Why pi

A river's windiness is determined by its "meandering ratio," or the ratio of the river's actual length to the distance from its source to its mouth as the crow flies. Rivers that flow straight from source to mouth have small meandering ratios, while ones that lollygag along the way have high ones. Turns out, the average meandering ratio of rivers approaches — you guessed it — pi. Albert Einstein was the first to explain this fascinating fact. He used fluid dynamics and chaos theory to show that rivers tend to bend into loops.

Both the Babylonians and Egyptians had rough numerical approximations to the value of pi, and later mathematicians in ancient Greece, particularly Archimedes, improved on those approximations.

By the start of the 20th century, about digits of pi were known. With computation advances, thanks to computers, we now know more than the first six billion digits of pi. Already a subscriber?

Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Fall Flash Sale. Read more from this special report: The Pi Day of the Century. Properties like this that stay the same when you change other attributes are called constants.

Because it's so easily observed you can measure it with a piece of string! From the side lengths, we can compute the circumference of the two squares. So we've proved some very loose bounds on Pi - and now you can see why Archimedes had to go up to a sided polygon before he started getting good results! These days, we have better tricks for estimating Pi than the circumscribed-circle method used by Archimedes, but progress was mind-numbingly slow - and came due to advances in calculus and computing infinite series.

The pictures are great with bright, vivid colors to bring math to life. The language is easy to follow and there is not a lot to read per page. This book is fun and brings math and science to life.

It is recommended to any young adults who need a refresher on the basics. Feb 11, Shannon rated it really liked it. Aimed at kids years old, I found this to be a great read for all ages.

I had this book as bathroom reading material, which I found to be the perfect way to read the book. In this way, you could read just a page or two at a time, and then have plenty of time between readings to really think about what you had learned.

The beginning of the book was excellent - talked about really interesting math history, such as how Egyptians used math to measure their fields, and who came up with different Aimed at kids years old, I found this to be a great read for all ages. The beginning of the book was excellent - talked about really interesting math history, such as how Egyptians used math to measure their fields, and who came up with different basic mathematical principles, and how they affect us, etc.

The rest of it though is a great read for young and old alike. Dec 02, Shakeel Jivraj rated it it was amazing Shelves: non-fiction , , math. In the classroom, we have to solve complicated and boring math problems. However, Johnny Ball takes us away from math class and helps us to understand why math is important in our everyday lives.

He tells us the story of math in a fun and interesting way. Who knew that pi is so important and math is not just about memorizing long formulas? Oct 24, Rachel rated it really liked it Shelves: non-fiction. Why Pi is a non fiction book about math and how math helps us in everyday life. There's all sorts of interesting facts about the days, months and years, about how the planets and stars move and how the egyptians used math and about how the most famous math geniuses figured out their famouse ideas.

This book is really, really interesting. I picked this book up because I needed a non fiction book for my goodread bookshelves. I finished this book because it had interesting facts about math. I would reco Why Pi is a non fiction book about math and how math helps us in everyday life. I would recommend this book to Patrick because he loves cramming his head with math facts and useless pieces of information and this book was full of facts and useless pieces of in formation.

Mar 26, Emily Galicia rated it it was amazing Shelves: march. This is a great book for young and old adults. I really think it is very informative.

This book makes you think about numbers by focusing on how numbers are used to measure things now and how they were used to measure things through the ages. When I read it I thought that none in my class would read i This is a great book for young and old adults. When I read it I thought that none in my class would read it because it is kind of long, but as second thought I think that this would be great help for those students who love to learn new things everyday.

Mar 21, Malea Potter rated it really liked it Shelves: march.