# Tag Info

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I don't see any logical connection to accelerating expansion. If shrinking of galaxies could explain away the acceleration of the expansion, then it could also explain away the expansion itself. Regardless of whether we're talking about expansion or acceleration of expansion, the effect isn't measured by watching the apparent sizes of galaxies get smaller ...

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Entropy isn't a force that causes things to happen. But anyway, the answer is no. Not all matter in the universe is expected to eventually collapse into black holes. See Adams and Laughlin, http://arxiv.org/abs/astro-ph/9701131 , section VD. Note also that black holes eventually evaporate, so when matter collapses into black holes, the result is that it ...

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This is a philosophical question so here is a philosophical answer. The scientific method in based on repeated observations and experiment. The whole science is just a collectivist instrument of acquiring knowledge. Being an instrument, it has its own limitations. Among them are: The tools employed by science are built by humans. As such, all tools use ...

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So first of all, there are several multiverse theories. As a cosmologist, I personally don't know anyone that subscribes to the one you've written here. The standard multiverse theory comes from quantum mechanics. In it, we say that every time an action is taken that (more or less) collapses a wavefunction in our universe, it simply means that other ...

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There are quite a few common misconceptions about the expansion of the universe, even among professional physicists. I will try to clarify a few of these issues; for more information, I highly recommend the article "Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe" from Tamara M. Davis and ...

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As I mentioned in the comments, your first two questions are based on an assumption about repeats that isn't justified. see Multiverse theory and infinite individuals for more details. Re the last question: the grandfather paradox is based on the existance of closed time-like curves, and the existance or otherwise of these is unrelated to the concept of a ...

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Depends. If you simple assume matter growing we would see the distance between the surfaces of celestial bodies diminishing. Given that we regularly monitor the distance between the surfaces of the Earth and Moon by laser ranging to accuracies of less than one cm (which means less than one part in $10^8$ over the time the project has been running). This is ...

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No (understandable/explainable) physical quantity could be infinite. "Infinity" is is physically very vague. When we say something is "infinite", it almost means we're throwing our hands up in despair that we can't explain something, or that quantity doesn't make sense in some particular framework. The whole point of physical quantities (observables) is to ...

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First of all, galaxies don't shrink. If our own galaxy were shrinking, then we would be moving towards our galactic centre, and we would observe a blueshift in that direction. Second, the accelerated expansion can be determined from the relation between redshift and brightness of distant supernovae. Neither redshift nor brightness would be affected by ...

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All points in the observable universe are "connected" in the sense that they can be acted upon by forces that have an infinite range (gravity and electromagnetism). However, points that are outside of our cosmological horizon (due to the expansion of the universe) are no longer causally connected with points in our local vicinity, since they are receding ...

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I guess that you are imagining an expansive force accelerating the Universe versus gravity pulling the Universe together, and that if somehow gravity were weaker, the expansive force would win. That is not the correct picture. In popular models, the accelerating Universe is caused by gravity, because of a vacuum energy with negative pressure (see dark ...

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"Metric expansion only occurs with proper distances (between events at the same cosmological time)" Why would this effect disappear when you integrate over paths in space-time (e.g. photon trajectories)? The redshifting of light by spacetime geometry is an observational fact, not an ad hoc conjecture. "Can the cosmological redshift be interpreted ...

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The radius of the observable universe is about 46 billion light years, which is considerably greater than its age of about 14 billion years. Since the radius of the observable universe is defined by the greatest distance from which light would have had time to reach us since the Big Bang, you might think that it would lie at a distance of only 14 billion ...

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