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“”Remember my son, the universe is a big place—perhaps the biggest!
The universe is everything!
All of space and time, and everything contained therein, is called the universe. This includes what we can see, what we can't see, what we know we can't see and what we don't know that we can't see. Even outside the universe is still part of the universe (though some think that our universe is in fact part of a larger "multiverse" meaning our concept of what constitutes the universe may have to change).
Where it came from nobody knows, except, of course, creationists who know that God was the one that made it (and specifically, their God). Where God came from, nobody knows. So we're all in the same boat, really.
It doesn't really matter that much, if you think about it.
 History of the universe
While some people think the universe was created over a six-day span around 6,000 to 10,000 years ago, the facts as measured show them to be painfully wrong, unless you subscribe to Last Thursdayism or a similar idea, but that is irrelevant conjecture here.
The universe seems to have formed approximately 13.8 billion years ago in a rapid and massive expansion of space-time called the Big Bang. After the initial inflation, the energetic particles cooled, and nuclear reactions created what was to become matter, which eventually clumped together to form galaxies and stars. Over the course of stellar evolution heavier elements were produced, leading to later generation stellar systems having planets sometimes largely made of those heavy elements - rocky planets.
Our solar system is roughly 4.5 billion years old, and features a handful of such rocky planets and smaller debris, along with four gas giants, which are largely composed of lighter elements and compounds. After a long period of cooling, our planet became hospitable to the evolution of the very complex organic compounds which are now known to be abundant in the universe. One collection of said compounds typed this not long ago, while another collection is now reading it.
 Future of the universe
The end of the universe is an interesting topic, hypothesized about by many people over the millennia.
 Human understanding
Until the modern "Scientific Age," the future of the universe was dominated by religious interpretations. By and large in Abrahamic and European-descended religions these involved some kind of ultimate "Day of Judgement" or universal catastrophe. Other faiths have envisaged some form of continued everlasting existence. Almost all of these ideas are initiated by an unwillingness to believe in personal discontinuation (death), and are still dealt out by the "priestly classes" as either comforts: "Don't worry about your condition here on Earth. Come the day you shall join the Lord in Heaven," or as threats: "If you don't obey the rules handed down then, come the day, you shall not be saved." Most of these scenarios depended on the self-aggrandizement (or cupidity!) of those in charge and the ignorance (or stupidity) of those having them lain upon them.
 The rise of science
As the educated began to explore the world around them and as education diffused downward in society, questions began to arise regarding the beginning and end of all things.
Envisaging a universe without a thinking, guiding force with a constant influence on events has, for most of recorded history, been a necessarily covert belief as such ideas have brought opprobrium and sanction upon anyone brave (or dumb) enough to express them. This is still the case in some parts of the world.
Natural philosophers, the precursors of today's scientists, began the description of the world about them in all the ancient civilizations of the world but very few dared to pronounce an atheistic worldview.
 Modern interpretation
The discovery by Edwin Hubble of the expansion of the Universe led to the concept of the Big Bang and the origin of the universe but its ultimate fate has long been the subject of discussion and controversy.
Leaving out the "Steady State" theory (a now discredited hypothesis that the universe is continually replenished by spontaneous production of atoms in empty space) there were until recently three possible routes for the Universe depending on the value of the Hubble Constant:
- continued expansion for eternity
- decreasing expansion to a halt
- decreasing expansion followed by contraction to a "Big Crunch"
It is now believed that the total matter and energy of the universe is mostly (at least 90% and up to 97%) physically undetectable (by any traditional means) but its presence can be inferred from its effects. This matter and energy has no effect on "normal" matter other than gravitationally.
It is calculated that there is much mass locked up in dark matter helping to hold galaxies together. This is required in order to explain the rotational velocities of stars at the outer edges of galaxies. With only the observable amount of mass, the outer stars should "spin off" and be lost to the galaxies.
Dark energy is believed to permeate all of space and to have a negative gravitational effect, thus causing all matter to accelerate away from its neighbours. (Imagine it as the pressure causing a balloon to expand. It is this energy which seals the eventual destiny of the Universe as a variant of (1) above i.e. ever increasing expansion.
