The Fossil Record

(S7L5.c)

(Plus, info about Half-Life 3!)

(And by that, I mean 3 half-lives)

The fossil record is why we know about the organisms that lived before us and how they changed. Species can often go thousands of years without change through evolution. With fossils, we can document change of these organisms. 

Sedimentary rock is the most common rock on the planet. Whether it's a coincidence or not, fossils also happen to be most common in sedimentary rock. These rocks also make it very easy for scientists to date generally. However, if a scientist wants to date a fossil more accurately, they must use half-lives. Suppose an element in a fossil has a half-life of 5,000 years. 15,000 years pass until it is found. That's 3 Half-Lives (pun defiantly intended).

3 Half-Lives

(Better known as: Half-Life 3 confirmed!)

(Copyright: the image of Half-Life 3 is not made by me, neither is the image of the Helix Fossil. [praise Helix!])