How the Universe we know came into existence? How do we explain the origin of the Universe? Well, I am sure that most of you will say “the big bang” and rightfully so, every other piece of evidence and data collected over the years by the cosmologists point towards the one possibility that it all might have started with a big bang after the singularity and cosmic inflation.
But wait, there is more. In the late 1920s, scientist Georges Lemaître began working on the idea that if the Universe is expanding (based on Hubble’s discovery), then it could be traced back to the time where it all started. Soon the entire scientific community was debating on the possible origin of the Universe.
Since then, many prominent theories have risen to the occasion through which various researchers tried to explain what might have happened in the past. Sure the big bang was and still is the best explanation that anyone can provide about the ultimate past of the Universe, but theories like steady-state Universe also drew attention from many.
No matter how convincing the big bang theory looks to one person, it’s not satisfactory to all. So here, we discussed 7 of the most popular alternatives of the Big Bang, explaining the origin of the Universe.
7. Theory of Eternal Inflation
Again, the big bang is the explosion, which kick-started the cosmic inflation. So this makes the theory of eternal inflation an extension of the big bang itself, at least to some extent. According to this theory, the phase where the Universe inflates will go on forever, throughout the larger parts of the Universe.
This leads to a multiverse where space is broken and divided into huge bubbles, with each bubble having different properties. The very first example of such a universe was provided by Paul Steinhardt, who is sometimes considered as the father of the inflationary model.
In 2007, Alan Guth, a cosmologist and theoretical physicist, stated in his paper “Eternal inflation and its implications” that even-though the inflation is eternal to the future, it is not so in the past. Guth’s work is crucial as it not only demonstrated how eternal inflation might be the likely outcome of the inflation, but it also tabulated whatever was known about the matter during that time.
6. Conformal Cyclic Model
Well, cyclic or oscillating models of the Universe first came into the spotlight in the early 1900s, when it was considered by various scientists and most notably Albert Einstein in 1930. Right now, there are four different variations of the cyclic model of the Universe and one of which is the Conformal Cyclic Cosmology devised by Roger Penrose.
The general idea behind the theory is that the big bang was not the beginning of the Universe rather than a period of transition. In other terms, the theory connects copies of FLRW spacetimes, which is equivalent to Einstein’s equations of general relativity, one on top of the other, where each represents a big bang and an infinite expansion after that.
Back in 2010, Penrose and his colleague Vahe Gurzadyan claimed to have discovered an excess of concentric circles during the study of cosmic microwave background compared to that of the standard Lambda-CDM model. However, these claims are still not proven and have been disputed among the scientific community.
5. Black Hole Mirage
Another alternative of the Big Bang theory is that the Universe actually emerged from a collapsing higher-dimensional star. In a recent study, a group of cosmologists hypothesized that the Universe might have been formed from the cosmic debris ejected when a four-dimensional star collapsed into a hyper-black hole. If this is the case, then it would largely explain why the Universe seems so uniform in all the directions.
According to the standard model of the Big Bang, it all started from the singularity, an infinitely dense and hot point which was followed by a bang. But what cosmologists failed to explain is what triggered this explosion. At present, all the understandings of physics, all known theories are unable to explain what happened that particular moment.
Another mystery is that how a super violent event like the Big Bang would have left behind a Universe that has a uniform temperature because there doesn’t seem to have been enough time since the cosmic explosion for the Universe to attain temperature equilibrium.
The team, including Niayesh Afshordi, an astrophysicist, came up with this idea while studying a proposal made by another group of physicists back in the year 2000. That model suggested that our 3D Universe is a membrane that floats through a four-dimensional “bulk universe“.
So the team figured out if the “bulk universe” has its own 4D stars, then after their collapse, it is possible that they form 4D black holes. In three dimensional space, it takes the 2-dimensional surface to form an event horizon (in reference to a black hole), so it would be a 3-dimensional object for a 4D black hole, which they named hypersphere.
