Sometimes objects are too large or too small to imagine. Scientists use scale models in order to visually represent things that are too small or too large to view.
The solar system is billions of miles across - in order to visualize the distances between planets and understand the scale of the universe, scientists can produce a scale model. A scale model of the universe on earth might be 1:100,000,000 the size of the actual universe (one hundred million times smaller).
Making a Scale Model:
To make a scale model, first you'll need the dimensions of the actual objects you'll be modeling. Lets use the sun as our example. The sun is 864,000 miles across (54,743,040,000 inches). To make a model of the sun that is 1:100,000,000, you divide the actual size of the sun by 100,000,000.
54,743,040,000 inches (size of actual sun) / 100,000,000 (the amount of times smaller we want our scale model to be) = 547.4 inches (45ft 7inches)
If we were to make a scale model of the sun that is 100,000,000 smaller than the actual sun, our model sun would be 45 feet and 7 inches across.
In this picture, a model is used in order to visualize how a hydroelectric power plant works.