
“The interior of the earth is extremely hot - several million degrees.”
From interview he gave to Conan O'Brien in The Tonight Show http://www.youtube.com/watch?v=Ns_4pzfOSTc on 11th November 2009. The real temperature in the inner core is about 9032 - 10832 ºF (5000-6000 ºC).
Quotes from Interviews