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]
<mailto:[email protected]>> 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
and accelerating forever and an infinite universe that is expanding
and accelerating forever?
John K Clark
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