Neil deGrasse Tyson
Self - Host

Carl Sagan
Self (archive footage) / Self (voice) (archive footage)

Seth MacFarlane
Giordano Bruno (voice) / Sherwood Rowland (voice) / President Harry S. Truman (v...

Stoney Emshwiller
/ Guard (voice)

André Sogliuzzo
Weichelberger (voice) / Christopher Wren (voice)

Christopher Emerson
/ Acolyte (voice)

Piotr Michael
Edmund Muskie (voice) / Lab Assistant (voice)

Enn Reitel
Henry Norris Russell (voice) /

Keythe Farley
/ (voice)

Patrick Stewart
William Herschel (voice)

Elizardo Torrez
Young Carl Sagan

Trang Vo
(voice) / Birthmark Woman

John Steven Rocha
Bellaramine (voice)

Paul Telfer
Angry Scholar #2 (voice)

Jonathan Morgan Heit
John Herschel (voice)

Cary Elwes
Edmond Halley / Robert Hooke (voice)

Tom Konkle
Samuel Pepys (voice)

Alexander Siddig
Isaac Newton (voice)

Alfred Molina
Ibn al-Haytham (voice)

Richard Gere
Clair Patterson (voice)