10 Things You Really Should Know About The Big Bang
Unless you grew up in the back woods with no access to books, TV or social media the chances are that you have heard of ‘The Big Bang’. We are not talking about the TV show (although we might do a list on that another time!), we are talking about the cosmological event that took place that started everything. The chances are that you do know that the phrase refers to the moment that our universe and everything in it came into being. Other than that the chances are that you don’t know all that much about it. Just about every book, article or TV program discussing ‘The Big Bang’ starts out clear and easy to understand but then, within minutes, descends into complex discussions on astrophysics. Before you know it the topic is completely beyond all but a PhD working at the Jet Propulsion Laboratory.
It is easy to dismiss complex phenomenon, particularly when they are esoteric in nature and seem irrelevant to our daily lives. But ‘The Big Bang’ is important. Every particle of matter that ever was came into being at that time, in a sense we were born all those billions of years ago. As the founding moment of our very existence it is important that we all understand the basic information about ‘The Big Bang’ and why it is important in our daily lives. With that in mind we have taken the time to cut through the complex physics and distil down to basic principles the 10 most important things you need to know about ‘The Big Bang’.
10The Big Bang Is Not The Only Expanding Universe Theory
Since ancient times philosophers have mused on the origins of the universe and considered whether it was finite or infinite. Once the Abrahamic religions became influential theories tended to support the existence of a finite universe as explained in Genesis. The first attempt to explain the existence of the Universe according to a set of defined physical rules came in 1225 when an English Theologian postulated that the universe was formed in an explosion which resulted in the stars nesting in spheres around the earth, rather like a set of Russian nesting dolls. Discussions continued and by the 17th Century Isaac Newton described a universe full of movement. A century later and Edgar Allan Poe put the understanding of the day into verse to describe a universe in a constant state of expansion and contraction.
By the 20th Century our telescopes were strong enough to enable scientists to observe that galaxies in the night sky were moving away from the Earth, around the same time Einstein’s Theory of Relativity showed that the universe could not be static. By the 1930s Lemaitre started speaking of the ‘primitive explosion’ or ‘Cosmic Egg’, a theory which later became known as ‘The Big Bang’. Not all scientists were happy to accept this theory, however (see below). Fred Hoyle proposed an alternative, the ‘Steady State Theory’ . This was predicated on the idea that the universe remained more or less the same at any point of time as new matter was created as the galaxies moved apart.
9The Name ‘The Big Bang’ Was Meant To Discredit The Theory
During the 1940s and 50s the scientific community was divided between the acceptance of ‘The Big Bang’ and ‘The Steady State’. Fred Hoyle, the major proponent of ‘The Steady State’ Theory was the host of a popular BBC radio program on Astronomy, heard throughout Britain and the Commonwealth it was also broadcast in the US. In one program discussing the origins of the universe he used the term ‘The Big Bang’ to distinguish Lemaitre’s primitive explosion from his own ‘Steady State’ theory. While Hoyle himself claims that this phrase was not meant to be pejorative or to discredit the theory it was widely regarded as such at the time. He continued to use the phrase both on the radio and in print and, because it was both catchy and descriptive, it stuck.
8The Big Bang Theory Was, At First, Considered An Attempt To Impose Religion On Science
The first book of the Bible, The Book of Genesis (see link above) tells us that the Universe came into being at the will of God, one moment it did not exist and then it did. In the early decades of the 20th Century most scientists involved in the study of the origins of the Universe favored a ‘Steady State’ agreeing with ancient philosophers that the universe could did not have a point of origin but was, instead, infinite and eternal. Lemaitre, the astronomer who first proposed ‘The Big Bang’ was not only a scientist but also a Roman Catholic Priest. His colleagues saw his proposal as an attempt to impose his religious beliefs on to scientific principles and called his theory ‘repugnant’. Even Einstein was initially unhappy with the theory although he did accept that his own model could not be accurate all the way into the distant past. He later graciously accepted his mistake and nominated Lemaitre for prestigious awards and it is thought that he said, of ‘The Big Bang’ that it was ‘the most beautiful and satisfactory explanation of creation to which I have ever listened’.
As telescopes became more and more powerful Lemaitre’s theory was vindicated and is, at present, accepted as the most accurate description of the origin of the Universe.
7Scientists Initially Attributed The Radio Signal Given Off By The Big Bang To Pigeons!
These days we can see through the Universe. At night we look up through the atmosphere and see the stars of the Milky Way laid out before us and even beyond to distant galaxies such as Andromeda. It was not always so. Just after ‘The Big Bang’ the Universe was smaller, hotter and a dense fog of plasma. Things changed about 380,000 years after ‘The Big Bang’, the Universe had expanded and cooled enough for atoms to come into being, as they could no longer absorb the radiation of the expanding Universe it became transparent (at least within a defined radius of a set point), this change released a huge amount of light.
