted).