# If Earth is about 4.6 billion years old, how many precessional cycles have occurred? How is this calculated?

##### 1 Answer

Apr 17, 2016

Nearly 180 thousand cycles.

#### Explanation:

Precession cycle period is 260 centuries.

So, the number cycles since the formation of the Earth 4.6 B years ago is 4600000000/26000 = 176923, nearly.

This has to be rounded to two significant digits (sd) as 180 thousands, on par with 2-sd approximation 4.6 B, for the age of the Earth.