It’s difficult to imagine, but they was once a time when our planet, our Sun, and our solar system did not exist. Where did everything come from? This is a very difficult question to answer, and many people (depending on their beliefs) have different ideas or theories to answer this question. Scientists who study the origin (beginning) of the universe and how it keeps changing are studying a field of science known as “cosmology.”
THE BIG BANG THEORY
Cosmologists have evidence that all the galaxies in the universe are moving apart from one another. Due to this, cosmologists know that there was once a time when all the galaxies and matter in the universe was tightly packed together; they call this point in history “time zero.” Using the collected evidence, time zero was approximately 10 to 15 billion years ago. All of this matter, under extreme pressure, “exploded” outwards in what cosmologists call the “Big Bang.” Just like an explosion, galaxies are still moving further apart from one another 10-15 billion years later. Even though scientists have come up with a theory for how the universe began, they still don’t know how to figure out what existed before the Big Bang.
THE ORIGIN OF THE SOLAR SYSTEM
Our solar system is not as old as the universe; our Sun is estimated to be 5 billion years old and the planet Earth is estimated to be about 4.5 billion Before our years old.solar system existed, matter swirled around in a large object called a “nebula.” A nebula contains countless particles of swirling gases and dust and is the place where stars are “born.” All matter has gravity. As these swirling particles were moving around in the nebula, some started to collide and join together. As an object gains more matter, it has more gravity and is able to pull more particles into it. This is how our Sun was formed. As our Sun was forming, cooler pieces of matter were joining together around the Sun. The chunks of matter eventually grew into the planets we know today.