Recurring Guest Characters Malala Yousefzai 1 guest appearances George Tilton 1 guest appearances Michael Faraday 2 guest appearances William Herschel 2 guest appearances Edmund Muskie 1 guest appearances Clair Patterson 1 guest appearances Cecilia Payne 1 guest appearances Annie Jump Cannon 1 guest appearances Marie Tharp 1 guest appearances Einstein's Father 1 guest appearances Sarah Faraday 1 guest appearances Sir Humphry Davy 1 guest appearances Electric Spark Girl 1 guest appearances Augustin Mouchot 1 guest appearances Ibn al-Hazen 1 guest appearances Guard 1 guest appearances Businesswoman 1 guest appearances Cab Driver 1 guest appearances Giordano Bruno 1 guest appearances Barack Obama 1 guest appearances ⇤ « 1 2 » ⇥