Big Bang Theory: How Do We Know The Big Bang Actually Happened?

The question on how the universe came to life has always bugged people's minds -- given the variety of views, explanations and theories from different scientists to choose from.

Among the most popular theories is the Big Bang Theory, which says that the universe came out from an expansion of a pack of infinite matter from a certain point 14 billion years ago. But how can people actually know that the Big Bang really happened?

Study.Com says that there are three evidence to the Big Bang Theory: the Expansion, Red Shift and Background Radiation also known as Cosmic Microwave Background.

According to BBC, the fact that the universe still continues to expand makes up a strong evidence of the theory. We may not see it with our naked eye, but other galaxies are moving away from us at speeds of hundreds of thousands of kilometers.

This observation is proven by the light that come from these galaxies, which appear redder than it used to be. Why? Because light waves are stretched when a galaxy moves away, making light seem to look like undergoing a red shift.

"After the Big Bang, the whole Universe was flooded with incredibly bright light," astronomer Maggie Aderin Pocock explained in her article. "As the Universe has expanded, that light has stretched into microwaves. A microwave telescope can see this ancient light from the very beginning of the Universe. In fact, a view through a microwave telescope shows the whole sky filled with a glow, day and night. This glow is called the Cosmic Microwave Background."

Meanwhile, scientists have discovered a number of ancient gas clouds about 13 billion light years away through the use of a technique called spectroscopy. These gas clouds were considered to be located close to the time of the Big Bang. If the Big Bang was indeed true, more galaxies and stars are expected to come out from gas clouds located in distant universe.