Physical world and mathematics

H2@C60

H2@C60 is an endohedral fullerene in which a single hydrogen molecule sits inside the carbon cage of C60, first made by molecular surgery at Kyoto University in 2005.

H2O (disambiguation)

H2O most commonly denotes the chemical formula of water, and also names a US Department of Energy hydropower office, an Australian television series, and a machine learning platform.

H2O@C60

H2O@C60 is an endohedral fullerene in which a single water molecule is permanently sealed inside a C60 carbon cage, first synthesized in 2011 at Kyoto University.

H3S

H3S, formed from hydrogen sulfide under about 150 gigapascals of pressure, superconducts at 203 K; its 2015 discovery was the first conventional superconductivity observed above 200 K.

H3S high-temperature superconductivity prediction

The H3S high-temperature superconductivity prediction is the 2014 theoretical forecast that compressed hydrogen sulfide forms H3S superconducting near 200 K, confirmed at 203 K in 2015.

H3S superconductor

H3S, or sulfur trihydride, is a hydrogen-rich compound that superconducts at 203 K under about 155 GPa of pressure, first reported in 2015 by researchers at the Max Planck Institute for Chemistry.

Haab'

The Haab' is the Maya solar calendar of 365 days, eighteen 20-day months plus the five-day Wayeb'. Called the vague year, it drifted one day every four years.

Haar measure

Haar measure is a measure on a locally compact group that is invariant under translation, finite on compact sets, and unique up to a positive constant; on R it coincides with Lebesgue measure.

Haar wavelet

The Haar wavelet is the simplest orthonormal wavelet, a step function equal to +1 and −1 on halves of its support, introduced by Alfréd Haar in 1909.

Sep 29, 2026

Haar wavelet transform

The Haar wavelet transform decomposes a signal or image into averages and differences at successive dyadic scales, and its coefficients are used for compression, denoising, and edge extraction.

Habitability of binary star systems

The habitability of binary star systems, also called life in binary star systems, asks whether planets orbiting two stars can keep stable orbits while receiving enough light for liquid water.

Habitability of red dwarf systems

Habitability of red dwarf systems, or life in red dwarf systems, is the debate over whether planets around red dwarf stars can sustain surface liquid water and life.

Habitable zone

The habitable zone, also called the Goldilocks zone, is the region around a star where a rocky planet with a suitable atmosphere could hold liquid surface water.

A haboob (Arabic habūb) is a wall of dust or sand pushed by thunderstorm outflow winds that can cut visibility to zero; the term began in Sudan and now covers similar storms worldwide, especially in Arizona.

Hadamard gate

The Hadamard gate is a single-qubit quantum gate, drawn as a box labeled H, that maps |0⟩ and |1⟩ into equal superpositions, so measurement gives 0 or 1 with equal probability.

Hadamard matrix

A Hadamard matrix is a square matrix whose entries are all +1 or −1 and whose rows are mutually orthogonal, achieving the largest determinant possible of n^(n/2).

Hadamard product (matrices)

The Hadamard product, also called the Schur product or entrywise product, multiplies two matrices of the same size entry by entry, unlike ordinary matrix multiplication.

Hadamard transform

The Hadamard transform, also called the Walsh-Hadamard transform, is a fast discrete linear transform that uses only additions and subtractions, with applications in signal processing and quantum computing.

Hadamard's inequality for integrals

Hadamard's inequality for integrals, more often called the Hermite–Hadamard inequality, bounds the integral of a convex function between its midpoint value and its endpoint average.

Sep 21, 2026

Hadas Shtrikman

Hadas Shtrikman is a physicist at the Weizmann Institute of Science in Rehovot, Israel, known for the first electronic Mach–Zehnder interferometer and superconductor vortex-matter experiments.

HadCM3

HadCM3 (Hadley Centre Coupled Model version 3) is a coupled atmosphere–ocean–sea ice climate model released by the Met Office Hadley Centre in 1999, requiring almost no flux adjustments.

HadCRUT

HadCRUT is a series of global historical temperature datasets produced jointly by the Met Office Hadley Centre and the University of East Anglia's Climatic Research Unit since 1850.

Hadean

The Hadean, formerly the Priscoan, is the earliest eon of geological time, spanning Earth's formation about 4.567 billion years ago to 4.031 billion years ago, known almost entirely from zircon grains.

Hadfield steel

Hadfield steel, also called mangalloy, is a high-manganese steel invented by Robert Hadfield in Sheffield in 1882, known for work hardening under impact in railroad crossings and crushers.

Hadley cell

The Hadley cell, or Hadley circulation, is an atmospheric circulation in which air rises near the equator and descends near latitude 30° in each hemisphere.

Hadley Centre for Climate Prediction and Research

The Hadley Centre for Climate Prediction and Research, founded in 1990 within the UK Met Office, is the United Kingdom's primary source of climate change information and climate models.

Hadron

A hadron is a composite subatomic particle made of quarks, antiquarks, and gluons bound by the strong interaction, dividing into baryons like the proton and mesons like the pion.

Hadron-Electron Ring Accelerator

The Hadron-Electron Ring Accelerator (HERA) was a particle collider at DESY in Hamburg, Germany, the first and only lepton-proton collider, operating from 1992 to 2007.

Hadronic emission

Hadronic emission is the production of gamma rays, neutrinos, and secondary particles when cosmic-ray protons or nuclei collide with gas, most commonly through pion-producing proton-proton interactions.