Eratosthenes Lesson

AI Creations | Vocabulary | IPA Symbols

AI Creations

These lessons have been crafted by artificial intelligence (AI), a type of computer software that is designed to perform tasks that would normally require human intelligence. These tasks can include learning, problem-solving, decision-making, and even communication. AI has the ability to analyze and interpret data, make predictions, and adapt to new situations. One of the major advantages of using AI to create lessons is that it can be done quickly and efficiently. AI algorithms can process vast amounts of information and generate insights that would be difficult for humans to discover on their own. This means that the lessons created by AI can be highly detailed and comprehensive, covering a wide range of topics and providing a deep understanding of the subject matter.


Did you know that there are over 600,000 words in English? That's a lot of words, and far more than any human being could ever manage to learn. Even Shakespeare only used around 55,000 different words in all of his works. Mind you, he did actually invent quite a few of them. To get a good mastery of English, you do need to expand your vocabulary as much as possible. The more words you know, the better your English will be. The Activities here will help you to quickly develop your vocabulary.

IPA Symbols

The International Phonetic Alphabet (IPA) is an essential tool for any student or teacher of the English language. Developed in the 19th century, the IPA provides a standardized way to represent the sounds of speech in written form. The British English IPA chart includes 44 symbols that represent the monophthongs, diphthongs, and consonant sounds of spoken British English. The Britlish Library offers a wide range of activities to help you master the British English IPA symbols, improve your pronunciation, and take your English language skills to the next level. Whether you're a student or a teacher, our activities are designed to help you learn, remember, and effectively use the IPA in your English language studies.


Prepositions are an essential part of the English language, as they help to convey the time and place of events in relation to others. However, learning prepositions can be a challenge for many students of English, as they often have few rules to follow. These Britlish Library Activities have been created to make learning and memorizing prepositions as easy and enjoyable as possible. Additionally, the Activities will also focus on the use of prepositions in phrasal verbs, which are equally important in achieving fluency in English. With interactive exercises and a focus on the most common prepositions, these Activities will help to improve your understanding and use of prepositions in English.

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I asked the OpenAI ChatGPT: “How did Eratosthenes calculate the size of the Earth and how accurate was he?”  I put what it said in a video which you will find in this lesson. Watch the video and then you should know enough about Eratosthenes and how he measured the world over two thousand years ago to answer the self-test exercises and practice material for the vocabulary in the video and for the IPA symbols.

How did Eratosthenes calculate the size of the Earth and how accurate was he? Eratosthenes was a Greek mathematician, geographer, and astronomer who lived in the 3rd century BCE. He is best known for his calculation of the size of the Earth, which he made using a simple and clever method that relied on the fact that at noon on the summer solstice, the Sun is directly overhead at the Egyptian city of Syene (now Aswan) but is at an angle of about 7.2 degrees from the vertical at Alexandria, a city located about 800 kilometers (500 miles) to the north. Eratosthenes reasoned that if the Earth were a perfect sphere, the angle between the Sun and the vertical at Alexandria would be the same as the angle between the vertical and a line drawn from the center of the Earth to Syene. By measuring the angle between the vertical and the Sun at Alexandria on the summer solstice, he was able to calculate the circumference of the Earth. Eratosthenes' calculation of the Earth's circumference was remarkably accurate. He estimated the circumference to be about 39,375 kilometers (24,662 miles), which is only about 16% larger than the true value of about 34,000 kilometers (21,000 miles). This error can be attributed to the fact that the Earth is not a perfect sphere, but rather is an oblate spheroid that is slightly flattened at the poles and bulges at the equator. Thank you. That was very informative. You’re very welcome. By the way! You might like to know that you can test your understanding of this topic in the Britlish Library at You can find a link below. Bye bye for now!

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