Our bubble in the universe

One of the most shocking results of the past few years certainly refers to the discovery of the accelerating expansion of the universe.  It has also been given the Nobel Prize for this achievement, accomplished through the observations of types of supernovae in galaxies far enough (beyond our local group).



To explain this evidence seems necessary to introduce the dark energy, a “something” that tend to favor a more clear-cut than expansion provided for by previous models.  It is obvious that the quantification of this effect is reflected on the Hubble constant (of which have been spoken about often) and that determines the rate of expansion of the universe (as well as his own age).  In fact, determining the Hubble constant via different methods (e.g. through observations of supernovae or analyzing cosmic microwave background noise) resulted in quite discordant results (a ten percent difference).  I won’t go in the techniques of determination, but the fact remains that the inaccuracy seems a bit too high to be due only to measurement errors.  Behold, then force resumed a hypothesis merely “theoretical” and not confirmed by any kind of observation: the Hubble bubble. A hypothesis not as strange as it may seem at first sight.  The local universe (observable) is considered to be homogeneous, but in fact we know very well that it is not.  Just look at the distribution of galaxy clusters.  However, in space there are no galaxies only, but there is intergalactic gas that may be more or less dense.  Although extremely rarefied, areas of greater or lesser density would create strong variations of large-scale gravity.  And if we were inside a large low-density area? A real “bubble”? What would cause this area relatively empty? Well, surely the objects to its borders would be drawn violently from areas outside greater density, causing a real escape in external galaxies compared to us.  This “local” gravitational action will bring to a reduction to the actual expansion of the universe.  The hypothesis could solve the apparent acceleration of the universe without having to ask for help to the dark energy.  The Hubble constant is obtained with the cosmic microwave background that would relate to the average value of the universe, while that obtained from type of supernovae would relate to a “near” gravitationally speed universe.  Recently, a group of researchers in Heidelberg simulated a situation in which our Galaxy was at the center of a spherical bubble, whose boundaries go far beyond our local group.  The result would explain at least a 25% of the difference between the two measurements obtained by the Hubble constant.  Not much, in truth.  But it is a geocentric Cosmos again?  Why we should be “different” from the rest of the local universe? Definitely there is something that creates a sense of annoyance and obsolete.  However, it is also an opposite consideration: why the universe should be perfectly homogeneous and constant density? In short, there is a purely theoretical research, but no less interesting.  On the other hand would be an explanation that would simplify the situation by eliminating or at least greatly reducing the importance of dark energy.  On the other hand, though, reminds me of some numerical models in which to change a little the various parameters you could get what you wanted.  Well … we’ll see.  It remains, however, an important fact: If all the various arrangements to the model and computer simulations will be made with “opinion” and it got one more important difference, the need for an unknown entity (dark energy) would be practically determined.


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