Estimates of the age of rain drops have been obtained from measuring the isotopic abundance of radon's short-lived decay progeny in rainwater.
ˈɛstᵻməts ʌvðɪ ˈeɪdʒ ʌv ɹˈeɪn dɹˈɑːps hɐvbɪn əbtˈeɪnd fɹʌm mˈɛʒɚɹɪŋ ðɪ ˌaɪsətˈɑːpɪk ɐbˈʌndəns ʌv ɹˈeɪdɑːnz ʃˈɔːɹtlˈɪvd dᵻkˈeɪ pɹˈɑːdʒəni ɪn ɹˈeɪnwɔːɾɚ.