Science

Radiocarbon dating: principles, practice, history and applications Radiocarbon dating Radiocarbon dating (C-14) determines the age of organic materials by measuring radioactive carbon-14. This article explains its physical basis, methods, calibration, limits, key us…

Radiometric dating Techniques that determine the age of materials by measuring radioactive isotopes and their decay products. Widely used in geology, archaeology and planetary science.

Random forest: ensemble decision-tree algorithm for classification and regression Random forest Overview of the random forest algorithm: an ensemble of decision trees for classification and regression, how trees are grown and aggregated, with OOB error, variable importance an…

Randomized Controlled Trial: methods, purposes, and key considerations Randomized controlled trial A randomized controlled trial (RCT) is a study design that assigns participants by chance to compare interventions, reduce bias, and provide evidence about effectiveness and safety…

Reductionism: concepts, types, history, uses and criticisms Reductionism Overview of reductionism: the idea that complex systems or theories can be explained by their parts. Covers forms (ontological, methodological), history, examples, uses, and limits…

Research: methods, history, applications, and key distinctions Research An overview of research: its aims, methods, settings, history, common types, applications across disciplines, and notable distinctions for researchers and organizations.

Sample (statistics): definition, types, sampling methods and uses Sample A sample is a subset of a population used in statistics for estimation and inference. This article explains notation, selection methods, common biases, applications, and key distin…

Sampling Overview of sampling as a general concept: converting continuous to discrete signals, selecting observations in statistics, taking material or environmental samples, and music samp…

Scanning electron microscope (SEM) Scanning electron microscope A scanning electron microscope uses a focused electron beam to image and analyze specimen surfaces, producing topographic, compositional, and structural information across many sci…

Science: methods, branches, history and significance Science Overview of science: its methods, major branches, development, validation, applications, limitations, and the roles of research and scientists in producing organized knowledge.

Science (journal) Science is a long-established, peer-reviewed weekly journal published by the American Association for the Advancement of Science, covering original research, reviews, and science p…

ScienceDaily — online source for science and technology news Science Daily ScienceDaily is an online news site that reports and summarizes developments in science, medicine, environment and technology for general readers, students and journalists.

Science fiction: an overview of themes, forms, and cultural impact Science fiction Science fiction is speculative fiction exploring imaginative scientific, technological, and social possibilities through novels, film, games and other media, shaping ideas about th…

Science tourism: visiting laboratories, observatories and scientific sites Science tourism Travel oriented toward scientific sites—museums, laboratories, observatories and campuses—blending education, heritage and public engagement through tours, events and citizen scien…

Scientific American Scientific American is a long-running popular science magazine that explains research, technology and scientific issues for general readers, published in print and online since 184…

Scientific law: concise empirical descriptions of natural regularities Scientific law A scientific law is a concise, generally empirically established statement—often mathematical—that describes regularities in nature, guides prediction, and complements explanatory…

Scientific method: principles, steps, history, and applications Scientific method A clear overview of the scientific method: its purpose, core steps, historical roots, practical uses, and limitations, with essential concepts and distinctions for readers.

Scientific model: definition, types, construction, uses and limitations Scientific model Concise guide to scientific models: what they are, main types, how models are built and tested, common applications (weather, epidemiology, engineering), and typical limitations an…

Scientific racism: history, methods, and why modern science rejects it Scientific racism Scientific racism is the misuse of scientific claims to justify racial hierarchies. This article explains its origins, common methods, historical consequences, and why contemporary…

Scientific theory: definition, development, and role in science Scientific theory A scientific theory is a well-tested explanatory framework that unifies observations, predicts outcomes, and adapts when evidence demands change. This article explains what theorie…

Scientist: role, methods, workplaces, and impact Scientist A scientist applies systematic methods to study natural and social phenomena, using observation, experiment and analysis to generate reliable knowledge and practical applications.

Scuba diving: underwater breathing, equipment, and safety Scuba diving Overview of scuba diving: what it is, main equipment, brief history, safety considerations, common uses, and distinctions like rebreathers and freediving.

