Sub-part-per-trillion test of the Standard Model with atomic hydrogen
TL;DR
Scientists made an incredibly precise measurement of light emitted by hydrogen atoms that tested one of physics' most fundamental theories - the Standard Model - to an accuracy of 0.7 parts per trillion. This measurement also resolved a long-standing disagreement about the size of protons by confirming the smaller value found in previous experiments with exotic atoms.
Quantum electrodynamics (QED), the first relativistic quantum field theory, describes light-matter interactions at a fundamental level and is one of the pillars of the Standard Model (SM). Through the extraordinary precision of QED, the SM predicts the energy levels of simple systems such as the hydrogen atom with up to 13 significant digits1, making hydrogen spectroscopy an ideal test bed. The consistency of physical constants extracted from different transitions in hydrogen using QED, such as the proton charge radius rp, constitutes a test of the theory. However, values of rp from recent measurements2-7 of atomic hydrogen are partly discrepant with each other and with a more precise value from spectroscopy of muonic hydrogen8,9. This prevents a test of QED at the level of experimental uncertainties. Here we present a measurement of the 2S-6P transition in atomic hydrogen with sufficient precision to distinguish between the discrepant values of rp and enable rigorous testing of QED and the SM overall. Our result ν2S-6P = 730,690,248,610.79(48) kHz gives a value of rp = 0.8406(15) fm at least 2.5-fold more precise than from other atomic hydrogen determinations and in excellent agreement with the muonic value. The SM prediction of the transition frequency (730,690,248,610.79(23) kHz) is in excellent agreement with our result, testing the SM to 0.7 parts per trillion (ppt) and, specifically, bound-state QED corrections to 0.5 parts per million (ppm), their most precise test so far.
- 1Measured the 2S-6P transition frequency in hydrogen to be 730,690,248,610.79(48) kHz, achieving unprecedented precision
- 2Determined the proton charge radius to be 0.8406(15) fm, which is 2.5 times more precise than previous atomic hydrogen measurements
- 3Confirmed the smaller proton radius value from muonic hydrogen experiments, resolving the 'proton radius puzzle'
- 4Tested the Standard Model to 0.7 parts per trillion accuracy - the most stringent test ever achieved
- 5Validated quantum electrodynamics bound-state corrections to 0.5 parts per million precision
M87's black hole flipped its magnetic field
Imagine a bar magnet with a north and south pole. Now imagine that magnet suddenly flipping so north becomes south and vice versa. That's essentially what happened with the magnetic field around the giant black hole at the center of galaxy M87 — except this black hole is 6.5 billion times heavier than our Sun. Scientists noticed this flip by watching the powerful beam of energy, called a jet, that shoots out from the black hole. The direction and behavior of that beam changed in a way that revealed the magnetic field had reversed. It's a big deal because those magnetic fields are thought to act like the engine that powers and steers these cosmic jets, and we've rarely caught one flipping in action.
The 2026 World Cup's grass is an engineering problem
Imagine you're trying to play soccer in 16 different places across the United States, Canada, and Mexico — some in freezing cold, some blazing hot, some in stadiums with roofs that block sunlight. Half of those stadiums normally use fake grass. Now FIFA, the organization that runs the World Cup, wants every single pitch to feel and play exactly the same way, like a video game where every level has identical physics. To do that, they hired grass scientists — yes, that's a real job — who figured out how to grow special grass on thin mats with plastic underneath so it can be transported like a carpet, stitched with synthetic fibers so it doesn't rip when players sprint and tackle, and tested by literally shooting balls at it with a cannon to make sure it bounces right. Different grass species are used depending on whether a stadium is hot, cool, or dark. It's basically a giant, living, high-tech floor installation that has to survive the world's best athletes running on it.
Non-Mendelian inheritance of DNA methylation patterns in mice
Imagine your DNA is like a huge book of instructions. Mendel's laws are the normal rules for how chapters of that book get passed from parents to children. But there's also a layer of sticky notes on top of the book—called epigenetic marks—that tell cells which chapters to read and which to ignore. This study found that most of the time (about 93%), these sticky notes follow the normal inheritance rules. But about 7% of the time, they do something unexpected: new patterns appear that neither parent had, or a mark from one parent somehow silences the same mark from the other parent (called paramutation), or males and females end up with completely different sticky notes even when they inherit the same DNA. Scientists discovered this by using a new ultra-precise DNA reading technology in mice, and it opens the door to understanding hidden layers of how traits—and possibly diseases—are passed down through generations.
Digital twin–guided ablation for ventricular tachycardia
Imagine your heart is a city, and ventricular tachycardia is like a traffic jam caused by a broken road — electrical signals get stuck going in circles instead of flowing properly, causing the heart to beat dangerously fast. Doctors can fix this by burning away the broken road using a procedure called ablation. The problem is, finding the exact broken road inside a beating heart is like navigating a city you've never visited before, while driving, in the dark. What these researchers did is take detailed MRI pictures of each patient's heart, build a 3D computer copy — a 'digital twin' — and then simulate where the electrical problem was happening inside that virtual heart. They tested their fix on the computer model first, figured out exactly where to go, and THEN performed the real procedure. What used to take three hours of exploratory surgery was done in about 30 minutes, because the doctors already had a GPS map before they started.