Enlarge / Old car radio in a classic car (credit: Lars Johansson/EyeEm via Getty)

Update, 1:15 pm: Ford reached out to Ars with its explanation for dropping AM from the next Mustang. "A majority of U.S. AM stations, as well as a number of countries and automakers globally, are modernizing radio by offering internet streaming through mobile apps, FM, digital and satellite radio options. Ford will continue to offer these alternatives for customers to hear their favorite AM radio music, news and podcasts as we remove amplitude modulation—the definition of AM in this case—from most new and updated models we bring to market," wrote a Ford spokesperson.

In its December reply to Sen. Markey, Ford also noted that even without an AM receiver, "with FM, satellite radio, mobile data, and others, vehicles and their drivers have numerous alternative sources to receive [FEMA's Emergency Alert System] alerts."

Original story: You have to hand it to AM radio—it has outlasted the 8-track, the cassette, and the compact disc as a way to deliver audio content to a car. This first-generation radio broadcast technology dates back to the dawn of the last century before it was superseded by FM, which has better sound fidelity and is less likely to suffer from interference.

Enlarge / Radio observatories like the Green Bank Telescope in Green Bank, West Virginia, are in radio quiet zones that protect them from interference. (credit: The Washington Post via Getty Images)

Visible light is just one part of the electromagnetic spectrum that astronomers use to study the Universe. The James Webb Space Telescope was built to see infrared light, other space telescopes capture X-ray images, and observatories like the Green Bank Telescope, the Very Large Array, the Atacama Large Millimeter Array, and dozens of other observatories around the world work at radio wavelengths.

Radio telescopes are facing a problem. All satellites, whatever their function, use radio waves to transmit information to the surface of the Earth. Just as light pollution can hide a starry night sky, radio transmissions can swamp out the radio waves astronomers use to learn about black holes, newly forming stars, and the evolution of galaxies.

We are three scientists who work in astronomy and wireless technology. With tens of thousands of satellites expected to go into orbit in the coming years and increasing use on the ground, the radio spectrum is getting crowded. Radio quiet zones—regions, usually located in remote areas, where ground-based radio transmissions are limited or prohibited—have protected radio astronomy in the past.

Enlarge / Map of the known corridors and rooms inside the Great Pyramid of Giza. Evidence of a secret corridor was detected in 2016 behind the famed chevron blocks on the north face (h). Another mysterious large void (i) was discovered in 2017—a possible hidden chamber. (credit: Procureur et al., 2023)

In 2016, scientists using muon imaging picked up signals indicating a hidden corridor behind the famous chevron blocks on the north face of the Great Pyramid of Giza in Egypt. The following year, the same team detected a mysterious void in another area of the pyramid, believing it could be a hidden chamber. Two independent teams of researchers, using two different muon imaging methods, have now successfully mapped out the corridor for the first time, according to a new paper published in the journal Nature Communications. Zahi Hawass, Egypt’s former antiquities minister, called it "the most important discovery of the 21st century."

As we've reported previously, 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 really 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.

There are many variations of muon imaging, but they all typically involve gas-filled chambers. As muons zip through the gas, they collide with the gas particles and emit a telltale flash of light, which is recorded by the detector, allowing scientists to calculate the particle's energy and trajectory. It's similar to X-ray imaging or ground-penetrating radar, except with naturally occurring high-energy muons rather than X-rays or radio waves. That higher energy makes it possible to image thick, dense substances like the stones used to build pyramids. The denser the imaged object, the more muons are blocked, casting a telltale shadow. Hidden chambers in a pyramid would show up in the final image because they blocked fewer particles.