Can you see the size of a bomb?

Many physical problems can be modeled by some basic equations, and in principle the corresponding phenomena should be possible to explain by solving the equations. However, in many cases this turns out to be unrealistic, even if we have large computers at our disposal, and hence it is often useful to adopt a phenomenological approach. One good example is the dimensional analysis, which offers a method for reducing the complex physical problems to the simplest (that is, most economical) form prior to obtaining a quantitative answer. In this talk I will illustrate the basic idea of this method through some examples including the famous Trinity Test.