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Decoding the loopy physics of hula hooping with high-tech earthquake sensors

Hula hooping may be literal child’s play, but as it turns out, the physics behind the gym-class staple is so complicated that scientists have spent decades trying to understand how the hula hoop defies gravity.

Multiple scientific papers have been devoted to this minor mystery: How do one’s hips and legs collude with friction and centrifugal forces to keep a simple toy spinning in midair? The still-unresolved question led a team of UC Berkeley-affiliated engineers to tackle the problem by using an innovative method to analyze motion-tracking data.

Their results, recently published in the journal Nonlinear Dynamics, challenge 20 years of conventional wisdom about hula hooping—and suggest a better way to model complex mechanical systems like the hula hoop’s twirl, which could be useful in fields like physical rehabilitation and robotics.

Identical vesicles, different behaviors: Model reveals how spontaneous asymmetry gives rise to lifelike behavior

In nonreciprocal active matter, agents act differently on each other, seemingly in violation of Newton’s third law. This principle can result in various active matter traits, such as self-propulsion, molecular regulation and collective motion.

A new model describes how such nonreciprocal interactions can emerge spontaneously between chemically active vesicles. Physicists from the Department of Living Matter Physics at the Max Planck Institute for Dynamics and Self-Organization (MPI-DS) found that such vesicles can dynamically switch between ignoring, attracting, repelling and chasing each other.

The study is published in the journal Newton.

SPINE: A machine-learning program is on the trail of ghost particles

Neutrinos are among the most abundant particles in the universe, but they are also among the most elusive. Nearly massless, they are produced by nuclear reactions in the sun, exploding stars, particle accelerators and even the decay of radioactive elements on Earth. They interact so weakly with ordinary matter that trillions pass through each person every second without leaving a trace. Studying these ghostly particles could help answer some of the biggest questions in physics, from the nature of dark matter to why matter exists at all.

Because neutrinos are so elusive, scientists build enormous detectors and intense particle beams to catch even a small number of them in action. But capturing a neutrino interaction is only the beginning. Scientists must then reconstruct what happened from an extraordinarily complicated picture of particle tracks, overlapping signals and background activity. Researchers at the Department of Energy’s (DOE) SLAC National Accelerator Laboratory have developed a machine-learning program called SPINE to tackle this challenge.

SPINE, which stands for Scalable Particle Imaging with Neural Embeddings, analyzes data from liquid argon time-projection chambers, the detector technology used by experiments including the Short-Baseline Neutrino program at the DOE’s Fermi National Accelerator Laboratory in Illinois and the Deep Underground Neutrino Experiment (DUNE), currently under construction in Illinois and South Dakota and expected to start taking data in 2030. SPINE learns from simulated detector images to identify particles, trace their paths and piece together the interactions that produced them.

Quantum gates set speed record at 6.8 nanoseconds with over 99.98% accuracy

Researchers from Jülich, Aachen and Cologne have performed a quantum operation on a qubit in just 6.8 nanoseconds—with more than 99.98% accuracy. Such operations typically take several tens of nanoseconds in superconducting quantum computers. The paper was published in Nature Communications.

6.8 nanoseconds—that’s how long it takes light to travel a distance of around two meters (6.6 feet) in a vacuum. In this tiny fraction of a second, researchers at the Peter Grünberg Institute for Functional Quantum Systems (PGI-13) and Quantum Control (PGI-8) at Forschungszentrum Jülich have succeeded in performing elementary computing operations on a quantum bit, or qubit for short.

Switching speed is a critical factor in quantum computing. This is because qubits are sensitive and retain their quantum states for only a limited time. The faster individual operations can be performed, the more can fit into this time window. This is important for complex algorithms and for resource-intensive error correction.

Quantum sensor loop design could improve magnetic measurements for medicine and communications

Adelaide University quantum engineers have found a new way to improve some of the world’s most sensitive sensors of electromagnetic fields, a breakthrough that could help advance brain imaging, medical diagnostics, communications technology and next-generation quantum devices.

The research, published today in Physical Review Applied, is led by the university’s Quantum and Nano Technology Group (QuaNTeG) and solves a long-standing problem that has limited the performance of superconducting quantum interference devices, known as SQUIDs.

SQUIDs are among the most sensitive magnetic field detectors ever created. They are used in specialized applications including brain imaging systems, scientific instruments and advanced radio-frequency sensors. However, while they can detect incredibly small changes in magnetic fields, they have struggled to accurately identify when a magnetic field is exactly zero.

