Earth timescale: 5×10^9, 8, 7, 6, 5, 4, 3, 2, 1, 0

Mnemonic Device:

• 5×10^9, 8, 7, 6, 5, 4, 3, 2, 1, 0

Explanation:

5×10^9 (about 5 billion years ago)
the birth of the earth
5×10^8 – the first fish
5×10^7 – the first monkeys
5×10^6 – the first humans
5×10^5 – the first babies with brains
getting much bigger after birth
5×10^4 – the first language
5×10^3 – the first writing, the first
cities, the first armies
5×10^2 – the first printed books, the
hemispheres merge
5×10^1 – the first commercial computers,
everything escalates
5×10^0 – the first 5 years of the 21st century,
global warming & warring