P. 4: I discussed interstellar flight in Space Shuttle terms with NASA’s John Cole at Marshall Space Flight Center, where he gave me an idea of the staggering amount of fuel a chemical rocket would need to go to the nearest star. But I mis-stated Cole’s comment; it would not require 10 to the 88th power in kilograms of fuel to reach Alpha Centauri (i.e., on a flyby mission). It would take that much fuel for a rendezvous mission, going to Alpha Centauri, decelerating at a destination planet, then launching again for return to Earth. The rocket equation again confounds our hopes — the requirement for propellant increases not proportionally but exponentially in relation to the final velocity required.

Bernard Haisch and Alfonso Rueda also discussed this not long ago in an article in Mercury (“Prospects for an Interstellar Mission: Hard Technology Limits but Surprising Physics Possibilities,” Mercury Vol. 29 No. 4, July/August, 2000). Their conclusion: a ‘Space Shuttle’ flyby of Alpha Centauri would take a rocket much larger than the Sun. A mission with return capability would require a rocket larger than the visible universe. So much for chemical propellants!

P. 81: When I looked at Gerald Smith and team’s AIMStar design at Pennsylvania State, I described how it would use antimatter to initiate a fusion reaction. However, I referred to the need for 30 to 130 milligrams of antimatter. This should have been 30 to 130 micrograms.

P. 195: Brett Holman writes from the University of Melbourne that German mathematician Karl Gauss probably considered using lanterns and mirrors to signal the Moon, not Mars as I had stated. Brett also calls attention to my description of Joseph von Littrow’s notion of a ditch in the Sahara Desert that could be filled with water and kerosene and set on fire as a beacon. “…while von Littrow does mention the geometrical pattern idea, he does not specify a location for it and furthermore, attributes the idea to a “German geometer” (who *might* have been Gauss),” Holman writes.

P. 197: A note from Vinton Cerf points out that the man I refer to as Kevin Ford from Intel Corporation is actually Kevin Fall. Apologies to Kevin, whom I met at a gathering of the InterPlanetary Internet SIG at JPL in 2003.

P. 203: I refer to the star Canopus as Alpha Argo (i.e., the brightest star in the constellation Argo), but Argo was in fact split up into smaller constallations in the 18th Century, and Canopus is now Alpha Carinae, brightest star in the constellation Carina. Thanks to Brett Holman for this one, too.