The Big Bang Theory

Podcast Transcript

Throughout history, philosophers have pondered how the universe began.

For centuries, it was just that…pondering.

It wasn’t until the 20th century that enough evidence began to accumulate about the universe that it was possible to establish a reasonable theory.

Ultimate, in 1927 a 31-year-old Catholic Priest from Belgium, using the latest scientific discoveries, proposed a theory to explain the origin of the universe.

Learn more about the Big Bang Theory, how it came about, and how we think it happened on this episode of Everything Everywhere Daily.

The origin of the universe is a pretty heady thing. It should come as no surprise that it is a question that philosophers have asked for thousands of years.

Aristotle believed that the universe was immortal. It has no beginning and simply always was.

Aristotle’s view was simply a belief that he held without any real evidence. It seemed reasonable to him, so he went with it.

While Aristotelian philosophy held sway for centuries, his belief in the origin of the universe did not.

All three of the major Abrahamic religions, Islam, Judaism, and Christianity, hold that the universe had a definite beginning.

In the Middle Ages, a host of Christian, Islamic, and Jewish philosophers pondered the question of a universe of a finite age.

The Jewish philosopher Maimonides claimed that it was impossible to prove that time was infinite or finite.

The Greek Byzantine philosopher John Philoponus, the Arab philosopher Al-Kindi, the Persian philosopher Al-Ghazali, and the German philosopher Immanuel Kant have all pondered the question of a finite and definite origin to the universe.

In 1225, the English theologian Robert Grosseteste actually came close to the modern theory when he posited that the universe began with an explosion.

Even Edgar Allan Poe threw his hat into the ring in the 19th century, claiming everything originated from a single primordial particle.

The point is pretty much every civilization and a great many philosophers over the centuries have pondered the question of the origin of the universe, with a bent amongst the monotheistic religions towards a universe with a finite origin.

Still, they all were just trying to make logical arguments based on zero evidence of how the universe actually worked.

It wasn’t until the start of the 20th century that there was a profound revolution regarding our understanding of how matter, energy, and the universe worked.

The ultimate development of the Big Bang Theory required not just an understanding of what was happening at a cosmological level but also an understanding of things at an atomic and subatomic level.

One of the biggest theoretical underpinnings of the Big Bang Theory was Einstein’s Theory of General Relativity, which held that the universe couldn’t be static. In fact, Einstein initially thought that he was wrong, but he turned out to have been right.

The thing that really laid the foundation for the development of the Big Bang Theory was the observation of red-shifted light from distant nebulae. This was first observed in 1912 by the American astronomer Vesto Slipher.

Edwin Hubble discovered that many of the observations made by Slipher weren’t of objects in our galaxies but rather were much further away. They were galaxies of their own, and the Milky Way wasn’t the totality of the universe. He also discovered that the redshift of the galaxy increased with its distance.

Here, I should explain precisely what red shift and blue shifts are because it is the fundamental thing that helps explain not only the Big Bang Theory but also a great deal of contemporary astronomy.

Light is a wave, just like sound. You are probably familiar with the Doppler effect, which is when an object moving toward you makes a higher-pitched sound, and when it moves away from you, it makes a lower-pitched sound.

Even though the sound coming from the source is constant, because it is moving relative to you, it sounds like it’s changing. When the object is moving towards you, the sound waves get pushed together, resulting in a higher pitch. When it moves away, the sound waves are pulled further apart, resulting in a lower pitch.

Light waves behave in exactly the same way. However, instead of changing pitch, they change color. A light-emitting object moving towards you will have the light waves pushed together, resulting in shorter wavelengths, moving it towards the blue end of the spectrum.

By the same token, if something is moving away, the light waves will be elongated, making the light waves longer moving it to the red end of the spectrum.

We actually know with a great deal of precision exactly what wavelengths of light are emitted from gases like hydrogen and helium when they are heated.

We can then measure what light we observe, compare it to what it gives off under laboratory conditions, and calculate the direction it is moving away or towards us, as well as the velocity.

When it was discovered that light from most distant galaxies was redshifted, it was groundbreaking. The galaxies weren’t stationary but were, in fact, moving and moving away from us.

In 1922, Soviet physicist Alexander Friedmann used Einstein’s equations to provide a theoretical model for an expanding universe. However, because he was in the Soviet Union and died in 1925, much of his work wasn’t known to the rest of the world.

In 1927, Georges Lemaître independently made the same discovery as Friedmann. Also, he showed the mathematical relationship between the velocity of galaxies and their distance, which was later independently discovered by Hubble. In other words, the further away galaxies were, the faster they were moving away from us.

