A popular scientific theory is that our universe originated with what is known as the Big Bang. This lesson explains what the Big Bang is and the evidence that supports it. Following the lesson, you can test your newfound knowledge with a quiz!
The Beginning of Time
When we look around at our surroundings as kids, many of us wonder how everything around us came into being. Trust me: this continues on all throughout adulthood and is why we have certain scientific fields!
Rarely the knowledge of what exists is enough to satisfy us, and we want to know how and why everything exists. These aren't easy questions to answer, and we may never know the answers with absolute certainty. However, we've learned a lot about the laws of nature in our quest for this knowledge. The laws of nature govern all things in the universe from the direction and speed a ball bounces to the way the planets move in their orbits. Our increased understanding of these laws over time eventually led us to describe an event known as the Big Bang, which is the idea that the universe began at a single moment in time with an intense burst of energy.
In order to understand the Big Bang, we need to begin with the discovery that started it all. The name Edwin Hubble may sound familiar to you, probably because of the famous Hubble telescope. Hubble didn't build the telescope, but it was named after him. One thing you may not know is that the foundation for the concept of the Big Bang theory comes from one of Hubble's discoveries: Hubble found that galaxies are moving away from us! He also found that this appears to occur at speeds proportional to their distance and that it's occurring in all directions. In other words, he observed that the universe is experiencing an ongoing process of expansion. This observation has come to be known as Hubble's Law.
The idea of expansion as explained by Hubble's Law supports the idea that the universe was once compressed into a much smaller space. Hubble's Law was used to develop a new theory of the creation and expansion of the universe that eventually came to be known as the Big Bang. Over time, the Big Bang theory has been modified and adapted, and the future will likely hold more adaptations as our understanding of the universe increases.
The Big Bang
Now let's look at the basic concept of the Big Bang theory. Current estimates say that the Big Bang occurred about 13.7 billion years ago (try not to let your head explode at that number)! The Big Bang began from a point that was infinitesimally small, tremendously dense, and extremely hot. When the energy in this state could no longer be contained in such a small space, the Big Bang occurred. You would be wrong if you think of the moment the Big Bang happened and imagine it looking like a balloon popping. Instead, imagine a balloon that is being steadily filled with air as it gets larger and larger. The Big Bang wasn't like a conventional explosion but rather a rapidly growing expansion of particles. This expansion is what Hubble discovered, and it's still occurring today.
It may seem unlikely to you that all parts of the universe were suddenly and spontaneously created during the Big Bang. But, believe it or not, this can be explained by quantum physics. Quantum physics are the governing laws of physics on the sub-atomic level. When observing sub-atomic particles, spontaneous creation similar to the Big Bang can be observed, even though it's on a much smaller scale. It's believed that the universe was once compacted into a space even smaller than these sub-atomic particles, and we can assume that it was also governed by the laws of quantum physics at the time of the Big Bang. This means that the universe could have spontaneously expanded into existence following the known laws of nature.
Let's take a couple of moments to review what we've learned. There's still a lot to be learned about how our universe formed, has evolved, is evolving, and how it may come to an end. Our present understanding has lead to the idea that the universe began with an intense burst of energy from a small, extremely dense point, at a single moment in time. This event is known as the Big Bang.
The Big Bang was more of a rapid expansion of particles than what you think of when you imagine a traditional explosion. This expansion is still going on today and is described by Hubble's Law. Hubble's observation of this expansion led to the eventual development of the Big Bang theory. The Big Bang can also be explained through the laws of quantum physics, which are the governing laws of physics on the sub-atomic level, and spontaneous creation on a much smaller scale can be observed.