The Apollo 8 crew were the first humans to pass through the Van Allen radiation belts, which extend up to  from Earth.
ðɪ ɐpˈɑːloʊ ˈeɪt kɹˈuː wɜː ðə fˈɜːst hjˈuːmənz tə pˈæs θɹuː ðə vˈæn ˈælən ɹˌeɪdɪˈeɪʃən bˈɛlts, wˌɪtʃ ɛkstˈɛnd ˌʌp tə fɹʌm ˈɜːθ.