Electrical energy transfers at near light speed, even though the electrons carrying the energy in circuits only move a fraction of a millimeter per second.

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.

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.

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.

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.

Light appears to slow as it travels through transparent materials due to interactions with the charged particles in the atoms of the material.

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

Light appears to slow down as it travels through different materials

Particles moving faster than the speed of light give nuclear reactors an eerie blue glow.

Electricity can be created by changing a magnetic field—a phenomenon known as electromagnetic induction.

View the electromagnetic spectrum and the properties of different types of light

Electricity can be lethal because it can disrupt the nervous system, which controls critical bodily functions that rely on electrical signals between cells, such as breathing and heart rate.

With a core consisting of a glass fiber roughly the width of human hair, fiber-optic cables transmit digital information via flashes of light that reflect within the glass.

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.

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.

Tesla's alternating current power's most of the world's electric grids

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

Watch lightning strike a building at 40,000 frames per second

Watch the motion of an individual photon using a high-speed camera

The unpredictability and brevity of lightning make lightning power impractical

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

On average, the human body produces about 100 watts of electricity—enough to power a light bulb—but some people can produce over 2,000 watts in short bursts, such as when sprinting.

If a source of music traveled past someone at twice the speed of sound, assuming sufficiently sensitive hearing and powerful equipment, they would hear the music backward.

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

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

Observations of colliding neutron stars by the Laser Interferometer Gravitational-Wave Observatory in 2017 confirmed that gravity travels at the speed of light.

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

How brain cells carry information

The hypothetical particle that travels faster than light

Gold has a yellowish appearance rather than the silvery color of most metals because of special relativity, which causes gold's electrons to absorb blue light.

The finite speed of light means we can only perceive the world's past

The first battery was invented to settle a dispute over what caused severed frog legs to twitch when connected to different metals.

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

The engineering underlying the electric grid and why it needs to be modernized

The characteristic zigzag of lightning originates from columns of conductive oxygen

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

Named after Nikola Tesla, who pioneered alternating current power systems, the Tesla coil was the first device to wirelessly transmit electricity.

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

Before the invention of transistors, vacuum tubes made radio possible

Thunder occurs when fast-flowing electricity heats and pressurizes air, causing it to expand and produce a shockwave at each point along the bolt at multiple frequencies.

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.

You can measure the speed of light with a microwave oven and chocolate, cheese, or other uniformly thick foods.

Tachyons are theoretical particles that travel through space faster than 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.

Units involving light, such as light-seconds and light-years, describe the distances traveled by light across that amount of time.

Being near a lightning strike—even without getting struck—can be fatal

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.

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.

The air around lightning can reach a temperature of about 30,000 degrees Celsius (54,000 degrees Fahrenheit)—five times hotter than the surface of the sun.

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.