The Big Bang Theory
The universe is believed to have begun in a Big Bang about 14 billion years ago. At that time, the entire Universe was inside a bubble that was thousands of times smaller than a pinhead. It was VERY hot and dense. Everything was in complete darkness because light didn’t exist yet. The bubble suddenly exploded with a tremendous flash of radiation. It started expanding, the universe unfolding, and getting cooler. Within 100 seconds it was as big as our solar system. While this was happening, the pure energy began to cool and create matter in the form of countless trillions of subatomic particles. Half of these particles were made of matter and the rest were made of antimatter. When the two meet, they destroy each other in a flash of energy. Fortunately there was a little bit more matter than antimatter. This residue is what our present day universe is made of. After the Big Bang, everything spread out and cooled off for about 330,000 years. Then the fog cleared and the universe became visible.
One piece of evidence that leads to the belief in the Big Bang theory is a discovery made by Edwin Hubble in 1929. He discovered that the universe is expanding at enormous speed. Hubble noted that galaxies outside our own were all moving away from us, each at a speed proportional to its distance from us. This must have meant that there was a point in time when the entire universe was contained in a single point in space. The universe must have been formed in the event of the Big Bang.
Another piece of evidence is the Cosmic Microwave Background. As you read above, the universe was very hot and it cooled as it was expanding. The heat left behind a “glow” that filled the entire Universe. The Big Bang theory not only predicts that this glow should exist, but also that it should be visible as microwaves.
To learn more about the Big Bang Theory, visit the sites below:
http://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang/
http://www.schoolsobservatory.org.uk/astro/cosmos/bb_evid
http://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang/
http://www.schoolsobservatory.org.uk/astro/cosmos/bb_evid