In elementary school, I thought the ball was getting bigger, but it was just the opposite. Later, I thought about it carefully, because the pressure on the big ball is small and the pressure on the small ball is large. After all the small balls were connected with the big ball, the small ball was eaten by the big ball. Just blow up the balloon. It's the hardest to blow at first, but it's easy to blow when it's big. That's why.