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Explore science by method, field & evidence.

One catalogue of research methods — learn how each one works, when to use it, and what it can’t do.

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Entries are compiled from published sources for reference. Verifying the accuracy and suitability of any information for your own use remains your responsibility.

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248
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MethodStatistics1,836AI & ML1,661Decision Sciences932Research Methods1,354Measurement1,745Causal & Evidence532Research Practice118
188 methods in Natural Sciences · AI & MLClear
Methods at the intersection of your two filters.
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oceanography

Acoustic Doppler Current Profiler

The Acoustic Doppler Current Profiler (ADCP) is an instrument that uses Doppler-shifted acoustic backscatter to measure water velocity profiles along a vertical profile. Developed by RD Instruments in the 1980s, it has become the standard method for high-resolution current profiling in oceanographic research. ADCPs pro

2 sources1983
acoustics

Acoustic Ray Tracing

Acoustic ray tracing is a computational technique for predicting sound propagation in rooms by treating acoustic energy as rays that reflect specularly off surfaces. Formalized by Allen and Berkley in 1979 via the image source method, ray tracing is one of the most computationally efficient methods for room acoustic si

3 sources1979
applied physics

Adsorption Isotherm (Langmuir-Freundlich)

Adsorption isotherms describe the equilibrium uptake of a substance on a solid surface as a function of gas or solution phase concentration at constant temperature. The Langmuir isotherm (1918) and Freundlich isotherm (1906) are classical empirical models. The Langmuir model assumes monolayer coverage and is mechanisti

3 sources1918
geophysics

Aerosol Optical Depth

Aerosol Optical Depth (AOD) is a dimensionless measure of aerosol light extinction in the atmosphere, quantifying how much sunlight is scattered and absorbed by particles suspended in air. Formalized by Ångström in 1929 and now routinely measured via satellite (MODIS, Sentinel-5P) and ground networks (AERONET), AOD is

2 sources1929
applied physics

Ambisonics

Ambisonics is a full-sphere spatial audio encoding and reproduction technique that captures and reproduces three-dimensional sound fields. Developed by Michael Gerzon in the 1970s, it uses spherical harmonics to represent sound at all directions around a central point. Unlike surround systems that use discrete channels

3 sources1973
particle physics

Anti-kT Jet Algorithm

The anti-kT jet algorithm, introduced by Cacciari and Salam in 2008, is a sequential recombination jet clustering algorithm widely used in high-energy physics to group final-state particles into jets. Unlike earlier algorithms, anti-kT produces jets with regular cone-like geometries in transverse momentum-rapidity spac

3 sources2008
astronomy

Asteroseismology

Asteroseismology is the study of stellar oscillations—tiny brightness and radial velocity variations caused by sound waves resonating inside stars. Proposed by Roger Ulrich in 1970 and established as a major field by the Kepler and TESS space telescopes, asteroseismology provides unprecedented precision in determining

3 sources1970
astronomy

Astrometry (Parallax)

Astrometric parallax is the foundational geometric method for measuring distances to nearby stars, based on observing the apparent shift in a star's position as Earth orbits the Sun. First successfully demonstrated by Friedrich Wilhelm Bessel in 1838 for the star 61 Cygni, parallax remains the most direct and reliable

3 sources1838
acoustics

Bark and Mel Scales

Bark and Mel scales are perceptual frequency scales that map physical frequency (Hz) to perceived pitch and auditory perception. Formalized by Zwicker (Bark, 1961) and Stevens (Mel, 1937), these non-linear scales reflect how the human ear processes sound. Bark scale divides hearing into 24 critical bands; Mel scale mod

3 sources1937
meteorology

Barnes-Cressman Analysis

Barnes-Cressman analysis is an objective interpolation method that creates gridded meteorological fields from irregularly spaced observations (station data, radiosonde profiles, buoys). It is widely used for synoptic analysis, quality control, and initialization of numerical weather models.

