Why Photons Carry Energy Without Having Mass | Sleepy Scientist Stories

Why Photons Carry Energy Without Having Mass | Sleepy Scientist Stories

The mind-bending reality of quantum mechanics - with Jim Al Khalili

The mind-bending reality of quantum mechanics - with Jim Al Khalili

Solving the secrets of gravity - with Claudia de Rham

Solving the secrets of gravity - with Claudia de Rham

 

Higgs decay to muon–antimuon pairs sheds light on the origin of mass

22 Dec 2025

Significant event Collision data from ATLAS showing a Higgs boson decaying to a muon–antimuon pair (red tracks). (Courtesy: CERN)

A new measurement by CERN’s ATLAS Collaboration has strengthened evidence that the masses of fundamental particles arise from their interactions with the Higgs field. Building on earlier results from CERN’s CMS Collaboration, the observations suggest that muon–antimuon pairs (dimuons) can be created by the decay of Higgs bosons.

In the Standard Model of particle physics, the fermionic particles are organized into three generations, broadly defined by their masses. The first generation comprises the two lightest quarks (up and down), the lightest lepton (the electron), and the electron neutrino.

 

Environmental physics should be on a par with quantum physics or optics

24 Sep 2025

As climate change intensifies, environmental physics must be taught to every physics undergraduate, explains Peter Hughes

Damaging effects. We now live in an increasingly urban world, with cities expanding into megacities that are causing significant environmental damage. (Courtesy: iStock/Daniel Stein)

The world is changing rapidly – economically, geopolitically, technologically, militarily, and environmentally. But when it comes to the environment, many people feel the world is on the cusp of catastrophe. That’s especially true for anyone directly affected by recurring environmental disasters, such as drought or flooding, where mass outmigration is the only option.

The challenges are considerable, and the crisis is urgent. But we know that physics has already contributed enormously to society, and environmental physics can make a huge difference by identifying, addressing, and alleviating the problems at stake. However, physicists will only be able to make a difference if we put environmental physics at the centre of our university teaching.

 

Slow spectroscopy sheds light on photodegradation

09 Dec 2025

Slow spectroscopy. The experiment detected extremely faint, long-timescale signals emitted by luminescent materials. This material is illuminated by a laser, and faint signals that persist long after excitation are not visible to the naked eye. (Courtesy: OIST)

Using a novel spectroscopy technique, physicists in Japan have revealed how organic materials accumulate electrical charge under long-term illumination by sunlight, leading to material degradation. Ryota Kabe and colleagues at the Okinawa Institute of Science and Technology have shown how charge separation occurs gradually via a rare multi-photon ionization process, offering new insights into how plastics and organic semiconductors degrade in sunlight.

In a typical organic solar cell, an electron-donating material is interfaced with an electron acceptor. When a donor absorbs a photon, one of its electrons may jump across the interface, creating a bound electron-hole pair that may eventually dissociate, yielding two free charges from which practical electrical work can be extracted.

 

Physicists take ‘snapshots’ of quantum gases in continuous space

18 Jul 2025 Nohora Hernández 

Say cheese! A dilute quantum gas in a red pancake-shaped trap (left) is quenched into a two-dimensional square lattice to “freeze” the atoms in place (right). It is then possible to take a “snapshot” of their positions by collecting their fluorescence via laser cooling. (Courtesy: Yao, R., et al. Phys. Rev.. Lett. 134 183402)

Three teams of researchers in the US and France have independently developed a new technique to visualize the positions of atoms in real, continuous space, rather than at discrete sites on a lattice. By applying this method, the teams captured “snapshots” of weakly interacting bosons, non-interacting fermions, and strongly interacting fermions, and made in situ measurements of the correlation functions that characterize these different quantum gases. Their work constitutes the first experimental measurements of these correlation functions in continuous space – a benchmark in the development of techniques for understanding fermionic and bosonic systems, as well as for studying intensely interacting systems.