By changing one's frame of reference in special relativity, electric forces can be reinterpreted as magnetic forces, highlighting how the two together constitute electromagnetism.

Discoveries in electromagnetism, which suggested that light traveled at a single speed, became the catalyst for overturning Isaac Newton's view that all speeds are relative.

The speed of electricity may refer to the movement of electrons, which is on the order of a fraction of a millimeter per second, or energy, which is near the speed of light.

Individuals moving at different speeds may disagree on the order of observed events because each experiences the passage of time differently, according to special relativity.

In the 1910s, physicists proved that the existing laws of physics made it impossible for solid magnets to exist—a finding overturned by quantum mechanics.

Within Einstein's picture of the universe, gravity is technically not a force because forces cause accelerations that deviate objects from their natural path, and moving solely due to gravity is natural.

Watch a timeline of the history of electricity, from observations of static electricity in antiquity to the War of the Currents—a rivalry to establish the ideal system for electric grids.

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

Visualize quantum field theory, where observable forces like electromagnetism result from energy and momentum being exchanged between universe-sized fields.

The centrifugal force is associated with the feeling of being pushed outward when moving in a circle, but it is a fictitious force arising from objects' tendency to move in straight lines.

Visualize how the order of events changes, according to special relativity, when the perspective is changed between observers who move relative to one another.

Certain objects are magnetic because their electrons' magnetic moment—an intrinsic quantum property—align within the object in specific patterns.

Electricity can flow indefinitely along a ring of superconducting material, which provides zero resistance to the movement of charges due to quantum effects.

While special relativity describes motion along flat spacetime—the underlying fabric of the universe—general relativity extends this theory to explain motion through curved spacetime.

You have never made physical contact with anything in your life because electrons in the outer layer of atoms on the surface of objects repel one another.

Electromagnetic induction creates electricity from a changing magnetic field

Unlike other metals, mercury is a liquid at room temperature because of special relativity, which affects the spatial distribution of electrons in the atoms.

According to the special theory of relativity, the faster objects move through space, the less they move through time, and therefore age more slowly.

Although the color of light changes due to motion between a source and an observer—the Doppler effect—relativistic motion further alters it due to time dilation.

Leptons do not experience the strong nuclear force that binds quarks together

According to the equivalence principle, objects in a closed space cannot tell the difference between whether they are accelerating or experiencing a uniform gravitational field.

Metal plates can be pushed together by empty space—the Casimir effect—because of virtual particles that cannot be observed but are predicted by quantum field theory.

Albert Einstein's theory of gravity arose from what he described as 'the happiest thought of his life': realizing that a person who fell off the roof of their house would not feel their own weight as they fell.

For the speed of light to be constant for all observers, space and time cannot be absolute, universal dimensions that are identical for everyone.

Virtual particles are not real—they cannot be directly observed—but they help scientists resolve how forces affect particles in quantum field theory.

The magnetic constant sets the strength of magnetic fields

Explore how excitatory cells, such as neurons and muscle cells, transmit information in the body via electrochemical signals, which can travel up to 120 meters (390 feet) per second.

Based on Newton's laws of motion, classical mechanics describes the motion of and forces on everyday objects.

Molten metal moving around Earth's inner core creates the planet's magnetic field, whose north and south poles do not align with the planet's geographic poles.

Every fundamental particle is a vibration in a field that spans the entire universe, according to quantum field theory.

Quantum electrodynamics is considered the first true quantum field theory, which applied quantum mechanics to the electromagnetic radiation field.

Almost three centuries before Albert Einstein presented the special theory of relativity, Galileo Galilei devised a principle of relativity involving uniform motion.

The one-electron theory describes the universe as having only one electron

Because they move at the cosmic speed limit through space, photons—particles of light—do not 'perceive' distance or the passage of time.

Measurements of an electron's magnetic moment help test the Standard Model

While charges consistently move in the same direction in a direct current, the flow of charges changes multiple times per second in an alternating current.

While moving through space faster than the speed of light is forbidden by special relativity, dark energy makes about 97% of galaxies appear to do so.

Electricity is produced when the ends of a battery are connected by a conducting wire, triggering chemical reactions that release the energy stored in chemical bonds.

Watch an animated derivation of the mass-energy equivalence, or E = mc², as a consequence of special relativity.

Transformers change the current and voltage across a set of wires by wrapping them around a magnetic core and using the magnetic field of one wire to induce a current in the other.

Antimatter particles possess the same mass and spin as their normal particle counterparts, but possess an opposite charge and transform into pure energy upon colliding with normal matter.

Gravity, electromagnetism, and two nuclear forces make up nature's fundamental forces

Photons are both particles of light and messengers of the electromagnetic force

The underlying fabric of the universe—spacetime—changes shape in the presence of mass and energy, which affects measurements of space and time.

Fundamental particles of the same type, such as all electrons or all photons, are identical because they are all vibrations in the same quantum field.

The Higgs boson provides a mechanism that explains why some particles have mass

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

Simulate the buildup and discharge of static electricity through friction by dragging the arm and leg of 'John Travoltage' along surfaces.

Although associated with his theories of relativity, Albert Einstein initially viewed the concept of spacetime, which originated with his teacher, Hermann Minkowski, negatively.

Visualize how alternating currents—electricity that periodically changes direction—are generated by rotating magnetic fields, as occurs in turbine-generator systems.

The strong nuclear force prevents most atoms from spontaneously breaking apart, even though protons in the nucleus repel one another.