I know this will seemingly sound stupid but I have had multiple people argue with me about it. They claim that if they tie a knot in a plastic baggy it doubles the weight from 1 gram to 2 grams. I tell them there is no way because the mass doesn't change. I've tried to bet them any amount of money they were willing to bet and I have had no takers. So is there any way the weight changes without changing the mass or gravity?