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The Universe

The Universe consists of everything in space, and  space itself.it is unimaginably large,constantly changing and getting larger all the time.

The Universe us everything that exists-from the smallest creatures on Earth,to the largest,distant structures in space.The Universe is also a dynamic place.Everything in it follows a life cycle,whether it is a human who lives for 70-80 years,or a star for 10 billion years.The process is continual as each object in The Universe is born,lives,and then dies.

Quasars are a type of active galaxy that produce huge amounts of energy.They are some of the most powerful objects in the universe.

Contents Of The Universe
Our planet seems important and large compared to a human that lives upon it.Yet the earth is a tiny speck when compared to the rest of the universe.Earth is one of the nine planets orbiting a star called Sun.
There are more stars than anything else in the universe.It is impossible to count them but we can estimate that there are at least 100 billion billion.
The Sun, like all other stars,is a glowing sphere of hot gas.it is fairly average,medium hot,yellow star which,along billions more,make up a galaxy.This vast spiral shaped grouping of stars is our home galaxy,the milky way.With about 30 others it forms a cluster of galaxies in space.Together they are called the local group.All over the Universe are many more clusters of galaxies which in turn are arranged in superclusters.
Wee see many galaxies from Earth but many more are beyond our vision.In all there are about 100 billion galaxies in the Universe.We can see them in every direction.Some are so close,or so large,we can make out their shapes and their individual stars.We see them through telescopes,either from land or orbit around Earth.

New stars are born in the eagle nebula,7,000 light years away.At the tips of huge columns of gas and dust are oval shaped clumps they look tiny compared to the columns,but they are new stars being born.

Measuring Distances
It is easy to make measurements on Earth.We use familiar systems such as the metric(kilometre,metre,centimetre) or imperial(Mile,yard,foot,inch) to measure how big,or long something is.These measuring systems are used to measure some of the smaller things in space such as a crater on the moon,or even the distance of pluto from the Sun.
Some things are so big,or so far away,these measuring systems will not work as tge numbers become too long to handle.Astronomers use diffrent units.Within the solar system they use Astronimical Unit(AU).One AU is the distance between the Earth and the Sun and this unit is used to measure the distance of other objects;the Sun to Mars is 1.5 AU,to Jupiter 5.2 AU and so on.
  When measuring outside the solar system,to stars and galaxies,or the size of a galaxy from side to side,Astronomers use light years(ly).Light travels faster than anything else,at  299,792 km per sec.A light year is the distance that light travels in a year.That is 9,460,700,000,000 Km,or to put another way,9,46 billion km or better still,put simply as 1ly.The milky way galaxy is 100,000 ly across.

American astronomer,Edwin Hubble(1889-1953)sits in front of the telescope he used to observe the Universe.In 1924,he presented the first evidence to show that other galaxies existed outside our own.In 1929,He proved that the universe is expanding.

Expanding Universe
Everything in the Universe is moving.
Earth spins on its axis once each day and we expirience,alternatley,day and night,as we bathe in sunlight,then face the dark space.
Every other planet and moon ,each tiny piece of space rock,and each of the countless stars spins in its own axis.
Such objects also move through space as they spin.Earth,for example travels around the Sun once every year,each complete trip is called an orbit.At the same time,Sun,Earth and all the other bodies that make up the solar system,move as whole.They orbit round the centre of the milky way galaxy.From our place in the milky way,wee look deep into space and see galaxies.The galaxies live in clusters which is rushing away both from our galaxy and each other.The further away the cluster,the faster it recedes.The Universe itself is expanding all the time,and has been doing so ever since it was created.