How do scientisit now how much fuel is available on earth?

Scientists assess Earth's fuel availability through a combination of geological studies, exploration, and advanced technologies like remote sensing. They analyze geological formations and historical data to estimate reserves of fossil fuels, while drilling and sampling provide direct evidence of quantities. Additionally, advancements in modeling and data analysis help project future availability based on consumption rates and discovery of new reserves. This comprehensive approach allows for a more accurate estimation of the planet's fuel resources.