Tales of Miletus was born around 624 BC in Miletus, Asia Minor (now Turkey), and died around 547 BC also in Miletus. He is described in some legends as a businessman, salt merchant, celibate advocate, or statesman of vision, but little is known about his life. Tales' works have not been able to survive to this day but based on traditions one can reconstruct some ideas.
Traveling extensively through the ancient centers of knowledge must have gained information on astronomy and mathematics by learning geometry in Egypt. In Babylon, under the rule of Nebuchadnezzar, he came into contact with the earliest astronomical tables and instruments, and it is said that in 585 BC he was able to predict the solar eclipse that would occur this year, haunting his contemporaries, and it is on this date that they rely to indicate approximately the year you were born ,. for at the time I should have been about forty or so. It is estimated that he died at 78 years of age.
Tales is considered the first philosopher and the first of the seven sages, disciple of the Egyptians and Chaldeans, and is commonly called the true "first mathematician", trying to organize geometry in a deductive way. It is believed that during his trip to Babylon he studied the result that comes to us as the "Tales Theorem" that an angle inscribed in a semicircle is a right angle.
He also owes another four fundamental theorems: "a circle is bisected by a diameter", "the base angles of an isosceles triangle are equal", "the pairs of opposite angles formed by two intersecting lines are equal", and "if two triangles are such that two angles and one side are equal to two angles and one side respectively, then they are congruent."
It seems likely that Tales was able to measure the height of an Egyptian pyramid by observing the length of the shadows at a time when the shadow of a vertical pole is equal to its height. "
Tales was the master of a group of followers of his ideas called the "Jániá School" and was the first man in history to be credited with specific mathematical discoveries and, as Aristotle said, "for Tales the primordial question was not what we know, but how we know".