For many JW's, they are convinced about their religion more than gravity. A JW may get up from his bed in the morning and ask, "What if gravity is wrong?" but will never ask, "What if the GB is wrong?"
I disagree. JW realize that GB direction is subject to error ( in fact gb admit it ), whereas gravity is not. However, JW are convinced that they can trust God more than in: scientific realism and in cause and affect if they had to choose.