Photon

Physicists have outlined an explanation for how a photon with an energy of 300 teraelectronvolts — among the most energetic gamma rays ever detected — could have travelled to Earth. The finding matters because such high-energy photons should in theory be absorbed or degraded over cosmic distances, so a viable propagation mechanism challenges existing models of intergalactic magnetic fields and fundamental physics.

A question about human eye biology is circulating: how does light physically reach the rods and cones at the back of the retina when layers of neurons, including bipolar and ganglion cells, sit in front of them? The inverted structure of the vertebrate retina means photoreceptors face away from incoming light, so photons must pass through other cell layers first. Responses typically explain that these layers are largely transparent, while some note the blind spot created where nerve fibres exit the eye.

Researchers report that a laser technique allows precise control over phonons — quantized vibrations — at the nanoscale. The advance could matter for developing smaller, faster electronic and thermal devices, as managing heat and vibrations at tiny scales is a major challenge in materials science and photonics research.

New research is using high-energy gamma rays from cosmic sources to probe whether the speed of light is truly constant for all photons, a cornerstone of Einstein's relativity. Some quantum gravity theories predict tiny energy-dependent differences in light's speed over vast cosmic distances, and gamma-ray observations offer one of the most stringent tests yet of Einstein's century-old rule.

A rigorous re-examination of cosmic gamma-ray observations has found no evidence that Lorentz invariance breaks down at high energies. Researchers applying unified statistical methods confirmed that the speed of light remains constant regardless of photon energy or direction, reinforcing Einstein's relativity and placing tighter limits on quantum-gravity models that predict energy-dependent light speeds.

Physicists report a breakthrough in controlling light in three dimensions, which they say unlocks quantum states previously considered impossible. The work could influence future research in quantum computing, photonics and advanced materials. Details of the finding and its practical implications remain limited, but the claim of reaching 'impossible' states is drawing attention across the physics community.

GE HealthCare is showcasing its photon-counting CT technology, a next-generation imaging approach that measures individual X-ray photons for sharper images at potentially lower radiation doses. The company's work in this area places it among the major imaging firms racing to bring the technology into routine clinical use, drawing attention from healthcare industry observers.