Even today, more than 13 billion years later, ultra-sensitive radio telescopes allow us to see back to that moment of change to transparency, to the oldest light in the Universe. Known as Cosmic Microwave Background Radiation or CMB, this light is detected as a radio signal set at a constant frequency that saturates the sky, emanating from every corner of the universe at once. When this radio signal was first discovered in 1964 scientists Penzias and Wilson thought that they were reading radio interference. They did everything they could think of to get rid of the noise including clearing away a nest of pigeons who had made the antenna their home. When even that did not work they realized they had been listening to the birth of the Universe and a few years later were honored for their research, and pigeon cleaning skills, with a Nobel Prize.
6All the Hydrogen and Helium In The Universe Was Formed In ‘The Big Bang’
Hydrogen and Helium are the lightest of all the elements. While they form only a minuscule percentage (less than 1%) of all elements on Earth they are abundant throughout the Universe, together accounting for 98% of all the mass of the Universe.
In the seconds after ‘The Big Bang’ the Universe was too hot to allow atoms, or even nuclei to form. Instead the Universe contained almost equal amounts of matter and antimatter, exotic particles such as quarks and anti-quarks annihilated themselves back into energy. As the Universe cooled and expanded there was no longer enough energy to allow this annihilation to occur and the Universe was left with an almost equal amount of protons and neutrons, the precursors of atoms. After, it is thought, about three minutes the Universe was cool enough to allow those neutrons and protons to condense out into Hydrogen and Helium (and a very small amount of lithium), much like water vapor turns to water droplets. Even then, these hydrogen and helium atoms were not stable but there was not enough energy to form larger particles. It was only after a billion years that the Universe had cooled enough to allow the formation of stable hydrogen and helium and for clouds of those gasses to gather together into huge, dense, proto-stars where they began to initiate nuclear reactions. It was from these reactions that all other elements were created.
5‘The Big Bang’ Caused Objects In The Universe To Move Faster Than The Speed Of Light
Much as many of us like to indulge in the popular science fantasy of faster than light travel we all know that the speed of light (300 million meters per second) is both a constant (it never changes) and an absolute (nothing can go faster). We know the time it takes the light from the Sun to hit the Earth and we know how long it takes light from neighboring stars to get to us too. We know that, because of this speed of light, when we gaze up at the heavens we are travelling back in time. When we look at the constellation, Cygnus, we see light that left the bright star Deneb over 1,000 years ago. Even looking on our closest neighbors, Proxima and Alpha Centauri, means looking on light that shone from those stars over 4 years ago.
Knowing all this it comes as a shock to think that anything could move faster than the speed of light and yet, in the moments after the Big Bang, The Universe did. In the initial milliseconds after the explosion The Universe expanded incredibly fast, a period known as inflation. In that short period the Universe doubled in size multiple times until it had expanded from the initial singularity to something around the size of a small car. If that does not seem very impressive, consider that this expansion took place in less than one trillionth of a trillionth of a second or, to all intents and purposes, instantaneously, at least from our perspective. Things slowed down after that although the Universe continued, and still continues, to expand.
So how come The Universe was able to expand at such high speeds? It turns out that the speed of light is a constant for objects travelling within space and time but is not a limiting factor to space time itself.
4The Big Bang Made The Universe Expand, It Does Not Mean Other Galaxies Are Moving Away From Ours
Because of the name it is tempting to think of ‘The Big Bang’ as a sort of genesis bomb, exploding in a center point and hurling all matter and creation outward in an ever expanding blast radius. This is a fundamentally flawed analysis.
As discussed in point 5 (above) The Universe inflated and expanded following the Big Bang, as stars and galaxies were formed the distances between them started to grow but those galaxies were and are not moving in and of themselves, there is no blast wave for them to ride. ‘The Big Bang’ did not happen at one central point, we could not (even were our technology to allow) travel to the center of The Universe to see the point where it all began. ‘The Big Bang’ happened everywhere, all at once, an explosion of space not in space. The most accurate analogy is the inflation of a balloon. As the balloon is inflated the effect of that inflation is felt and seen on every part of the surface at the same time. Individual points on the balloon remain the same but the distance between them grows.
Of course, given that this topic considers astronomical physics, there are exceptions that cause confusion. Some galaxies are moving, in fact Andromeda, the closest neighbor to our own Milky Way galaxy is moving towards us because the two galaxies are close enough to exert a gravitational influence on each other. When we consider other, more distant, galaxies, however, they are moving away from us because of expansion and not because of any other reason.
