With a little help from the sun, blue jeans are going “green.” By accident, researchers stumbled on a new way to give jeans their iconic blue hue. The light-driven process could help dye denim with fewer harsh chemicals.  Denim is usually dyed with indigo. But this compound doesn’t easily dissolve in water. So harsh chemicals are used to break it down into a liquid that can turn the fabric blue. Each year, tens of thousands of tons of these harsh chemicals go into making denim across the world. Many are then dumped as waste into streams. “It’s very toxic to both the environment [and ..read more

The sun is the closest star to Earth. That gives all Earthlings, especially astronomers, a front-row seat to its activities. One of the most striking features of the sun’s activity is what astronomers call the solar cycle. This is an epic rise and fall in the sun’s level of activity that repeats every 11 years or so. Astronomers owe the discovery of the solar cycle to sunspots. Ever since Galileo first pointed a telescope at the sun in 1610, people have witnessed the occasional emergence of these dark splotches on the sun. As the sun rotates, completing one spin every 27 days, those spots appe ..read more

Neutrinos are extra hard to spot. These subatomic particles have almost no mass, making them especially difficult to find and study. If only neutrino detectors could grow on trees, thought Steven Prohira. Or — could they? In fact, he now proposes, forests might indeed be used one day to spot ultra-high-energy neutrinos. Trees could act as natural antennas, he suggests. Pohira is a physicist at the University of Kansas in Lawrence. He studies subatomic particles from space, including the neutrinos that shower down on Earth. Trees might pick up radio waves produced by certain types of neutrino i ..read more

Paul Smith recalls the first time he captured a sprite. He was shocked. It was the summer of 2017. Smith had gone out to California’s Mojave Desert to photograph a meteor shower. While driving, “I thought I saw sprites out of the corner of my eye,” he says. “Just flashes on the horizon.” These sprites were no fairytale creatures. They’re jagged, blood-red glows that sometimes appear above powerful thunderstorms. While setting up to view the meteors, Smith aimed one camera at the distant storm — on the chance there really were sprites there. “After about an hour, I caught this one sprite,” he s ..read more

Roses are red and blueberries look blue. But the berry’s color is not really true. The fruit’s waxy coat just masquerades as blue. A waxy covering coats some blue-colored fruits — such as blueberries, dark grapes and certain plums. This wax contains a host of tiny structures, each less than a thousandth the thickness of a piece of paper. Such nanostructures scatter blue and ultraviolet (UV) light. To our eyes, that makes these fruits look blue. Birds — which can see UV light — probably see such delicious snacks as bluey-UV. Blue is not a common color in nature. While some fruits do appear blue ..read more

Nearly a decade ago, Neil Zeller spied a mysterious purple glow in the night sky. Zeller was on a family vacation in British Columbia, Canada. One August 2014 night, he glimpsed something strange while photographing the northern lights. A band of purple light ran east to west across the sky. This was south of the auroras that made up the northern lights. The purplish-white streak looked almost like the vapor trail of an airplane — yet not quite. Intrigued, Zeller swiveled his camera toward the mystery light. Later, he found that other aurora chasers online had seen similar purple streaks. They ..read more

Physicists are fascinated by many grand puzzles. The nature of space and time? Sure. How the universe came to be? Of course. But how lawn sprinklers spin? Yes, that too. In the 1980s, physicist Richard Feynman made one sprinkler-related question quite popular. It centered on a style of sprinkler that squirts water out the ends of an S-shaped tube. The sprinkler normally spins away from the escaping water. But what happens if you stick the sprinkler in a tank of water and have it suck in water? The question seems simple. But it involves complex fluid flows — and complex rules of physics. Some p ..read more

Ah, the refreshing sound of a cool drink of water being poured. You might feel thirsty just thinking about it. Or, if you’re a scientist, you might feel curious. Mouad Boudina certainly was. He’s a mechanical engineer at Seoul National University in South Korea. He and his colleagues wanted to know how pouring conditions affect the volume of cascading water. The key, they learned, was how much a stream of water rippled as it fell. As a smooth stream of water falls, it tends to form lumps and bumps. Then, it breaks into droplets. (This happens due to a physics effect called the Rayleigh-Plateau ..read more

2-D material (noun, “Too-dee Muh-TEE-ree-uhl”) So-called two-dimensional, or 2-D, materials are super flat. These materials are not literally two-dimensional. They have length, width and height. But they’re just one or two atoms thick. So their height is practically zero. Hence: 2-D material. Graphene is the most famous of these materials. But there are many other 2-D materials with a wide range of useful properties. Graphene is a single layer of carbon atoms bonded together. It’s super strong, lightweight and flexible. That could make it useful for making small, bendy electronics. Or it coul ..read more

If you take more than 10 percent of the fruit in a stacked produce display — watch out. Sloped produce displays in grocery stores can cause chaos when they collapse. But figuring out how much fruit can be removed before a lot more comes tumbling down has proven surprisingly tricky. Such collapsing fruit displays provide a way to study the forces behind other even more important events, says Eduardo Rojas. He’s thinking about avalanches and landslides. A physicist, Rojas works at the University of Antofagasta in Chile. Those Earth tumbles are even more complicated than a crumbling stack of frui ..read more