James Gregory

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Introduction References & Edit History Quick Facts & Related Topics

Images

Gregorian telescopeJames Gregory's telescope design (1663) uses two concave mirrors—a primary parabolic-shaped mirror and a secondary elliptic-shaped mirror—to focus images in a short telescope tube. As indicated by the yellow rays in the figure: (1) light enters the open end of the telescope; (2) light rays travel to the primary mirror, where they are reflected and concentrated at the prime focus; (3) a secondary mirror slightly beyond the prime focus reflects and concentrates the rays near a small aperture in the primary mirror; and (4) the image is viewed through an eyepiece.

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Galaxy clusters like Abell 2744 can act as a natural cosmic lens, magnifying light from more distant, background objects through gravity. NASA's James Webb Space Telescope may be able to detect light from the first stars in the universe if they are gravitationally lensed by such clusters. (astronomy, space exploration, galaxies)

How Fast Is the Universe Expanding?

solar eclipse, sun, moon, astronomy, space

How Do You Tell the Difference Between Total, Annular, Solar, and Lunar Eclipses?

Arrangement of the phases of the moon in total eclipse with Blood Moon

9 Celestial Omens

number zero, 0 balloon

Is Zero an Even or an Odd Number?

Solar system illustration. (Sun; planets)

A Model of the Cosmos

Discover

World Data Locator Map: Australia

Is Australia an Island?

Four year old boy with grandfather and father lighting Hanukkah menorah. Photo taken on: December 21st, 2009

Which Is Correct: Hanukkah or Chanukah?

Christmas tree, holiday, pine

How Did the Tradition of Christmas Trees Start?

Ruminant. Deer. Red deer. Cervus elaphus. Buck. Stag. Antlers.

9 of the World’s Deadliest Mammals

Hemp (Cannabis sativa).

9 Mind-Altering Plants

Nativity Scene, Adoration of the Magi, Church of the Birth of the Virgin Mary, Montenegro

Why Is Christmas in December?

The Jeff Koons tulips sculputure outside the Guggenheim Museums in Bilbao, Spain, Basque Country.

What’s the Difference Between Modern and Contemporary Art?

James Gregory: Facts & Related Content

Written and fact-checked by The Information Architects of Encyclopaedia Britannica

Facts

Also Known As	James Gregorie
Born	November 1638 • Scotland
Died	October 1675 (aged 36) • Edinburgh • Scotland
Subjects Of Study	area • convergence • curve • divergence • fundamental theorem of calculus • infinite series • photometry • reflection • refraction • squaring the circle • telescope • trigonometry

Photos

Gregorian telescopeJames Gregory's telescope design (1663) uses two concave mirrors—a primary parabolic-shaped mirror and a secondary elliptic-shaped mirror—to focus images in a short telescope tube. As indicated by the yellow rays in the figure: (1) light enters the open end of the telescope; (2) light rays travel to the primary mirror, where they are reflected and concentrated at the prime focus; (3) a secondary mirror slightly beyond the prime focus reflects and concentrates the rays near a small aperture in the primary mirror; and (4) the image is viewed through an eyepiece.

See All Images →

How did Ptolemy explain retrograde motion?

Ptolemy

Egyptian astronomer, mathematician, and geographer

Understanding Newton's theory of universal gravitation

Isaac Newton

English physicist and mathematician

Galileo

Galileo

Italian philosopher, astronomer and mathematician

Hipparchus

Greek astronomer

Fermat, portrait by Roland Lefèvre; in the Narbonne City Museums, France

Pierre de Fermat

French mathematician

Leonhard Euler

Leonhard Euler

Swiss mathematician

Eudoxus of Cnidus

Greek mathematician and astronomer

Ibn al-Haytham

Arab astronomer and mathematician

Regiomontanus

German mathematician

Heron of Alexandria

Greek mathematician

Minggantu

Chinese astronomer and mathematician

Abū al-Wafāʾ

Persian mathematician

Boscovich, detail of a portrait by an unknown artist; in Dubrovnik Cloister, Croatia

Ruggero Giuseppe Boscovich

Italian astronomer and mathematician

Gilles Personne de Roberval

French mathematician

Willebrord Snell

Dutch astronomer and mathematician

James Stirling

British mathematician

Colin Maclaurin, engraving by S. Freeman; in the British Museum.

Colin Maclaurin

Scottish mathematician

Playfair, John

John Playfair

Scottish geologist and mathematician

Blaise Pascal

Blaise Pascal

French philosopher and scientist

Giordano Bruno

Giordano Bruno

Italian philosopher

Quiz

Michael Faraday (L) English physicist and chemist (electromagnetism) and John Frederic Daniell (R) British chemist and meteorologist who invented the Daniell cell.

Faces of Science

View of the Andromeda Galaxy (Messier 31, M31).

Astronomy and Space Quiz

Nicolaus Copernicus. Nicolas Copernicus (1473-1543) Polish astronomer. In 1543 he published, forward proof of a Heliocentric (sun centered) universe. Coloured stipple engraving published London 1802. De revolutionibus orbium coelestium libri vi.

All About Astronomy

Equations written on blackboard

Numbers and Mathematics