Ka = KiloYears   = 1000¹ = 10³  = 1,000                 = Thousand Years
Ma = MegaYears = 1000² = 10⁶ = 1,000,000          = Million Years
Ga = GigaYears  = 1000³ = 10⁹ = 1,000,000,000  = Billion Years

How long man live with respect to the age of the Earth?

The most accurate age of the Earth is ~ 4.55 Ga (according to the Pb-Pb age dating method). Now let's imagine these 4.55 billion years being only one year, and then make some calculations to relatively see how long man lives with respect to the age of the earth:

4.55 Ga     = 1 year (365.25 days)
380 Ma      = ~1 month
12.47 Ma   = 1 day
0.52Ma      = 1 hour
8657 yrs    = 1 min
144 yrs      = 1 sec
72 yrs        = 0.5 sec (the average human life expectancy)

How can geologist who lives for only 0.5 second in one year to know or even guess what happened through this year? Amazing, isn’t it?!
 

Hitoshi Banno