Although it is over 2000 years old, Eratosthenes Eratosthenes of Cyrene was a Greek polymath. He was a man of learning, becoming the chief librarian at the Library of Alexandria. He invented the discipline of geography, including the terminology used today.Eratosthenes
Full Answer
What is the true circumference of the Earth?
Earth’s Measurements . With a circumference of 40,075 km, Earth is the fifth largest of the planets in the Solar System. The meridional circumference that is from pole to pole is 40,008 km. The difference is caused by the flattening of the poles, such that the Earth has an oblate spheroidal shape.
Who was first estimated the circumference of the Earth?
What Is The Circumference Of The Earth? The circumference of the Earth is 40,075 km, and the Greek geographer Erastosthenes was the first person to estimate the Earth's circumference nearly accurately.
Who is the first person to measure Earth circumference?
Who Was The First Person To Accurately Measure The Circumference Of The Earth?
- Measuring the Earth. Eratosthenes is considered the inventor geography, particularly because he developed the system of latitudinal and longitudinal lines to map the world.
- Method. ...
- Errors and Estimates. ...
What do scientist calculated the Earth's circumference?
To calculate the circumference of the Earth, Eratosthenes measured the angle of the shadow to the Earth . He had had previously determined that on June 21, the date of the summer solstice, the Sun cast no shadow at the bottom of a water well located in Cyrene (also spelled "Gyrene").
How did scientists measure the circumference of the earth?
Eratosthenes sent a man to Syene from Alexandria on foot to measure the distance between Alexandria and Syene. Thus, Eratosthenes measured the distance between the two cities is 800 km. He multiplied by 800 km to 50 and calculated that the Earth's circumference is 40,000 km.
How do you measure the circumference of the earth with a stick?
0:412:02How Eratosthenes calculated the Earth's circumference - YouTubeYouTubeStart of suggested clipEnd of suggested clipSo on June 21st he planted a stick vertically in the ground and waited to see if a shadow would beMoreSo on June 21st he planted a stick vertically in the ground and waited to see if a shadow would be cast at noon. It turns out there was one and it measured about seven degrees.
How was the circumference of the Earth first measured?
Eratosthenes erected a pole in Alexandria, and on the summer solstice he observed that it cast a shadow, proving that the Sun was not directly overhead but slightly south. Recognizing the curvature of the Earth and knowing the distance between the two cities enabled Eratosthenes to calculate the planet's circumference.
Who measured the circumference of the earth perfectly?
EratosthenesThis illustration shows how Eratosthenes actually calculated the circumference of the Earth. At noon on the summer solstice, Eratosthenes measured the length of the shadow cast by a column of known height at Alexandria. With these two lengths, he could solve for the angle between them (θ).
How did aryabhata measure the circumference of the earth?
Using trigonometry, he calculated the height of a mountain (in present-day Pakistan) by observing the peak from two different points on the plain. He then calculated the angle of dip from the peak to the horizon using an angle measuring instrument.
How did Ptolemy calculate the circumference of the earth?
By measuring the length of the shadow in Alexandria at noon on the Summer Solstice when there was no shadow in Syene, he could measure the circumference of the Earth! At Syene: The Sun is directly overhead, no shadows are cast at that moment.
How do you measure a circumference?
To calculate the circumference of a circle, multiply the diameter of the circle with π (pi). The circumference can also be calculated by multiplying 2×radius with pi (π=3.14).
How was the circumference of a circle discovered?
Archimedes envisioned a hexagon inscribed within a circle with radius ½. The formula for circumference is 2πr. Hence, with ½ as a radius, the circumference of his circle would be π. He then conjectured that the hexagon's perimeter would approach the circumference of the circle (π).
What is the circumference of the Earth by modern measurements?
roughly 40,000 kilometersToday we know our planet's circumference is roughly 40,000 kilometers (24,850 miles).
When was the circumference of the Earth discovered?
