Dec 15

Eratosthenes results released

Earth-rulerThe organization of Eratosthenes in the International Year of Light has released the results of the measurements that were made by schools between the 14th and 25th of September 2015.

The data was collected by 174 schools from different countries, mostly from Europe and South America:  18 from Uruguay, 2 from Romania, 1 from Portugal, 5 from Peru, 1 from Morocco, 2 from Mexico, 1 from Italy, 1 from Honduras, 1 from France,  42 from Spain, 5 from Colombia, 45 from Brazil and 50 from Argentina.

Approximately 8000 students were involved in the activity and presented results about the size of the gnomon and the size of the shadow measured at solar noon.

With the results reported by schools the analysis were performed:

  1. Optimization of the NS component of distance and measurement day.
  2. Schools were paired maximizing the NS component of distance and considering that their measurements were made on the same day. Thus 200 pairs of schools were selected.
  3. Radius obtained are calculated from the measurements reported by schools. 28 results were discarded because they were clearly out of range of possible measurements and therefore must be bad measurements or bad registration of the measurements.
  4. A histogram was compiled with the remaining 172 values that ranged between 5,500km and 7,000km.
  5. The average value of the data is R = 6.363km and standard deviation S = 316km. The standard error of mean Sp, S obtained by dividing by the square root of the number of measurements, it turns Sp = 22km.

Only statistical errors were considered, as  schools were not asked to report on the estimates of the errors of their measurements.  According tabulated values the Earth's radius is R = 6371 km, very close to the calculated value obtained from the data of the school measurements.

Eratosthenes project has been performed by the EAAE in association with other organizations since 1997.

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Jun 11

Reproducing Eratosthenes' Experiment

Once again in 2011 EAAE has launched Eratosthenes Experiment. This year was coordinated by Anna Artigas and Guido Robotti.

On June 21st, 2011, school teachers and students from all over Europe made their measurements and launched the results on the EAAE's webpage of the project. Some teachers also participated on the videoconference promoted for schools to cooperate about the event.

Students measuring the shadow of a gnomon at Legnica, Poland.

Most schools, from Northern Europe to Southern Europe were able to measure the shadow of the Sun due to good weather conditions in most of Europe. Only Stafford Grammar School in the United Kingdom reported bad weather conditions.

A School Group measuring the shadow of a gnomon at Batalha, Portugal.

Nonetheless the measurement of average of Earth's perimeter was 39864.64 km, a measurement that has a 0.358% error compared to the accepted value of 40007.86 km for the meridional perimeter.

During the video conference that was controlled by Alexandre Costa and Jordi Delpeix Borrell, students from different schools shared their results and the motivation they had in participating this event. All of them showed the interest in participating next year.

A scene from the beginning of the videoconference with some of the participants.

Students had possibility of presenting pictures and some schools also presented videos they already had posted on YouTube about the event.

Sharing a YouTube video nearly at the end of the videoconference..

We hope next edition of Eratosthenes is even better.

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Apr 11

Here comes the 2011 Eratosthenes Project campaign

Once again in 2011 the EAAE is proud to announce the opening of the campaign to reproduce the Eratosthenes Experiment at a global scale. Following the 2010 campaign's success next this activity will be repeated at the next European Summer Solstice on 21st of June 2011.

Every school in Europe is invited to participate in this global experience in order to measure the Earth circumference. With the only help of the shadow projected by a stick, the participating students will be able to repeat the Erastothenes calculation. Moreover, a video conference will allow all participants to see how the activity is performed in the Bibliotheca of Alexandria, the mythic place where this measure was done by the greek mathematician more than 2000 years ago. All information concerning the event will be held on http://www.eaae-astronomy.org.

A screenshot of the project's webpage.

Materials that will help the schools to reproduce the Eratosthenes Experiment locally where created and are also available on the website as well as calculators to help schools confirm their calculations based on their measurements.These calculators can also be used by small children school to make the calculations that the children cannot perform because the don't have the mathematical skills to do them.

The project intends to allow schools to reproduce the Eartothenes Experiment locally.


The Eratosthenes website also has links to several complementary Didactical Materials that can be used by teachers when preparing this project or for many other purposes. EAAE members, Anna Artigas and Guido Robotti, will coordinate the 2011 campaign of the project.

The EAAE Eratosthenes Project

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