The scientists predicted how much the ground would sink at an Indonesian coal mine due to mining in multiple layers. They used a computer program to simulate different mining methods and depths. They realized that mining the lower layers first is better than mining the upper layers. They found that when the lower layers are mined, the ground sinks a lot more. By making the support pillars wider and the mining sections narrower, they discovered they could reduce the amount the ground sinks when mining in multiple layers at the mine.