Theories can attempt to answer these questions, but only by observation can the hard evidence needed to prove or disprove a theory be attained. Nowadays the science of astronomy uses scientific techniques to probe our Universe, showing it to be even stranger and bigger than we ever realized. We have discovered a Universe containing unusual places and objects like planetary nebulae, red giant stars, hot white dwarf stars, multiple star systems, colliding galaxies and black holes. While cosmologists try to explain the beginnings of the Universe by trying to understand the properties of the Big Bang, the study of stars has led us to realize that our own Sun is a middle age star, in a part of the galaxy we call the Milky Way. The stars are accessible to everyone on any dark night making it one form of science where you can make observations of the Universe from your backyard.
Amateur astronomers pursue such a hobby in their spare time, purely for the pleasure of it.