Infinite vs Finite Logic
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13-05-2017, 03:48 PM
RE: Infinite vs Finite Logic
we don't know. we all die not knowing.

that's that.
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13-05-2017, 05:29 PM
RE: Infinite vs Finite Logic
(01-05-2017 05:29 PM)John Derderian Wrote:  
(01-05-2017 05:14 PM)Brian37 Wrote:  I lean to "all this" being both infinite and finite depending on point of view.

I think "all this" is on for a while, decays to off, then becomes fuel for another big bang then is on again for a while.

This is not what the current models say. By the Standard Model, the universe is either finite or infinite. We just don't have enough information to know which it is yet, although people seem to be leaning toward infinite these days. It does not change back and forth. It is also not just a question of your point of view. There are real physical consequences of it being one or the other. By the Standard Model, if the universe is finite in spatial extent, it is also finite in time; it will eventually stop expanding and collapse back in on itself. If it is infinite in spatial extent, it is also infinite in time; it will continue expanding forever.

Thanks. I had wondered about the link between the two given the intertwined nature of space-time.

To me this suggests that the universe is finite.
- The universe has a beginning ~13.8 billion years ago.
- In an infinite universe the beginning should be infinitely far in the past. And the word "beginning" becomes silly but we're straining the English language here. Any fraction of infinity being infinity, we can never get to a finite beginning no matter how thinly you slice it. That's the bugger of infinity, you can't get there from the finite. Nor can you get to the finite from the infinite. They aren't on speaking terms.
- Since we can observe one end of time, this implies a finite temporal extent and thus a finite spatial extent.

Now I'm sure that people who actually get paid to figure this stuff out have noticed this detail so I suspect that my reasoning is faulty and I may have divided by zero somewhere. I simply don't know enough to spot where I've gone wrong...

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Flesh and blood of a dead star, slain in the apocalypse of supernova, resurrected by four billion years of continuous autocatalytic reaction and crowned with the emergent property of sentience in the dream that the universe might one day understand itself.
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13-05-2017, 06:39 PM
RE: Infinite vs Finite Logic
(01-05-2017 04:52 PM)Saucy Jack Wrote:  I was mainly checking that my logic was sound. The guy on Facebook was ascerting that if we don't know where the universe ends, that it is not finite by definition. I say that this is illogical. It's like saying the answer is either A or B but because we don't know whether or not it's A it has to be B.

The universe is expanding.
The furthest galaxies away from us appear to be receding faster than the speed of light. Ask "the guy on Facebook" how he will ever know what's going on out there, and how that is different from "infinite" ?

Insufferable know-it-all.Einstein God has a plan for us. Please stop screwing it up with your prayers.
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13-05-2017, 11:35 PM (This post was last modified: 13-05-2017 11:40 PM by Robvalue.)
RE: Infinite vs Finite Logic
I was thinking about whether there is a finite or infinite amount of energy in our reality. The idea of an infinite expanse with an infinite amount of objects (or other forms of energy) in it is extremely hard to imagine. Or even a finite space with infinite objects in it, somehow. I assume we'd expect everything that came from an initial super-concentrated collection of objects to be finite in scope, but there could also be objects everywhere that we can't detect, and maybe we never will.

This is of course completely unfalsifiable speculation, with no reason to actually think things are infinite in nature. I just find it interesting to think about. Attempts to rule out infinity from reality tend to beg the question, in my experience. Our models can certainly indicate finiteness though. Finiteality? Finality? Finitability? -ness?

I have a website here which discusses the issues and terminology surrounding religion and atheism. It's hopefully user friendly to all.
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14-05-2017, 01:43 AM
RE: Infinite vs Finite Logic
My brain is hurting.I don't think I can make any sense of arguments presented here.
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14-05-2017, 07:48 AM
RE: Infinite vs Finite Logic
(13-05-2017 11:35 PM)Robvalue Wrote:  I was thinking about whether there is a finite or infinite amount of energy in our reality. The idea of an infinite expanse with an infinite amount of objects (or other forms of energy) in it is extremely hard to imagine. Or even a finite space with infinite objects in it, somehow. I assume we'd expect everything that came from an initial super-concentrated collection of objects to be finite in scope, but there could also be objects everywhere that we can't detect, and maybe we never will.

This is of course completely unfalsifiable speculation, with no reason to actually think things are infinite in nature. I just find it interesting to think about. Attempts to rule out infinity from reality tend to beg the question, in my experience. Our models can certainly indicate finiteness though. Finiteality? Finality? Finitability? -ness?
The only thing that matters to us is whether there energy available to us locally will be exhausted at some point. It might be theoretically infinite but that does no good if it's so spread out that we don't have the energy we need available to us locally. If there's infinite energy and our planet is a frozen ball of mud and everything is inert, who cares?
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14-05-2017, 09:12 AM
RE: Infinite vs Finite Logic
(13-05-2017 05:29 PM)Paleophyte Wrote:  Thanks. I had wondered about the link between the two given the intertwined nature of space-time.

