a universe will expand forever?
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In absence of dark energy, a flat universe expands forever but at a continually decelerating rate, with expansion asymptotically approaching zero. With dark energy, the expansion rate of the universe initially slows down, due to the effect of gravity, but eventually increases.
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Isothermal expansion can surely be irreversible if you make it so. In fact, any process is usually at least a bit irreversible, and truly 100% reversible processes are impossible.
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After inflation, the expansion of the universe continued, but at a slower rate. As space expanded, the universe cooled and matter formed, and then protons and neutrons formed. ... So Inflation Theory explains why the CMB is so nearly uniform, and also how galaxies, stars, planets and people came to be!
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String theory (or, more technically, M-theory) is often described as the leading candidate for the theory of everything in our universe. But there's no empirical evidence for it, or for any alternative ideas about how gravity might unify with the rest of the fundamental forces.
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The closed universe, which is a universe where space-time is curved back on itself, one that has a finite size but no center and no edge. The open universe, which is a model of an infinite universe involving curved space-time, which does not curve back on itself.
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The vacuum of outer space is not caused by the expansion of the universe, but is caused by gravity. First of all, when we say outer space (the space outside the atmosphere of planets and stars) is a "vacuum" or is "empty", we really mean that outer space is nearly empty or almost a perfect vacuum.
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The most widely accepted explanation is the big bang theory. Learn about the explosion that started it all and how the universe grew from the size of an atom to encompass everything in existence today.
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The Short Answer: The big bang is how astronomers explain the way the universe began. It is the idea that the universe began as just a single point, then expanded and stretched to grow as large as it is right now (and it could still be stretching).
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Where is the centre of the universe? There is no centre of the universe! According to the standard theories of cosmology, the universe started with a "Big Bang" about 14 thousand million years ago and has been expanding ever since. Yet there is no centre to the expansion; it is the same everywhere.
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"Quantum mechanical fluctuations can produce the cosmos," said panelist Seth Shostak, a senior astronomer at the non-profit Search for Extraterrestrial Intelligence (SETI) Institute. "If you would just, in this room, just twist time and space the right way, you might create an entirely new universe.
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0 has a decimal expansion, too, so all real numbers have a decimal expansion, and moreover, all of them (except arguably 0) have an infinite decimal expansion (though some also have a finite decimal expansion).
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When used as adjectives, endless means having no end, whereas eternal means lasting forever.
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When used as adjectives, infinite means indefinably large, countlessly great, whereas unlimited means limitless or without bounds. Infinite is also numeral with the meaning: infinitely many.
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But a real doppelganger may exist outside of our own universe. Some scientists now believe that we live in a multiverse where there are infinite possibilities and other 'Earths' where identical versions of ourselves are living out slight variations to our life.
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As adjectives the difference between perpetual and eternal is that perpetual is lasting forever, or for an indefinitely long time while eternal is lasting forever; unending.
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The universe's dark energy may be growing stronger with time, study suggests. Dark energy, a mysterious invisible force believed to play a role in how the universe expands, may be growing stronger over time, according to a new study. ... "This could mean dark energy is getting stronger as the cosmos grows older."
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As there is no such thing,( physical. construct) as time, we will. never run out of it. The concept we humans have of time, as such, will probably cease in an instant , we have no measurements of what will come after that point in history.