Question

According to modern science, Earth is about 4.5 billion years old and written human history extends back about10,000 years. Suppose the entire history of Earth is represented with a 100-meter-long timeline, with the birth of Earth on one end and today at the other end.

a. What distance represents 3 billion years?

b. How far from the end of the timeline does written human history begin?

Answer 1

a. Earth is about 4.5 billion years old. If the entire history of Earth is represented with a 100-meter-long timeline, with the birth of Earth on one end and today at the other end, then 3 billion years would be represented by a distance of (100/4.5)*3 meters or, 66.67 meters approximately ( on rounding off to 2 decimal places).

b. We know that 1 billion = 1000 million and 1 million = 1000 thousand so that 1 billion = 1000*1000 thousand and 4.5 billion = 4.5*1000*1000 thousand. Since 4.5 billion years is represented by a distance of 100 meters and since the written human history extends back about 10,000 years, hence the distance from the end of the timeline that the written human history extends is [(10000/4.5*1000*1000*1000)] *100 meters = (2/9)*10^-3 meter.