2 sources1959
astronomy

Baryon Acoustic Oscillations

Baryon Acoustic Oscillations are imprints of sound waves in the early universe that appear as a characteristic scale in the large-scale distribution of galaxies today. First predicted theoretically by Piet Peebles and Joseph Yu in 1970, and detected observationally by the Sloan Digital Sky Survey in 2005, BAO provides

3 sources1970
geoscience

Basin Subsidence Analysis

Basin subsidence analysis is the quantitative study of how sedimentary basins deepen over geological time, driven by tectonics, isostasy, and load. Formalized by McKenzie (1978) and Sclater and Christie (1980), this method reveals the mechanical causes of basin development, predicts subsurface temperature and pressure

3 sources1978
thermodynamics

Battery Equivalent Circuit Model

The Battery Equivalent Circuit Model (ECM) represents battery electrochemical behavior using an electrical circuit analogy. It includes an ideal voltage source (open-circuit voltage dependent on state of charge), internal resistance(s) for ohmic losses, and capacitive/resistive elements for transient response. ECM enab

2 sources2004
particle physics

BDT Particle Identification

Boosted Decision Trees (BDTs) are powerful multivariate classifiers used in particle physics to distinguish between different particle types based on detector signatures. By combining many weak decision trees through adaptive boosting, BDTs achieve superior discrimination power compared to simple cuts, enabling improve

3 sources2000
acoustics

Beamforming

Beamforming is a spatial signal processing technique that uses microphone arrays to selectively enhance sound from a desired direction while suppressing sounds from other directions. Formalized by Van Veen and Buckley in 1988, beamforming is fundamental to hands-free speech communication, hearing aids, sonar, radar, an

3 sources1988
acoustics

BEM Acoustics

The Boundary Element Method (BEM) is a numerical technique for solving acoustic wave equations in complex geometries. Unlike finite element methods (FEM) that mesh entire volumes, BEM discretizes only the acoustic boundaries (surfaces), reducing computational cost and memory. First applied to acoustics by Burton and Mi

3 sources1971
oceanography

Benthic Index of Biotic Integrity

The Benthic Index of Biotic Integrity (B-IBI) is an ecological assessment metric that measures the health and integrity of benthic (seafloor) communities based on the composition, abundance, and diversity of benthic fauna. Developed by James Karr in 1981 for freshwater fish assemblages and later adapted for marine bent

2 sources1981
thermodynamics

Betz Limit

The Betz Limit states that no wind turbine can extract more than 59.3% of the kinetic energy from flowing wind, regardless of design. This fundamental thermodynamic limit arises because extracting energy slows the wind, which then blocks further energy extraction. Albert Betz derived this limit in 1920 from momentum an

2 sources1920
quantum computing

Born-Oppenheimer Approximation

The Born-Oppenheimer (BO) Approximation is a foundational assumption in molecular quantum mechanics that nuclei can be treated as fixed while solving for electrons, and vice versa. Introduced by Born and Oppenheimer in 1927, this separation reduces the complex many-body electronic-nuclear problem to a sequence of simpl

3 sources1927
fluid dynamics

Boundary Layer Theory

Boundary Layer Theory is the analytical and approximate framework for understanding viscous flow near solid surfaces, pioneered by Ludwig Prandtl in 1904. The central insight is that at high Reynolds numbers, viscous effects are confined to a thin layer near walls (the boundary layer), while the flow outside remains es

3 sources1904
thermodynamics

Boussinesq Approximation

The Boussinesq Approximation simplifies the governing equations for natural convection by treating density as constant except in the buoyancy term. This approximation is valid when temperature variations produce small density changes and allows researchers to solve coupled heat-fluid flow problems without solving the f

2 sources1903
thermodynamics

Brayton Cycle

The Brayton Cycle (also called Joule Cycle) describes the thermodynamic process in gas turbines and jet engines. It consists of four processes: isentropic compression in a compressor, isobaric combustion (heat addition), isentropic expansion in a turbine, and isobaric heat rejection. The Brayton Cycle is the foundation

2 sources1873
meteorology

Bulk Aerodynamic Flux

The bulk aerodynamic method estimates surface energy and momentum fluxes from standard meteorological observations. Rather than measuring turbulent fluxes directly, it parameterizes them using measurements of wind speed, temperature, and moisture at a reference height (typically 10 m) and surface conditions, multiplied

