One reason why we have homes is to give us shelter.
Explanation: Homes protect us from weather like storms, extreme cold, extreme hot. Also, we can live in our own space with homes and not be squeezing together outside. Also, with homes, we have a safe place to sleep at night, because it wouldn't be good to sleep on the road
The 3.9 billion year old rock has undergone three half-lives (3.9 divided by 1.3 = 3). After 3 half-lives, 12.5% of the potassium-40 remains undecayed.
