Original sentence: Just before noon on September 1, the British astronomer, Richard Carrington, observed the largest flare, which caused a massive coronal mass ejection (CME), to travel directly toward Earth, taking eighteen hours.This is remarkable because such a journey normally takes three to four days
Edited sentence: Just before noon on September 1, the British astronomer, Richard Carrington, observed the largest flare, which caused a massive coronal mass ejection (CME), to travel directly toward Earth, taking 18 hours.This is remarkable because such a journey normally takes 3 - 4 days