Metal detectors identify induced magnetic fields in conductive objects

Fluxgate magnetometers detect magnetic fields using electromagnets

Instead of a compass needle's movement indicating a magnetic field, an alternating current produces an oscillating magnetic field in a metal bar. An external magnetic field creates an imbalance in the oscillations, which can be measured quantitatively.

Electromagnetic induction creates electricity from a changing magnetic field

The phenomenon was discovered in 1831 by Michael Faraday when an electric current was induced in a wire wrapped around an iron ring after a second wrapped wire not connected to the first was connected or disconnected from a battery.

Faraday cages protect enclosed objects by redirecting electrical currents

Constructed from conductive materials, the cage allows electrons to distribute themselves evenly throughout its surface and travel to ground, keeping the interior neutrally charged and preventing any internal electricity. The same principle blocks electromagnetic waves by redirecting the electric field component, preventing telecommunication signals from entering the apparatus.

How electrical transformers use coils of conductive wire to change voltage levels

Two sets of wires are wrapped around a magnetic core, each a different number of times. As alternating current flows through one wire, it generates a changing magnetic field that induces an alternating current in the second wire. If the second wire has fewer coils, the voltage steps down—decreases. If the second wire has more coils, the voltage steps up.

Particle accelerators detect subatomic particles using millions of sensors

Calorimeters measure the energy of particles. Tracking devices can measure momentum and charge from the trajectory of particles, which is determined by recording tiny electrical signals. Time-of-flight detectors provide particle velocities directly and particle mass indirectly, giving physicists a suite of properties to compare with those of known matter.

Wireless charging uses a magnetic field to move charged particles in a battery

Based on the concept of electromagnetic induction, when a compatible device is placed on a charging pad with correct alignment, the alternating current flowing through the pad creates a changing magnetic field. This magnetic field induces a current in the device, recharging the battery without a connecting wire.

How helium enables MRI machines to look inside organisms

By cooling the machine's magnets with liquid helium to extremely low temperatures, they can generate and maintain powerful magnetic fields that align the hydrogen atoms in living things to point toward a patient's head or feet. A radio pulse nudges these atoms, which realign and induce a measurable signal in nearby electrical coils. These signals are captured in slices and then stacked into a 3D reconstruction.

Hacking the body for a future that didn't happen

Journalist Adi Robertson experimented with one of the most accessible biohacks: magnets. Having a tiny magnet in their right ring finger meant they could sense magnetic fields, attract small metal objects, and more. But magnets weaken over time, eroding this new sense. Such implants do more than offer a new way of interacting with the world, they also pose new complications, such as the inability to get an MRI.

Electromagnetic repulsion prevents objects from making contact with one another

The feeling of touching something is a sensation caused by the electromagnetic force between the electrons on the surface of objects. Since this force grows to infinity with proximity, no two surfaces can ever achieve matter-to-matter contact.

Learn why magnets, like statically charged balloons, can deflect water

While the oxygen atom in water molecules strongly attracts hydrogen's electrons—producing an uneven charge distribution that pulls water toward balloons that have been rubbed against surfaces—the presence of a magnetic field alters the path of these electrons, which produce their own tiny magnetic fields. The interaction of these fields repels water away from magnets, making it diamagnetic.

Fluorescent bulbs can be illuminated by overhead power lines without making contact

The electromagnetic fields produced by the alternating current in transmission lines can induce the motion of charges in nearby objects. This motion yields electric currents that can light up bulbs but are too small to harm humans.

CT scanners at airports take images across energy bands to identify baggage contents

Old X-ray scanners' inability to distinguish between water and explosives has driven strict liquid bans and longer wait times through airport security. New scanners combine multi-angle images across the energy spectrum to determine an object's density and atomic composition for improved threat detection.

Contactless credit cards descend from a batteryless Cold War listening device

The same physics that let Soviet spies eavesdrop on the US ambassador in 1945 underlie contactless payment methods today. The device is a passive chip powered wirelessly by incoming radio waves.

Environmental DNA monitoring can help detect the presence of invasive species

Genetic material that organisms deposit into water, soil, or air can be identified by analyzing samples from each environment, allowing land managers to more reliably detect and track organisms than visual surveys alone. eDNA has been used to develop early warning surveillance systems for various invasive marine species.

An exoplanet detection method involves measuring a host star's auroras

Astronomers have reported indirectly identifying a planet by observing its debris interacting with the magnetic field of the star it orbits. The interaction is a larger-scale version of the auroras observed on Jupiter, which are produced when material released by its moon, Io, interacts with the gas giant's magnetic field.

The adaptations of metallophiles and how they can be harnessed for bioremediation

These extremophiles have adapted to biomes with very high concentrations of metals and toxic chemicals by developing mechanisms to isolate these substances within cellular compartments and break them down into less harmful forms with specialized proteins. They have the potential to support the decontamination of metal-rich wastewater and soil, as well as the extraction of rare-earth metals.

Dark matter's limited force interactions make its detection difficult

Despite making up the vast majority of matter in the universe, dark matter can only be directed indirectly via its influence on other objects through gravity, the weakest of the fundamental forces. This means direct detection of dark matter may only be possible with future, more sensitive instruments.

