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--------------------- 2440 - BIG BANG to today?
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- We will start with the Big Bang as a moment in time, not a point in space. Specifically, it's the moment when time itself began, the instant from which all subsequent instants have been counted.
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- The Big Bang wasn't really an explosion but rather a period when the universe was extremely hot and dense and space began to expand outward in all directions at once.
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- The model of the Big Bang states that the universe was an infinitely small point of infinite density, that's just a way of saying that we don't quite know what was going on then. Mathematical infinities don't make sense in physics equations, so the Big Bang is really the point at which our current understanding of the universe breaks down.
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- The universe's next phase was to grow really big really fast. Within the first 0.000,000,000,000,000,000,000,000,000,0001 seconds after the Big Bang, the cosmos could have expanded exponentially in size, driving apart areas of the universe that had previously been in close contact.
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- This era, known as “cosmic inflation“, remains hypothetical, but cosmologists like the idea because it explains why far-flung regions of space appear so similar to one another, despite being separated by vast distances. So vast that even the speed of light would not allow the far flung regions to communicate with each other
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- A few milliseconds after the beginning of time, the early universe was really hot , between 7 trillion and 10 trillion degrees Fahrenheit. At such temperatures, elementary particles called quarks, which are normally bound tightly inside of protons and neutrons, wandered around freely.
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- Gluons, which carry a fundamental force known as the strong force, were mixed in with these quarks in a primordial fluid that permeated the cosmos. Researchers have managed to create similar conditions in particle accelerators on Earth. But the difficult-to-achieve state only ever lasted a few fractions of a second, in terrestrial atom smashers as well as in the early universe.
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- There was a lot of action in the next stage of time, which began around a few thousandths of a second after the Big Bang. As the cosmos expanded, it cooled, and soon conditions were cool enough to allow quarks to come together to form protons and neutrons.
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- One second after the Big Bang, the universe's density dropped enough that neutrinos, the lightest and least-interacting fundamental particle , could fly forward without hitting anything, creating what's known as the cosmic neutrino background, which scientists have yet to detect.
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- After the first 3 minutes of the universe's life, protons and neutrons fused together, forming an isotope of hydrogen called deuterium as well as helium and a tiny amount of the next-lightest element, lithium.
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- Once the temperature fell further, this process stopped. Finally, 380,000 years after the Big Bang, things were cool enough so that hydrogen and helium could combine with free electrons, creating the first neutral atoms.
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- Photons, which had previously run into the electrons, could now move without interference, creating the “cosmic microwave background” , that was first detected in 1965.
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- For a very long time, nothing in the universe gave off light. This period, which lasted around 100 million years, is known as the “Cosmic Dark Ages“. This epoch remains extremely difficult to study because astronomers' knowledge of the universe comes almost entirely from starlight. Without any stars, it's difficult to know what went on.
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- By around 180 million years after the Big Bang, hydrogen and helium began to collapse into large spheres, generating infernal temperatures in their cores that lit up into the first stars.
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- The universe entered a period known Reionization, because the hot photons radiated by early stars and galaxies broke neutral hydrogen atoms in interstellar space into protons and electrons, a process known as ionization.
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- Just how long reionization lasted is difficult to say. Because it occurred so early, its signals are obscured by later gas and dust, so the best scientists can say is that it was over by around 500 million years after the Big Bang.
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- Next small early galaxies began to merge together into larger galaxies and, around 1 billion years after the Big Bang, supermassive black holes formed in their centers. Bright quasars, which produce intense beacons of light that can be seen from 12 billion light-years away, turned on.
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- The universe continued to evolve over the next several billion years. Spots of higher density from the primordial universe gravitationally attracted matter to themselves. These slowly grew into galactic clusters and long strands of gas and dust, producing a beautiful filamentary cosmic web that can be seen today.
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- 4.5 billion years ago, in one particular galaxy, a cloud of gas collapsed down into yellow star with a system of rings around it. These rings coalesced into eight planets, plus various comets, asteroids, dwarf planets, and moons, forming a familiar stellar system. The planet third from the central star managed to either retain a lot of water after this process, or else comets later delivered a deluge of ice and water.
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- On that third, watery world, between 3.8 and 3.5 billion years ago, tiny, simple microbes came into existence. These life-forms emerged and evolved into sea monsters and gigantic, leaf-eating dinosaurs.
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- Eventually, about 200,000 years ago, along came upright creatures capable of marveling at our mysterious universe and discovering how the whole thing came to be.
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- Physicists and astronomers still don't quite know what's in store for the universe in the future.. That depends on the details of “dark energy“, a still-mysterious force driving apart the cosmos and whose properties have not been well measured.
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- In one possible future, the universe will continue to expand forever, long enough that all the stars in all the galaxies will have run out of fuel, and even black holes will evaporate into nothing, leaving behind a dead cosmos permeated by inert energy.
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- Or, another possibility, gravity will eventually overcome dark energy's expansionary force, pulling all matter back together in a sort of reverse Big Bang known as the Big Crunch.
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- Alternatively, dark energy could accelerate everything apart farther and farther from everything else, creating what's known as the Big Rip, in which the cosmos literally tears itself apart.
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- What will happen God only knows. When it happens I won’t be writing about.
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- See also other Reviews:
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- 2392 - the origins of existence.
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- 2360 - why the Big Bang is called the primeval atom?
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- 2352 - the birth of the Universe.
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- 2248 - from the Big Bang and back again.
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- 2242 - how can we understand it?
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- 2146 - astronomy is seeing history.
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- 2065 - Big Bang antimatter mystery.
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- September 3, 2019.
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--------------------- Tuesday, September 3, 2019 -------------------------
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