42,772 articles
Perry Byerly
Perry Byerly was an American seismologist at UC Berkeley who directed its seismographic stations for 38 years and joined the National Academy of Sciences in 1946.
Perseids
The Perseids, also called the Perseid meteor shower, are an annual meteor shower peaking around August 13, caused by debris from comet 109P/Swift-Tuttle and known for bright fireballs.
Perseus (Περσεύς) (constellation)
Perseus (Περσεύς), one of Ptolemy's 48 constellations, is a northern constellation named after the Greek hero who beheaded Medusa, best known for Algol and the Perseids.
Perseus Arm
The Perseus Arm is one of the major spiral arms of the Milky Way, lying outside the Sun between the Sagittarius Arm and the Outer Arm.
Perseus molecular cloud
The Perseus molecular cloud is a giant star-forming cloud of gas and dust in the constellation Perseus, about 1,000 light-years from the Sun and over 500 light-years wide.
Perseverance Mine (Western Australia)
The Perseverance Mine is an underground nickel sulfide mine at Leinster in the Northern Goldfields of Western Australia, the largest orebody of BHP's Leinster Nickel Operation, suspended from October 2024.
Persi Diaconis
Persi Diaconis is a Stanford mathematician and statistician who spent ten years as a professional magician and proved that seven riffle shuffles randomize a deck of cards.
Persis Drell
Persis Drell is a particle astrophysicist and Stanford professor who directed SLAC National Accelerator Laboratory from 2007 to 2012 and served as Stanford's 13th provost from 2017 to 2023.
Persistence diagram
A persistence diagram is a multiset of points in the extended plane, each recording the birth and death scales of a topological feature in persistent homology.
Persistence of vision
Persistence of vision is the traditional theory that an image lingers after its source disappears, long used to explain film and animation but largely refuted by vision research.
Persistent current
A persistent current is an equilibrium current flowing indefinitely around a ring without applied voltage, common in superconductors and predicted for normal-metal mesoscopic rings in 1983.
Persistent scatterer InSAR
Persistent scatterer InSAR (PSInSAR, or PSI) is a radar technique that measures surface deformation with millimeter-scale velocity precision at phase-stable ground points in time series of interferometric SAR images.
Persistent scatterer interferometry
Persistent scatterer interferometry, developed at the Politecnico di Milano and first reported in 2000, is a radar technique measuring millimeter-scale ground deformation from stacks of satellite SAR images.
Personal income in the United States
Personal income in the United States is a Bureau of Economic Analysis national accounts measure summing all income received by persons from all sources, published monthly.
Perspectives on Science
Perspectives on Science is a peer-reviewed academic journal publishing science studies with historical, philosophical, and sociological perspectives, founded in 1993 and published by MIT Press.
Persulfate oxidation
Persulfate oxidation is an advanced oxidation process in which persulfate salts are activated by heat, UV light, or metals to generate sulfate radicals that degrade organic contaminants in water, wastewater, and soil.
Pertechnetate
Pertechnetate is the monovalent anion TcO₄⁻, the oxyanion of technetium in its +7 oxidation state, best known as the form in which technetium-99m is administered for thyroid scintigraphy.
Perturbation (astronomy)
A perturbation, also called an orbital or gravitational perturbation, is a deviation of an orbit from the ideal Keplerian ellipse, caused by third bodies and other forces.
Perturbation theory
Perturbation theory, also called perturbation analysis, is a group of methods for approximating hard mathematical and physical problems by starting from a related exactly solvable one.
Perturbation theory (quantum mechanics)
Perturbation theory in quantum mechanics, also called Rayleigh–Schrödinger perturbation theory, is a family of approximation methods for energy levels and states of nearly solvable systems.
Perturbative string gravity
Perturbative string gravity is the body of results showing that quantum gravity emerges automatically from string theory, whose closed strings contain a massless spin-2 graviton and whose consistency conditions reproduce Einstein's equations.
Perturbed angular correlation
Perturbed angular correlation (PAC) is a nuclear spectroscopy method that uses coincidence counting of cascade gamma rays to measure hyperfine interactions, applied mainly in condensed matter research.
Perturbed parameter ensemble
A perturbed parameter ensemble, or perturbed physics ensemble, is a climate modeling method that runs one model many times with varied parameter values to sample uncertainty.
Perylene
Perylene, also known as peri-dinaphthalene, is a polycyclic aromatic hydrocarbon, C20H12, with five fused rings, used as a fluorescent probe and the basis of perylene diimide pigments and organic electronic materials.
Peshtigo fire
The Peshtigo fire, also called the Great Peshtigo Fire, was an 1871 firestorm in northeastern Wisconsin and Michigan that killed over 1,150 people, the deadliest wildfire in United States history.
Pessimistic induction
The pessimistic induction, also called the pessimistic meta-induction, is an argument in the philosophy of science that uses the history of abandoned theories to argue current theories are probably false.
PET physics
PET physics is the physics of positron emission tomography, in which annihilation photon pairs from an injected tracer are detected in coincidence to form 3D images.
PET-RAFT polymerization
PET-RAFT polymerization is a photoinduced variant of RAFT polymerization in which a visible-light-activated photocatalyst generates propagating radicals from a thiocarbonylthio chain transfer agent, tolerating oxygen.
Petahertz field sampling
Petahertz field sampling is the direct, time-domain measurement of the oscillating electric field of light at petahertz frequencies, using attosecond gates shorter than half an optical cycle.
Petahertz optical oscilloscope
The petahertz optical oscilloscope is an all-optical technique for measuring the electric field of an optical pulse, reported by Kyung Taec Kim and colleagues in 2013.