Physical world and mathematics

Kīlauea

Kīlauea, also known as Kilauea Volcano, is an active shield volcano on the Island of Hawaiʻi and one of the most active on Earth; its 2018 eruption destroyed over 700 structures.

Kilian Muñiz

Kilian Muñiz (1970–2020) was a German-Spanish organic chemist and ICREA Research Professor at the Institute of Chemical Research of Catalonia in Tarragona, known for catalytic alkene diamination.

Killing form

The Killing form is a symmetric bilinear form on a Lie algebra, defined as a trace in the adjoint representation, used to test solvability and semisimplicity.

Killing horizon

A Killing horizon is a null hypersurface in spacetime on which a Killing vector field, the generator of a symmetry, is normal to the surface.

Killing vector field

A Killing vector field, also called a Killing symmetry, is a vector field leaving a manifold's metric unchanged, describing continuous spacetime symmetries in general relativity.

Kilo-Degree Survey

The Kilo-Degree Survey (KiDS) is an optical imaging survey by ESO that mapped the Universe's matter distribution through weak gravitational lensing from 2011 to 2019.

Kilogram

The kilogram (kg) is the SI base unit of mass, defined since 20 May 2019 by fixing the Planck constant, replacing the platinum-iridium prototype kept near Paris.

Kilogram-force

The kilogram-force (kgf), also called the kilopond (kp), is a deprecated metric unit of force: the gravitational force on one kilogram, equal to exactly 9.80665 newtons.

Kilometre

The kilometer (kilometer, symbol km) is an SI unit of length equal to 1,000 meters, used for road distances and travel speeds in most of the world.

Kilometres per hour

The kilometer per hour (km/h), often written kph, is a unit of speed accepted for use with the SI, whose coherent speed unit is the meter per second (3.6 km/h).

Kilonova

A kilonova, also called a macronova, is a days-long supernova-like transient powered by radioactive decay of heavy elements forged when two neutron stars or a neutron star and black hole merge.

Kilowatt-hour

The kilowatt-hour (kWh) is a unit of energy equal to one kilowatt of power sustained for one hour, or exactly 3.6 megajoules. It is the standard commercial unit for billing electrical energy.

Kim R. Dunbar

Kim R. Dunbar is an inorganic chemist at Texas A&M University since 1999 whose research spans molecule-based magnetic materials, anion–π interactions, and dirhodium compounds for cancer therapy.

Kimberlite

Kimberlite, also known as blue ground, is an ultramafic volcanic rock occurring in vertical pipes, named after Kimberley, South Africa, and the primary source of diamonds.

Kimihiko Hirao

Kimihiko Hirao (平尾公彦), born 1945 in Niihama, Japan, is a Japanese theoretical chemist known for the SAC method, multireference perturbation theory, and long-range-corrected density functionals.

Kimihisa Yamamoto

Kimihisa Yamamoto (山元公寿) is a Japanese polymer and materials chemist, professor at Institute of Science Tokyo, known for phenylazomethine dendrimers and the atom hybrid method.

Kimmeridge Clay

The Kimmeridge Clay is a gray, organic-rich Jurassic marine mudstone outcropping from Dorset to Yorkshire and is the major oil source rock for the North Sea.

Kin Fai Mak is a condensed matter experimental physicist known for studies of atomically thin 2D materials and, since 2024, a director at the Max Planck Institute for the Structure and Dynamics of Matter.

Kincade Fire

The Kincade Fire was a 2019 wildfire near Geyserville in Sonoma County, California, California's largest that year at 77,758 acres, traced to a broken PG&E jumper cable.

Kinematic time dilation in gravitational fields

Kinematic time dilation in gravitational fields is the velocity-dependent part of a moving clock's rate in a gravitational potential, always combined with gravitational redshift in tests.

Kinematic wave theory

Kinematic wave theory is a simplified description of unsteady shallow water flow in which friction balances the water's weight component, so flow-dependent celerity can steepen waves into shocks.

Kinematics

Kinematics, often called the geometry of motion, is the branch of mechanics that describes motion without reference to the forces causing it, using position, velocity, and acceleration.

Kinesiology

Kinesiology, also known as human kinetics, is the scientific study of human movement, spanning biomechanics, exercise physiology, and motor behavior. In Canada it is also a regulated health profession.

Oct 22, 2026

Kinetic ballooning mode

The kinetic ballooning mode (KBM) is a drift-Alfvénic microinstability of tokamak plasmas, driven by pressure gradient and thought to limit the H-mode edge pedestal width.

Kinetic diameter

Kinetic diameter is the effective size a gas molecule presents to its surroundings, used to predict whether it can pass through the pores of molecular sieves such as zeolites.

Kinetic energy

Kinetic energy is the energy an object possesses because of its motion, given by K = ½mv² and measured in joules, the same unit as work.

Kinetic exchange models of markets

Kinetic exchange models, or kinetic exchange models of markets, are agent-based econophysics models where agents exchange money in random pairwise transactions, yielding an exponential bulk and a Pareto rich tail.

Kinetic friction

Kinetic friction is the force that opposes the sliding of two surfaces in contact, equal to μk times the normal force by Amontons' 1699 law, and consistently lower than static friction.