To me this suggests that the universe is finite.
- The universe has a beginning ~13.8 billion years ago.
- In an infinite universe the beginning should be infinitely far in the past. And the word "beginning" becomes silly but we're straining the English language here. Any fraction of infinity being infinity, we can never get to a finite beginning no matter how thinly you slice it. That's the bugger of infinity, you can't get there from the finite. Nor can you get to the finite from the infinite. They aren't on speaking terms.
- Since we can observe one end of time, this implies a finite temporal extent and thus a finite spatial extent.

Now I'm sure that people who actually get paid to figure this stuff out have noticed this detail so I suspect that my reasoning is faulty and I may have divided by zero somewhere. I simply don't know enough to spot where I've gone wrong...

I think the spot where you've gone wrong, at least in this particular comment, is that "infinite in time" can apply separately at either end of the timeline (or at both). There's nothing wrong with the idea that the universe started with the Big Bang a finite time in the past, but will continue to exist infinitely long in the future; that it has a beginning but no ending. In fact, this is one of the two possibilities of the Standard Model. (The other is a universe with both a beginning and an ending.)

There used to be models of an infinite universe with no beginning, in which the universe has always existed. These aren't considered seriously anymore (at least by scientists) because the evidence does not support them. They were reasonable conjectures at the time they were made because we didn't have the same data then.
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14-05-2017, 09:23 AM
RE: Infinite vs Finite Logic
(14-05-2017 09:12 AM)John Derderian Wrote:  There used to be models of an infinite universe with no beginning, in which the universe has always existed. These aren't considered seriously anymore (at least by scientists) because the evidence does not support them. They were reasonable conjectures at the time they were made because we didn't have the same data then.

Actually, the eternal (in the past) universe theory is still being taken seriously. One of my favourite smart people, Sean Carroll, is currently studying this. His hypothesis is that the Big Bang was only a moment past through which we cannot see, but that the universe - or perhaps multi-verse - existed for an infinite amount of time previous to the inflationary expansion. http://www.preposterousuniverse.com/blog...-big-bang/

It's pretty interesting stuff. I won't pretend to understand it all, the math is way above my pay grade. But, if proven correct, it would put the final nail in the deist coffin.

No Big Bang? Quantum equation predicts universe has no beginning



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14-05-2017, 10:03 AM
RE: Infinite vs Finite Logic
(14-05-2017 09:23 AM)Heath_Tierney Wrote:  Actually, the eternal (in the past) universe theory is still being taken seriously. One of my favourite smart people, Sean Carroll, is currently studying this. His hypothesis is that the Big Bang was only a moment past through which we cannot see, but that the universe - or perhaps multi-verse - existed for an infinite amount of time previous to the inflationary expansion. http://www.preposterousuniverse.com/blog...-big-bang/

Yes, I should have spoken more carefully. In the past, there were steady-state models with no Big Bang or anything like it. These are no longer tenable thanks to modern data. There can still be models with no actual beginning, but containing a Big Bang or something enough like it to be consistent with the data. As another example, there have long been so-called cyclic models where the universe explodes in a Big Bang, eventually re-collapses, and after the collapse explodes again, and keeps doing this forever.
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14-05-2017, 11:46 AM
RE: Infinite vs Finite Logic
(14-05-2017 07:48 AM)mordant Wrote:  
(13-05-2017 11:35 PM)Robvalue Wrote:  I was thinking about whether there is a finite or infinite amount of energy in our reality. The idea of an infinite expanse with an infinite amount of objects (or other forms of energy) in it is extremely hard to imagine. Or even a finite space with infinite objects in it, somehow. I assume we'd expect everything that came from an initial super-concentrated collection of objects to be finite in scope, but there could also be objects everywhere that we can't detect, and maybe we never will.

This is of course completely unfalsifiable speculation, with no reason to actually think things are infinite in nature. I just find it interesting to think about. Attempts to rule out infinity from reality tend to beg the question, in my experience. Our models can certainly indicate finiteness though. Finiteality? Finality? Finitability? -ness?
The only thing that matters to us is whether there energy available to us locally will be exhausted at some point. It might be theoretically infinite but that does no good if it's so spread out that we don't have the energy we need available to us locally. If there's infinite energy and our planet is a frozen ball of mud and everything is inert, who cares?

I agree, it's of no practical importance.

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