240 BCEratosthenes made several important contributions to mathematics and science, and was a friend of Archimedes. Around 255 BC, he invented the armillary sphere. In On the Circular Motions of the Celestial Bodies, Cleomedes credited him with having calculated the Earth's circumference around 240 BC, with a high precision.
How did Eratosthenes measure the circumference of the Earth with just a stick?
The Greeks before Eratosthenes had divided the circle in degrees and measured angle. He applied this knowledge with what he had discovered to measure the circumference of the Earth. He first measured the angle of the sun's rays off the stick by dividing the length of shadow by the height of the stick.
How do you find the circumference of the Earth using a shadow?
The answer is 360°/10° = 36. This tells us that Earth's circumference is simply equal to 36 times the distance between the pair of trees! When the shadows of two vertical structures point toward or away from each other, the size of Earth can readily be calculated. Mission accomplished!
How did Eratosthenes calculate the diameter of the earth?
In the third century BCE , Eratosthenes, a Greek librarian in Alexandria , Egypt , determined the earth's circumference to be 40,250 to 45,900 kilometers (25,000 to 28,500 miles) by comparing the Sun's relative position at two different locations on the earth's surface.
Who was the first person to estimate the circumference of the Earth?
The Greek mathematician Eratosthenes, however, was able to estimate Earth’s circumference more than 2,000 years ago, without the aid of any modern technology.
How many kilometers is the circumference of the Earth?
Today we know our planet's circumference is roughly 40,000 kilometers (24,850 miles). Not bad for a more than 2,000-year-old estimate made with no modern technology!
What did Eratosthenes assume about the Sun?
Eratosthenes assumed the sun was far enough away from our planet that its rays were effectively parallel when they arrived at Earth. This told him the angle of the shadow he measured in Alexandria was equal to the angle between Alexandria and Syene, measured at Earth’s center. If this sounds confusing, don’t worry!
How to set up a meter stick?
If you have a volunteer to help, have them hold the meterstick. Otherwise, bury one end of the meterstick in a bucket of sand or dirt so it stays upright.
Do you need a ruler to measure the Earth's size?
The earth is massive, but you don't need a massive ruler to measure its size. All you need are a few household items--and little bit of geometry! Credit: George Retseck
Can you measure the circumference of the Earth with a meterstick?
In the age of modern technology this may seem like an easy question for scientists to answer with tools such as satellites and GPS—and it would be even easier for you to look up the answer online. It might seem like it would be impossible for you to measure the circumference of our planet using only a meterstick.
What was the first instrument to measure the size of the Earth?
Eratosthenes Of Cyrene made the first measurement of the size of Earth using a gnomon, an ancient time measuring instrument that cast a shadow. It was probably the first device for indicating the time of day dating from about 3500 B.C. The length of the shadow this simple instrument cast, it gave an indication of the time of day.
Who wrote about the circumference of the Earth?
For some reason, recalculated the distance between Rhodes and Alexandria and decreased the figure to 180,000 stadia. Claudius Ptolemy, a Greek writer, known as a mathematician, astronomer, geographer wrote about Earth’s circumference in his works, and he based his material on Posidonius’ research.
How did Posidonius calculate the circumference of the Earth?
Posidonius attempted to calculate the circumference of the Earth by assuming the cities of Rhodes (Greece) and Alexandria (Egypt) were on the same meridian. He also thought that the star Canopus touched the horizon at Rhodes at a meridian altitude of 7 30' or V48 of the circumference of a circle at Alexandria.
What is the instrument used to calculate the time, season, and so on?
A simple astronomic instrument, the 'gnomon' used to calculate the time, season, and so on) is composed of a vertical gnomon and a horizontal ruler. Image: Cultural Chin. To calculate the circumference of the Earth, Eratosthenes measured the angle of the shadow to the Earth.
What is the geoid?
The map is called a geoid, the result of two years of orbital surveys by the European Space Agency (ESA) Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite that also studies ocean circulation and the movement of ice.
Why is the Earth not a perfect sphere?
