Natural motion depends on the element concerned: the aether naturally moves in a circle around the heavens, while the 4 Empedoclean elements move vertically up (like fire, as is observed) or down (like earth) towards their natural resting places.
nˈætʃɚɹəl mˈoʊʃən dᵻpˈɛndz ɔnðɪ ˈɛlɪmənt kənsˈɜːnd: ðɪ ˈiːθə nˈætʃɚɹəli mˈuːvz ɪn ɐ sˈɜːkəl ɚɹˈaʊnd ðə hˈɛvənz, wˌaɪl ðə fˈoːɹ ɛmpˈɛdəklˌiən ˈɛlɪmənts mˈuːv vˈɜːɾɪkli ˌʌp lˈaɪk fˈaɪɚ, ˌæzˌɪz əbzˈɜːvd ɔːɹ dˌaʊn lˈaɪk ˈɜːθ təwˈɔːɹdz ðɛɹ nˈætʃɚɹəl ɹˈɛstɪŋ plˈeɪsᵻz.