Physical world and mathematics

NORC at the University of Chicago

NORC at the University of Chicago, formerly the National Opinion Research Center, is an independent survey research organization founded in 1941 and affiliated with the university since 1947.

Norden E. Huang

Norden E. Huang (黄锷) is a Taiwanese oceanographer who created the Hilbert–Huang Transform at NASA's Goddard center, serving as Chief Scientist for Oceanography from 2000 to 2006.

Nordihydroguaiaretic acid (NDGA), also called masoprocol, is a phenolic lignan extracted from the creosote bush. Once a widely used food antioxidant, it was removed from the US GRAS list in 1968 over kidney toxicity.

Nordström's theory of gravitation

Nordström's theory of gravitation is a relativistic theory of gravity proposed by the Finnish physicist Gunnar Nordström in 1912 and 1913, the main rival to general relativity until observations ruled it out.

Nordtvedt effect

The Nordtvedt effect is a predicted violation of universal free fall for massive self-gravitating bodies, proposed by Kenneth Nordtvedt in 1968 and tested by lunar laser ranging.

Norepinephrine

Norepinephrine, also called noradrenaline, is a catecholamine that works as a neurotransmitter and adrenal hormone in the fight-or-flight response, and intravenously it is the first-line vasopressor for septic shock.

NorESM

NorESM, the Norwegian Earth System Model, is a coupled Earth system model developed in Norway since 2007; its simulations feature in IPCC reports and CMIP6.

Norethynodrel

Norethynodrel is a synthetic progestin steroid of the 19-nortestosterone family, best known as the progestin in Enovid, the first oral contraceptive marketed in the United States in 1960.

Norgestrel

Norgestrel is a totally synthetic progestin used in oral contraceptives; approved in the US in 1973, it returned in 2023 as Opill, the first nonprescription daily oral contraceptive.

Norihiro Tokitoh

Norihiro Tokitoh (時任宣博) is a Japanese organic and main-group chemist at Kyoto University known for making unstable heavy-element compounds isolable, including the first bismuth–bismuth double bond.

Oct 10, 2026

Noriko Arai

Noriko Arai (新井紀子, born 1962) is a Japanese mathematician and professor at the National Institute of Informatics in Tokyo who led the Todai Robot Project.

Oct 10, 2026

Norio Miyaura

Norio Miyaura (宮浦憲夫), born in Hokkaido in 1946, is a Japanese organic chemist at Hokkaido University known for the Suzuki–Miyaura reaction and the Miyaura borylation.

Noritaka Mizuno

Noritaka Mizuno (水野哲孝) is a Japanese catalytic and materials chemist, a professor at the University of Tokyo known for selective oxidation catalysis with hydrogen peroxide.

Noritatsu Tsubaki

Noritatsu Tsubaki is a Japanese chemist and professor at the University of Toyama since 2001, known for over 35 years of C1 catalysis, converting CO2, methane, and methanol into fuels and chemicals.

Norketamine

Norketamine, also called N-desmethylketamine, is the major active metabolite of ketamine, formed mainly by the liver enzyme CYP3A4 and retaining anesthetic and psychoactive activity at roughly one-third of ketamine's potency.

Norleucine

Norleucine (Nle), also called α-aminocaproic acid, is a nonproteinogenic amino acid and straight-chain isomer of leucine that substitutes for methionine in bacterial proteins, serving as a research tool and a contaminant in recombinant protein production.

Norm (mathematics)

In mathematics, a norm, or vector norm, is a function on a vector space that assigns each vector a length, satisfying positivity, homogeneity, and the triangle inequality.

Norm of a field element

The norm of a field element, N of alpha, is the determinant of the multiplication-by-alpha map for a finite field extension, taking values in the base field K.

Norma Arm

The Norma Arm is a spiral arm of the Milky Way with near-side and far-side portions, about 3 to 4 kpc from the Galactic center.

Normal (geometry)

A normal, or normal vector, in geometry is a vector or line perpendicular to a curve or surface at a point, used in differential geometry and computer graphics.

Normal coordinates

Normal coordinates are local coordinates on a manifold, built from the exponential map at a point, in which the metric is Euclidean and geodesics through the center are straight lines.

Normal curvature

Normal curvature is the component of a curve's curvature along the normal of the surface it lies on, measuring how the surface itself bends the curve.

Normal derivative

The normal derivative measures a function's rate of change in the direction perpendicular to a boundary, and prescribing it yields the Neumann boundary condition, named after Carl Neumann.

Normal dispersion

Normal dispersion is the behavior of a transparent optical material whose refractive index decreases as wavelength increases, so blue light refracts more strongly than red light.

Normal distribution

The normal distribution, also called the Gaussian distribution or bell curve, is a symmetric continuous probability distribution defined by a mean and a standard deviation, central to statistics.

Normal extension

A normal extension is an algebraic field extension E/F in which every irreducible polynomial over F with a root in E has all its roots in E; together with separability, normality makes the extension Galois.

Normal family

A normal family is a family of functions in which every sequence has a subsequence converging uniformly on compact subsets, introduced by Paul Montel in 1907.

Normal fault

A normal fault is a dip-slip fault on which the hanging wall moves downward relative to the footwall, forming where the crust is pulled apart by extension.

Normal force

The normal force, also called the normal reaction, is the contact force a surface exerts on an object perpendicular to that surface, equal to the weight mg on a horizontal surface.