How did the universe form? How did it become the seemingly infinite place we know of today? These are questions that have been driving philosophers and scholars crazy since the beginning of time, and some wild and pretty interesting stories have been discovered.
The Big Bang Theory is the most well known explanation about how the universe began. As a summary, it says the universe as we know it started with an infinitely hot and dense hypothetical point, then somewhat inflated: first at unimaginable speed, and then at a more measurable rate, over the next 13.8 billion years to the cosmos that we know today.
Current instruments don’t allow astronomers to observe what had happened back at the universe’s birth, but much of what we understand about the Big Bang Theory comes from mathematical models and equations. Astronomers can, however, see the “echo” of the expansion through a phenomenon known as the cosmic microwave background.
What does the theory say?
So, scientists hypothesise that 13.8 billion years ago, there was an infinitely dense and small point of singularity with an infinite amount of heat. Then suddenly explosive expansion began which expanded the universe out faster than the speed of light. This was a period of cosmic expansion, which only lasted a few fractions of a second; about 10-32 of a second, according to physicist Alan Guth’s 1980 theory.
However, after the Universe formed, lasting from approximately 10-43 to 10-11 seconds after the Big Bang, are the subject of extensive speculation. Given that the laws of physics as we know them could not have existed at this time, it is difficult to conclude how the Universe could have been governed. What’s more, experiments that can create the kinds of energies invol ved have not yet been conducted. Still, many theories prevail as to what took place in this initial instant in time, many of which are compatible.
The earliest known period of the universe. This is between 0 seconds and 10-43 seconds after the Big Bang. At this time, all matter was condensed on a single point of infinite density and extreme heat. During this period, it is believed that the quantum effects of gravity dominated physical interactions and that no other physical forces were of equal strength (and of course not of greater strength) to gravitation. Due to the extreme heat and density of matter, the state of the universe was highly unstable. It thus began to expand and cool, leading to the manifestation of the fundamental forces of physics.
The Inflation Epoch began after the creation of the first fundamental particles in the Universe, lasting from 10-32 seconds in Planck time to an unknown point. Most cosmological models suggest that the Universe at this point was filled homogeneously with a high-energy density, and that the incredibly high temperatures and pressure gave rise to rapid expansion and cooling.
This began at 10-37 seconds, where the phase transition that caused the separation of forces also led to a period where the universe grew exponentially. It was also at this point in time that baryogenesis occurred, which refers to a hypothetical event where temperatures were so high that the random motions of particles occurred at relativistic speeds.
As a result of this, particle–antiparticle pairs of all kinds were being continuously created and destroyed in collisions, which is believed to have led to the predominance of matter over antimatter in the present universe. From this point onward, the Universe began to cool and matter formed.
As the universe continued to decrease in density and temperature, the energy of each particle began to decrease and phase transitions continued until the fundamental forces of physics and elementary particles changed into their present form. Since particle energies would have dropped to values that can be obtained by particle physics experiments, this period onward is subject to less speculation.
Over the course of the several billion years that followed, the slightly denser regions of the distributed matter of the Universe began to become gravitationally attracted to each other. They therefore grew even denser, forming gas clouds, stars, galaxies, and the other astronomical structures that we regularly observe today.
This is what is known as the Structure Epoch, since it was during this time that the modern Universe began to take shape. This consists of visible matter distributed in structures of various sizes, ranging from stars and planets to galaxies, galaxy clusters, and superclusters – where matter is concentrated – that are separated by enormous gulfs containing few galaxies.
Today, cosmologists have fairly precise measurements of many of the parameters of the Big Bang model, not to mention the age of the Universe itself. And it all began with the noted observation that massive stellar objects, many light years distant, were slowly moving away from us. And while we still are not sure how it will all end, we do know that on a cosmological scale, that there isn’t long left!
A quote to end off with…
“On the big bang theory: For every one billion particles of antimatter there were one billion and one particles of matter. And when mutual annihilation was complete, one billionth remained: and that is our present universe.”Albert Einstein