The New Childrens Encyclopedia

OUR UNIQUE WORLD

31

AGE OF THE DINOSAURS

225 million years ago: all

land joined into one

continent, Pangaea.

PANGAEA

225 million years ago: the

age of the dinosaurs begins.

HUMANKIND

145 million years ago: the

modern continents begin

to take shape.

65 million years ago:

mass extinction of

species, including the

dinosaurs.

TAKE A PICTURE

Auroras are created when high-energy

particles are drawn in at the poles by the

magnetic field. This energizes atoms in the

atmosphere, which show as curtains of light.

250,000 years

ago, modern

humans

appeared.

Today

DAY AND NIGHT

Our planet doesn’t stand

still. Every 24 hours it revolves

once around its axis, so that half

the planet is in sunlight and the

other half is in darkness. If it

didn’t rotate, one side would have

permanent day and the other,

permanent night.

Magnetic field Our Earth acts

like a huge bar magnet, which is

why it has north and south

poles. The magnetic field is

thought to be produced by

movement in the liquid

outer core. The molten

metal carries an electrical

charge, which generates an

electromagnetic field as

it swirls around.

FIRST

QUARTER

WAXING

CRESCENT

NEW

MOON

WANING

CRESCENT

LAST

QUARTER

WANING

GIBBOUS

FULL

MOON

WAXING

GIBBOUS

EARTH

Phases of the moon If you look at

the night sky you will see that the

appearance of the Moon changes over

the course of a month. As the Moon

orbits the Earth, the angle between it

and the Sun shifts, so that the amount of

the Moon’s face that is lit by the Sun

changes. It is difficult to see a new

Moon since the light is shining

on the side we cannot see. A

slender crescent then appears

and gradually increases

(waxes) until the full face

is lit. It then starts to

decrease (wane) back

into darkness.

We only ever see the same face of the
Moon because for every orbit it makes
around Earth it spins once on its axis.

SUN

EARTH