Classificação da Biblioteca do Congresso dos E.U.A. (LCC)QB799-903

21st century(10) academic(8) American author(7) ancient(12) animals(29) Asimov(12) astrobiology(14) astrology(96) astrophysics(635) attic(6) bears(8) biography(46) black holes(271) chemistry(11) children(86) children's(126) children's literature(19) Christmas(29) classical mythology(5) cosmogony(8) cosmology(439) cosmos(7) Creation(15) dark matter(7) digital(9) divination(8) earth(29) easy reader(19) education(24) educational(9) elementary(20) etymology(12) evolution(13) folklore(25) galaxies(246) galaxy(53) Galileo(5) general relativity(28) general science(6) Grade 2(14) gravity(24) Greek(14) Greek mythology(9) green(8) guide(21) history(144) history of science(89) imagination(8) informational(76) informative(9) juvenile(44) juvenile literature(6) juvenile non-fiction(17) kids(43) legends(13) light(14) maps(15) math(24) mitologia(5) moon(26) myth(14) myths(25) natural science(29) nature(75) observation(16) outer space(116) photographs(9) photography(24) physics/astronomy(11) picture book(215) planet(10) planetology(8) planets(163) popular science(77) primary(8) professional(9) quantum mechanics(6) quantum physics(6) quasars(28) reader(9) reference(151) reference guide(5) relativity(35) religion(17) research(8) school(16) science(2,825) science and technology(11) science fiction(26) science nonfiction(26) scientists(8) Sirius(13) solar system(259) space exploration(29) spacetime(7) stars(1,115) string theory(10) thesis(5) time(9) universe(99) weather(8)