The Universe is big, so big that we can't imagine it's vastness. The Universe is expanding and not only expanding but the expansion is being accelerated. The diameter of visible Universe is approximately 95 billion light years, which contains billions of galaxies and each galaxy contains billions to trillions of stars. We can't see across 95 billion light years because light from that part of the Universe have not reached us yet. So, there is a lot of Universe that we can't see. It appears that the Universe has a quite big size. But, there remains a question that will the Universe remain forever? or the Universe will end? The short answer is "yes" the Universe has an ending. We will discuss some possible scenarios in which the Universe will end.
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| Image Of Universe By Hubble Space Telescope |
Big Crunch
One of the possible scenarios the Universe could end is "big crunch". The Universe is expanding and there is a mysterious force speeding up the expansion known as "dark energy. There is a possibility that in the future gravity could dominate over dark energy and stop the expansion of the Universe and cause it to contract rather than expanding. The galaxies would began to move towards each other and merge with each other and Universe will become smaller and smaller over time. As, the Universe will become smaller, the temperatures will rise and the Universe will become incredibly hot. The individual stars will dissolve even before they began to collide with each other, for two reasons. First, the radiation from the other stars in the heavens will gain energy as the universe contracts; thus, the stars will be bathed in the blistering blue shifted light of other stars. Second, the temperature of the background microwave radiation will be vastly increased as the temperature of the universe skyrockets. The combination of these two effects will create temperatures that exceed the surface temperature of the stars, which will absorb heat faster than they can get rid of it. In other words, the stars will probably disintegrate and disperse into super hot gas clouds. Intelligent life, under these circumstances, would inevitably perish, seared by the cosmic heat pouring in from the nearby stars and galaxies. There is no escape. As Freeman Dyson has written, “Regrettably I have to concur that in this case we have no escape from frying. No matter how deep we burrow into the Earth to shield ourselves from blue-shifted background radiation, we can only postpone by a few million years our miserable end. The Universe will ultimately collapse into a singularity from which the Universe started. There is a big bounce theory which states that this has happened a lot of times and the Universe goes through an infinite cycle of expansion and contraction. The singularity in which our Universe collapsed could reemerge again into another Universe.
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| The Big Bounce Cycle |
The possibility of big crunch depends on the critical density of Universe. Does the Universe have enough matter whose gravity could reverse the expansion of the Universe? If the density of Universe is enough to reverse the expansion, then possible fate of the Universe will be big crunch. If the density of the Universe is not enough, then possible fate could be big freeze or big rip.
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| Visualization Of Big Crunch |
Big Freeze
Another possible scenario resulting fate of the Universe is "big freeze". In big freeze the Universe will continue expansion forever. The second law of thermodynamics states that total entropy always increases, so eventually, the universe will grow cold as matter and heat become more diffuse. All intelligent life in the universe will eventually freeze in an agonizing death, as the temperature of deep space plunges toward absolute zero, where the molecules themselves can hardly move. At some point trillions upon trillions of years from now, the stars will cease to shine, their nuclear fires extinguished as they exhaust their fuels, forever darkening the night sky.the larger the universe becomes, the more anti-gravity there is to push the galaxies apart, which in turn increases the volume of the universe. This vicious cycle repeats itself endlessly, until the universe enters a runaway mode and grows exponentially fast. Eventually, this will mean that thirty-six galaxies in the local group of galaxies will make up the entire visible universe, as billions of neighboring galaxies speed past our event horizon. With the space between galaxies expanding faster than the speed of light, the universe will become terribly lonely. Temperatures will plunge, as the remaining energy is spread thinner and thinner across space The cosmic expansion will leave only a cold, dead universe of black dwarf stars, neutron stars, and black holes. And even further into the future, the black holes themselves will evaporate their energy away, leaving a lifeless, cold mist of drifting elementary particles. In such a bleak, cold universe, intelligent life by any conceivable definition is physically impossible. The iron laws of thermodynamics forbid the transfer of any information in such a freezing environment, and all life will necessarily cease.
The big freeze scenario depends on the density of the Universe. If the Universe has low density then the Universe will end as big freeze.
Big Rip
In addition to the Big Freeze and Big Crunch, a third alternative began to emerge from the data, the Big Rip, which is like the Big Freeze on steroids. It is a vastly accelerated time frame for the life cycle of the Universe. Since it's birth the Universe is expanding and also the expansion is being accelerated by dark energy. The space between the galaxies expand so, they move apart. The space between galaxies also expand but here gravity is strong enough to keep them together. In the Big Rip, the distant galaxies eventually move away from us so fast that they exceed the speed of light and disappear from view. (This does not violate special relativity, because it is space that is expanding faster than light. Material objects cannot move faster than light, but empty space can stretch and expand at any speed.) This means that the night sky will become black, because light from the distant galaxies is moving away so quickly it can’t reach us. Eventually, this exponential expansion becomes so great that not only is the galaxy torn apart, the solar system is ripped apart, and the very atoms making up our bodies are also torn apart. Matter as we know it cannot exist in the final stages of the Big Rip. The atoms will also be affected. Because the space will expand faster than light there will be not interaction between the particles. The Universe would dissolve into countless lonely particles and they won't be able to touch anything. Scientific American writes, “Galaxies would be destroyed, the solar system would unbind and eventually all the planets would burst asunder as the rapid expansion of space rips apart its very atoms. Finally, our Universe would end in an explosion, a singularity of literally infinite energy.”
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| From Big Bang To Big Rip |
These were some possible scenarios regarding fate of the Universe.
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