evidence: A few weeks ago, I was surprised upon glancing at The New York Times to see a front-page article claiming that new scientific evidence showed conclusively that wearing masks does nothing to prevent the spread of the SARS-CoV-2 virus (Bret Stephens. The mask mandates did nothing. Will any lessons be learned? The New York Times; 21 February 2023). Even the high-quality surgical-standard N95 masks. This opinion piece by Bret Stephens reported on what he described as "the most rigorous and comprehensive analysis" of the effects of masks, published in Cochrane Reviews, a healthcare journal. Masks, he claimed, have no effect. [...] Fortunately, there are still people trying to build actual knowledge about important matters, without deciding in advance what their conclusions will be. An excellent illustration is a review article (Mira L. Pöhlker et al., Rev. Mod. Phys.; in the press; preprint available at https://arxiv.org/abs/2103.01188) looking at what we know about the aerosols and droplets that are expelled by individuals suffering from a number of respiratory pathogens. It considers the complicated physics of how these particles are generated in the respiratory tract, how they behave in the air and how far they generally travel, as well as how well masks do in blocking their passage. [...] Conclusion? Masks do have an effect. They do work, imperfectly, to stop pathogens spreading. Intuitively, I’m not in the least surprised, but it’s nice to see some detailed evidence.