The BBC recently published a post by one of its science editors entitled “What is the point of the Large Hadron Collider?” The author goes over several justifications for such large projects. There is the idealistic view: Big science projects are important for improving our understanding of the universe, which to many is important to our society in its own right. There is also the pragmatic view: We don’t know what will come out of the research but at the very least many important inventions and a lot of technological progress have been made as a result of such projects in the past.
I would say that both points of view are compelling. The latter is obviously important, but the former is also a good point to make. A great deal of what people devote resources to in modern society is largely extraneous. We already spend a great deal of money on things that we want but don’t actually need. I would say that large science projects are a way to devote a tiny fraction of our resources to projects that in some way advance human society. Science, like literature, music, visual arts, theater, architecture, cuisine, and many other things, is an important part of what makes our society and our culture what they are today.