Enlarge / A visibly emotional Peter Higgs was present when CERN announced Higgs boson discovery in July 2012. (credit: University of Edinburgh )

Peter Higgs , the shy, somewhat reclusive physicist who won a Nobel Prize for his theoretical work on how the Higgs boson gives elementary particles their mass, has died at the age of 94 . According to a statement from the University of Edinburgh, the physicist passed "peacefully at home on Monday 8 April following a short illness."

“Besides his outstanding contributions to particle physics, Peter was a very special person, a man of rare modesty, a great teacher and someone who explained physics in a very simple and profound way," Fabiola Gianotti, director general at CERN and former leader of one of the experiments that helped discover the Higgs particle in 2012, told The Guardian . "An important piece of CERN’s history and accomplishments is linked to him. I am very saddened, and I will miss him sorely.”

The Higgs boson is a manifestation of the Higgs field, an invisible entity that pervades the Universe. Interactions between the Higgs field and particles help provide particles with mass, with particles that interact more strongly having larger masses. The Standard Model of Particle Physics describes the fundamental particles that make up all matter, like quarks and electrons, as well as the particles that mediate their interactions through forces like electromagnetism and the weak force. Back in the 1960s, theorists extended the model to incorporate what has become known as the Higgs mechanism, which provides many of the particles with mass. One consequence of the Standard Model's version of the Higgs boson is that there should be a force-carrying particle, called a boson, associated with the Higgs field.

Enlarge / An artist's conceptual rendering of antihydrogen atoms falling out the bottom of the magnetic trap of the ALPHA-g apparatus. (credit: Keyi )

CERN physicists have shown that antimatter falls downward due to gravity, just like regular matter, according to a new paper published in the journal Nature. It's not a particularly surprising result—it would have been huge news had antimatter been found to be repulsed by gravity and "fall" upward—but it does tell us a bit but more about antimatter and brings physicists one step closer to resolving one of the most elusive mysteries surrounding the earliest moments of our universe.

As the name implies, antimatter is the exact opposite of ordinary matter, as it is made of antiparticles instead of ordinary particles. These antiparticles are identical in mass to their regular counterparts. But just like looking in a mirror reverses left and right, the electrical charges of antiparticles are reversed. So an anti-electron would have a positive instead of a negative charge while an antiproton would have a negative instead of a positive charge. When antimatter meets matter, both particles are annihilated and their combined masses are converted into pure energy. (It's what fuels the fictional USS Enterprise , as any Star Trek fan can tell you.)

As far as we know, antimatter doesn’t exist naturally in the known universe, although we can now create small amounts at places like CERN's Antimatter Factory . But scientists believe that ten billionths of a second after the Big Bang, there was an abundance of antimatter. The nascent universe was incredibly hot and infinitely dense, so much so that energy and mass were virtually interchangeable. New particles and antiparticles were constantly being created and hurling themselves, kamikaze-like, at their nearest polar opposites, thereby annihilating both matter and antimatter back into energy in a great cosmic war of attrition.

Enlarge / An artist’s composition of the Milky Way seen with a neutrino lens (blue). (credit: IceCube Collaboration/NSF/ESO)

Scientists with the IceCube Neutrino Observatory have unveiled a striking new image of our Milky Way galaxy as seen by ghost-like messenger particles called neutrinos. This new analysis—announced at a Drexel University event today, with a paper being published in the journal Science tomorrow—offers the strongest evidence to date that the Milky Way is a source of high-energy neutrinos, shedding more light on the origin of high-energy cosmic rays.

"I remember saying, 'At this point in human history, we're the first ones to see our galaxy in anything other than light,'" said Drexel University physicist and IceCube member Naoko Kurahashi Neilson of the moment she and two graduate students first examined the image. “Observing our own galaxy for the first time using particles instead of light is a huge step. As neutrino astronomy evolves, we will get a new lens with which to observe the universe.”