In 1931, he wrote papers that made two important contributions to this subject of this episode. He proposed that the expansion of the universe was, in fact, accelerating and that if you were to trace everything backward, you would eventually reach a point where the entire universe was what he called a primeval atom. He also called it the “cosmic egg.”

Georges Lemaître is widely considered to be the originator of the Big Bang Theory.

Lemaître was not the sort of person you’d normally expect to be making theoretical proposals for the origin of the universe. Georges Lemaître was a Jesuit Catholic priest who studied for the priesthood while working on his Ph.D.

His idea that everything in the universe expanded from a single point was not well-received at first. However, it was actually his colleagues from the physics world that rejected it, not the religious ones. Many physicists thought the idea seemed too religious.

One of the alternative theories that was floated in the years after was the steady state theory by English astronomer Fred Hoyle.

Hoyle held that the average density of the universe remained stable and more matter was created as the universe expanded.

He inadvertently coined the term ‘big bang’ in a 1949 interview he conducted with the BBC when he said, “These theories were based on the hypothesis that all the matter in the universe was created in one big bang at a particular time in the remote past.”

Over time, competing theories for the beginning of the universe began to fall by the wayside

One of the biggest discoveries that confirmed the Big Bang Theory was the discovery of cosmic microwave background radiation in 1964. This background radiation, which permeates the Universe, is left over from the Big Bang.

This was exactly what had been predicted and offered empirical solid evidence for the Big Bang.

Eventually, supporters of the steady-state theory fell aside as the evidence piled up, and the term ‘big bang’ began being used more prominently to describe the theory in the 1970s.

The Big Bang Theory has proven to be a robust explanation for the abundance of light elements, the distribution of background radiation, and the structure of the observable universe.

So, I’ve been talking about the Big Bang Theory in the abstract, just referring to it. What does it really entail?

What I’m going to go over is the current most widely held belief based on current evidence. The evidence doesn’t just come from astronomy but also from the world of quantum and atomic physics as well.

Everything is believed to have started with a singularity about 13.8 billion years ago. Everything in the entire universe was condensed down to a point: all the stars, all the galaxies, all the matter, all the energy.

What happened is often called an explosion, but it wasn’t. An explosion is an expulsion of matter into space. This was an expansion of space itself.

This is a really hard concept to wrap your head around because it is something that we can’t relate to with our relationship with the universe.

We have no idea why the singularity expanded. We have no idea what came before the singularity. As far as we know, there is no way to know.

However, there are guesses as to what immediately after the expansion began. When I say immediately, I do mean immediately. An incredible amount happened in just the first second.

When the singularity began to expand, things were incredibly dense and incredibly hot. It was so hot and so dense we don’t really have the physics to understand it. At 10-³⁶ seconds, it is believed that all the fundamental forces in the universe may have been merged.

Within the tiny fractions of a second after that, the fundamental forces may have separated. Subatomic particles, such as gluons, then things that make protons and neutrons, appeared.

During this first second, space was expanding faster than the speed of light. This didn’t violate the laws of physics because it wasn’t something going faster than light, it was space itself expanding.

Temperatures dropped quickly simply because space was increasing quickly.

The subatomic particles eventually cooled and began forming protons and electrons, which themselves joined to form hydrogen and a small amount of helium.

Eventually, over hundreds of millions of years, hydrogen began to coalesce into stars, and then stars began to form galaxies.

That is a really, really truncated version of everything, but the important thing to know is that in that first tiny, tiny, tiny fraction of a second, space expanded VERY rapidly. From a linear distance, it may have gone from one nanometer to 10.6 lightyears in diameter before 10^?32 seconds had elapsed.

After that initial expansion, things slowed but never stopped expanding.

The Big Bang Theory has survived because it continues to explain so much of what we observe in our universe. However, it doesn’t explain everything, and there are observations that will require modifications to the theory.

One thing that still can’t be explained is the imbalance between matter and antimatter, which I’ve covered in a previous episode. There had to be some reason for the imbalance, and there isn’t really any proof yet to explain the imbalance one way or another.

Another wrench throwien into things are recent observations made by the James Webb Space Telescope. The Webb can see across almost the entire observable universe, which means observing some of the oldest galaxies in the universe.

What they’ve found is that there are galaxies that are far larger and older than the current theory suggests should be possible.

Of course, there is also the problem of dark matter and dark energy, which may or may not even exist, and gravitational anomalies that may explain it.

None of this means that the Big Bang Theory needs to be completely overturned, but it does mean that as we discover more, the theory needs to be modified to fit the new discoveries.

The Big Bang Theory has proven to be a successful explanation for the observations we’ve made across multiple fields in physics.

Even if new discoveries can be fit into the theory, there will still be things that will be beyond the limits of our understanding, and that is just the nature of the universe.