How things looked like at the beginning of the universe?

The Big Bang theory is still a dominant theory when talking about the birth of our Universe. It has been estimated that Big Bang occurred some 13.7 billion years ago.

The early Universe consisted of a hot, dense primordial soup of gases and particles but it hasn't stayed long in this state because of its rapid expansion which made it less dense and cooler.

The density in all areas of the Universe wasn't the same and has increased due to gravity and began to contract further, forming the first galaxies and stars. It has been estimated that the first galaxies and stars were born approximately 500 million years after the Big Bang.

Majority of astronauts believe that these first stars had gigantic size and that they primarily consisted of the simplest chemical elements, only hydrogen and helium. It took many years for first heavier elements to develop and it is believed that they were created by different nuclear processes in the first stars.

Hydrogen and helium still remain the most dominant elements in our Universe but without the creation of heavy elements there wouldn't be formation of planets and life as we know it.

Why is Big Bang theory generally accepted among the most astronomers? The science usually points to the fact that the main premises of Big Bang theory such as the expansion, the early hot and dense state, the formation of early stars and galaxies - have all been derived from many different observations that do not depend on any cosmological model.

As the science of astronomy continues to progress it is very likely that Big Bang theory will have to be refined in years to come. There are plenty new things waiting to be discovered in the vast unlimited spaces of our Universe.