What is the BIG BANG?
Why do people start to use this word a lot lately even a show called BIG BANG in CBS prime time? Why do we spend billions dollars each year to prove the Big Bang theory? Why more people are interested in it even last September, there was a big news around the world about CERN in Europe attempted to replica a small big bang?
The reason - Because BIG BANG is the well known, respected, and scientific theory; it explains where every thing in this universe was coming from. Don't you want to know where we come from? I do; that is why I did some reading about it, and I like to share it.

BIG BANG theory
Basically in the theory of Big Bang, our universe began from an explosion of an extreme tiny area with extreme dense and extreme hot about 13.7 billion years ago. At a fraction of a second from the Big Bang, there was a tremendous energy that no matter can be formed, and the universe expanded rapidly just in a period of a fraction of a second. They call that event “the cosmic inflation”. As the time went by, the universe kept expanding; the matter began to form, and the radiation began to loose energy even today. The result of this is the formation of the universe that comprises of billions of galaxies, and each galaxy has billions of stars, and stars (solar system) have planets, moons, etc. The stars, we can see with our own eyes, are in our own “Milky Way Galaxy”; the rest can be seen by giant telescopes. Our sun is one of those billion billion stars in the universe, and it provides our solar system the energy and gravity.

Initially, the astronomers thought that our universe is static (no change). But in 1929 Edwin Hubble (Nobel Price astronomer) found through his telescope that the universe was expanding. Just the rule of logic, if the universe is expanding, it must be smaller in the past;  therefore there must be an explosion at one point in the past, and that point is the origin of our universe and time.

How our universe is formed?
The 1st billion years -
There were many events going on for the 1st billion years especially the 1st second of the Big Bang. But only few main events would be described here, and they are:
a) The vast hot explosion called cosmic inflation occurred in a fraction of a second in less than a second from the big bang,
b) Just 1 second from the Big Bang, the 4 basic forces of nature emerge,
c) Just in a few minutes from the big bang, protons & neutrons combine to form nuclei of the simple elements of Hydrogen & Helium,
d) Hydrogen & Helium elements are the 1st ones to be formed in the universe,
e) The universe keep expanding and cooling down even today allowing the photons (light) to rush outward as they can be seen today as CBM (Cosmic Microwave Background),
f) Hot expanding gases of these elements (hydrogen & Helium) had been formed into large giant pockets.

One billion years to present -
Stars began to form from those gas pockets, and later they clustered together to form galaxies. The galaxies did form into their own clusters. As time went by, some old stars exploded. The explosion of big stars was called supernova; it generated heavy elements such as iron, gold, lead, uranium and ejected them across the universe. A supernova could generate Black Hole which pulled down every thing including light that passed through its horizon (hole). While some old stars have been dying, the new stars, and galaxies have been formed even at the present time.

How big is the universe?
As stated earlier the universe has been expanding even today. So how big is the universe at the present time?
No one really knows for sure. It is so complicated to explain, and the current diameter of our visible universe is guessed to be about 28 billion year lights. They use “light year” as the unit length to measure the distance between stars and galaxies. One light year equals to 9,461,000,000,000 km (5,880,000,000,000 miles). Imagine the diameter of our earth is only 7926 miles, and the distance between earth and sun is only 149,597,870 miles. So when we look at the sky at night, we should think that we are a very tiny creature in this universe. Perhaps we compare ourselves to ants or microbes to our earth.

What is our solar system? it consists of a star (Sun), 8 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune), many satellites of the planets such as Moon to Earth and Europa to Jupiter, dwarf planets such as Pluto and Eris, Asteroids, Comets, meteorites, and other bodies on the outer ring. They are all orbiting the Sun because of the sun gravity. The sun provides energy to all bodies in the our solar system. Our solar system began to form about 4.6 billion years ago in our Milky Way Galaxy, and it is expected to be around for  5 billion more years.

Will the solar system exist for ever?
No, the sun is expected to be running out of fuel (nuclear fusion) in about 5 billion years. This means that our solar system will change including our earth. The earth will evaporate due to the hotter sun, and it will be absorbed by the sun far before the sun dies. The sun will no longer provide energy and gravity to our solar system, and a few billion years later it will become a dark dwarf floating in the Milky Way galaxy. Mercury, Venus, and perhaps Mars will have the same fate as our Earth. Other bodies which are far away from the sun may run away due to no more gravity from the sun.

Besides the sun running out of fuel to provide energy to the solar system, there is another problem that our solar system and our Milky way will face in 3 billion years. The astronomers expect that our nearest neighbor galaxy called “Andromda”, 2.2 million light years away from us, will collide with our Milky Way galaxy. It would be possible that our solar system will not survive from this gigantic collision.

Here are some other subjects that are related to the BIG BANG & Universe, and they need to be written:
How is a star formed? How is a galaxy formed? What is black hole? What is dark matter? What is dark energy? Who is Albert Einstein? What are the 4 basic forces of the nature? Any idea of why the Big Bang occurs? Or is it coming from nothing (emptiness)?