Physical world and mathematics

Japan Proton Accelerator Research Complex

The Japan Proton Accelerator Research Complex (J-PARC; 大強度陽子加速器施設) is a proton accelerator laboratory in Tokai, Japan, run by KEK and JAEA and known for the T2K neutrino experiment.

Japan Standard Time (日本標準時)

Japan Standard Time (日本標準時), also called Tokyo Standard Time, is the single time zone of Japan, defined as UTC plus 9 hours with no daylight saving.

Japan Trench

The Japan Trench is an oceanic trench off northeastern Japan where the Pacific Plate subducts beneath the overriding plate, causing major earthquakes, including the 2011 magnitude 9.0 Tohoku quake.

Japanese calendar

The Japanese calendar is Japan's system of timekeeping: the Gregorian calendar, adopted in 1873, paired with imperial era years such as Reiwa, while the old lunisolar calendar survives in festivals.

Japanese clock (和時計)

Wadokei, also called Japanese clocks, are Edo-period mechanical clocks (1603 to 1868) adapted from European designs to show seasonal time, in which hour lengths changed with the seasons.

Japanese era name (元号)

The Japanese era name (元号, gengō or nengō) is a name given to a span of years in Japanese dating, as in Heisei or Reiwa, in official use since 701.

Japanese Industrial Standards (JIS, 日本産業規格) are Japan's voluntary national standards for industrial products, technologies, data, and services, established under the 1949 Industrial Standardization Act and binding when cited in regulation.

Japanese traditional time units (fubetsu and temporal hours)

Japanese traditional time units, known as futeijihō or temporal hours, split each day into six daytime and six nighttime toki whose lengths varied with the seasons until 1873.

Japanese units of measurement

Japanese units of measurement, known as shakkan-hō (尺貫法), are the customary units Japan adopted from China, used officially until metrification in 1959; the shō and tsubo survive in sake, rice, and real estate.

Jarad Mason

Jarad Mason is an American inorganic chemist and Harvard University associate professor known for metal-organic frameworks, permanently porous liquids that store gases, and solid-state refrigeration, and a recipient of the Presidential Early Career Award.

Jared Kaplan

Jared Kaplan is an American theoretical physicist and AI researcher who co-founded Anthropic, leads its science team, and led the 2020 neural scaling laws research at OpenAI.

Oct 10, 2026

Jarl Waldemar Lindeberg

Jarl Waldemar Lindeberg (1876–1932) was a Finnish mathematician who spent his career at the University of Helsinki and proved the central limit theorem under the Lindeberg condition.

Jarlskog invariant

The Jarlskog invariant is a quantity in particle physics measuring CP violation in the Standard Model, independent of the parametrization of quark mixing, introduced by Cecilia Jarlskog in 1985.

Jarosite

Jarosite is a potassium iron sulfate hydroxide mineral, KFe₃(SO₄)₂(OH)₆, that forms in acidic, oxidizing environments; on Mars it was found by the Opportunity rover in 2004, evidence of past water.

Jaroslav Heyrovsky

Jaroslav Heyrovský was a Czech chemist who founded polarography, an electrochemical analysis method using the dropping mercury electrode, and received the 1959 Nobel Prize in Chemistry alone.

Oct 10, 2026

Jaroslav Kurzweil

Jaroslav Kurzweil, born in Prague in 1926, was a Czech mathematician whose 1957 Riemann-type definition of the gauge integral, the Kurzweil–Henstock integral, generalized the Lebesgue integral.

Jarrell tornado

The Jarrell tornado was an F5 tornado that struck Jarrell, Texas, and its Double Creek Estates subdivision on May 27, 1997, killing 27 people and producing extreme damage.

Oct 22, 2026

JARVIS-DFT

JARVIS-DFT (Joint Automated Repository for Various Integrated Simulations, DFT database) is a NIST database of density functional theory calculations for about 80,000 crystalline materials, established in 2017.

Jascha Repp

Jascha Repp is a German experimental physicist and professor at the University of Regensburg since 2007, known for controlling and measuring individual molecules with scanning probe microscopes.

Jasmonic acid

Jasmonic acid (JA), a lipid-derived plant hormone with the formula C12H18O3, regulates plant defense responses against herbivores and pathogens as well as fruit ripening and root growth.

Jason Dunion

Jason Dunion is an American research meteorologist at NOAA's Hurricane Research Division known for Saharan Air Layer research and over 50 Hurricane Hunter flights, who received the 2025 PECASE award.

Jason Love (chemist)

Jason B. Love is a British inorganic chemist, Professor of Molecular Inorganic Chemistry and Head of the School of Chemistry at the University of Edinburgh.

Jason ROV

Jason is a two-body deep-ocean remotely operated vehicle built and operated by Woods Hole Oceanographic Institution, rated to 6,500 meters and reaching 98 percent of the global seafloor.

Jason Valentine

Jason Valentine is an optical physicist and mechanical engineering professor at Vanderbilt University, known for a 2008 Nature paper reporting the first bulk optical metamaterial with a negative refractive index.

Jason W. Fleischer

Jason W. Fleischer is an American physicist and Professor of Electrical and Computer Engineering at Princeton University, known for the first observation of two-dimensional discrete solitons.

Jason-1

Jason-1 was a joint NASA and CNES oceanography satellite launched December 7, 2001, continuing the TOPEX/Poseidon sea-surface height record until transmitter failure ended it in 2013.

Jason-2

Jason-2, also called the Ocean Surface Topography Mission, was a satellite operated by CNES, NASA, EUMETSAT, and NOAA that measured sea surface height from 2008 to 2019.

Jason-3

Jason-3 is a U.S.-European ocean-observing satellite launched in 2016 by NOAA, NASA, CNES, and EUMETSAT, the fourth Jason mission measuring sea surface height to study sea level rise and climate.

Jasper

Jasper is an opaque, impure variety of cryptocrystalline silica, typically red to reddish-brown from hematite inclusions; the name comes from ancient Greek for "spotted stone," and it has been used since prehistory.