Lifeboat Foundation

Physicists used to think they had a good idea of the size of the proton. Values derived from measurements of hydrogen’s emission spectrum and from electron-scattering experiments agreed with a proton radius of around 0.88 femtometers (fm). Then, in 2010, confidence was shaken by a spectral measurement that indicated a proton radius of approximately 0.84 fm [1]. In the years since, this “proton radius puzzle” has become even more of a head-scratcher, with some experiments supporting the original estimate and others finding an even greater discrepancy. Simon Scheidegger and Frédéric Merkt at the Swiss Federal Institute of Technology (ETH), Zurich, have now made precise new measurements of the transition energies between one of hydrogen’s metastable low-energy states and several of its highly excited states [2] (Fig. 1). These measurements allow the researchers to derive some of the atom’s properties, such as its ionization energy, with greater confidence, which should help clear up some of the confusion.

The 2010 study that “shrank the proton” (as the title of the editorial summary in Nature jokingly stated) concerned the 2 S –2 P_1/2 Lamb shift [1]. According to Dirac’s predictions, the 2 S and 2 P_1/2 levels of atomic hydrogen should be degenerate. The Lamb shift refers to the lifting of this degeneracy by quantum electrodynamic (QED) effects, the largest contribution being the electron “self-energy” due to interactions with virtual photons. Once this and other QED effects are accounted for, a tiny shift of the bound-state energy levels remains, which can be attributed to the proton’s finite size. By measuring this residual energy shift, one can determine the proton radius directly. The authors of the 2010 study did so using hydrogen atoms in which the electron was replaced by its heavier cousin, the muon, since the finite-size effect is stronger in this system.

Ever since that surprise result, researchers have tried to pin down the proton radius both directly, via the finite-size effect, and indirectly, via the Rydberg constant. The Rydberg constant relates an atom’s energy levels to other physical constants and is one of the key inputs used in calculations of the proton radius. Determining its value requires painstaking measurements of the transition energies between hydrogen’s various states. Several groups have made monumental efforts in this regard, but the values they derive for the proton radius have been all over the place. A 2018 measurement of the 1 S –3 S transition by a group in France gave a value of about 0.88 fm [3], a 2019 measurement of the classic Lamb shift (this time in regular hydrogen) by a group in Canada came up with a value of about 0.833 fm [4], and a 2017 measurement of the 2 S –4 P transition by a group in Germany suggested a similarly low value of about 0.834 fm [5]. In 2020, the group in Germany arrived at a slightly higher value of 0.848 fm [6]. In 2022, finally, from measurements of the 2 S –8 D transition, a group at Colorado State University proposed a “compromise value” of about 0.86 fm [7].

The particle accelerators that enable high-energy physics and serve many fields of science, such as materials, medical, and fusion research, are driven by superconducting magnets that are, to put it simply, quite finicky.

When we recycle electronic devices we can no longer use, we expect to make the most out of the precious natural resources that went into building them. But electronic waste is notoriously difficult to recycle because it’s hard to separate the different metals in the waste from each other.

Experiments with liquid metals could not only lead to exciting insights into geophysical and astrophysical flow phenomena, such as atmospheric disturbances at the rim of the sun or the flow in the Earth’s outer core, but also foster industrial applications, for example, the casting of liquid steel.

However, as liquid metals are non-transparent, suitable measurement techniques to visualize the flow in the entire volume are still lacking. A team of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has now, for the first time, obtained a detailed three-dimensional image of a turbulent temperature-driven liquid metal flow using a self-developed method. In the Journal of Fluid Mechanics, they report on the challenges they had to overcome on the way.

Ever since researchers have been investigating the properties of turbulent flows in fluids, they have used an experiment that initially seems quite simple: the fluid is filled into a container/vessel whose base plate is heated and whose lid is cooled at the same time. A team of the Institute of Fluid Dynamics at HZDR is investigating the very details of this process.

From creating images, generating text, and enabling self-driving cars, the potential uses of artificial intelligence (AI) are vast and transformative. However, all this capability comes at a very high energy cost. For instance, estimates indicate that training OPEN AI’s popular GPT-3 model consumed over 1,287 MWh, enough to supply an average U.S. household for 120 years.

The printed solenoids could enable electronics that cost less and are easier to manufacture — on Earth or in space.

Imagine being able to build an entire dialysis machine using nothing more than a 3D printer.

This could not only reduce costs and eliminate manufacturing waste, but since this machine could be produced outside a factory, people with limited resources or those who live in remote areas may be able to access this medical device more easily.

Superconductivity makes physics seem like magic. At cold temperatures, superconducting materials allow electricity to flow indefinitely while expelling outside magnetic fields, causing them to levitate above magnets. MRIs, maglev trains, and high-energy particle accelerators use superconductivity, which also plays a crucial role in quantum computing, quantum sensors, and quantum measurement science. Someday, superconducting electric grids might deliver power with unprecedented efficiency.

Challenges with Superconductors

Yet scientists lack full control over conventional superconductors. These solid materials often comprise multiple kinds of atoms in complicated structures that are difficult to manipulate in the lab. It’s even harder to study what happens when there’s a sudden change, such as a spike in temperature or pressure, that throws the superconductor out of equilibrium.

Research utilizing the James Webb Space Telescope highlights the destructive power of ultraviolet “winds” on the gas in protoplanetary disks surrounding young stars, shedding light on the intricate dynamics that limit the formation of gas giants in the cosmos.

Ultraviolet “winds” from nearby massive stars are stripping the gas from a young star’s protoplanetary disk, causing it to rapidly lose mass, according to a new study. It reports the first directly observed evidence of far-ultraviolet (FUV)-driven photoevaporation of a protoplanetary disk. The findings, which use observations from the James Web Space Telescope (JWST), provide new insights into the constraints of gas giant planet formation, including in our own Solar System.

Insights into gas giant planet formation.

The mysteries of photosynthesis have been unveiled at the atomic level, providing significant new insights into this plant super-power that transformed the Earth into a green landscape over a billion years ago.

John Innes Centre researchers used an advanced microscopy method called cryo-EM to explore how the photosynthetic proteins are made.

The study, published in Cell, presents a model and resources to stimulate further fundamental discoveries in this field and assist longer-term goals of developing more resilient crops.