In celebrating cancer immunotherapy—harnessing the immune system to battle tumors—did we risk hyping an approach whose ultimate impact remains unknown? ... Ultimately, we concluded, cancer immunotherapy passes the test. It does so because this year, clinical trials have cemented its potential in patients and swayed even the skeptics.The runner-ups were mostly biology as well (more proof we are living in the Biological Century), although two physics breakthroughs did make the list. One, the Fermi satellite's discovery of pi-zero decays in the spectra of supernovae, indicating that SN do in fact accelerate protons and are in fact the source of cosmic rays. Two, the development of a new technology for solar cells made out of perovskite crystals that are competitive with silicon cells in terms of efficiency, but are much cheaper and easier to manufacture. Anyway, here's the video:
If you want more physics, Physics World has their own roundup, naming the Ice Cube discovery of cosmic neutrinos as Breakthrough of the Year. Elsewhere, Ed Yong rounds up his list of the Top Science Longreads of 2013.