Look at the world around you! Haven’t you ever stopped to wonder how all of this started? How the world as we know it formed? This question has existed for almost as long as humanity has existed, and many people tried to answer this question with varying results. After some stumbling that involved assigning the credit of the creation of the universe to a God or some other supernatural deity, in the 13th century, Siger of Brabant suggested that the universe was eternal. Although this idea was condemned by the church in 1277, it took root, and would not be challenged until the 20th century. The model that is accepted right now, like all good things, involves a bang. 😉
The Big Bang model is often misunderstood, and many consider it to be something similar to an explosion in an empty space. This is perhaps due to the name, “The Big Bang”, which makes it sound like a noisy and large explosion. In reality, rather than an explosion in space, you can consider it to be an expansion in space. We will look at more details about this model now.
Index
History and Initial Discoveries
It’s around 1920, and the universe is considered to be static and eternal. Einstein has finished work on his General Theory of Relativity, but something doesn’t seem right. Relativity implies that the universe is not stationary. Einstein tries to solve this by bringing in the cosmological constant. But of course, he had to abandon it once Edwin Hubble made his breakthrough.
Let us make one thing clear though. Hubble was standing on the shoulders of giants. Without the work of Vesto Slipher and Henrietta Swan Leavitt, Hubble’s work would not have been possible. But anyway, he made two key discoveries.
The first one, published in 1929, involves the discovery of the Andromeda Galaxy. He showed us that the universe was larger and more vast than we originally thought. The second, and more important one, was of red shift of various stars. Published as Hubble’s Law, he showed that the further away a galaxy or star is, the faster it moves away from us. This implies not just that the universe was not static, but that it was expanding.
If the universe was expanding, then it made sense that when you go back in time, the universe would have been a single point.
The Belgian physicist and cosmologist Georges Lemaître is often mentioned as the father of the physical big bang because he was the first to suggest that the universe must have started from a single point in 1931. But, ironically, the name “The Big Bang” itself was not coined by any of the supporters of this idea, but one of the dissenters, who used it to mock it. Meet Fred Hoyle.
He was strongly against the concept that all matter was created in a single ‘explosion’ and used the phrase mockingly. Even though his thoughts were rejected, his term caught on. As he himself put it in 1995, “Words are like harpoons. Once they go in, they are very hard to pull out”.
Observational Evidence Explained
After touching a little bit on the history of its discovery and nomenclature, let us look at some of the more prominent evidence (a little of which was already mentioned before) with a higher degree of detail.
Hubble’s Law
Hubble’s law, or the Hubble-Lemaitre law, is an observation in cosmology, consisting of two key points.
- Far away stars and galaxies seem to exhibit a red shift, that is, they seem to be moving away from us.
- The further away from us, a body is, the greater the red shift we observe from that body.
This was the observational evidence that pointed to an expanding universe.
Not only did this law imply that the universe was expanding, but it also implied that the rate of expansion is also increasing. The implication that the rate of expansion of the Universe is increasing is that the universe will not recycle or recreate itself. The idea long held was the matter was eternal because the universe would stop expanding and start contracting. This contraction would result in a new big bang starting the universe over again. The increase in the rate of expansion of Hubble’s Law makes this idea of an alternating expanding and contracting universe impossible.
CMB
CMB, or Cosmic Microwave Background, is electromagnetic radiation that is remnant from the early universe. Due to this, it is also known as relic radiation. It is faint cosmic background radiation filling all of space. Using an optical telescope, the space between galaxies is black. When the optical telescope is replaced by a sensitive radio wave detector, there’s a faint uniform glow detected. The most intense glow was observed in the microwave region.
This is the map of the CMB captured by Plank.
Although CMB points towards the big bang model, there seem to be certain anomalies. As seen from the map captured by Plank, the distribution of the CMB is not uniform, that is, there are warmer, slightly redder areas, and colder, bluer areas. This does not agree with the uniform expansion in all directions, as this would mean that the CMB was equally distributed everywhere.
CMB also provides insights with regards to the existence of dark matter and dark energy.
What is Big Bang Explained…
It is known now that the Big Bang model adequately explains the birth of the universe and how it all started. But beyond that, it also talks about some of the observations made and provides a framework with which to move ahead with future studies. In this section, we will glance at some of those points.
The first second after the bang
The first second after the big bang happened and the universe began, the temperature was around 5.5 Billion ℃. At this time, the universe was a giant soup of nucleons and electrons, and if we were there to witness it, we might not have been able to see any light. This is because the electrons flying around would scatter the light. This is the cause of the CMB we discussed before, the afterglow of the big bang.
Over time, however, the free electrons met up with nuclei and created neutral atoms. This allowed light to shine through about 380,000 years after the Big Bang.
The Age of the Universe
We have already discussed Plank’s map of CMB which was taken in 2013. This helped show that the universe was older than we originally thought. Originally, it was understood that the universe was 13.7 billion years old. But the data from Plank says that the age is actually 13.88 billion years old!
Faster Inflation and the Multiverse
The universe is not only expanding but getting faster as it inflates. This means that with time, nobody will be able to spot other galaxies from Earth or any other vantage point within our galaxy. So, if you wait long enough, eventually, a distant galaxy will reach the speed of light. What that means is that even light won’t be able to bridge the gap that’s being opened between that galaxy and us. There’s no way for extraterrestrials on that galaxy to communicate with us, to send any signals that will reach us, once their galaxy is moving faster than light relative to us.
Many scientists consider the universe to be one of many universes, a system of multiverses. Our universe may be one of many found in a bubble. It is not impossible, but much more research has to be done on this subject.
In the present time…
The beginning of all of the spacetime still remains shrouded in mystery to us. Although scientists have been slicing away layers of time to get to the beginning, we still have not been able to reach the singularity at t = 0. One of the major factors influencing this is the fact that the laws of nature start to break down the closer we approach 0, hence we have no framework to go about exploring and studying. We hope that many more discoveries will be made soon, and the question “how did this all begin?” will be answered, once and for all eternity.
