Why is there so many people in Earth?

This is what's called a "geometric progression". Take a checkerboard and put a penny on the first square. Put two pennies on the 2nd square and twice that many on the 3rd square -- that's 4. Double it again, that's 8 pennies on the 4th square, 16 on the 5th, 32 on the 6th, 64 on the seventh and 128 on the 8th. That's one row down and 7 rows to go. See how fast those pennies pile up?