DK - WOW! The Visual Encyclopedia of Everything

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The Universe is everything that exists, from the

smallest particle on Earth to the vast galaxies of deep space. Every part of it, including space and time, came into existence in the Big Bang – a huge explosion that occurred about 13.8 billion years ago. At that time, the Universe looked nothing like it does today, and it has been expanding, cooling, and changing ever since.

UNIVERSEThe hydrogen and helium of the very young Universe formed stars, which in turn produced all the other elements in today’s Universe, including those that make Earth and everything on it, including you.

10

BILLION YEARS AGO

13.8

BILLION YEARS AGO

380,000

YEARS LATER

12

BILLION YEARS AGO

Colours denote minute

variations in the temperature

of the matter – the red

areas are the hottest

The smallest, reddest galaxies date from about 800 million years after the Big Bang and are the oldest known

Galaxies and stars account for just 15 per cent of all matter in the Universe

THE BIG BANGIn the beginning, the Universe

was unimaginably small, dense, and incredibly hot. Within a trillionth of

a second it ballooned from being smaller than an atom to bigger

than a galaxy. It was made of tiny particles of energy that turned

to particles of matter. Within three minutes, the Universe

was made almost entirely of the nuclei of hydrogen and

helium atoms.

FORMATION OF GALAXIESOver millions of years, hydrogen and helium

clumped together to form vast clouds.

These broke into fragments, which

collapsed under gravity and became

stars. About one billion years after

the Big Bang, a Universe of

dwarf galaxies had formed.

These collided, merged,

and changed shape to

become spiral and

elliptical galaxies.

COSMIC BACKGROUNDBy looking at the heat left over

from the Big Bang, known as

the cosmic microwave background radiation,

scientists are able to build up a

picture of the early Universe. This image is a heat map of

the Universe 380,000 years

after the Big Bang. It shows that matter was not evenly

distributed – the hotter

areas (red) are more densely

packed regions, where

galaxies will form.

128_129_Universe.indd 128 03/01/19 12:10 PM