2 sources1981
particle physics

Calorimeter Calibration

Calorimeter calibration establishes the relationship between the measured energy deposited in a detector and the true energy of incident particles. Precise calibration is essential for physics measurements, Higgs boson properties, and new physics searches at colliders, requiring careful control of systematic uncertaint

3 sources1990
acoustics

Cepstral Analysis

Cepstral analysis is a spectral analysis technique that decomposes signals into independent components by inverting the log-magnitude spectrum. Pioneered by Bogert, Healy, and Tukey in 1963, cepstral analysis reveals periodic structure in spectra (pitch, echo patterns) and separates source excitation from filter respon

3 sources1963
meteorology

Cloud Condensation Nuclei Analysis

Cloud condensation nuclei (CCN) analysis examines the number and properties of aerosol particles capable of nucleating cloud droplets at various supersaturation levels. This field involves measuring CCN concentrations, characterizing their chemical composition and size, and relating aerosol properties to cloud microphy

2 sources1959
astronomy

CMB Anisotropy Analysis

The Cosmic Microwave Background is the ancient light from when the universe first became transparent, about 380,000 years after the Big Bang. Its tiny temperature variations (anisotropies) across the sky encode a wealth of information about the universe's composition, geometry, and history. First discovered by Arno Pen

3 sources1965
oceanography

CO2SYS

CO2SYS is a widely-used software package for calculating the speciation and equilibrium state of the marine carbonate system from measurements of two carbonate parameters. Developed by Ernie Lewis and Doug Wallace in 1998, CO2SYS enables oceanographers to compute all carbonate species (dissolved CO2, bicarbonate, carbo

2 sources1998
applied physics

Cosmological Perturbation Theory

Cosmological perturbation theory describes how small density fluctuations in the early universe grow into galaxies, clusters, and large-scale structure under gravity. Originating from James Jeans's 1902 stability analysis and extended by Lifshitz, Bardeen, and others, this theory is the foundation of structure formatio

3 sources1902
quantum computing

Coupled Cluster CCSD

Coupled Cluster theory, particularly CCSD (Singles and Doubles) and CCSD(T) with perturbative triples, is one of the most accurate methods for molecular electronic structure. Developed by Jiri Cizek in 1966, CC theory treats the ground state wave function as an exponential of excitation operators applied to the Hartree

3 sources1966
particle physics

CP Violation Measurement

Charge-Parity (CP) violation measurement is the experimental study of asymmetries between particle and antiparticle processes, a fundamental probe of physics beyond the Standard Model. By comparing decay rates and asymmetries in kaons, B mesons, and neutrinos, physicists constrain new sources of CP violation and addres

3 sources1964
nuclear physics

Criticality Safety Analysis

Criticality safety analysis is a systematic evaluation of fissile material systems to ensure nuclear chain reactions remain controlled, originating from Hahn and Strassmann's 1938 discovery of nuclear fission. It determines safe limits on fissile mass, concentration, geometry, and spacing using neutron transport calcul

2 sources1938
applied physics

CSTR Model

The CSTR (Continuous Stirred-Tank Reactor) model describes the behavior of an ideal mixed reactor where fresh feed is continuously added, products are withdrawn, and contents are kept uniform by vigorous stirring. This fundamental model, formalized by Octave Levenspiel in the 1960s, is widely used to design and scale b

3 sources1962
oceanography

CTD Profiling

Conductivity-Temperature-Depth (CTD) profiling is the primary method for measuring vertical profiles of seawater properties in oceanography. Developed by Neil Brown in 1977, CTD instruments are equipped with sensors for conductivity, temperature, and pressure (depth), and are typically mounted on water-sampling rosette

2 sources1977
oceanography

Degree Heating Weeks

Degree Heating Weeks (DHW) is a thermal stress metric that quantifies accumulated heat exposure above a coral bleaching threshold, computed from satellite sea surface temperature data. Developed by NOAA's Coral Reef Watch program in 2003, DHW provides a standardized index for predicting and monitoring coral bleaching s

