How Did the Universe Get Started?

The timeline of the universe
This represents a timeline of the universe from the Big Bang through the present. At the left is the "birth event" of the cosmos, known as the "Big Bang". NASA / WMAP Science Team

How did the universe begin? That's a question scientists and philosophers have pondered throughout history. When you're outside on a starry night looking up at the sky, it's impossible NOT to think about where it all came from. It's the job of astronomy and astrophysics to provide an answer. 

However, it's not an easy one to tackle. In 1959 a survey of scientists across America asked them “What is your concept of the age of the universe?” More than two thirds of them responded that there was no origin of the universe.

They thought it was eternal because they had little data to tell one way or the other.

Five years later, in 1964, radio astronomers Arno Penzias and Robert Wilson discovered a microwave signal buried in data they were taking to look for signals being bounced from Echo balloon satellites. They attempted to filter out the signal, assuming that it was merely unwanted noise. However, they soon realized that the signal was coming from spaces. Although they didn't know it at the time, they had discovered the Cosmic Microwave Background (CMB). The CMB had been predicted by a theory called the Big Bang. This discovery was the first evidence that the universe had a beginning.

The Big Bang

Once it was understood that the universe had a beginning, scientists began to dig into the data to figure out how it came into existence. They could also investigate answers to the question: what existed before it?

What started the birth of the universe? 

The answer is that the universe sprang into existence from a singularity — a term physicists use to describe regions of space that defy the laws of physics. We know very little about singularities, but we suspect that others exist in the cores of black holes.

Inside a black hole, all the mass it gobbles up gets squeezed into a tiny point, infinitely massive, but also very, very small. Imagine cramming Earth into something the size of a pinpoint. A singularity would be smaller. 

The second part of the question, as to what existed before the Big Bang, is open to a LOT of speculation. By definition, nothing existed prior to the beginning, but that fact creates more questions than answers. For instance, if nothing existed prior to the Big Bang, what caused the singularity to be created in the first place? It's a "gotcha" question astrophysicists are still trying to understand. 

Once the singularity was created (however it happened), it began to expand through a process called inflation. The universe went from very small and very dense, to very hot and then cooled as it expanded.  This process now referred to as the Big Bang, a term first coined by Sir Fred Hoyle during a British Broadcasting Corporation (BBC) radio broadcast in 1950.

Although the term implies some kind of explosion, there really wasn’t an outburst or a bang. It was really the rapid expansion of space and time. Think of it like blowing up a balloon: as you blow air in, the exterior of the balloon expands outward.

The Moments after the Big Bang

The early universe was not bound by the laws of physics as we know them today. So, we really cannot predict with great accuracy what it looked like during the first few minutes of its existence. In spite of this, scientists have been able to construct an approximate representation of how the universe evolved.

First, the infant universe was initially so hot and dense that even elementary particles such as protons and neutrons could not exist. Instead, different types of matter (called matter and anti-matter) collided together, creating pure energy. But as the universe began to cool during the first few minutes, protons and neutrons began to form. Slowly, these protons, neutrons and electrons came together to form hydrogen and small amounts of helium. During the billions of years that followed, stars, planets and galaxies formed to create the current universe.

Evidence for the Big Bang

The CMB signal detected by Penzias and Wilson, a discovery for which they later won a Nobel Prize, is often described as the “echo” of the Big Bang. Since the Universe did have, it left behind a signature of the event, just like an echo heard in a canyon represents a “signature” of the original sound. The difference is that instead of an audible echo, the Big Bang left behind a heat signature throughout all of space. That signature has been specifically studied by the Cosmic Background Explorer (COBE) spacecraft and the Wilkinson Microwave Anisotropy Probe (WMAP). These orbiting missions looked at the microwave background in greater detail.

Alternatives to the Big Bang Theory

While the Big Bang theory is the most widely accepted model that explains the origins of the universe, and is supported by all the observational evidence, there are other models that use the same evidence to tell a slightly different story.

Other theories argue that the Big Bang theory is based on a false premise — that the universe is built on an ever expanding space-time. They suggest a static universe, which is what was originally predicted by Einstein’s theory of general relativity. Einstein’s theory was only later modified to accommodate the way the universe appears to be expanding.  And, expansion is a big part of the story, particularly as it involves the existence of dark energy. Finally, a recalculation of the mass of the universe seem to support the Big Bang theory of events.


While our understanding of the actual events is still incomplete, data from the earliest times in the universe are helping shape that understanding to be sharper and clearer than before. What we do know is that we live in an expanding universe that continues to create stars, planets, and most likely, life. Stay tuned! 

Updated and edited by Carolyn Collins Petersen.

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Your Citation
Millis, John P., Ph.D. "How Did the Universe Get Started?" ThoughtCo, Jun. 12, 2017, Millis, John P., Ph.D. (2017, June 12). How Did the Universe Get Started? Retrieved from Millis, John P., Ph.D. "How Did the Universe Get Started?" ThoughtCo. (accessed December 16, 2017).