Against all expectations, researchers control the magnetic core of a single atom

Researchers at Delft University of Technology (the Netherlands) have succeeded in controlling the magnetism in the nucleus of a single atom with radio waves. This came as a surprise: until now, physicists believed that this nuclear spin could not be manipulated directly. The discovery could open up new possibilities for storing and reading quantum information. The research is published in the journal Nature Communications.

In metals such as iron and nickel, every atom is slightly magnetic. But inside the atom, different magnetic “compass needles,” known in quantum mechanics as spins, are also at work. “By far the strongest magnetism comes from the electrons,” says lead researcher Sander Otte. “But in some atoms, the nucleus also carries a spin. That spin is much weaker, but it is also much better shielded from the outside world.”

Otte’s group studies spins using a converted scanning tunneling microscope. This enables electrical signals to be directed with extreme precision at a single atom. In the past, the researchers mainly focused on the electron spin, which is the easiest to read out. The nuclear spin appeared only indirectly, through the so-called hyperfine interaction. This causes the spins of the nucleus and the electron to become slightly entangled.

Can gravitational fields break and reconnect? Einstein’s equations suggest they can

More than a century after Einstein first devised the equations that describe gravity, physicists are still finding new ways of interpreting them. Luca Comisso, an associate research scientist in Columbia University’s departments of Astronomy and Physics and the Columbia Astrophysics Laboratory, and Felipe A. Asenjo of Universidad Adolfo Ibáñez in Chile, recently found a new way of looking at Einstein’s equations that reveals a striking analogy with “magnetic reconnection” in plasmas, which occurs when magnetic field lines break and reconnect, powering explosive phenomena such as solar flares.

Their work shows that something similar can happen to gravity: Under the right conditions, gravitational field structures can also break and reconnect—a process they call “gravitational reconnection.” When they do, energy moves out of the gravitational field and into matter.

The findings, published in Physical Review D, could help physicists better understand some of the universe’s most extreme events, including the collision of black holes. In these environments, gravity is so powerful that space-time becomes highly distorted, making its behavior extraordinarily difficult to calculate. The researchers’ approach offers a way to identify fundamental rules governing how gravitational fields behave, potentially revealing insights that conventional computer simulations alone cannot provide.

Sound-levitated particles reveal how static charge builds up

When two objects touch and then separate, they can swap tiny amounts of electric charge, even if they are made from exactly the same material. This ‘triboelectric effect’ is the source of everyday static electricity, but it is still poorly understood in large samples of powder, where vast numbers of particles are constantly colliding with each other.

Through new research published in Physical Review E, Tom O’Hara and colleagues at the University of Bristol have investigated the effect using acoustic levitation: using sound waves to trigger repeated collisions between pairs of particles. Their experiment shows for the first time how charge builds up on repeatedly colliding particles, before leveling off at a set limit.

Could next-gen artificial intelligence help map out future space outposts?

Planning a successful trip can be challenging, especially when your destination is in outer space. Even before liftoff, space missions require extraordinary amounts of scientific preparation and data analysis to succeed, which can take years to complete. However, as space agencies race to establish a permanent presence on the moon, using artificial intelligence to combine such information into a single system could make mission planning much more efficient.

One such system, developed by Gokce Inal, a Ph.D. candidate in civil, environmental and geodetic engineering at The Ohio State University, is an AI framework designed to help scientists evaluate potential lunar landing sites, identify dangerous hazards future crews might face, and scour new regions for scientifically valuable geologic features.

“AI systems are going to become critical tools for space exploration that will help humans analyze the millions of images and data sets that future missions will require,” she said. “This work is meant to serve as a bridge between those two worlds, AI and planetary science.”

Mutated immune cells raise red flags in lupus

Scientists at La Jolla Institute for Immunology (LJI) and the University of Washington (UW) have discovered that patients with lupus have unusual mutations that may turn their bodies into battlegrounds.

These mutations are widespread in immune cells called neutrophils. Other immune cells see the mutated neutrophils as a threat—and they try to fight back. This internal battle may contribute to the development of painful inflammation, debilitating joint pain and other serious lupus symptoms throughout the body.

“This may get to the very crux of the disease pathogenesis,” says LJI professor Stephen Schoenberger, Ph.D., who co-led the new Nature study with UW School of Medicine professor Tomas Mustelin, M.D., Ph.D.