Scientific theories are like maps.
“Maps are approximate pictures of an underlying reality; a map of Oskaloosa, Iowa is only an approximate representation of the real Oskaloosa. The only perfect map of Oskaloosa is Oskaloosa itself, which is too big to fit into the glove compartment of your car and thus not very useful. Just as map makers idealize and leave out certain features of the terrain, scientists simplify and idealize their theories. What is included or left out will depend on the purpose of the map or theory. If you are driving across the country, you might just need a course-grained map that shows the major highways. If, on the other hand, you were going to visit your great-aunt on Ford Avenue in Oskaloosa, you would need a fine-grained map that shows the street grid of Oskaloosa, but not all the highways in the country.”
“The course- and fine-grained maps (and theories) must agree with each other and the observations of the underlying reality. If a highway map places a river in a particular location, the river must be in the same location on the local map, and must agree with observations of where the river actually is. One cannot just move roads and rivers around for the purpose of making the maps easier to draw.”
“Science requires different levels of abstraction for different phenomena. Scientific theories can be big picture and course-grained like a highway map, or fine-grained like a local street map. Both are equally valid; they just need to agree with each other and conform to reality.”
— The Origin of Wealth by Eric D. Beinhocker