3‘The Big Bang’ Does Not Mean That There Was Nothing Before It Happened
It is tempting, particularly for laymen, to believe that the very existence of ‘The Big Bang’ means that nothing existed before it took place. We know, after all, that 13.8 billion years ago, the largest explosion in history took place and that, as they say, is that.
That may not, however, be completely correct, after all the explosion must have come from somewhere, have had some cause… We do not yet have technology or knowledge sophisticated enough to allow us to view events before ‘The Big Bang’ but scientists have a number of competing theories. These include that ‘The Big Bang’ happened within a black hole created by the collapse of an earlier universe or that our Universe sprang into existence within a larger Multiverse (perhaps itself started by its own big bang and so on and so forth). Of course for us, in our Universe, time or what we consider Real Time as opposed to Imaginary Time, started at ‘The Big Bang’, eminent scientists such as Stephen Hawking consider that it is pointless considering what happened before then as the event was the beginning of time as we know it
2The Expansion Caused By ‘The Big Bang’ Means That Eventually We Will Not Be Able To See Any Other Galaxies
Look beyond the beautiful stars of our own Milky Way, our domestic back yard and we can see many other galaxies full of stars of their own. Even with the naked eye we can see our neighboring galaxies, Andromeda and the Large and Small Magellanic Clouds, upgrade to even a small telescope and many more suddenly become visible. Because, of course, The Universe is expanding and because this rate of expansion is increasing, these galaxies are moving farther and farther away from us (see point 4 above).
The farthest point that we are able to view with all our modern technology, is called The Hubble Distance. This is equivalent to 14 billion light years. Of course ‘The Big Bang’ happened almost 14 million years ago so we should still be able to see the entire Universe, right? Wrong! The expansion of the Universe since the Big Bang means that it is much larger than 14 Billion Light Years of distance. The mechanics of the expansion, discussed above, and the ability for space time to expand faster than the speed of light means that the Universe beyond the Hubble Distance is expanding faster than the speed of light therefore light from those regions cannot reach us. Once the expansion of the Universe moves our neighboring galaxies beyond that distance we will no longer be able to see them.
1The Universe Is Flat
For centuries debate ranged as to the nature of the Earth, was it flat or round, was it the center of the Universe. These days of course we all know that the Earth is round and that far from sitting at the center of everything it is a small planet orbiting a rather average sun in a rather average galaxy. The only thing that we know is special about the Earth is the existence of life but of course that might be terribly ordinary, we just don’t know one way or another.
Having been firmly put in our place over hundreds of years and now with all humanity subscribing to the round Earth reality over the flat Earth fiction we have pretty much all come to accept that the Universe is also anything but flat, after all when we look up into the night sky the heavens gaze back at us in glorious 3D with layer upon layer of stars (which makes us understand why mediaeval English theologians (see 10 above) thought the way they did) all at different distances and all at different angles. But… looks can be deceiving.
Scientists have come up with a number of explanations for the shape of the Universe, if it exceeds a specific density it would be finite but with no end. An analogy would be a sphere; the Earth is finite in size but we cannot walk off it, we simply return to the point at which we started. If the density of the Universe is less than a specific density it will be curved in the other direction, boundless and expand forever with no limitations. If the density of the Universe matches the critical density exactly it will be flat, it will therefore be infinite but the rate of expansion will gradually reduce to zero (but only after an infinite amount of time). The most recent measurements of density and of the CMB indicate that the Universe is likely to be flat.
But what does this mean in reality, given that we experience a 3 dimensional life? The explanation for a flat universe boils down to high school geometry: the Universe is flat because parallel lies do not meet and triangles formed from three points always have internal angles that add up to 180 Degrees..
Given all these difficult and confusing concepts it is not surprising that people find the astrophysical and cosmological aspects of ‘Big Bang’ theory confusing and inaccessible. The theory talks of a ‘Bang’ but it was not an explosion. It tells us that other galaxies are moving away from ours but they are not propelled and the theory even causes us to question absolutes that we thought we knew, telling us that the Universe is flat and that movement faster than the speed of light is possible.
The more we think about ‘The Big Bang’ the more difficult and mind bending the concepts appear to be, the thought that our Universe was created from the black hole that remained after the death of another or that we are living in but one Universe within a multiverse are ideas that we struggle with. The one thing we do know is that the story of our cosmic origins will never cease to surprise us. The sum total of human knowledge and abilities may not be expanding at the same rate as the Universe but what we know now dwarfs what we knew 100 years ago and what we discover in the next 100, whether in the field of cosmology or any other, will surprise us. After all, if the Universe is flat anything is possible!