The Earth Is Not A Perfect Sphere. Today we know that our Earth is not a perfect sphere and it has a weird shape because the Earth’s gravity isn’t uniform. A while back, scientists presented the most accurate map ever produced of the Earth’s gravity.
Is the Earth's equatorial circumference greater than its polar circumference?
The map clearly shows that Earth’s equatorial circumference is greater than its polar circumference. Modern scientists have learned much about the shape and size of our planet, but ancient attempts to gain similar information were quite successful too. Written by Cynthia McKanzie - AncientPages.com Staff Writer.
Who was the first person to measure the circumference of the Earth?
The first known scientific measurement and calculation was done by Eratosthenes, who achieved a great degree of precision in his computation. Treated as a sphere, determining Earth's circumference would be its single most important measurement. Earth deviates from spherical by about 0.3%, as characterized by flattening .
What is the unit of measurement of the Earth's circumference?
In modern times, Earth's circumference has been used to define fundamental units of measurement of length: the nautical mile in the seventeenth century and the metre in the eighteenth.
How did Posidonius calculate the circumference of the Earth?
Posidonius calculated the Earth's circumference by reference to the position of the star Canopus. As explained by Cleomedes, Posidonius observed Canopus on but never above the horizon at Rhodes, while at Alexandria he saw it ascend as far as 7#N#+#N#1⁄2 degrees above the horizon (the meridian arc between the latitude of the two locales is actually 5 degrees 14 minutes). Since he thought Rhodes was 5,000 stadia due north of Alexandria, and the difference in the star's elevation indicated the distance between the two locales was 1/48 of the circle, he multiplied 5,000 by 48 to arrive at a figure of 240,000 stadia for the circumference of the earth. It is generally thought that the stadion used by Posidonius was almost exactly 1/10 of a modern statute mile. Thus Posidonius's measure of 240,000 stadia translates to 24,000 mi (39,000 km), not much short of the actual circumference of 24,901 mi (40,074 km). Strabo noted that the distance between Rhodes and Alexandria is 3,750 stadia, and reported Posidonius's estimate of the Earth's circumference to be 180,000 stadia or 18,000 mi (29,000 km). Pliny the Elder mentions Posidonius among his sources and without naming him reported his method for estimating the Earth's circumference. He noted, however, that Hipparchus had added some 26,000 stadia to Eratosthenes's estimate. The smaller value offered by Strabo and the different lengths of Greek and Roman stadia have created a persistent confusion around Posidonius's result. Ptolemy used Posidonius's lower value of 180,000 stades (about 33% too low) for the earth's circumference in his Geography. This was the number used by Christopher Columbus in order to underestimate the distance to India as 70,000 stades.
What is the circumference of the Earth?
Jump to navigation Jump to search. The distance around Earth, either around the Equator or around the poles. For modern definitions and measurements, see Earth radius. Earth's circumference is the distance around Earth. Measured around the Equator, it is 40,075.017 km (24,901.461 mi).
Why is circumference considered a pendulum?
In 1791, the French Academy of Sciences selected the circumference definition over the alternative pendular definition because the force of Earth's gravity varies slightly over the surface of the Earth, which affects the period of a pendulum.
How many miles is 360 of a circle?
360 of a circle, one minute of arc is 1. /. 21600 of a circle – such that the polar circumference of the Earth would be exactly 21,600 miles. Gunter used Snell's circumference to define a nautical mile as 6,080 feet, the length of one minute of arc at 48 degrees latitude.
How many miles is the Earth's circumference?
Measured around the Equator, it is 40,075.017 km (24,901.461 mi). Measured around the poles, the circumference is 40,007.863 km (24,859.734 mi). Measurement of Earth's circumference has been important to navigation since ancient times. The first known scientific measurement and calculation was done by Eratosthenes, ...
Who was the first person to measure the circumference of the Earth?
