Question

. Universal Clock.
According to modern science, Earth is about 4.5 billion years old and written human history extends back about 10,000 years. Suppose you represent the entire history of Earth by 12 hours on a clock, with the birth of Earth at the stroke of midnight and today at the stroke of noon.
a. How much time on the clock represents 1 billion years?
b. At what time on the clock does written human history begin?
The answer to part (b) should be determined up to a hundred of a "second."

Answer 1

a)
12 hours -> 4.5 billion years
x hours -> 1 billion years
So 12/4.5 = x/1 \(\implies\) x=12/4.5 hours

b)
12 hours -> 4.5 billion years
x hours -> 0.00001 billion years (i.e. 10, 000 years)
So 12/4.5 = x/0.00001 \(\implies\) x=(0.00001)12/4.5 hours \(\times\cfrac{3600~secs}{1~hr}\), then round to hundredths of a second.

Answer 2

Thank you so much!

Answer 3

You're welcome.