Eratosthenes | Biography, Discoveries, Sieve, & Facts (2025)

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Eratosthenes | Biography, Discoveries, Sieve, & Facts? ›

In addition to calculating Earth's circumference, Eratosthenes created the Sieve of Eratosthenes (a procedure for finding prime numbers), tried to fix the dates of literary and political events since the siege of Troy, and is thought to have created the armillary sphere (an early astronomical device for representing ...

Eratosthenes was also the first to calculate the tilt of the Earth's axis, which he figured with remarkable accuracy; the finding was reported by Ptolemy (85-165 CE). Eratosthenes also calculated the distance from the Earth to the Moon and to the Sun, but with less accuracy. He made a catalog of 675 stars.

The 3rd-century bc Greek scientist Eratosthenes of Cyrene developed a systematic procedure for finding prime numbers that is known as the sieve of Eratosthenes. Prime numbers are not divisible by an integer greater than 1, except themselves. The procedure results in all the natural numbers (1, 2, 3…)

The Sieve of Eratosthenes is a powerful concept that can be used to find many prime numbers with relative speed and ease. It works on a simple principle: Any multiple of a prime number cannot be a prime number. For example, since 3 is prime, 6, 9, 12, 15, and all other multiples of 3 cannot be prime numbers.

In mathematics, the sieve of Eratosthenes (Greek: κόσκινον Ἐρατοσθένους), one of a number of prime number sieves, is a simple, ancient algorithm for finding all prime numbers up to any given limit.

Eratosthenes was an ancient Greek mathematician, geographer, and astronomer. He existed from 276 B.C. until 194 B.C. and is most notable for having the first accurate calculation of the Earth's circumference. He lived and worked in the Egyptian city of Alexandria for much of his life.

CE book which attributes it to Eratosthenes of Cyrene, a 3rd cent. BCE Greek mathematician, though describing the sieving by odd numbers instead of by primes.

However, for the simple implementations of the Sieve of Eratosthenes using a vector<bool> is faster. You are limited by how fast you can load the data into the cache, and therefore using less memory gives a big advantage.

The Sieve of Eratosthenes drains out composite numbers and leaves prime numbers behind. Make a list of all the integers less than or equal to n (and greater than one). Strike out the multiples of all primes less than or equal to the square root of n. Then the numbers that are left are the primes.

The Sieve of Eratosthenes is an algorithm used to find all prime numbers less than a number. The way it works is that, starting from 2, it creates a list of all integers from there until n. Then, starting with 2 (which is the smallest prime), every multiple of 2 is marked as not a prime.

What is the Sieve of Eratosthenes task? ›

The Sieve of Eratosthenes is a very simple and popular technique for finding all the prime numbers in the range from 2 to a given number n. The algorithm takes its name from the process of sieving—in a simple way we remove multiples of consecutive numbers. Initially, we have the set of all the numbers {2,3,...,n}.

Eratosthenes method was very simple; he measured the length of a shadow from a vertical stick of a known height in two cities on the same day. The ratio between the north-south distance between the two cities and the angles measured gave a ratio which allowed Eratosthenes to calculate the size of the Earth.

The Sieve of Eratosthenes is one way to find prime numbers. It works by systematically eliminating non-prime numbers. This excellent resource has been designed to help pupils to use the Sieve of Eratosthenes to find the prime numbers less than 100.

Eratosthenes (born c. 276 bce, Cyrene, Libya—died c. 194 bce, Alexandria, Egypt) was a Greek scientific writer, astronomer, and poet, who made the first measurement of the size of Earth for which any details are known.

This illustration shows how Eratosthenes actually calculated the circumference of the Earth. At noon on the summer solstice, Eratosthenes measured the length of the shadow cast by a column of known height at Alexandria.

For a number to be called as a prime number, it must have only two positive factors. Now, for 1, the number of positive divisors or factors is only one i.e. 1 itself. So, number one is not a prime number. Note: 2 is the smallest number that satisfies the definition of prime numbers.

The Earth's circumference was first accurately measured more than 2,200 years ago by a Greek astronomer named Eratosthenes. Eratosthenes method was very simple; he measured the length of a shadow from a vertical stick of a known height in two cities on the same day.

While serving as the head librarian and scholar at the Library of Alexandria, Eratosthenes wrote a comprehensive treatise about the world, which he called "Geography." This was the first use of the word, which in Greek means "writing about the world." Eratosthenes' work introduced the concepts of torrid, temperate, and ...

Earth's circumference was first accurately measured more than 2,000 years ago by the Greek astronomer Eratosthenes, who at the time lived in the Egyptian city of Alexandria.

On that day, the sun at noon was directly overhead at Aswan. On the same day, Eratosthenes measured the shadow of the a stick at noon in Alexandria. The length of that shadow was not zero because the sun was not directly overhead in Alexandria.