Origin of the Universe
For so long as humans pondered on how the universe was created. Religiously, it is said that a higher and supreme being created this world. However, from a scientific point of view, the universe can be traced back all the way to an event called the Big Bang.
Hot, dense, tiny, powerful, etc, just a few attributes of the catastrophic yet necessary event that made this universe. Now the big bang is somewhat of a misconception of the event. The creation of the universe was neither big nor created a bang. Then what was it and why was it then coined with the term Big bang?
The Big bang was simply the point in time when all the matter in the universe was initially in a super-hot, super-dense state and expanded rapidly consequently cooling and forming what we see as the universe. The name was first coined by a man named Fred Hoyle on a 1949 radio broadcast where he was promoting his own theory of the creation of the universe called the Steady State theory (where all the matter in the universe came from an orderly tiny burst of matter or "mini bangs" everywhere). It is kind of ironic that the big bang was called so since he said it as a jab against the theory.
At the beginning matter and space were tightly packed then upon expansion, space expanded upon itself creating more space while matter just proliferated in the newly formed space.
Timeline of the Big bang
- Planck's Epoch (10^-43 seconds): This is the earliest known meaningful time. This is because it takes light the same amount of time to travel through Planck's length (10^-35m), the shortest measurable length (and also the size of the universe at this time) after which our laws of physics break down. The temperature of the universe at this time is about 10^32°C.
- Grand Unification Epoch (10^-43 seconds to 10^-36 seconds): This is the time where elementary particles (that is normal particles and antiparticles) are formed and the force of gravity separates from the remaining fundamental forces, which remains unified.
- Inflationary Epoch (10^-36 seconds to 10^-32 seconds): In this incredibly tiny timespan, the universe undergoes what is known as Cosmic inflation where it rapidly expands by a scale factor of 10^26 to a size of 10 centimeters.
- Electroweak Epoch (10^-32 seconds to 10^-12 seconds): Separation of the strong nuclear force from the weak nuclear force and electromagnetic force occurs. This results in the creation of some exotic particles (such as the bosons).
- Quark Epoch (10^-12 seconds to 10^-6 seconds): As the universe begins to cool to about 10^15°C, quarks, neutrinos, and electrons are formed. This is like a quark soup since the temperature is too hot for any particles to interact to form larger ones. There is then annihilation of quarks and antiquarks but due to a slight asymmetry where one in every billion pair of matter-antimatter pair survives (Baryogenesis), the race is won by normal matter. This is the reason why we see an abundance of baryonic matter ( normal matter) in the universe and almost no non-baryonic matter.
- Hadron Epoch (10^-6 seconds to 1 second): At this span of time, the universe has cooled to about a trillion degrees making it possible for quarks to combine to form hadrons. Hadrons are nuclear particles such as protons and neutrons. Now there is an extremely large number of permutations that could be made by quarks to form new particles but most of them are very unstable and have an immensely short lifespan. Massless neutrinos are also formed from the interaction of electrons and protons to form neutrons. This is the era where major subatomic particles are made.
As we know it, the universe is just a second old after all these occurrences. It is pretty outstanding that so much of our world was created in as little as the blink of an eye.
- Nucleosynthesis (1 second to 20 minutes): At this time, the universe has cooled off enough to allow nuclear fusion of protons and neutrons to form the basic elements we know ( Hydrogen, helium, and lithium). Though this thermonuclear reactions only happens for a short period of time as the universe's temperature falls below the threshold temperature.
- Photon Epoch ( 3 minutes to 240,000 years): This is also known as the Radiation domination era. The universe begins to cool even further and recombination and decoupling occur. Here electrons are captured by nuclei thereby neutralizing the universe. Since photons could only travel a very little distance due to interactions with other subatomic particles, this made the universe opaque. Upon neutralization, the universe becomes transparent and the photons which have been interacting with electrons and protons in an opaque baryonic soup are free to proliferate. These photons make up what is known as the Cosmic Background Radiation.
- The Dark Age (300,000 years to 150 million years): The universe is still dark and is dominated by a form of matter called Dark matter which till today has no definite explanation. It is the period after the formation of the first atoms and before the formation of the first stars.
- Re-ionization Epoch (150 million years to 1 billion years): Here the universe is re-ionized by the intense gamma-ray bursts of the Quasars formed during this era. The universe is then filled with ionized plasma.
- Stars and Galaxy Formation (300 million years till date): The primordial gases are then collected and compacted by the force of gravity (which is the strongest on large-scale processes but weakest on small-scale processes). These gases then collapse under the influence of gravity and are ignited to start thermonuclear reactions causing the formation of the very first stars. The first stars are supermassive stars with a very short lifespan and the amount of energy they radiate is nothing short of incredible. These stars are then gathered by the immense force of gravity and also the enigmatic dark matter to form clusters and superclusters which results in galaxy formation.
- Solar System Formation ( 8.5 billion years to 9 billion years): The Sun was actually formed at a very late period. It them captured matter in the form of rocky bodies (terrestrial planets) and gaseous bodies (gas Giants). This is the present world we now observe.
From a chaotic series of events to an orderliness which is ever so suitable for life. The current age of the observable universe is about 13.7 billion years and it keeps expanding. Yes, space expands upon itself to create new space.
Now you may wonder, what happened before the big bang?
Well, nothing! Literally nothing. This is because not only matter was encased in the super-hot, super-dense state during the big bang but also all its properties such as time, light, length, mass, etc. So asking what happened before the big bang is as meaningless as asking what happened before everything was created. Nothing was there. The big bang is the first point of creation. It is the very beginning of the world.
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