Distinguishing between natural and artificial, or induced, radioactivity

Naturally occurring radioactivity comes from radioactive elements underground, cosmic radiation from the sun and other objects in space, and radioactive atoms that make up the molecules we breathe, eat, and drink. Artificial radioactivity is predominantly generated for medical applications and industrial activities.

Microchip fabricators create light by heating tin droplets to over 220,000 Kelvin

Every second, lasers strike 50,000 droplets moving at 250 kilometers (155 miles) per hour, vaporizing the tin in supernova-like miniature explosions that produce ultraviolet light. Knowing this light will spread via diffraction as it passes through a filter during manufacturing, designers reverse-engineer the filter design based on the required final microchip pattern.

Hospitals have been adding weapon detection systems to emergency rooms in response to violence

Healthcare workers are five times more likely to experience violence at work than employees in other industries, according to pre-pandemic federal data. Yet, despite growing awareness of these threats, fewer than one in three hospitals have installed metal detectors.

Symmetric patterns of magnetic stripes seen on either side of mid-ocean ridges

The symmetry provides evidence of seafloor spreading, where new oceanic crust is created at mid-ocean ridges, which pushes older ocean crust away on either side. Matching the pattern to magnetized material in rocks on Earth’s surface provided a timeline of ocean floor recycling.

Some animals possess sensitive hearing to help pinpoint prey and map the world

Bats and dolphins produce sound to reflect off surfaces and create a mental image of their surroundings. Owls' faces are dish-shaped to help funnel sounds to their ears, including that of mice moving along leaves or snow. Pinnipeds, such as seals and walruses, hear in both air and water.

Enhanced geothermal power systems can trigger earthquakes

These systems inject fluid into rock to create cracks that allow deeper reservoirs of fluid to escape or to create networks where water can be deposited for heating. This injection can increase subterranean pressure and potentially trigger earthquakes, necessitating the use of sensors and moderated drilling technologies.

Watch how deep-sea mining equipment collects and processes polymetallic nodules—metal-rich, potato-shaped rocks—from the ocean floor and creates environmentally damaging plumes of sediments.

Transistors are the foundation of electronic signal processing

Small amounts of voltage can allow or block the flow of electrons across a transistor made from modified layers of semiconducting materials. The conducting (1) and insulating (0) states can be quickly modified as binary code is processed in a computer system.

The most common types of touchscreens are capacitive and resistive

Capacitative screens are coated with a conductive material that creates a uniform electric field, which is disrupted by fingers. This disruption is registered by the device across a grid to determine where contact was made. Resistive screens identify touch when fingers push gap-separated sheets into contact with one another.

Radioactive elements can introduce software errors because the ionizing radiation they produce can detach electrons from atoms, and computer code relies on the distribution of electrons.

Planeterrellas create artificial auroras that mimic the atmospheric displays of light by setting up an electric field between two metal balls in a jar filled with a small amount of air.

See how fireworks are made and learn how metals like magnesium and copper are responsible for different colors.

Pure water does not conduct electricity because this flow of energy requires the movement of charged particles, and water is a neutral molecule.

Power lines are dotted with large, brightly colored balls to improve the visibility of these thin wires to helicopters and small planes and help prevent potential crashes.

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

The history of many kitchen appliances involves unexpected discoveries and applications, including wartime radar turned hamster defroster and replacing an 'ice king' with heat-stealing boxes.

Tattoos remain visible on your skin thanks to immune cells called macrophages

When you complete a CAPTCHA on a website to prove you are human, you may be unknowingly training algorithms for self-driving cars, whose systems require training data to help identify crosswalks, bicycles, and other outdoor objects.

Some coin denominations have ridges etched on their sides, partly to prevent counterfeiting, in a practice called 'reeding.'

Dirty lightning is a thunderstorm created from friction between rising and falling flows of ash and smoke during volcanic eruptions.

Memecoins are a type of cryptocurrency—a form of digital currency with a wide variety of uses—created around popular 'memes,' or viral internet jokes.

When caught in the mouths of cardinal fish, seed shrimp release glowing, bioluminescent chemicals, which alert predators of the cardinal fish, prompting the shrimp's ejection.

Objects can be 3D printed with light by projecting 2D computerized tomography (CT) scans onto rotating cylinders of resin, which solidify upon exposure.

Sony set the standard for cylinder-shaped batteries when it repurposed manufacturing equipment used to make rolls of magnetic recording tape.

Long before Major League Baseball began allowing instant replay for balls and strikes, an umpire reluctantly used the technology to determine whether a hit was a home run, a move that inadvertently ushered in a new era for the sport.

Track the location of the Voyager probes, currently between 13 and 15 billion miles away from Earth.

The concept of phantom limbs, the perception that amputated limbs are still present, dates back to a French military surgeon in the 16th century.

A century of Billboard issues documenting the evolution of popular music.

Explore what it's like inside a patient isolation unit, used in situations such as treating a patient or suspected patient with Ebola.

Hedge funds, the private investment firms that trade a wide swath of financial assets, make money by imposing steep fees on investors and from the fund's investment performance.

The 1987 Nintendo video game 'Stadium Events' isn't known for being particularly fun, but its scarcity has made it a highly sought-after item that has sold for up to $35K at auction.

Listen to an in-depth conversation on the links between Parkinson's disease and herbicide exposure and the challenging pace of scientific investigation.

Some researchers have labeled nomophobia, the fear of being without your phone, as 'the phobia of the 21st century.'