There is no doubt that the Big Bang model of cosmology is one of the most widely accepted theories that explain the origin of the universe. However, it would be inappropriate to say that the entire world agrees with this theory because there have been disagreements even in the scientific community.
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Scientific ideas are always changing, based on new evidence. The universe is about 13.8 billion years old, while humans have only been on earth for 800,000 years, and the Big Bang theory was propounded only about 100 years ago. Although the available scientific evidence supports the Big Bang model and refutes other theories, a new model may some day be proposed which provides an even better fit.
In this article, we will discuss other possibilities that have been proposed as alternatives to the Big Bang model.
1. Steady State Universe
One of the most popular theories that once stood against the Big Bang theory is the Steady State Universe theory. This theory directly contradicted the Big Bang theory by stating that the Universe doesn’t have a beginning, nor does it have an end. Instead, it is constantly expanding, however, the overall density stays the same, or in other words, it looks the same always.
The galaxies, planets, and other forms of matter are always being created, and since the density is the same, the old ones are becoming unobservable with new creations. This theory was proposed by Sir James Jeans in 1920 and was re-established in 1948 by Hermann Bondi and Thomas Gold.
The late cosmologist Geoffrey Burbidge championed the Steady State cosmology early in his career and was one of the last serious cosmologists to refuse to abandon Steady State, even after the evidence disproved it. Instead, he came up with an oscillating-universe model, which incorporated many small big bangs. So, he accepted the Big Bang, just in a slightly different form.
2. Bouncing Cosmology
In the Big Bang model, the universe expanded from a single point of almost infinite gravity and density, and it kept expanding. This is called the inflationary model.
The Bouncing Cosmology, or Big Bounce, model agrees with the rapid expansion of the universe. However, this theory states that the universe has been undergoing a state of expansion and contraction, one following the other cyclically, bouncing each time it shrinks to a certain size. Others propose that the cosmos only bounced once. In this model, the Universe had been contracting before the bounce, since the infinite past, and it will expand forever after.
This theory was first propounded by Silva Neves in a paper published in the journal General Relativity and Gravitation. Silva Neves is a researcher at the Mathematics, Statistics & Scientific Computation Institute (IMECC-UNICAMP) of the University of Campinas, Brazil.
3. Plasma Universe (the Electric Universe theory)
In the Electric Universe theory, gravity takes a backseat while the main focus shifts to plasma and electromagnetism. In this theory, plasma is considered to be an integral part of cosmological events and to the working of the universe itself. The theory proposes that electric currents that flow along plasma filaments shape and power galaxies. The currents stream into stars, powering them like fluorescent bulbs. They induce the births of planets.
The Electric Universe theory was first proposed by Hannes Alfvén in the 1930s. Alfvén argued that if plasma pervaded the universe, it could then carry electric currents capable of generating a galactic magnetic field. He later won a Nobel Prize for his work in magnetohydrodynamics.
There is absolutely no evidence for the Electric Universe theory, and it does not even meet the definition of theory, as it cannot be used to make predictions about natural events or phenomena that have not yet been observed. It has been popularized recently by a number of lay-scientists in search of a simpler way to explain the Universe.
4. The Black Hole theory
The Black Hole theory states that our universe originated from a black hole present in another universe. Hence, we are living beyond its event horizon.
This theory has been around for some time. The researchers at the Perimeter University presented a paper detailing how black holes can be considered to be the origin of our universe. In a different version, studied recently by theoretical physicist Nikodem Poplawski at Indiana University, the observable universe is the interior of a black hole existing as one of possibly many inside a larger parent universe, or multiverse.
In this regard, we can say that behind every black hole lies a new universe. Since we cannot cross the event horizon of a black hole, there is likely no way to prove or disprove this theory.
5. Is our universe a simulation?
One of the more popular-culture questions about our universe recently was whether we all are living in a simulation. This idea got mainstream attention from movies like The Matrix, and off-the-cuff comments by Elon Musk, who stated in an interview that it could be entirely possible.
Scientists began to work on the same idea and the results show that our universe isn’t created by a computer program. The study was done by theoretical physicists from the Oxford University in the U.K.
The researchers looked into the possibility of creating a computer that can compute everything in this universe. And, this hypothetical computer must be powerful enough to calculate the motion of every particle in this world.
Their conclusions were out of this world! For the computer to even record the data of a few electrons, its memory will require more atoms than what’s available in the universe, and with the addition of every few particles, the complexity goes up exponentially.
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Hence, it is probably safe to say that we are not located in some alien hard drive.
The Big Bang theory still stands as the most widely accepted explanation for the origin of the universe. However, we must also understand that nothing in science is forever.
Things can always change and new information can come in. Yes, the Big Bang model is not completely proven, but at the moment, it is the only theory that explains the available scientific evidence and observations.