Today is the day when the greatest we have ever known has been resurrected, to bring us into a bright new world and new understanding. That's right - the Large Hadron Collider has been successfully restarted after a two year upgrade, and is once more ready to explore the world of subatomic particle physics!

The LHC was built through the 2000s, and started up in 2008 only to have a major meltdown almost immediately. It was repaired and restarted the following year, and started hunting the Higgs boson.  Most of you will remember nearly three years ago now when the LHC made headline around the world for this discovery, and was forevermore made part of particle physics.

Then in 2013 the decision was made to turn it off again. With the Higgs successfully detected and studied, the teams want to go after bigger game. They want to explore even higher energy particle collisions, and to do that they needed to upgrade the machine. And for obvious safety reasons, that meant stopping the data collection. (The details of this upgrade have been covered in extensive detail in other articles, and so I will not repeat them here.)

Now it has been restarted, and over the coming weeks the engineers running the beams hope to increase the beam energy to 13GeV, which will nearly double the energy in the first run. Then they will spend the next two or three years collecting data on these higher energy collisions, and announce whatever they might discover.

And that is the exciting part. As physicists, we knew the Higgs would be found somewhere. Although there were discussions of alternatives, no theory could resolve the problems in the Standard Model as well as the minimal Higgs model. And for technical reasons, we knew it had to be in the energy range that the LHC could reach. While the Higgs was a major discovery, it was expected.

Now we enter the unknown. Look on the arXiv preprint server (the repository for all research articles in physics) and you will find thousands of articles proposing new effects that the LHC could detect in the next few years. We know that dark matter and dark energy exist, but we have no idea what they look like or where they will be found - the LHC can explore many possibilities now. There are good reasons to believe that we will find higher dimensions of spacetime, or produce tiny short-lived black holes in this energy range. There are reasons to believe that we might find an entire duplicate copy of the Standard Model in this energy range. Or maybe just a fourth generation of particles. And those are just the well accepted and well studied options - there are many more which could be surprises!

One cannot help but feel we have just entered an amazing new era of physics research today...