Grete Hermann: the quantum physicist who challenged Werner Heisenberg and John von Neumann

22 Apr 2025

Part of our International Year of Quantum Science and Technology coverage

Sidney Perkowitz uncovers the pioneering work of the German physicist and philosopher Grete Hermann, who sparred with the likes of Werner Heisenberg and John von Neumann – but whose contributions to quantum science have only recently come to light

Great mind Grete Hermann, pictured here in 1955, was one of the first scientists to consider the philosophical implications of quantum mechanics. (Photo: Lohrisch-Achilles. Courtesy: Bremen State Archives)

In the early days of quantum mechanics, physicists found its radical nature difficult to accept – even though the theory had successes. In particular Werner Heisenberg developed the first comprehensive formulation of quantum mechanics in 1925, while the following year Erwin Schrödinger was able to predict the spectrum of light emitted by hydrogen using his eponymous equation. Satisfying though these achievements were, there was trouble in store.

Long accustomed to Isaac Newton’s mechanical view of the universe, physicists had assumed that identical systems always evolve with time in exactly the same way, that is to say “deterministically”. But Heisenberg’s uncertainty principle and the probabilistic nature of Schrödinger’s wave function suggested worrying flaws in this notion. Those doubts were famously expressed by Albert Einstein, Boris Podolsky and Nathan Rosen in their “EPR” paper of 1935 (Phys. Rev. 47 777) and in debates between Einstein and Niels Bohr.

 

Tennis-ball towers reach record-breaking heights with 12-storey, 34-ball structure

18 Apr 2025

How high can you go with towers made from tennis balls? Andria Rogava brings you his crazy, new 12-storey edifice.

Oh, balls A record-breaking 34-ball, 12-storey tower with three balls per layer (photo a); a 21-ball six-storey tower with four balls per layer (photo b); an 11-ball, three-storey tower with five balls per layers (photo c); and why a tower with six balls per layer would be impossible as the “locker” ball just sits in the middle (photo d). (Courtesy: Andria Rogava)

A few years ago, I wrote in Physics World about various bizarre structures I’d built from tennis balls, the most peculiar of which I termed “tennis-ball towers”. They consisted of a series of three-ball layers topped by a single ball (“the locker”) that keeps the whole tower intact. Each tower had (3n + 1) balls, where n is the number of triangular layers. The tallest tower I made was a seven-storey, 19-ball structure (n = 6). Shortly afterwards, I made an even bigger, nine-storey, 25-ball structure (n = 8).

 

Superconducting device delivers ultrafast changes in magnetic field

23 Apr 2025

How it works Artist’s impression of how an ultrafast disruption of superconductivity in a YBCO thin film triggers an abrupt magnetic field quench, setting off dynamics in a neighbouring magnetic system. (Courtesy: Giovanni de Vecchi and Joerg M Harms/MPSD)

Precise control over the generation of intense, ultrafast changes in magnetic fields called “magnetic steps” has been achieved by researchers in Hamburg, Germany. Using ultrashort laser pulses, Andrea Cavalleri and colleagues at the Max Planck Institute for the Structure and Dynamics of Matter disrupted the currents flowing through a superconducting disc. This alters the superconductor’s local magnetic environment on very short timescales – creating a magnetic step.

Magnetic steps rise to their peak intensity in just a few picoseconds, before decaying more slowly in several nanoseconds. They are useful to scientists because they rise and fall on timescales far shorter than the time it takes for materials to respond to external magnetic fields. As a result, magnetic steps could provide fundamental insights into the non-equilibrium properties of magnetic materials, and could also have practical applications in areas such as magnetic memory storage.

 

Dual-robot radiotherapy system designed to reduce the cost of cancer treatment

23 Apr 2025

KOALA research team Left to right: Mai Ibraheam, Olivia Masella, Joshua Chapman, Magdalena Bazalova-Carter and Jacob Atkinson. (Courtesy: Daniel Cecchi, University of Victoria)

Researchers at the University of Victoria in Canada are developing a low-cost radiotherapy system for use in low- and middle-income countries and geographically remote rural regions. Initial performance characterization of the proof-of-concept device produced encouraging results, and the design team is now refining the system with the goal of clinical commercialization.

This could be good news for people living in low-resource settings, where access to cancer treatment is an urgent global health concern. The WHO’s International Agency for Research on Cancer estimates that there are at least 20 million new cases of cancer diagnosed annually and 9.7 million annual cancer-related deaths, based on 2022 data.

 

Top-quark pairs at ATLAS could shed light on the early universe

22 Apr 2025

Top observation CERN’s ATLAS experiment has confirmed that heavy quark–antiquark pairs are created in the collision of lead ions. (Courtesy: CERN/ATLAS Collaboration)

Physicists working on the ATLAS experiment on the Large Hadron Collider (LHC) are the first to report the production of top quark–antiquark pairs in collisions involving heavy nuclei. By colliding lead ions, CERN’s LHC creates a fleeting state of matter called the quark–gluon plasma. This is an extremely hot and dense soup of subatomic particles that includes deconfined quarks and gluons. This plasma is believed to have filled the early universe microseconds after the Big Bang.

“Heavy-ion collisions at the LHC recreate the quark–gluon plasma in a laboratory setting,” Anthony Badea, a postdoctoral researcher at the University of Chicago and one of the lead authors of a paper describing the research.

 

Speedy worms behave like active polymers in disordered mazes

24 Apr 2025 Isabelle Dumé

Worms move faster in an environment riddled with randomly-placed obstacles than they do in an empty space. This surprising observation by physicists at the University of Amsterdam in the Netherlands can be explained by modelling the worms as polymer-like “active matter”, and it could come in handy for developers of robots for soil aeriation, fertility treatments and other biomedical applications.

When humans move, the presence of obstacles – disordered or otherwise – has a straightforward effect: it slows us down, as anyone who has ever driven through “traffic calming” measures like speed bumps and chicanes can attest. Worms, however, are different, says Antoine Deblais, who co-led the new study with Rosa Sinaasappel and theorist colleagues in Sara Jabbari Farouji’s group.

 

Delayed Big Bang for dark matter could be detected in gravitational waves

30 Nov 2024

Energy transition Dark matter may have been created after the Big Bang, something that could soon be tested by gravitational wave detectors. (Courtesy: Shutterstock/Tomertu)

New constraints on a theory that says dark matter was created just after the Big Bang – rather than at the Big Bang – have been determined by Richard Casey and Cosmin Ilie at Colgate University in the US. The duo calculated the full range of parameters in which a “Dark Big Bang” could fit into the observed history of the universe. They say that evidence of this delayed creation could be found in gravitational waves.

Dark matter is a hypothetical substance that is believed to play an important role in the structure and dynamics of the universe. It appears to account for about 27% of the mass–energy in the cosmos and is part of the Standard Model of cosmology. However, dark matter particles have never been observed directly.