The first person in the Western tradition to have figured out how to measure the circumference of the Earth was Eratosthenes of Cyrene (276-194 BC). Eratosthenes studied under Lysanias of Cyrene and Ariston of Chios. He also is said to have studied in Athens for several years.
What is the circumference of the Earth?
Like the age of the Earth, the circumference of the Earth is of a scale far beyond everyday human experience and yet humans, with their mammalian brains adapted to survive and escape predators rather than unravel the secrets of the universe, were able to measure it.
Why is the Sun's position at different latitudes angular?
If the sun’s rays were parallel, any angular difference in the sun’s position at different latitudes could only be due to the Earth’s curvature. Based on this knowledge, Eratosthenes was able to measure the Earth’s circumference.
How accurate was Eratosthenes' measurement?
The only measurement he made himself was probably the angular distance between the sun and the zenith on the summer solstice in Alexandria. Nonetheless, historians agree that Eratosthenes’ calculation of Earth’s circumference was very accurate, given the resources that he had at the time.
Why is Eratosthenes' measurement important?
Another reason that Eratosthenes’s measurement is important today is that there is a small but vocal movement that denies that Earth is spherical, or even spheroidal, and insists that Earth is actually flat. They insist that we have been wrong about the shape of the Earth for 2,500 years.
When did philosophers start to think of the Earth as spherical?
The idea that Earth is spherical only became common knowledge about 2,500 years ago . That is when philosophers began to think about the shape of Earth and its dimensions. When philosophers began to think of Earth as spherical, however, a new question emerged.
Who was the first Greek scientist to think scientifically about the world?
The first figure to think scientifically about the world in the Greek tradition appears to have been Thales of Miletus (624-547 BC). The life and work of Thales are shrouded in legend. He was a native of Miletus, though some ancient authors apparently believed that he was Phoenician.
When was the Earth's circumference first measured?
How was the size of Earth first measured? Earth's circumference was first accurately measured more than 2,000 years ago by the Greek astronomer Eratosthenes, who at the time lived in the Egyptian city of Alexandria.
How many miles is the Earth's circumference?
He calculated Earth's circumference at 26,000 miles (42,000 km), only five percent away from the modern accepted value of 24,901 miles (40,074 km).
Overview
Earth's circumference is the distance around Earth. Measured around the Equator, it is 40,075.017 km (24,901.461 mi). Measured around the poles, the circumference is 40,007.863 km (24,859.734 mi).
Measurement of Earth's circumference has been important to navigation since ancient times. The first known scientific measurement and calculation was done by Eratosthenes, who achieved a g…
History
The measure of Earth's circumference is the most famous among the results obtained by Eratosthenes, who estimated that the meridian has a length of 252,000 stadia, with an error on the real value between −2.4% and +0.8% (assuming a value for the stadion between 155 and 160 metres). Eratosthenes described his technique in a book entitled On the measure of the Earth, which …
Historical use in the definition of units of measurement
In 1617 the Dutch scientist Willebrord Snellius assessed the circumference of the Earth at 24,630 Roman miles (24,024 statute miles). Around that time British mathematician Edmund Gunter improved navigational tools including a new quadrant to determine latitude at sea. He reasoned that the lines of latitude could be used as the basis for a unit of measurement for distance and proposed the nautical mile as one minute or one-sixtieth (1/60) of one degree of latitude. As one …
See also
• Earth radius
• Spherical Earth
• Nautical mile
Bibliography
• Krebs, Robert E.; Krebs, Carolyn A. (2003). "Calculating the Earth's Circumference". Groundbreaking Scientific Experiments, Inventions, and Discoveries of the Ancient World. Greenwood Publishing Group. p. 52. ISBN 978-0-313-31342-4.
• Nicastro, Nicholas (25 November 2008). Circumference: Eratosthenes and the Ancient Quest to Measure the Globe. St. Martin's Press. ISBN 978-1-4299-5819-6.
External links
• Carl Sagan demonstrates how Eratosthenes determined that the Earth was round and the approximate circumference