When the team simulated the collapse of a 4D star, they discovered that the ejected material from that star is likely to form a 3D membrane around that 3D event horizon and expand slowly. Based on this, Afshordi and his team theorized that the Universe might just be a part of the membrane, and the cosmic growth is the expansion of the membrane.
4. Plasma Universe Theory
Image Courtesy: Luc Viatour
While our current understanding of the Universe holds gravity as the main force behind almost everything, a new approach, which is also known as plasma cosmology, instead puts much greater emphasis on electromagnetism. Although there are many different flavors of this theory, some core features are the same throughout.
The plasma universe theory basically suggests that everything in the Universe, i.e., the Sun, stars, comet tails, all are a result of some electrical processes.
Different plasma theories state that the space we observe is filled with enormous filaments of electrons and ions, and these are distorted due to the strong electromagnetic forces, thus giving birth to huge physical matters like galaxies. Firm believers of this theory generally assume that the Universe is actually infinite in age and size.
3. Slow Freeze Theory
Image Courtesy: NASA
After decades of research and assumptions, cosmologists all over the world now finally agree that at the beginning, all matter exploded from a singularity before the dense and the hot Universe ballooned dramatically in an event called cosmic inflation. Then it continued to expand slowly for billions of years.
But the event of singularity possesses many theoretical challenges, where physicists are not able to relate it to the quantum mechanics and the general relativity, our best explanation of nature’s forces to date.
So to solve this, physicist Christof Wetterich from the Heidelberg University published a paper, where he argued that the Universe we know might have actually begun as cold and sparse, activating from a freeze after a long long time.
In his theory, he suggested that the fundamental particles became heavier over the course of time, while the gravity weakened. Suppose if the masses of the particles have been increasing, the radiation from the early Universe could deceive it to be hotter, and the objects in space could appear to be moving away from each other even if they weren’t in actuality.
In his paper, he also said that his intention is not to discard the standard model of the Big Bang as both the slow freeze and the Big Bang are rather consistent in major observations.
Science and religion have been the best of enemies since the time of Nicolaus Copernicus and Galileo. There is perhaps no room for religion when we talk about science and vice-versa, but in this case, we can make one exception. Creation theories in Hindu mythology have been considered one of the most ancient and significant of all other religious counterparts.
Over the years, several prominent cosmologists and physicists, including Carl Sagan and Niels Bohr have admired the Hindu mythology and noted that timescales and theories in Hindu astronomy appear to closely correspond to those of modern scientific theories.
According to Carl Sagan, the Hindu religion is the only religion whose universal timescale is almost identical to that of the modern astronomy. It spans from an ordinary day to the day of Brahma (the creator), which is 8.64 billion years old. Almost double the age of the Solar System and half of the Universe.
Bindu Visphot is a Sanskrit term that literally means “point-explosion,” which we can easily relate to the Big Bang. According to the Hindu Vedas, the Bindu-Visphot produced the sound “OM”, which have several different meanings, but point towards the one thing only and that’s the ultimate reality. This sound of “om” has been interpreted by many as the early disturbances detected by the cosmologists in the form of Background Cosmic Radiation.
1. Steady State Universe
Basically, the Steady-State theory suggests that the Universe doesn’t have any beginning, and it’s eternal. The idea of steady-state was first propounded in 1948 by three cosmologists Hermann Bondi, Fred Hoyle, and Thomas Gold. It was derived from the perfect cosmological principle, which itself states that the Universe is the same no matter where you look, and it will always be the same.
In steady-state, the non-stop creation of matter causes the density of matter present in the expanding Universe to remain unchanged. This way, this theory closely attached to the perfect cosmological principle, where the observable Universe is just the same from anywhere, anytime. Thus it doesn’t have any beginning or end (achieved when the matter is continuously generated to cease the density of the Universe).
In the first half of the 20th century, the steady-state Universe was the most popular universal theory alongside the big bang but was discarded in the 1960s, after the discovery of cosmic microwave background.