LC ClassificationQB

aliens(249) asteroids(280) astrobiology(310) astrology(642) astrophysics(3,425) biography(3,866) biology(501) black holes(691) calendar(129) children(1,002) children's(1,346) cosmogony(95) cosmology(8,710) cosmos(403) creation(235) dark matter(181) earth(1,779) education(312) educational(182) elementary(217) evolution(485) exploration(373) Extraterrestrials(176) fall(770) galaxies(517) galaxy(183) Galileo(864) general relativity(132) general science(213) geography(779) geology(627) gravity(184) history(6,757) history of science(3,022) informational(878) Jupiter(249) juvenile(437) juvenile non-fiction(293) kids(309) maps(267) Mars(1,015) Mars (Planet)(65) math(1,854) meteors(193) moon(1,913) nasa(389) natural science(728) nature(1,470) Newton(86) observation(84) outer space(1,002) philosophy of science(195) photographs(356) photography(767) physics/astronomy(130) picture book(2,266) planet(235) planetology(49) planets(4,600) Pluto(247) popular science(1,856) quantum mechanics(191) quantum physics(283) quasars(80) reference(2,726) relativity(404) religion(513) Renaissance(296) science(45,704) science and technology(292) science fiction(696) science nonfiction(306) scientists(364) solar system(4,544) space exploration(772) space flight(198) spacetime(110) spring(519) stars(3,247) string theory(292) summer(291) theoretical physics(135) time(2,342) universe(2,030) weather(892) winter(634)