2 sources2003
quantum computing

Density Functional Theory

Density Functional Theory (DFT) is a computational method for determining the properties of materials and molecules by modeling the ground state electron density. Developed by Walter Kohn and Lu Jeu Sham in the 1960s, DFT reduces the complexity of quantum chemistry from tracking individual electron coordinates to optim

3 sources1965
fluid dynamics

Detached Eddy Simulation

Detached Eddy Simulation (DES) is a hybrid turbulence modeling approach introduced by Spalart in 1997 that combines the computational efficiency of RANS in attached boundary layers with the accuracy of LES in separated wake regions. By automatically switching between RANS and LES based on local grid spacing and turbule

3 sources1997
fluid dynamics

Direct Numerical Simulation

Direct Numerical Simulation (DNS) is a computational approach that solves the Navier-Stokes equations without turbulence models, resolving all scales of motion from the largest energy-containing eddies down to the smallest dissipative scales (Kolmogorov microscales). Pioneered by Steven Orszag in 1971, DNS provides com

3 sources1971
nuclear physics

Dosimetry Measurement

Dosimetry measurement is the experimental quantification of radiation dose and exposure, originating from Röntgen and Becquerel's 1890s discoveries. It employs specialized detectors (ion chambers, TLD, Geiger counters) to measure photon and particle energy deposition in biological tissue or materials, providing direct

2 sources1896
oceanography

Drifter Lagrangian Analysis

Drifter Lagrangian analysis tracks the motion of water parcels using surface drifters (buoys with attached drogues) to measure ocean currents directly. Developed by Robert Davis in the 1980s, this method provides direct observation of water parcel trajectories and enables estimation of eddy diffusivity, transport pathw

2 sources1985
meteorology

Dual-Polarization Radar

Dual-polarization (dual-pol) radar is a weather radar system that transmits and receives electromagnetic waves in both horizontal and vertical polarizations simultaneously. This technique, operational in weather services since the 2010s, provides detailed information about precipitation particle type, shape, and size d

2 sources1990
particle physics

Effective Field Theory

Effective Field Theory (EFT) is a general framework for studying physics at low energies in terms of the relevant degrees of freedom, without requiring complete knowledge of high-energy physics. By expanding in powers of energy, EFT provides model-independent parameterizations of new physics effects and systematic meth

3 sources1979
thermodynamics

Effectiveness-NTU Method

The Effectiveness-NTU method is an alternative approach to heat exchanger analysis that measures thermal performance relative to the theoretical maximum possible heat transfer. It is particularly powerful for design problems where outlet temperatures are unknown. The method uses effectiveness (ratio of actual to maximu

2 sources1984
oceanography

Ekman Transport

Ekman transport is the net volume flux of water driven by wind stress balanced with Coriolis force in the surface boundary layer. Derived by Vagn Walfrid Ekman in 1905 from the principle that wind stress is transmitted through the water column in a spiral pattern, Ekman transport is responsible for coastal upwelling an

2 sources1905
applied physics

Electrochemical Impedance Spectroscopy

Electrochemical Impedance Spectroscopy (EIS) is a powerful technique for characterizing electrochemical systems by applying a small AC voltage over a range of frequencies and measuring the resulting current response. Developed in the late 1960s, EIS reveals the frequency-dependent resistance and capacitance of interfac

3 sources1969
meteorology

Empirical Orthogonal Teleconnection

Empirical orthogonal function (EOF) analysis is a statistical technique that identifies dominant spatial patterns and temporal variability in atmospheric or oceanic data. When applied to geographically distant locations, EOF analysis reveals teleconnection patterns—coherent patterns of variability that link weather sys

2 sources1956
astronomy

Epoch of Reionization 21-cm

The 21-centimeter line observation of neutral hydrogen is a powerful technique for studying the Epoch of Reionization, when the first stars and galaxies ionized the intergalactic medium about 13 billion years ago. Proposed by Scott and Rees in 1990, this method probes the universe's transition from the dark ages to the

3 sources1990
fluid dynamics

Eulerian-Lagrangian Model

The Eulerian-Lagrangian Model (ELM) is a framework for simulating multiphase flows by treating the continuous phase (liquid or gas) using Eulerian descriptions (fixed grid) and discrete dispersed phases (particles, droplets, bubbles) using Lagrangian tracking. Developed by Crowe and collaborators in 1977, this approach

