## Python 裡使用超過 Double Precision 的運算

There is no error with the program; this discrepancy is caused by a loss of numerical accuracy in the eigenvalue calculation due to the limitation of hardware double precision (16-digit).

Note that this library is incredibly slow for large matrices, so is best avoided for most applications.

## NASA 的 JPL 回答「你們用的圓周率是 3.14 嗎？」的問題

NASAJPL 回答了他們所使用的圓周率：「How Many Decimals of Pi Do We Really Need?」。

For JPL's highest accuracy calculations, which are for interplanetary navigation, we use 3.141592653589793.

The most distant spacecraft from Earth is Voyager 1. It is about 12.5 billion miles away.

It turns out that our calculated circumference of the 25 billion mile diameter circle would be wrong by 1.5 inches. Think about that. We have a circle more than 78 billion miles around, and our calculation of that distance would be off by perhaps less than the length of your little finger.