What is the geological time scale based on?

The geological time scale refers to the arrangement of major and distinguishable events that have taken place in the geological past and also provides a glimpse of how the earth and the organisms have undergone significant evolution over a due course of time. It is based on the presence of fossils on the rocks of various sequences, and also the classification of rock types and the correlation of rocks of different locations.  It shows right from the time of formation of the earth, which is approximately 4.6 billion years ago.

This time scale is one of the main components of geology and is widely used by the paleontologists, geologists and other earth-related scientists, in order to construct the relation of various events that have occurred in the past.  

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.