European Space Agency (ESA) (21. marts 2013). "Planck reveals an almost perfect Universe" [Planck afslører et næsten perfekt univers]. ESA Newsletter (engelsk). ESA. Hentet 2013-03-23. Finally, the Planck data also set a new value for the rate at which the Universe is expanding today, known as the Hubble constant. At 67.15 kilometres per second per megaparsec, this is significantly less than the current standard value in astronomy. The data imply that the age of the Universe is 13.82 billion years
S. I. Chase, Olbers' Paradox, entry i the Physics FAQ; se også I. Asimov, "The Black of Night" (Nattemørket) i Asimov on Astronomy (Doubleday, 1974), ISBN0-385-04111-X.