3 sources1977
thermodynamics

Exergoeconomic Analysis

Exergoeconomic analysis combines thermodynamics and economics by assigning monetary costs to exergy streams. It reveals how thermodynamic irreversibilities translate into economic losses within industrial systems. This approach enables engineers to identify the most economically significant inefficiencies and make info

2 sources1993
thermodynamics

Exergoenvironmental Analysis

Exergoenvironmental analysis extends exergy-based methods to quantify and allocate environmental impacts of thermal systems. It assigns environmental costs to exergy streams based on upstream lifecycle impacts, revealing which components contribute most significantly to environmental burdens. This enables engineers to

2 sources2009
astronomy

Exoplanet Transmission Spectroscopy

Transmission spectroscopy is a technique for studying the atmospheres of exoplanets by analyzing the light passing through the planetary atmosphere during transit. Pioneered by David Charbonneau in 2002 with the detection of sodium in HD 209458b's atmosphere, this method has become the primary tool for characterizing e

3 sources2002
particle physics

Feynman Diagram

Feynman diagrams are graphical representations of particle interactions introduced by Richard Feynman in 1949. They provide an intuitive and systematic way to visualize and calculate amplitudes for quantum field theory processes, converting complex mathematical expressions into geometric pictures that reveal the underl

3 sources1949
thermodynamics

Fick's Laws

Fick's Laws describe how species diffuse through media due to concentration gradients. The First Law (steady-state) relates diffusion flux to concentration gradient, while the Second Law (transient) describes how concentration changes over time. These laws are fundamental to mass transfer analysis, applying to gases, l

2 sources1855
thermodynamics

Finite-Time Thermodynamics

Finite-Time Thermodynamics (FTT) relaxes the classical assumption that thermodynamic processes occur reversibly (infinitely slowly). Instead, it analyzes real thermal systems operating at finite rates with irreversibilities. FTT reveals fundamental trade-offs: to complete a process quickly requires accepting large irre

2 sources1996
optics

Fourier Optics

Fourier optics is a mathematical framework that analyzes optical systems and phenomena using Fourier transforms and frequency-domain methods. Grounded in Joseph Fourier's 1822 work on heat diffusion and Ernst Abbe's microscopy theory, this approach decomposes optical fields into plane waves or spatial frequencies, reve

3 sources1822
acoustics

FxLMS Active Noise Control

The Filtered-x Least Mean Squares (FxLMS) algorithm is an adaptive filter used in active noise control (ANC) systems to reduce unwanted sound by generating anti-noise. Pioneered by Widrow and Stearns in 1975 and refined by Eriksson and colleagues, FxLMS is the most widely deployed algorithm in commercial noise-cancelin

3 sources1975
particle physics

Geant4 Simulation

Geant4 is a Monte Carlo simulation toolkit for the passage of particles through matter, developed by an international collaboration. It provides a comprehensive framework for modeling detector geometries, simulating particle interactions, and predicting detector responses, making it essential for designing and optimizi

3 sources2003
geophysics

General Circulation Model

A General Circulation Model (GCM), also called a Global Climate Model, is a three-dimensional numerical representation of the Earth's atmosphere, oceans, ice, and land surface that simulates physical processes governing weather and climate. Pioneered by Manabe and Wetherald in 1975, GCMs are the primary tools for under

2 sources1975
geoscience

Geochronological Dating

Geochronological dating is the determination of absolute ages of rocks and minerals using the decay of radioactive isotopes. Pioneered by Rutherford and Soddy (1902), this method provides numerical anchors for geological timescales and enables quantitative understanding of geological processes. Modern techniques (K-Ar,

3 sources1902
geoscience

Geologic Mapping

Geologic mapping is the systematic observation and documentation of rock types, structures, and relationships exposed on the land surface. Pioneered by William Smith in 1799, this foundational field method remains essential for understanding subsurface geology, economic geology, hazard assessment, and paleoenvironmenta

3 sources1799