The Big Bang idea, first proposed roughly a century ago, is the only remaining theory for the origin of the universe. It is consistent with all of the evidence, including the expansion of the universe, the emergence of light elements, the presence of the cosmic microwave background, and the growth of the cosmic web.
The universe started as a small, hot, dense dot that slowly expanded into the vastness we see today over the course of 13.8 billion years. According to Big Bang theory, this is how the universe began.
Breaking some eggs is necessary to produce the ultimate in cosmic breakfasts. And the Big Bang hypothesis has had to contend with a number of formidable opponents throughout the years. Let’s take a closer look at those other options or why they didn’t really work out.
Infinite space and time
Scientists (and basically everyone who thinks about it for any duration of time) used to agree that the cosmos was just… the way things were before the Big Bang hypothesis was conceived. And it’s been like way since time immemorial. And it will always be. There may have been a creation event in the distant past, depending on your religious beliefs, but that creation was of a world that looked and behaved much as it does now.
Even when the odd comet or star explosion occurred, the cosmos as a whole just was. On a wide scale at least, it was the same as it had been from the beginning of time.
When astronomer Edwin Hubble realised that the cosmos was expanding, everything changed. Suddenly, the notion of an everlasting universe was thrown into disarray. After all, if the cosmos is ever expanding, the universe would always be different in the past from the present.
The data demonstrated that the cosmos we inhabit is dynamic and ever-changing.
Although the universe is expanding, many scientists remained sceptical of the Big Bang theory, despite this fact. The steady state model, initially presented by astronomer Fred Hoyle, was the most popular hypothesis in the early 20th century.
There is constantly fresh matter being created in the vacuum to replace the expanding cosmos in the steady state scenario. In other words, the universe expands while maintaining its density, preserving the eternal universe’s basic themes. Under other words, the cosmos is active in the steady state model, yet it remains unchanged over long durations.
With the discovery of quasars and the cosmic microwave background, the steady state was brought to a halt (CMB). Quasars are very brilliant radio emitters found only in the far reaches of the cosmos, whereas the cosmic microwave background (CMB) is a radiation field that encompasses us completely. These are simple to explain in the Big Bang picture: In an earlier time in cosmic history, when things were different, the light comes from. However, under the steady state hypothesis, the early cosmos should resemble the present world.
Hannes Alfvén, a Nobel Prize-winning physicist, has emerged as a new challenger to question the Big Bang. Magnetohydrodynamic theory was created by Alfvén, who was a master of understanding the forces in electrically charged gases, known as plasmas.
We should look at what we see in the cosmos as the result of electromagnetism rather than gravity, according to Alfvén. Solar system evolution, star formation, and the expansion of the cosmos were all part of this.
According to Alfvén, the cosmos is made up of massive concentrations of matter and antimatter that are perpetually engaged in conflict. CMB light is formed when these bubbles collide, he hypothesised, producing in our perception of an expanding cosmos.
For Alfvén, there is no way to make an electric universe fit all the evidence, including Hubble’s law. General relativity and the expansion of space explain the relationship between galaxy distance and the speed at which they recede for neighbouring galaxies. All galaxies faded at the same pace in Alfvén’s model. Hannes, I’m really sorry for whatever inconvenience this has caused you.
The Cosmology of the Mixmaster
No scientific hypothesis is flawless, including the Big Bang theory. The smoothness of the cosmos at enormous scales is a perplexing phenomenon. The temperature of the cosmos is essentially the same in regions that are incredibly far apart. To make things fair in the early world, there simply wasn’t enough time.
In 1969, physicist Charles Misner came up with a solution to the horizon problem known as mixmaster cosmology (yes, named after the brand of kitchen blenders). The early cosmos in a mixmaster world was utterly disorganised, with space sloshing back and forth ceaselessly. Material was jumbled up at microscopic sizes (leading to formations like galaxies) and evened out at big scales by this chaotic process (to make the overall universe homogenous).
Despite their catchy moniker, mixmaster models were unable to explain the horizon problem due to mathematical complications. Inflation, on the other hand, was able to provide a more straightforward explanation.
The Big Bang has a beginning, which is one of the most difficult concepts to grasp. Before and after the cosmos existed, there were two distinct periods of time. Attempts to explain the origins of the universe using the Big Bang concept have been made numerous times over the years, but none of them have been able to describe the genuine beginning of the universe.
If you replace the Big Bang with another unique incident, you haven’t truly changed anything. The cyclic models, in essence, portray an infinite cosmos, but with more stages.
Every single one of these theories relies heavily on speculative science. It’s possible that “branes” from higher dimensions continually merging, causing fresh Big Bangs. It’s also possible that inflation never stops, in which case a new universe is just around the bend. It’s possible that the universe may someday collapse, shrink to a tiny quantum level, and then rebound back to its original size.
But none of these ideas can explain the fact that our universe is expanding at an ever-increasing rate, with no sign of halting. It appears that the universe is a one-time event.
The Big Bang must be included in any comprehensive picture of the universe since it describes all of the data. As a result, the Big Bang will always triumph in the end.