Model: Suppose that you know very little about Earth’s interior and wanted to find out how accurate Halley’s model was. How would you go about evaluating the validity of the model? What sort of evidence would you need to collect and how could you collect it? 

which

what is a measurement of the earth’s history divided into time periods?

> fossil record <

sedimentary rock

> geologic time scale <

radioactive elements

the answer is lactic acid from anaerobic respiration. the acid in lactic acid is what creates sore and burning muscles. if you think about how acid burns that will give you a clue for questions like this.