**Essay** #22 History Of Inventions

Hello, in today’s essay I will be talking about Johannes Kepler, Galileo Galilei, the slide rule, and John Napier. Let’s get started.

**Johannes Kepler**

Johannes Kepler was born in 1571 in the holy Roman empire, whose grandfather was a mayor, and his father was a mercenary. His mom took him to see a comment when he was only six years old and when he was nine he saw a solar eclipse. He almost became a minister but moved to astronomy instead; he published the first book that defended Copernicus heliocentric theory, “Mysterium Cosmographicum” (The Cosmographic Mystery), and established his reputation and astronomy skills. It helped him introduced himself to Tyco Brahe. His book on the orbit of mars was published in 1609; he was best known for his three laws of planetary motion, he sent copies of that book to important astronomers. His laws weren’t immediately received but soon they were. And unlike others, Johannes Kepler became famous during his lifetime.

**Galileo Galilei**

Galileo Galilei was born in 1564 and died in 1642, his father was a talented musician, and people paid him to play music for them, so that’s how they earn money. He learned how to do early science from his dad, and he wanted to become a priest, but his father convinced him to be a physician. He turned out to become a true scientist. He designed a new military compass and thermometer, and he improved the telescope in 1609. He applied math to physics. Overall he is was a great scientist and had a major impact on history, and his greatest discoveries were:

- the four moons of Jupiter,
- that the earth is not in the center of the universe, aka heliocentric theory. Did you know that he was put in house arrest for saying that the earth was not in the center of the universe? Yes, he spent the last 9 years of his life in hose arrest. And finally,
- the telescope.

**The slide rule**

John Napier invented logarithms and in 1614 he wrote a book that was technically a table full of logarithms. The astronomers and sailors had to do long multiplications and divisions, which was very cumbersome, so Napier’s logarithms book was greatly valued by them. However it was still difficult to use that large book. Then the slide rule was invented in 1630 by William Oughtred. The slide rule made it easier to multiply and divide, therefore that huge book of tables, become obsolete rapidly. More complex rules add more features were added and the slide rule quickly became popular; even Johannes Kepler used it. Improved models were continually developed, slide rules were integral to engineering. In fact, the slide rule became the symbol of engineers, just like the statoscope is the symbol of doctors. Then, calculators made their appearance in the world and soon took over the slide rule.

**John Napier**

John Napier was born in Edinburgh, Scotland 1550, he entered University at the age of 13, he became interested in theology. His greatest achievement was most likely the logarithm. Napier was very motivated to serve others, he also invented his “bones,” they were popular tools at simplified calculations, of course they weren’t his actual bones. He calculated 10 million logarithms for his book of logarithms. His book caught the attention of a prominent English mathematician, Henry Briggs, professor at Gresham College, which not only used it in his astronomy studies, but began to teach logarithms to his students. Napier certainly made possible the advancement of science through his many discoveries.

Thank you for reading this essay about Johannes Kepler, Galileo Galilei, the slide rule, and John Napier. What do you think about these great man of the past and their discoveries? I hope you have a nice day, night, or evening wherever you are. I’ll see you next time.