And here’s a link to NASA’s Earth Observatory. More stories at: https://www.universetoday.com/ New Delhi: An Indian origin man from Ireland has claimed that he walked a distance equal to the Earth’s circumference — 40,070 km — in less than four years, without leaving his immediate neighbourhood in the city of Limerick. And More…, Episode 688: Remnants From the Early Universe. Earth moves in an apparent diurnal motion, where at a fixed position in the earth, the sky rather than Earth appears to be rotating. As earth is not a perfect sphere, circumference measured around the poles is 39,940.653 Km, and circumference measured around the equator is 40,075.017 Km. In 200 B.C. The meridional circumference that is from pole to pole is 40,008 km. Get help fast. https://www.youtube.com/channel/UC0-KklSGlCiJDwOPdR2EUcg/, Astronomy Cast: You can use Eratosthenes' method to calculate the circumference of the earth yourself. to the north, was not perfectly lined up with the parallel rays of the sun at local noon on the summer solstice. Get better grades with tutoring from top-rated professional tutors. https://www.amazon.com/Universe-Today-Ultimate-Viewing-Cosmos/dp/1624145442/, Audio Podcast version: Anything sticking up out of the earth in Alexandria -- like a stick -- cast a shadow at the same moment a stick in Syene cast no shadow. [all drawing notes assume you are not doing animation, which honestly would explain everything better than drawings]. Today we know how to measure circumference of many things, including earth, using many modern tools, but Eratosthenes did it with a well, the sun, and a stick. Rising to 29,029 feet (8,848 meters) is the highest peak above sea level on earth, Mt Everest in Asia. With a circumference of 40,075 km, Earth is the fifth largest of the planets in the Solar System. Countries Where Illegal Wildlife Trade Is A Major Threat To Wildlife. Eratosthenes did the measurement and found the angle was 7.2°, which meant central angle was also 7.2°. Earth rotates around the north-south path once in approximately 24 hours. No shadow appeared in the well. With developments in technology, earth’s measurements, including the circumference have been accurately measured. This proportion (circumference to diameter) is the definition of the constant pi. Are you looking for the circumference and diameter of the Earth? Post was not sent - check your email addresses! Earth's core is about 4,400 miles (7,100 km) wide, slightly larger than half the Earth's diameter and about the same size as Mars' diameter. The equatorial circumference of the Earth is 40,075 km. [insert cross-section drawing of well with sun rays shining straight down into it]. It’s rotating rapidly, which causes the equator to bulge out. Imagine being the head librarian of the greatest library on the planet and a library patron asks you a simple question: He did not know, but like any good mathematician and scientist, he intended to find out using his available resources. How Much Of The Amazon Rainforest Is Left? One complete trip around earth (one rotation) is 360°, so any arc of the circle or sphere is a fractional slice of 360°. At local noon on every summer solstice (earth's longest day and shortest night), the sun's rays went straight down the well, which meant Syene was perfectly lined up with those parallel sun rays. Whatever angle it creates on one parallel line, it creates the same angle on the other. Countries Doing The Most To Combat Climate Change. Local and online. Earth’s surface area is an estimated 510 km2, and about 29% of the area is land while the other 71% consists of water. The lowest elevation on land is the Dead Sea, at 1,369 feet (417.27 meters) below sea level. They knew the circumference of a sphere formula, 2πr. And he did it with just a little knowledge about geography and mathematics, a well, and a stick. This is the distance around the equator of the Earth. Chad Weber – [email protected], Support Universe Today podcasts with Fraser Cain, The Guide to Space is a series of space and astronomy poddcasts by Fraser Cain, publisher of Universe Today, Episode 691: Interview: Seth Shostak from the SETI Institute. They knew it was a sphere, while today we know it is a squashed sphere, an oblate spheroid. ITunes: https://itunes.apple.com/us/podcast/universe-today-guide-to-space-audio/id794058155?mt=2 The circumference of the Earth would then be 50 times the overland distance between Alexandria and Syene. [insert drawing of tiny earth and big sun at opposite sides of screen, showing parallel sun rays striking earth] That means the sun's rays hitting Eratosthenes' home in Alexandria are parallel to the sun's rays hitting Syene, a town far to the south, which today we call Aswan. Before Erastosthenes, other scholars had attempted to estimate the figure, but their methods were not recorded, and their estimations were far from accurate. Generations of careful Egyptian land surveyors knew Syene was 5,000 stadia -- ancient measurement units equivalent to 804 kilometers or 500 miles -- south of Alexandria. Like us on Facebook: https://www.facebook.com/universetoday You have probably noticed that, since diameter is twice the radius, the proportion between the circumference and the diameter is equal to π: C/D = 2πR / 2R = π. Thus the circumference can be estimated by multiplying the distance between the two cities, 5000 stadia, by 50, equaling 250,000 stadia. Earth takes up only a small portion of the sun's circumference. Back in 240 B.C.E., a Greek named Eratosthenes calculated the circumference of the earth. It's a common misconception that Eratosthenes was measuring the circumference of the round earth in his shadow experiment. Earth, unlike other planets, has only one moon while a total of 166 moons in the solar system have been identified. If Eratosthenes could accurately measure the angle of the shadow of a stick driven perpendicular into Alexandrian ground, he could use only two pieces of information to calculate the circumference of the earth: Circumference is the distance around a circle or sphere.