Answer:
I've been around for millions of years, but I am no more than a month old. What am I?
You find me behind the stars; or in a sixth seventh or third. It takes something round a computer and me to make pie. I am bigger than anything you can think of.
I am found in the sea and on land but I do not walk or swim. I travel by foot but I am toeless. No matter where I go, I am never far from home. What am I?
A butcher is 6 feet tall and wears size 12 shoes. What does he weigh?
Physicists have built devices to move me very fast. My last seven letters can be commonly found in newspapers magazines and journals.
No matter how little or how much you use me, you change me every month.