Exploration Human-alien encounters 23 Interplanetary voyages 23 Science and civilization 14 Space ships 14 Exploration of outer space 12 Space flight 11 more ... Extraterrestrial beings 8 Scott, Montgomery (Fictitious character) 8 Interstellar travel 7 Sulu, Hikaru (Fictitious character) 7 Women ship captains 7 Astronauts 6 Life on other planets 6 McCoy, Leonard (Fictitious character) 5 Wormholes (Physics) 4 Discoveries in geography 3 Enemies 3 Kirk, James T. (Fictitious character) 3 Spock (Fictitious character) 3 Video recordings for the hearing impaired 3 Enterprise (Imaginary space vehicle) 2 Exploración 2 HAL (Fictitious character) 2 Hallucinations and illusions 2 Headache 2 Helium 2 History 2 Introduced organisms 2 Science fiction films 2 less ...