Nobody, knows why we sleep, but we all need to. Sleep helps our body and brain develop and grow.
Our body needs sleep to stay healthy and fight sickness. During sleep, our muscles, bones and skin can grow, and muscles, skin and other parts can fix injuries.
Our brain needs sleep. Sleep helps our brain to remember what we learn. It also helps to pay attention and concentrate. 
Thank you for reading....
Yes, sleeping on earth does not hurt the only person
Yes, absolutely