At a talk for non-specialists on 21 February, David Tong outlined three big problems in physics , which I oversimplify/misrepresent as follows:
Dark energy. We've known for nearly a hundred years that the universe is expanding. It as if there is an antigravity force causing everything to repel everything else. We have no idea what it is. It’s 70% of the energy of the universe, it’s increasing all the time and we don’t understand it. Our best calculations are wrong by a factor of 1060 .So, Tong concluded, there is a lot in the fundamental physics that we simply don’t understand, and that it seems unlikely we’re going to get guidance from experiment. Looking to history, however, it is precisely when there is a crisis that physics has thrived. He is optimistic about progress.
Black holes. Information that goes into a black hole is lost forever. It does not reappear in Hawking radiation. But this cannot be.
Holography. It may be that our three dimensional world is actually a mirage. The correct description will be one in which the laws of physics are written on a two dimensional surface, and the laws of physics we can see in the universe are encoded on this surface in the same way that a hologram encodes a three dimensional surface.
Note : Some people say there are three great mysteries in science as a whole: the origin of the universe, the origin of life and the origin of consciousness.
Image: Douglas Griffin