 The universe is the space which contains all the galaxies, stars, planets, moons, living organisms and every thing.  The sun and the earth are a tiny part in the universe.

 In the universe, groups of stars are gathered to form galaxies.  The universe contains many galaxies and each galaxy has a distinctive shape according to harmony and order to groups of stars in it

 The sun is one of stars of our galaxy (milky way)

 The Milky Way Galaxy:  In the center of the galaxy a lot of old stars gather surrounded by small stars located in the spiral arms of the galaxy.  Our sun is a star of millions of stars in this galaxy.

 The universe:  It is a wide and extended space that contains galaxies.  The number of galaxies in the universe is about 100,000 million galaxies.

 Galaxies:  Galaxies gather in clusters including the milky way which contains the sun.

 The Milky Way:  It contains the sun and the solar system.  The milky way is given that name because it appears in the sky at night as a splashing milk or spreading straw.

 The solar system:  It is the sun and eight planets revolving around it

 The earth:  The planet of life.

 The solar system:  Planets around the sun and the surrounding planets revolve around the center of the galaxy (Milky Way).

 The sun takes about 220 million years to complete one rotation around the center of the galaxy.  The solar system is located in one of the spiral arms of the milky way on the edge of the galaxy.

 Measuring the distance through the universe:  The distance between stars are very large, so the distance in the far space are not measured in kilometers, but they are measured in a unit called “light year”.  Light year:  It is the distance covered by light in one year and it is equal km per second, this distance is million km.

1-The Big Bang: 1- through the big bang: The process of expansion and changing of the gaseous ball components started and it continues to this day

2-Through 1 second after explosion: The temperature decreased to about million (10 billion) Degrees.

3- Within minutes after the explosion: The atomic particles produced from explosion merged together producing gaseous clouds of hydrogen and helium with a ratio of 75% : 25% respectively.

4-After 1000 million (1 billion) years from the big bang: The gaseous clouds merged forming homogenous masses which will produce the matter of galaxies.

5- within 2000 : 3000 million (2 : 3 billion ): years from the big bang: The gravity helped in gathering of more masses forming “ancestral galaxies” leaving areas of empty space between them.

 After 3000 million years from the big bang: Galaxies began to form.

 After 5000 million years from the big bang: Our galaxy the milk way took its disc form.

 After 10,000 million years from the big bang:  The sun was born.  Then the earth and planets were created.

 After million years from the big bang:  Earliest life forms began to appear on the earth.

 After million years from big bang:  The universe as it now.