Sex determination: mechanisms, examples, and evolutionary context Sex determination Overview of biological sex determination: genetic and environmental systems, hermaphroditism, examples across animals and plants, and developmental and evolutionary implications.

Sextant (navigational instrument) Sextant A sextant is a precision optical instrument used to measure angles between a celestial object and the horizon to determine a vessel's position at sea; it remains a reliable backup…

Sievert — unit of equivalent and effective ionizing radiation dose Sievert The sievert (Sv) is the SI unit that quantifies the biological effect of ionizing radiation on humans, combining absorbed energy with radiation and tissue weighting factors to asse…

Skeptical Inquirer — magazine of science, reason, and critical inquiry Skeptical Inquirer A bimonthly American magazine published by the Committee for Skeptical Inquiry that examines scientific topics and critiques pseudoscience and extraordinary claims.

Space: physical concept, outer space, mathematical spaces, and cultural meanings Space Overview of 'space' covering physical and outer space, mathematical definitions, history, human exploration, law and policy, environmental issues, and cultural uses in arts and med…

Specific impulse (Isp): a measure of rocket and jet propulsion efficiency Specific impulse Specific impulse (Isp) quantifies how efficiently a rocket or jet engine uses propellant. It links thrust, propellant flow and vehicle performance and guides trade-offs between thr…

Spermatic cord — anatomy, function, development and clinical importance Spermatic cord The spermatic cord is a bundle of structures that runs between the abdomen and each testicle, containing the vas deferens, vessels, nerves and coverings important for testicular bl…

Spontaneous generation (historical scientific theory) Spontaneous generation Historical belief that complex life could arise from nonliving matter; traced from ancient authorities through microscopy to experiments by Redi, Spallanzani and Pasteur and its le…

Square metre (m²): definition, notation, conversions and uses Square metre The square metre (m²) is the SI derived unit of area, defined by a square with 1 metre sides. This article explains its definition, notation, scaling with prefixes, common conversi…

Statistical hypothesis testing Statistical hypothesis test A formal procedure for deciding whether data support a given hypothesis. Uses test statistics, p-values, significance levels and error rates to assess evidence in scientific and pr…

Structure (organization of parts and their relationships) Structure An overview of structure as the arrangement and relationships among parts across disciplines — from crystals and organisms to sentences, buildings, and social systems.

Sydney funnel‑web spider (Atrax robustus) Sydney funnel-web spider Atrax robustus, the Sydney funnel‑web spider, is a venomous Australian species known for its distinctive funnel webs, potent neurotoxic venom, and historical medical significance a…

Systems Science: principles, subfields, history and applications Systems science Systems science studies how parts interact to form wholes. It develops concepts and methods for analyzing and designing natural, engineered and social systems, emphasizing emergenc…

Theoretical computer science: foundations, models, and applications Theoretical computer science A concise guide to the foundations of theoretical computer science: its main subfields, models of computation, historical roots, practical uses, and how it connects to other discip…

Transduction: conversion processes in physiology, genetics, and engineering Transduction Transduction describes processes that convert one form of signal, energy, or information into another. It appears in physiology (sensory signals), genetics (phage-mediated gene tra…

Twofish — a 128-bit symmetric block cipher Twofish Twofish is a symmetric block cipher with 128-bit blocks and up to 256-bit keys. Designed as an AES finalist, it emphasizes key-dependent S-boxes, a complex key schedule, and freedo…

Unit of length A unit of length is a standard quantity used to measure distance or size. This article explains common systems, notable units, history, and contexts where different length measures…

United States Naval Research Laboratory The U.S. Naval Research Laboratory (NRL) is the principal corporate research institution for the U.S. Navy and Marine Corps, performing basic science, applied research, and technol…

X-ray crystallography: determining molecular arrangements by diffraction X-ray crystallography A concise overview of X-ray crystallography: how it reveals atomic arrangements, the physical principles, historical milestones, methods, applications in chemistry and biology, and…

Zootaxa: international journal of animal taxonomy and systematics Zootaxa Zootaxa is a peer‑reviewed journal specializing in animal taxonomy and systematics. Founded in 2001 and published by Magnolia Press (Auckland), it issues frequent papers describing…