Columbia Encyclopedia

Search results

267 results found

radio-frequency identification

(Encyclopedia)radio-frequency identification (RFID), a technology that uses radio waves to transmit data and uniquely identify an animal, person, or thing. An RFID system typically consists of a tag and a reader. T...

Hipparchus, Greek astronomer

(Encyclopedia)Hipparchus, fl. 2d cent. b.c., Greek astronomer, b. Nicaea, Bithynia. He is the first systematic astronomer of whom there are records. He made his observations chiefly on the island of Rhodes. Ptolemy...

Eddington, Sir Arthur Stanley

(Encyclopedia)Eddington, Sir Arthur Stanley, 1882–1944, British astronomer and physicist. He was chief assistant (1906–13) at the Royal Observatory, Greenwich, and was from 1913 Plumian professor of astronomy a...

atomic clock

(Encyclopedia)atomic clock, electric or electronic timekeeping device that is controlled by atomic or molecular oscillations. A timekeeping device must contain or be connected to some apparatus that oscillates at a...

FM, abbreviation for frequency modulation

(Encyclopedia)FM: see modulation; radio. ...

saros

(Encyclopedia)saros: see eclipse.

Baily's beads

(Encyclopedia)Baily's beads: see eclipse.

umbra

(Encyclopedia)umbra: see eclipse; sunspots. ...

Stonehenge

(Encyclopedia)Stonehenge stōnˈhĕnjˌ [key], group of standing stones on Salisbury Plain, Wiltshire, S England. Preeminent among megalithic monuments in the British Isles, it is similar to an older and larger mon...

penumbra

(Encyclopedia)penumbra pĭnŭmˈbrə [key]: see eclipse; sunspots. ...