Who invented longitude and latitude?

Answer 1

Hipparchus (c. 190 BCE - c. 120 BCE) was a Greek astronomer, geographer, and mathematician. The

appearance of a nova in the constellation Scorpius inspired him to

investigate how stars are born and die. With only the power of his eyes,

he created the first accurate star map, a catalogue of 1,080 stars, giving

their position and relative brightness. In comparing his chart with one

compiled by Timocharis and Aristyllus of Alexandria 150 years earlier,

Hipparchus discovered that the earth's axis is precessing, or wobbling,

slowly like a top. His calculation of the inclination of the ecliptic, its

equation, and his estimate of the annual precession of the equinoxes were

all remarkably accurate. He determined the perigee and mean motion of the sun and of the moon, and

he calculated the extent of the shifting of the plane of the Moon's motion. Hipparchus' star catalogue

was used for over 1600 years, and his system of star magnitudes is still in use. His main contribution to

geography was in applying rigorous mathematical principles in determining the location of places on

the earth's surface, being the first to do so by specifying a position's latitude and longitude. In the

Almagest, Ptolemy made use of a catalogue of stars, whose position Hipparchus had fixed by

calculating celestial angular measurements, corresponding to latitude and longitude on earth.

Recognizing that the earth was round, he constructed the first globe and was the first to divide a circle

into 360 degrees. Hipparchus invented an improved type of astrolabe, which he used to determine

accurately the celestial coordinates of stars and a planisphere that allowed stereographic projections

(also invented by Hipparchus), making it possible to tell time at night from stellar projections. He

calculated the length of the year as 365.24667 days, correct to within 6.5 minutes and by making

observations of eclipses, found the distance to the Moon. It isn't known who discovered that the

noontime shadow of an upright rod (called a gnomon, derived from the Greek word for "one who

knows or examines") is longest at the winter solstice and shortest at the summer solstice. It is known

that the Egyptians used the sundial as early as 1500 BCE, and the Greeks learned of it from the

Babylonians. The L-shaped figure comprised of the upright rod of a sundial and its shadow is often

referred to as a gnomon. By keeping a record of the number of days that elapsed while the shadow of a

gnomon passed from its shortest to its greatest length and then back to its shortest length, ancient

people learned to measure the length of the year.

Hipparchus was born in Nicaea (now Iznik) in Bithynia (now Turkey). He probably spent some years in

Alexandria but settled in Rhodes where he made most of his observations. What set him apart from

other ancient astronomers was that he collected data based on careful observations and then formed

theories to fit the observed facts. Except for a short commentary on an astronomical poem by Arastus,

all of Hipparchus works are lost. Most of what is known about him comes from the writings of Strabo

of Amaseai (fl. c. CE 21) and Ptolemy's Almagest, written in the 2nd century CE, which was based on

Hipparchus' findings. Hipparchus' contributions to astronomy were the most important before the time

of Copernicus in the early sixteenth century.

Most scientific historians credit Hipparchus with founding trigonometry. The word is derived from two

Greek words, trigonum, meaning "triangle," and metron, meaning, "measure," combining to mean

"measurement of triangles." In ancient times there was no name for trigonometry, which was not

considered a branch of mathematics, merely a collection of techniques and formulas ancillary to

astronomy. Hipparchus introduced trigonometric functions in the form of a table of chord arcs used to

solve the problem of the computation of specific positions from geometric models. This table is

practically the same as that of natural sines. It is likely that he had some means of solving triangles in

spherical trigonometry. It is also suspected that Ptolemy's Theorem, which gives the necessary and

sufficient conditions that a convex quadrilateral be inscribable in a circle, is due to Hipparchus. The

theorem implicitly gives formulas for the sines and cosines of the sum and difference of angles, from

which all trigonometric relations can be deduced.

Quotation of the Day: "Even if he did not invent it, Hipparchus is the first person of whose

systematic use of trigonometry we have documentary evidence." - T. L. Heath

[The time the professor alluded to must have been 9:36 p.m. A quarter of the time since noon is 2 hr.

24 min., and a half of the time till noon the next day is 7 hr. 12 min. Together these give us 9 hr. 36

min. This is the answer to the puzzle, but how was the solution found?]

Answer 2

Hipparchus was a Greek astronomer, (someone who would study the sky) geographer, and mathematician Born in Nicaea in Bithynia (and is now Iznik in Turkey) and is considered the true founder of his science and the first systematic astronomer on record.