---
title: "When and how did scientists measure the radius of the earth?"  
description: "When and how did scientists measure the radius of the earth?"  
author: "samay srivastava"  
published: 2018-03-09  
canonical: https://answers.mindstick.com/qa/37636/when-and-how-did-scientists-measure-the-radius-of-the-earth  
category: "science"  
tags: ["physics"]  
reading_time: 2 minutes  

---

# When and how did scientists measure the radius of the earth?

When and how did scientists [measure](https://answers.mindstick.com/qa/32242/why-nepal-rejects-india-s-offer-to-jointly-re-measure-mount-everest) the radius of the earth?

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## Answers

### Answer by Sanjay Goenka

In **200 B.C**., the size of the earth was actually calculated. **[Eratosthenes](https://www.britannica.com/biography/Eratosthenes#:~:text=Eratosthenes%2C%20in%20full%20Eratosthenes%20of,method%20of%20measuring%20Earth)** used the **Angular Displacement** method to find the size of the earth and he used the methods of **Aristotle’s idea.\** \
![When and how did scientists measure the radius of the earth?](https://answers.mindstick.com/questionanswer/a87df6af-5d05-42ff-ae9f-faedbd91ffde/images/c9c295f5-a303-4b65-bbc0-95b8b2304368.jpeg)\
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**Magnitude of earth** The **diameter** of the earth at the equator is **12,756 Km**. in modern times we have developed technologies that can measure it in seconds. But in ancient times, there was no such technology and the ancient methods were used by our great scientists. One of those was **Eratosthenes** who used the old technique to find out the radius of the earth. He has known the facts that in summers, the **first day of summer** the Sun passed directly **overhead at Syene, Egypt.** And on the same day in **mid-time of the day** he measured the angular momentum of the Sun from the overhead at the **city of Alexandria** which was **5000 stadia away.** He found with the angular displacement that there is **7.2 angular displacement** and at last he calculated the **[circumference of the earth was 40,000.](https://imagine.gsfc.nasa.gov/features/cosmic/earth_info.html)** \
Eratosthenes also knows the fact that the **circumference is equal to the two times the multiplication of the pie and radius.** And hence with the help of these formulae, he inferred that the **[earth’s radius was 6,366 Km](https://imagine.gsfc.nasa.gov/features/cosmic/earth_info.html).** the interesting fact is that this distance is approximately matching the **modern distance of radius as the circumference** is **40,070** and the **radius is 6,376 km** and it is measured by the spacecraft using the orbit of the earth. \
The radius of the earth in its **equator is 6,378 Km** and but in another case in the polar of the earth is **6,357 Km.** \
**Earth’s specifications**\
The average distance from the Sun is **149,598,262 Km.** The perihelion is **147,098,291.** The aphelion of the earth is **152,098,233.** The length of the solar day is **23.934hrs** The length of the year in the earth is **365.26days.** The inclination of the equatorial is **23.4393 degrees.**

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Read More: [Who Is The Ministry of Earth Sciences?](https://answers.mindstick.com/qa/45060/who-is-the-ministry-of-earth-sciences)


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