Physics Glossary

Matter's mirror twin, made of particles with the same mass but opposite charge, which annihilates on contact with ordinary matter.

The event marking the start of the observable universe, roughly 13.8 billion years ago, from an extremely hot, dense state.

A region of space where gravity is so strong that nothing, not even light, can escape once it crosses the boundary.

The class of particles that carry the fundamental forces, including photons, gluons, and the Higgs boson.

The maximum mass a white dwarf can carry before its own gravity overwhelms it and forces a further collapse.

A theorized burst of exponential expansion in the first fraction of a second after the Big Bang.

The faint afterglow of the Big Bang, still detectable today as microwave radiation filling every direction of the sky.

The mysterious force making up most of the universe's total energy, driving its expansion to accelerate rather than slow down.

An invisible substance that outweighs ordinary matter in the universe and reveals itself only through its gravity.

The event where one celestial body passes into the shadow of another, or blocks it from view entirely.

The boundary around a black hole beyond which nothing, not even light, can escape.

A planet that orbits a star other than our own sun.

Any particle that makes up matter itself, following a rule that no two can occupy the exact same quantum state.

The effect where a spinning massive object drags the fabric of spacetime around with it.

The straightest possible path an object can travel through curved spacetime, which is what we experience as an orbit or a falling trajectory.

The particle that carries the strong force, binding quarks together inside protons and neutrons.

The bending of light around a massive object, which can magnify, distort, or even duplicate the image of what lies behind it.

A ripple in the fabric of spacetime, produced by some of the universe's most violent events.

The rule that you cannot know a particle's exact position and exact momentum at the same time.

The particle whose discovery in 2012 confirmed how other particles get their mass.

A family of fundamental particles that includes the electron and its heavier and lighter siblings, along with neutrinos.

The boundary marking everything a single point in spacetime could possibly influence or be influenced by, shaped by the speed limit of light.

The distance light travels in one year, used as a unit for measuring vast distances across space.

The rule that measures intervals between events in spacetime, distinguishing which events could influence each other from which never can.

A space that looks flat in any small local region, even when the space as a whole is curved, the basic mathematical setting for spacetime in general relativity.

The mathematical object that defines how distances and time intervals are measured at every point in spacetime, varying with the presence of mass and energy.

An almost massless, chargeless particle that barely interacts with anything and passes through matter unhindered.

The incredibly dense, city sized remnant left behind after a massive star collapses in a supernova.

The time actually experienced by a clock or object along its own path through spacetime, which can differ depending on speed and gravity.

A rapidly spinning neutron star that sweeps beams of radiation across space like a lighthouse.

The process by which a quantum system loses its delicate superposition through contact with its surroundings.

A link between particles where measuring one instantly tells you about the other, no matter how far apart they are.

The phenomenon where a particle passes through a barrier it should not have enough energy to cross.

A fundamental building block of matter that combines in groups to form protons, neutrons, and other particles.

An extremely bright, distant galactic core powered by a supermassive black hole devouring surrounding material.

The stretching of light's wavelength toward the red end of the spectrum, used to measure how fast an object is moving away from us.

The radius at which an object's escape velocity equals the speed of light, marking the boundary of a black hole.

A point where gravity becomes so extreme that general relativity's equations break down and predict infinite density.

The single four dimensional fabric that combines the three dimensions of space with time, and that mass bends.

The bending of spacetime's geometry caused by mass and energy, which general relativity identifies as the true source of gravity.

The theory that describes all known fundamental particles and three of the four forces that govern them.

The explosive death of a star, briefly outshining an entire galaxy and seeding space with heavy elements.

The ability of a quantum system to exist in multiple states at once, until it is measured.

The mathematical object that describes everything knowable about a quantum particle before you measure it.

The dense, slowly cooling remnant left behind after a sun like star runs out of fuel.

The complete path an object traces through spacetime over its history, linking every moment it experiences into one continuous thread.