@dalehileman,
Max gave you already part of the answer.
Age of the earth = 4.6 By.
Number of seconds in one year = 31 536 000
So, 1 second in earth years is 4,600,000,000/31,536,000 = 145.86
Three seconds is 145.86*3 = 437.6 years.
437 years ago it was 1577.
At that time, following 2007 Hyde estimate, world population was 550 millions.
Today, it's 7,239 millions.
So, it's almost doubled four times.