“Fora moment James wondered if he had done his sums right.” Why wasJames doubtful about his sums and calculations?

Jamesbecame doubtful about his sums and calculations when he looked upfrom his window and saw a star-studded night sky. He knew thatsomewhere amongst those stars was Comet Dutta, which was headingfor a collision with the earth. It was hard for him to believe thecalamity of the future on such a peaceful night.