The Universe We think of the earth as a big place, but try to think of sheer vastness of the universe. The moon is 385,000km from earth. The sun is 150million km and the nearest star Alpha Centauri is a staggering 40 billion km. The nearest galaxy Andromeda is about a million times farther.

The Home galaxy Along with 7 other planets, the earth orbits the Sun. Pluto is classed as a dwarf planet. This solar system is a tiny dot in our galaxy, the Milky Way. The Milky way is made up of approx 400 billion stars that stretches 100,000 light years from side to side. Light from Andromeda takes 2.5 million earth years to reach us.

Interstellar space The Milky way and Andromeda are members of a small gathering of at least 35 galaxies called the Local Group. Which in turn is part of a cluster of galaxies called the Local Supergroup.

Measuring distance Space is too large to measure in normal kilometres so we use 2 units : AU – astronomical unit which is the average distance between earth and the Sun and is approx 150 million kms. Light Years – The distance light travels in a vacuum in a year which is approx 10 trillion kms.

The Big bang theory In 1924 Edwin Hubble announced that galaxies were moving away from Earth. The more distant the galaxy the faster it was receding. For the universe to be expanding like this, a force of incredible magnitude must have set matter on this outward path. The name coined for this initial event was called the BIG BANG.

The BIG BANG The big bang was not a violent explosion but an unfolding of space and matter from a point no larger than the full stop you are about to put on your page NOW.

The Universe A fraction of a second (one millionth of a second) after the Big Bang, the universe was a hot seething mass of radiation and exotic particles. These expanded and cooled and more familiar particles of protons, neutrons and electrons that make up everyday matter formed. Now the famous nebula MZ3, called Fourmi, between 3000 and 6000 light years

The Universe Gradually elements came into being, mostly Hydrogen and Helium and these collapsed under the influence of gravity to create galaxies, stars and planets. The most convincing evidence for the Big Bang Theory is CBR cosmic background radiation. An all sky glow from the remaining heat of the big bang approx minus 270 degrees C, or about a hundred million times cooler than a birthday candle.

The Big Crunch After the Big Bang a scenario occurs where all matter returns to its original form called the Big Crunch. This will only occur if the universe has too much matter which will collapse under the force of gravity. This is called a CLOSED universe. If expansion continues forever, we call that an “OPEN” Universe.

Flat Universe The universe is precisely balanced between open and closed. That means it will expand forever, but also decelerate and never coming to a halt. Another scenario is that the universe is forever expanding and accelerating with time.

Work sheets Geocentric and Heliocentric views of the universe The universe an introduction 1b