The presence of this dark energy is what leads astrophysicists to believe that the fate of the universe is to be a low temperature (10−30Kelvin) sea of photons. The whole process passes through the 'using up' of available hydrogen and helium, the 'evaporation' of neutron stars and of black holes and the eventual decay of even protons and neutrons. This will take a length of time of up to 101500 (yes, that is ten to the one-thousand, five hundred) years.
However, if the current rate of cosmic inflation continues unabated, the universe will cease to be habitable long before then. At the current rate, in a mere 20 billion years, the universe will be expanding so rapidly that atoms will no longer be able to hold on to their electrons. This is called the "Big Rip".
 Science fiction
Various times "close" to the end have been described, or occupied by characters, in science fiction. There's a nice restaurant at the end of the Universe, which is animal-friendly, allowing pet monkeys a seat at the table. After a hard night's carouse, the Big Bang Burger Bar at the other end of town is a great place to get a mighty wadge of chips, for soaking up the undesirable toxins that invariably accompany your intoxicant of choice.
The "universe" is jargon in thermodynamics. The universe is made up of the system and the surroundings according to thermodynamics. According to the Second Law of Thermodynamics, the entropy of the universe is always increasing. In a constant-pressure system, heat leaves the system in an exothermic process, but energy is conserved.
 Poetic interpretations
- Robert Frost:
- "Some say the world will end in fire,
- some say in ice.
- From what I've tasted of desire
- I hold with those who favor fire.
- But if it had to perish twice,
- I think I know enough of hate
- To say that for destruction ice
- Is also great
- And would suffice."
- T.S. Eliot:
- "This is the way the world ends
- Not with a bang but a whimper."
While it is a term most commonly associated with science fiction, cosmologically speaking, the "multiverse" is the hypothetical realm which contains our universe, as well as many possible others. Many physicists do take multiverse theory kinda-sorta-seriously, including Andrei Linde, Alan Guth, Stephen Hawking, Michio Kaku, David Deutsch, Max Tegmark, Steven Weinberg, Hugh Everett, Raj Pathria, Alexander Vilenkin, and Brian Greene.
Perhaps there have been multiple universes with multiple big bangs, and each new universe receives a different roll of the cosmic dice, thus having different laws of physics. There are some theory who can lead to a multiverse: eternal inflation, string theory, superstring theory, black-hole cosmology, M-theory, Brane cosmology, Holographic principle and the many-worlds interpretation. This is a philosophically satisfying interpretation of the fine-tuned universe problem. However, it's also completely stark-raving unfalsifiable:
“”For a start, how is the existence of the other universes to be tested? ... [I]nvoking an infinity of unseen universes to explain the unusual features of the one we do see is just as ad hoc as invoking an unseen Creator. The multiverse theory may be dressed up in scientific language, but in essence it requires the same leap of faith.
Until we develop instruments which can actually see outside of the universe, or create a universe in a jar that we can poke with scientific instruments (slightly more likely) this remains a theory to stay grounded in sci-fi.
Alternatives to the multiverse are Ekpyrotic cyclical universe (Paul Steinhardt and Neil Turok), fecund universe or cosmological natural selection (Lee Smolin), conformal cyclic cosmology (Roger Penrose and Vahe Gurzadyan), cyclical Baum–Frampton model (Lauris Baum and Paul Frampton), loop quantum cosmology (Martin Bojowald, Abhay Ashtekar and Carlo Rovelli), eternal static universe, or the simulated universe (Nick Bostrom). And of course Goddidit.
 See also
- ↑ Was there a before for the Big Bang to be after?
- ↑ Again, creationists know that their God has always existed.
- ↑ http://www.space.com/scienceastronomy/051018_science_tuesday.html
- ↑ Christian Second Coming, Norse Ragnarok
- ↑ Buddhist Nirvana
- ↑ Scientific American
- ↑ One fairly understandable explanation
- ↑ This subject is constantly changing, so beware of what you read on the web - it may be out of date.
- ↑ A Brief History of the Multiverse