This September, it's been 16 years since I started studying physics. That's 2^2^2 years which have gone by and bye. Stefan started in 1987. The first physics headline I can recall consciously taking note of was the 1995 discovery of the top quark, and Stefan cites inspiration by the Supernovae 1987a. This got us into a conversation about the most striking insights physics has delivered since we went to university. Here are our winners:
The biggest surprise for everybody except Raffael Sorkin was that the Cosmological constant is not zero. Since 1998, evidence has been adding up and up that our universe undergoes accellerated expansion caused by a small, positive cosmological constant. For more, read my earlier post on the Cosmological Constant and its cousins.
When I was a graduate student, physicists were still debating whether black holes exist or if black holes are just a mathematically possible solution to Einstein's field equations that is however not realized in nature. The first evidence was available already back then, but it took a while for more observations to be made and gradually everybody came to accept that black holes exist for real. (Well, almost everybody.) For more on black holes, see here.
Suspected by many, it still took several decades to unambiguously show that neutrinos have mass. Due to the neutrinos' weak interaction, many years of data had to be collected over different propagation distances at different energies. It wasn't until 2001 that the option of decay rather than oscillation could be ruled out by the SNO results. Yet, the neutrino sector of the standard model still has some mysteries to offer.
In my quantum mechanics class, EPR-type tests of Bell's theorem were Gedankenexperimente. Now they are reality. So are other tests of the foundations of quantum mechanics, down to single photons, double-slit experiments with atoms, while our understanding of entanglement and decoherence has increased and superpositions of larger and larger molecules succeed.
And on the computational side, amazing simulations of large scale structure formation have become possible. If you haven't seen the Millenium Simulation, it's time well spent.
The recent issue of Physik Journal (the membership journal of the German Physical Society) has an article "Physik im Aufwind" that summarizes recent statistical trends in physics. The below shows the number of beginning students in physics by year. I started in the middle dip. It is good to see that physics is drawing in more young people again.