Question: What is the biggest question in Physics at the moment?

Arttu Rajantie answered on 22 Jun 2011:

Physics is full of big questions, but many of them are currently out of our reach. One of the biggest questions that we may actually be able to answer in the next ten or twenty years is why (and perhaps also whether) the universe went thought a period of accelerating expansion in its very first moments. This period, which we call inflation, explains why the universe is so big and how all the galaxies formed, but currently we do not understand what caused it.