People have a lot of hair.
The average human head has around 100 thousand hairs.
Hair doesn't seem to grow very fast though. Head hair grows on average half an inch per month.
But that builds up. Half an inch per month, twelve months a year, 100 thousand hairs per head.
Every year, the average human head grows almost ten miles of hair.
That means in an average life time, a person will grow well over 600 miles of it.
If you laid it out and started walking, it would take 8 and a half days of non stop walking to get to the other end.