As previously reported , ever since French physicist Pierre Auger proposed in 1939 that cosmic rays must carry incredible amounts of energy, scientists have puzzled over what produces these powerful clusters of protons and neutrons raining down into Earth's atmosphere. One way to identify the sources is to backtrack the paths that high-energy cosmic neutrinos traveled on their way to Earth since they are created by cosmic rays colliding with matter or radiation, producing particles that then decay into neutrinos and gamma rays.

Enlarge / Cosmic rays showering down on Earth's atmosphere are the basis of a new wireless alternative system to GPS navigation. (credit: 2015 Hiroyuki K.M. Tanaka)

GPS is now a mainstay of daily life, helping us with determining locations, navigation, tracking, mapping, and timing across a broad spectrum of applications. But it does have a few shortcomings, most notably not being able to pass through buildings, rocks, or water. That's why Japanese researchers have developed an alternative wireless navigation system that relies on cosmic rays, or muons, instead of radio waves, according to a new paper published in the journal iScience. The team has conducted their first successful test, and the system could one day be used by search and rescue teams, for example, to guide robots underwater, or help autonomous vehicles navigate underground.

"Cosmic-ray muons fall equally across the Earth and always travel at the same speed regardless of what matter they traverse, penetrating even kilometers of rock,” said co-author Hiroyuki Tanaka of Muographix at the University of Tokyo in Japan. “Now, by using muons, we have developed a new kind of GPS, which we have called the muometric positioning system (muPS), which works underground, indoors and underwater.”

As previously reported , there is a long history of using muons to image archaeological structures , a process made easier because cosmic rays provide a steady supply of these particles. Muons are also used to hunt for illegally transported nuclear materials at border crossings and to monitor active volcanoes in hopes of detecting when they might erupt. In 2008, scientists at the University of Texas, Austin , repurposed old muon detectors to search for possible hidden Mayan ruins in Belize. Physicists at Los Alamos National Laboratory have been developing portable versions of muon imaging systems to unlock the construction secrets of the dome (Il Duomo) atop the Cathedral of St. Mary of the Flower in Florence, Italy, designed by Filippo Brunelleschi in the early 15th century.

Enlarge / Archaeologists used cosmic rays to detect a secret underground burial chamber from the Hellenistic period in Naples, circa late fourth century/early third century BCE. This is a laser-scanned 3D view of the underground part of the site (credit: V. Tioukov et al., 2023)

The ruins of the ancient necropolis of Neapolis lie some 10 meters (about 33 feet) below modern-day Naples, Italy. But the site is in a densely populated urban district, making it challenging to undertake careful archaeological excavations of those ruins. So a team of scientists turned to cosmic rays for help—specifically an imaging technique called muography, or muon tomography —and discovered a previously hidden underground burial chamber, according to a recent paper published in the Scientific Reports journal.

As we've reported , there is a long history of using muons to image archaeological structures , a process made easier because cosmic rays provide a steady supply of these particles. An engineer named E.P. George used them to make measurements of an Australian tunnel in the 1950s. But Nobel-prize-winning physicist Luis Alvarez put muon imaging on the map when he teamed up with Egyptian archaeologists to use the technique to search for hidden chambers in the Pyramid of Khafre at Giza. Although it worked in principle, they didn't find any hidden chambers.

Muons are also used to hunt for illegally transported nuclear materials at border crossings and to monitor active volcanoes in hopes of detecting when they might erupt. In 2008, scientists at the University of Texas, Austin , tried to follow in Alvarez’s footsteps, repurposing old muon detectors to search for possible hidden Mayan ruins in Belize. And physicists at Los Alamos National Laboratory have been developing portable versions of muon imaging systems to unlock the construction secrets of the soaring dome (Il Duomo) atop the Cathedral of St. Mary of the Flower in Florence, Italy, designed by Filippo Brunelleschi in the early 15th century. The dome has been plagued by cracks for centuries, and muon imaging could help preservationists figure out how to fix it.