Astronomers and geologists give this broad outline of the ages of the universe and the earth.
Era, period and epoch |
Years ago |
Characteristics |
Origin of the universe |
20,000- |
|
(estimates vary markedly) |
10,000 |
|
Origin of the sun |
5,000 |
|
Origin of the earth |
4,600 |
|
Pre-Cambrian |
||
Archean |
4,000 |
First signs of fossilised microbes |
Proterozoic |
2,500 |
|
Palaeozoic |
||
cambrian |
570 |
First appearance of abundant fossils |
Ordovician (obsolete) |
500 |
Vertebrates emerge |
Silurian |
440 |
Fishes emerge |
Devonian |
400 |
Primitive plants emerge; age of fishes |
carboniferous |
350 |
Amphibians emerge; first winged insects |
Permian |
270 |
Reptiles emerge |
Mesozoic |
||
Triassic |
250 |
Seed plants emerge |
Jurassic |
210 |
Age of dinosaurs |
cretaceous |
145 |
Flowering plants emerge; dinosaurs extinct at end of this period |
|
|
|
|
Palaeocene |
65 |
||
Tertiary: |
Eocene |
55 |
Mammals emerge |
Oligocene |
40 |
||
Miocene |
25 |
||
Pliocene |
5 |
||
Quaternary: |
Pleistocene |
2 |
Ice ages; Stone Age man emerges |
Holocene or Recent |
c. 11,000a |
Modern man emerges |
a 11,000 years, not 11,000m years.
These are the letters of the Greek alphabet and their names. The first column gives the upper-case symbol and the second column the lower-case symbol in each case.
Ααalpha
Bβbeta
Γγgamma
Δδdelta
Εεepsilon
Ζζzeta
Ηηeta
Θθtheta
Ιιiota
Κκkappa
Λλlambda
Μμmu
Ννnu
Ξξxi
Οοomicron
Ππpi
Ρρrho
Σςor σsigma
Ττtau
Υυupsilon
Φφphi
Χχchi
Ψψpsi
Ωωomega