tag:blogger.com,1999:blog-5801278565856116215.post3968383954539683336..comments2017-11-21T17:10:54.008+00:00Comments on Disagreeable Me: A part is more complex than the wholeDisagreeable Mehttp://www.blogger.com/profile/15258557849869963650noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-5801278565856116215.post-38312669543908534062013-08-07T19:08:15.552+01:002013-08-07T19:08:15.552+01:00Excellent point. Taking quantum mechanics into con...Excellent point. Taking quantum mechanics into consideration, it is probably not fair to say that the universe is simpler if it is infinite, but only if you allow the many worlds interpretation.<br /><br />If you do not assume the MWI, then this initial configuration of particles is replaced by the information which would encode the outcome of every random quantum event leading up to today - a massive amount of data that's not required in an infinite universe because all possibilities are realised somewhere.<br /><br />On the other hand, if you do assume the MWI, the universe is not simpler because it is infinite in spatial extent, but because it has infinite instances corresponding to all the different ways quantum events could have turned out. <br /><br />Again, infinity reduces complexity.Disagreeable Mehttps://www.blogger.com/profile/15258557849869963650noreply@blogger.comtag:blogger.com,1999:blog-5801278565856116215.post-24639375919988108002013-08-07T18:50:44.647+01:002013-08-07T18:50:44.647+01:00I don't know what you mean by 'specific co...I don't know what you mean by 'specific configuration of particles'. No cosmological model does provide this, since those processes are of statistical nature (in particular in the early universe, which is dominated by quantum fluctuations if you accept inflationary scenarios), so you only describe the statistical properties of random fields.<br /><br />You can quantify the amount of information by the entropy density, and with that there is basically no difference between finite and infinite models.<br /><br />energie_sombrehttps://www.blogger.com/profile/04172527415105196442noreply@blogger.comtag:blogger.com,1999:blog-5801278565856116215.post-65490429565032415112013-08-07T13:13:06.276+01:002013-08-07T13:13:06.276+01:00Yes, you need to define all the parameters that de...Yes, you need to define all the parameters that define the universe, including matter density, rarity of events, physical laws etc.<br /><br />What you don't need to specify is the specific configuration of particles that exists at the moments just after the big bang, because in an infinite universe all such configurations will exist somewhere.<br /><br />Conversely, a finite universe does need this specific configuration and this is an absolutely enormous amount of information, far more than anything else that defines the universe.<br /><br />The infinite universe is simpler since you don't need this information to define it.Disagreeable Mehttps://www.blogger.com/profile/15258557849869963650noreply@blogger.comtag:blogger.com,1999:blog-5801278565856116215.post-55317056477829506792013-08-07T13:02:50.480+01:002013-08-07T13:02:50.480+01:00You're right of course about the open universe...You're right of course about the open universe being infinite.<br /><br />But also in this case, you need to know the initial conditions. You still want to know what e.g. the distribution of matter is, or how rare certain events are.energie_sombrehttps://www.blogger.com/profile/04172527415105196442noreply@blogger.comtag:blogger.com,1999:blog-5801278565856116215.post-76949585968212188642013-08-07T11:11:48.597+01:002013-08-07T11:11:48.597+01:00Hi energie_sombre,
There is neither evidence that...Hi energie_sombre,<br /><br />There is neither evidence that it is finite or infinite, but it certainly seems to be flat to within our ability to measure it, which as you say might imply an infinite size if it is flat (or open). It is interesting that a flat universe would have precisely zero energy, which might hint at a reason for how it could be precisely flat.<br /><br />But when you discount the possibility that it is perfectly flat as being too improbable, you're forgetting the possibility that it is open. Even if we rule out a flat universe entirely, there's still a 50% chance it's open, which would mean infinite.<br /><br />>The description of such models need a certain number of parameters, e.g. initial conditions, the matter density, the curvature, etc.<<br /><br />I see you've missed the point of my post. An infinite universe is simpler because you don't need to specify initial conditions, as all possible initial conditions will be found in that infinity.<br />Disagreeable Mehttps://www.blogger.com/profile/15258557849869963650noreply@blogger.comtag:blogger.com,1999:blog-5801278565856116215.post-87786838408944739382013-08-07T00:39:49.074+01:002013-08-07T00:39:49.074+01:00My two thoughts about an infinite universe:
First...My two thoughts about an infinite universe:<br /><br />First, there is no evidence that it is infinite, according to all current observations. Time towards the past is certainly not without limits, there was the Big Bang after all (and if there was pre-BB stuff, this must have been of a very different nature). Towards the future, the universe might go on forever, but the conditions change drastically. If the expansion keeps on accelerating, configurations that you see now, with young stars, clusters of galaxies etc., will not exist anymore a hundred billion years from now.<br /><br />Spatially, it is extremely unlikely that the universe is infinite. Inflation tells us that the universe is flat, which is what we observe. This would indeed imply an infinite spatial extend. But flatness is only necessary within a certain range, to the high degree that inflationary models tell us. That means that before inflation, the universe could have had any geometry within that range, and flatness (= infiniteness) is only one single, unlikely, possibility out of that range.<br /><br />Second, cosmologists describe the universe in a statistical sense. Nobody can predict the exact formation of the Earth, the solar system, or the Milky Way. We can only predict the distribution of planets, stars, and galaxies. The description of such models need a certain number of parameters, e.g. initial conditions, the matter density, the curvature, etc. These numbers can describe both finite and infinite universes, none is simpler than the other.energie_sombrehttps://www.blogger.com/profile/04172527415105196442noreply@blogger.com