On Friday, January 24, 2020 at 3:50:54 PM UTC-7, Brent wrote: > > > > On 1/24/2020 2:08 PM, John Clark wrote: > > On Fri, Jan 24, 2020 at 3:06 PM 'Brent Meeker' via Everything List < > [email protected] <javascript:>> wrote: > > >> >> If you're assuming that Real Numbers exist and that even a 1 cm >>> universe would need a infinite number of labels >> >> >> * > But not an infinite range of labels.* >> > > OK now it's official, I have no idea what you're talking about. > > >> I ask my question again: >>> *What is the difference between a "finite" universe that is expanding >>> and accelerating and an infinite universe that is expanding and >>> accelerating?* >> >> >> * > Imagine the Earth is expanding like a balloon and at an accelerating >> pace. * >> > > A balloon is a terrible analogy for the Earth and a inflating balloon is > an even worse analogy for a universe that will expand and accelerate > forever. With the balloon you're standing outside of it watching the > balloon expand into something that's already there, > > > But you don't have to stand outside of it. Everything in the analogy is > observable for a Flatland creature living on the sphere. > > but you can't stand outside of the universe and the universe is not > expanding into anything that's already there. > > >> *> You can't go fast enough to circumnavigate it because there's a speed >> limit. * >> > > And to call that speed limit the speed of light would be true but tends to > trivialize it, really it's something far more fundamental and profound, > it's the very speed of causality. > > > So what. I'm making an analogy, not a model. > > > >> *> In your imagination is it finite or infinite? Are there locations on >> it which are finite distances apart? Is there a set of such locations >> connecting any two points? Is the sum of the distances between locations >> of such a set finite?* >> > > I would say a infinite amount of information would be needed to adequately > > > Nobody asked about the amount of information. That's a red herring that > LC threw in. The question was about the expansion and size of the universe. > > describe the evolution of the phase space (all possible values of the > position and momentum of the particles in the universe) of such a expanding > accelerating universe. It's infinite because no amount of approximation > would be good enough for prediction, due to the accelerated creation of new > space there will always be more values of position and momentum that > particles can be in tomorrow than they can be in today. By the way, all > this talk about the distance between particles in a expanding accelerating > universe is rather ambiguous if you don't specify when, and "now" has no > meaning everybody agrees with. > > And I've heard a bunch of bad analogies but I still haven't heard a direct > answer to my question: > What is the difference between a "finite" universe that is expanding > > > As in my analogy, in a finite universe there are a finite number of > intervals of finite distance that can link any two points in the universe. > Of course this refers to it being finite at a given time, and you raised > the problem of defining what counts as "at the same time". The answer is > that it is at the same time if it is at the same degree of > expansion...operationally it means that two distant events are "at the same > time" if the isotropic temperature of the CMB looks the same to them. > > Brent >
*You sometimes refer to the scale factor in GR being a function of time, namely a(t). But in relativity each observer has a clock, and time is what the observer reads on his clock. So what time are you referring to; the clock of a bird's eye observer outside the universe? TIA, AG * > > and accelerating forever and an infinite universe that is expanding and > accelerating forever? > > John K Clark > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] <javascript:>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/CAJPayv28VWSwcimZqwLvHfJkkUruOSi4%3DZKn8QtvYF4Un4t6og%40mail.gmail.com > > <https://groups.google.com/d/msgid/everything-list/CAJPayv28VWSwcimZqwLvHfJkkUruOSi4%3DZKn8QtvYF4Un4t6og%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > > > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/b1716c23-f8fc-4d26-86d9-5c8a47bb6300%40googlegroups.com.
