Eratosthenes and the Earth’s Circumference

Eratosthenes was one of the most famous mathematicians in the early times. He was famous for his sieve – a strategy for finding prime numbers – but one of his greatest achievements was estimating the circumference of the earth. In this post, we learn how Eratosthenes used mathematics to solve the size of the earth. We  leave out some of the technical details (such that the assumption that the sun is so far away that its rays are almost parallel), since this post is for elementary school mathematics students.

How did he do it?

Eratosthenes knew that at noon in Syene, the sun casts no shadows. This can be tested using a sundial – a device used to tell the time using its shadow during the ancient time.

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WordPress Blogging Tutorial 3 – Publishing Your First Blog

In the previous article, we have discussed the basics of blogging. We have typed our draft, inserted pictures and saved it. In this post, we are going to discuss the finishing touches of our first post and then publish it.

Before we publish our first blog, we must do two more things: We will add categories and then add tags.  We want search engines (Google, Yahoo, MSN) to see our post.  The best way of doing this is placing  categories and tags in each of our post.  Of course, at first, search engines will not place our blog at the top list during a search, but as more visitors visit our blog, and as more articles are being posted, it will increase its search engine rankings, and will increase the probability of being listed when a search is performed.

A category is a content specification of a post. For instance, since our blog is about high school mathematics, we might want include categories such as Algebra, Geometry, Trigonometry, Probability, Statistics and Calculus. Of course, we can add more categories such as Math Games, Famous Mathematicians, or anything related to high school mathematics. Our first post, the Pythagorean Theorem falls under Geometry and Trigonometry categories.

Tags are the keywords that are related to our article.  The possible tags for our post The Pythagorean Theorem are Pythagorean theorem, proof without words, Pythagoras, and right triangles. Notice that tags are more content-specific than categories. » Read more

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