The Celestial Sphere and Early Observations
Our ancestors saw the same night sky as we do today, they saw thousands of stars that seemed to be fixed on some celestial dome or sphere, slowly round us. They kept tracking of their positions by inventing constellations, or shape that can be traced by connecting the dots.
They require quite a bit of imagination to see, but our ancestors were creative And bored, so they projected a little bit of themselves on the stars. They also saw other objects, most notably the sun and moon, as well as five planets, all of which moved according to their own pattern, unrelated to the stars.
the geocentric model
(earth-centered universe)
Back then in ancient times, they believed that earth was the center of the universe with mysterious heavens swirling around us.
The planets move more slowly than the stars, and these constellations they crossed in doing so were view special
These constellations came to comprise the zodiac, which still the focus of astrology today.
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In the 1920s in California
Astronomer Edwin Hubble observed distant galaxies using an extremely powerful telescope. He made two mind-boggling discoveries.
If the universe is always getting bigger, then long ago it was smaller. And long, LONG ago, it was much smaller. That means billions of years ago, everything in the universe was contained in a tiny ball that exploded! Wow!
This breakthrough idea later became known as the Big Bang!
The  Big Bang was the moment 13.8 billion years ago when the universe began as a tiny, dense, fireball that exploded. Most astronomers use the Big Bang theory to explain how the universe began. But what caused this explosion in the first place is still a mystery.
Stage 1: the Big Bang
In this stage, the universe has been created from an elementary primeval atom. The matter was very hot and dense and has a volume of few millimeters and then it was shattered to form matter and space objects.
Stage 2: the universe first Spurt
In this stage, the universe started growing in doubling the size by 90 times this stage is also called inflation. The size of the universe was increasing exponentially. After this, the universe continues growing but at a slower rate.
Stage 3: creation of elements and light
After 3 minutes of the big bang, light elements were created. With high temperature and high speed and force neutrons and protons collided to form deuterium which is one of the hydrogen isotopes. Because of the high temperature, atoms were able to collide with each other and as a result of that collision light was emitted
Stage 4: Detectable light
About 380,000 years after the Big Bang, the temperature decreased to a limit where electrons could combine with the nucleus to form atoms. This phase is known as "recombination," and the absorption of free electrons caused the universe to become transparent. The light that was unleashed at this time is detectable today in the form of radiation from the cosmic microwave background.
Stage 5 & 6 : Reionization
Formation of stars and galaxies after 400 million years of Big Bang
Stage 7: The creation of our solar system
The solar system is 4.6 billion years old. All was formed from a cloud of gas dust and cloud
Stage 8 : Dark Matter existence
By observing the speed of stars in deferent locations, some of the hypothesis suggests that dark matter is formed from a substance that does not interact with light which makes it undetectable and invisible
Stage 9: the universe expansion and motion
In the 1920s, astronomer Edwin Hubble made a revolutionary discovery about the universe. Using a newly constructed telescope at the Mount Wilson Observatory in Los Angeles, Hubble observed that the universe is not static, but rather is expanding.
Stage 10: We Still Need to Know More
While much has been discovered about the creation and evolution of the universe, there are enduring questions that remain unanswered. Dark matter and dark energy remain two of the biggest mysteries, but cosmologists continue to probe the universe in hopes of better understanding how it all began.