Philips Atlas of the Universe

THE SOLAR SYSTEM

Began Ended

(million years ago)

PRE-CAMBRIAN ERA

Archæan 3800 2500 Start of life

Proterozoic 2500 590 Life in the seas

PALAEOZOIC ERA

Cambrian 590 505 Sea life

Ordovician 505 438 First fishes

Silurian 438 408 First land plants

Devonian 408 360 Amphibians

Carboniferous 360 286 First reptiles

Permian 286 248 Spread of reptiles

MESOZOIC ERA

Triassic 248 213 Reptiles and

early mammals

Jurassic 213 144 Age of dinosaurs

Cretaceous 144 65 Dinosaurs, dying

out at the end

CENOZOIC ERA

Tertiary Period

Palaeocene 65 55 Large mammals

Eocene 55 38 Primates begin

Oligocene 38 25 Development

of primates

Miocene 25 5 Modern-type

animals

Pliocene 5 2 Ape-men

Quaternary Period

Pleistocene 2 0.01 Ice Ages. True men

Holocene 0.01 Present Modern men

PERIODS IN EARTH‘S HISTORY

crosses the celestial equator

around 22 March (vernal

equinox – the Sun moving

from south to north) and

22 September (autumnal

equinox – the Sun moving

from north to south). The

solstices are the times when

the Sun is at its furthest

from the equator of the sky.

The dates of the equinoxes

and solstices are not quite

constant, owing to the

vagaries of our calendar.

 Stromatolites, Australia,

1993. These are made
      up of calcium carbonate,
      precipitated or accumulated
      by blue-green algae.
      They date back for at least
      3,500,000 years, and are
      among the oldest examples
      of living organisms.

 The Great Pyramid of

Cheops.Although it is

essentially a tomb, the Great

Pyramid is astronomically

aligned with the position

of the north pole of the sky

at the time of the ancient

Egyptians. Due to precession

the position of the pole

changes, describing a circle

in a period of 25,800 years.

 The seasons are due

not to the Earth’s changing

distance from the Sun, but

to the fact that the axis of

rotation is inclined at 23^1 / 2 °

to the perpendicular to the

plane of the Earth’s orbit

around the Sun. During

northern summer, the

northern hemisphere is

inclined towards the Sun;

during southern summer

it is the turn of the southern

hemisphere. The Sun

Spring Northern

Hemisphere

Autumn Southern

Hemisphere

Summer Northern

Hemisphere

Autumn Northern

Hemisphere

Summer Southern

Hemisphere

Sun

Winter Northern

Hemisphere

Winter Southern

Hemisphere

Spring Southern

Hemisphere

B Atl of Univ Phil'03stp 31/3/03 4:03 pm Page 37