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The development of time-resolved, multiscale and multi-modal X-ray imaging techniques at advanced light sources raises challenges on the data processing end — but image processing methods from other research areas will help.

Topological defects play an important role in biology, as shown by a growing body of evidence. Aleksandra Ardaševa and Amin Doostmohammadi survey the new research directions that are opening.

Machine learning methods have proved powerful in particle physics, but without interpretability there is no guarantee the outcome of a learning algorithm is correct or robust. Christophe Grojean, Ayan Paul, Zhuoni Qian and Inga Strümke give an overview of how to introduce interpretability to methods commonly used in particle physics.

Wigner crystals — ordered arrays of electrons — have been recently found in various 2D materials, but the first studies of these crystals in 2D electron systems (2DESs) date back from the 1980s. Mansour Shayegan gives a brief history of Wigner crystals and highlights future prospects.

Quantum machine learning may provide powerful tools for data analysis in high-energy physics. Sau Lan Wu and Shinjae Yoo describe how the potential of these tools is starting to be tested and what has been understood thus far.

Machine learning methods relying on synthetic data are starting to be used in mathematics and theoretical physics. Michael R. Douglas discusses recent advances and ponders on the impact these methods will have in science.

Although participating in outreach activities has many benefits for early-career researchers, outreach programmes are not always structured in a way that helps them participate. Three physicists explain why this motivated them to start a spin-off company dedicated to outreach.

Integrated approaches with advanced machine learning techniques are becoming necessary to take full advantage of the advanced experimental capabilities of next-generation synchrotrons. Yijin Liu and colleagues discuss the emergence of synergistic machine-and-data intelligence in synchrotron technology, and how it may accelerate scientific discovery.

The Indian space science program dates back to the 1960s, but has hit the headlines in the 21st century after successful missions to the Moon and Mars. Scientists from the Indian Space Research Organisation (ISRO) reflect on the past successes and share their plans for the future.

Since the launch of arXiv 30 years ago, modes of information spread in society have changed dramatically — and not always for the better. Paul Ginsparg, who founded arXiv, discusses how academic experience with online preprints can still inform information sharing more generally.

Anecdotal but elusive reports suggest that hot water quenched in a cold container can sometimes begin to freeze sooner than warm water under similar initial conditions. John Bechhoefer and colleagues discuss recent experiments that show how this ‘Mpemba effect’ can be reliably reproduced and quantitatively understood.

Writing on behalf of the Sudbury Neutrino Observatory (SNO) collaboration, Arthur McDonald recalls the discoveries that followed the SNO result on solar neutrino fluxes, published 20 years ago.

Large-scale projects have become increasingly important in physics. They are also a source of greenhouse gas emissions. Clarisse Aujoux, Odile Blanchard and Kumiko Kotera describe how to use transparent, open data to estimate these emissions — the first step in taking effective action to reduce them.

For almost 50 years the HITRAN molecular spectroscopic database has been the standard archive for transmission and radiance calculations. Laurence Rothman reviews its history and some applications.

In every breath, humans take in particles that may be deposited on the respiratory tract and exhale particles that may contain pathogens. Lidia Morawska and Giorgio Buonanno explain how physics advances are needed to understand these processes.

If graphene and related 2D materials are to be used commercially, buyers need to have confidence in the measured properties of the material they obtain from suppliers. Scientists from international standards committees describe how the first joint ISO/IEC measurement standard, published this month, will help.

Nuclear physics experiments give reaction rates that, via modelling and comparison with primordial abundances, constrain cosmological parameters. The error bars of a key reaction, D(p,γ)³He, were tightened in 2020, revealing discrepancies between different analyses and calling for more accurate measurements of other reactions.

Advanced metallic alloys can benefit from clusters of dopant atoms and intermetallic particles to improve their performance. Suhas Eswarappa Prameela, Peng Yi, Michael Falk and Tim Weihs discuss how atomic-scale defects can be used to form these clusters and particles.

As the construction of the Electron–Ion Collider (EIC) is starting, the EIC Project Director Jim Yeck shares his experience on the main ingredients for success of big science projects.

Faced with an economic crisis as large and rapid as that precipitated by the COVID-19 pandemic, economists have turned to new ‘fast indicators’ based on big data, as Andy Haldane and Shiv Chowla of the Bank of England explain.