Many questions that at first sight have no dynamical context can be understood using dynamical systems. Here are some examples (of varying difficulty): Why is e irrational? Is every digit from 1 to 9 appearing infinitely often as a leading digit of a power of 2 (in the decimal expansion)? (What about the frequencies of appearance?) If Q is an indefinite quadratic form in 3 or more variables that is not a multiple of a form with rational coefficients, is then the set obtained by evaluating Q at the integer points dense in the real numbers? (this was a conjecture by Oppenheim and is now a theorem by Margulis) We will discuss the relationship between the above questions and dynamics, answer the first two (easier) questions, and discuss an important theorem by Ratner concerning the structure of orbits for some dynamical systems.