| A common theme of the newsletter this year has been the pace of progress in physics. I fretted that particle physics has plateaued relative to the heady days of the 20th century, speculated that precise cosmological and astrophysical experiments might lead to breakthroughs, and celebrated the booming study of exotic phases of quantum matter.
Despite my qualms about the field's uneven progress and long-term trajectory, there was certainly no shortage of intriguing research to write about this year. Looking back on the physics Quanta Magazine covered in 2024, numerous developments took place that struck me as unexpected, delightful or both.
What's New and Noteworthy
In January, a literal trial by fire demonstrated the sophistication of modern geophysics. The Earth split and unleashed a river of lava just uphill of the town of Grindavík in southwest Iceland. Fortunately, protective walls had been erected in accordance with precise forecasts of which areas would most likely find themselves in danger, and the town was largely saved. It's famously hard to give more than a few minutes' warning against volcanic eruptions and earthquakes, so I was impressed to learn that geophysicists had succeeded in giving the residents of Grindavík so much time to prepare.
The main bombshell of the year landed in early April. The Dark Energy Spectroscopic Instrument collaboration unveiled its first year of data, which contained a hint that dark energy — the mysterious engine driving the accelerated expansion of the universe — may be weakening. If confirmed, the finding would challenge the widespread belief that dark energy is an unvarying entity intrinsic to space itself. The data set is intricate, and the hint is rather subtle, so most physicists are maintaining a wait-and-see (if not outright skeptical) attitude. But if further data in the coming years strengthens the result, the theoretical implications would be huge.
Later that month, after working as a physics journalist for five or six years now, I had my first opportunity to cover news in string theory. A leading framework for a theory merging gravity and quantum mechanics, string theory received immense attention in the 1990s, when proponents suspected they were on the verge of explaining everything down to the mass of the electron. But the equations proved more difficult, and had many more solutions, than physicists had initially hoped. I was under the impression that the research program had largely stalled. But in fact, intrepid theorists are still grinding away at the theory's difficult mathematics, and two groups recently harnessed machine learning to achieve a long-held goal: taking a particular solution of string theory and calculating the masses of fundamental particles that come out of it. The research does not imply that string theory describes the particles of the real world, but it's a crucial step toward determining whether string theory can describe the real world.
Another highlight came in September, when we published the physicist Matt Strassler's intuitive explanation of how the Higgs boson gives mass to the fundamental particles. Discovering and verifying the equations that describe our world is naturally the top goal of physics. But telling a comprehensible story of what those equations mean is also, in my opinion, a worthy objective. I hadn't expected to extend my understanding of the Higgs boson much beyond the common metaphor that the Higgs field fills the universe like molasses, which gives particles mass as they struggle through it. But that picture has shortcomings, so I was delighted by Strassler's truer account of the Higgs field as a background entity that "stiffens" other fields, giving their vibrations a preferred frequency that we measure as particles of a given mass.
My last big surprise of the year was also conceptual. Physicists proposed a way to detect a single unit of gravitational energy, known as a graviton. They previously thought such a feat would require Death Star–level engineering, yet this proposed experiment could be done in years, not centuries.
Yet soon after I started digging, I found that the experiment would be contentious in a way that mirrors the history of the photon, the particle of light. I was astonished to learn that "discovering" the photon had required a series of increasingly sophisticated experiments that played out over decades — a far cry from the just-so story that Albert Einstein had sewn everything up in 1905. Truly proving the existence of the graviton will, it seems, entail a similar ordeal.
And with that, cheers to another year of fascinating physics research. I'm looking forward to seeing what new experiments, theories and interpretations 2025 will bring. | 
