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September 19th, 2018, 07:53 PM   #21
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There is no logical error is stating the assumptions that you are going to incorporate into your system. Maths does itself significant favours by incorporating infinite objects because they are very useful.
Infinities are very useful but as approximations only. They are misleading and dangerous when used as the actual values of real world quantities. Maths need to be clear that Actual Completed Infinity cannot exist.

Is spacetime infinite - no obviously - but Cantor and co have the applied mathematicians thinking there is a valid mathamatical concept of Actual Infinity that legitimises infinite space time. People are wasting serious amounts of time thinking about something that does not exist.
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September 19th, 2018, 07:57 PM   #22
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They are misleading and dangerous when used as the actual values of real world quantities.
Nobody who knows what they are talking about uses infinities as actual values of real world quantities. And if anybody does use them as such, that is a problem of the user, not of the mathematics.

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Applied mathematicians thinking there is a valid mathamatical concept of Actual Infinity that legitimises infinite space time.
I rather suspect that you don't know what you are talking about here.
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September 19th, 2018, 08:00 PM   #23
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Originally Posted by Devans99 View Post
Infinities are very useful but as approximations only. They are misleading and dangerous when used as the actual values of real world quantities. Maths need to be clear that Actual Completed Infinity cannot exist.

Is spacetime infinite - no obviously - but Cantor and co have the applied mathematicians thinking there is a valid mathamatical concept of Actual Infinity that legitimises infinite space time. People are wasting serious amounts of time thinking about something that does not exist.
1. Approximations? ...

2. I think the 'Applied Mathematicians' can think for themselves.

3. It seems the only time that's getting wasted is any time spent on this thread.
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September 19th, 2018, 08:01 PM   #24
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Rather than just being rude, give me one example from nature of actual completed infinity or show me how the construct an actually infinite set.
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September 19th, 2018, 08:08 PM   #25
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Rather than just being rude, give me one example from nature of actual completed infinity or show me how the construct an actually infinite set.
I'm sorry if you thought I was being rude. I was simply suggesting that you don't understand how people are using infinities, and that you are not in a position to state what applied mathematicians believe because that is for them to do.

The idea that you don't understand how infinities are being used is borne out by your suggestion that having examples of (I assume) physical infinities is in any way relevant to how they are used.
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September 19th, 2018, 08:11 PM   #26
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Nobody who knows what they are talking about uses infinities as actual values of real world quantities
Check the Wikipedia page for universe (https://en.m.wikipedia.org/wiki/UniVerse) for example:

‘Because we cannot observe space beyond the edge of the observable universe, it is unknown whether the size of the Universe in its totality is finite or infinite’.

This is typical of the confusion maths treatment of infinity is causing in the physical sciences.
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September 19th, 2018, 08:17 PM   #27
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Another example is the debate over whether space and time are continuous or discrete:

- Assume time is continuous
- take any system over any finite time period
- then the system evolves through an actual Infinity of states in a finite time
- Reductio ad absurdum, time is discrete.

Do you not see how simple things are once we remove the logic error of Actually Infinite?
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September 19th, 2018, 08:18 PM   #28
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It there some part of that that is unreasonable? I mean, if you have some evidence about the unobservable universe, I reckon there'd be a whole heap of people that'd like to see it.

They'll be less interested if it's just you plugging finitist dogma though.
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September 19th, 2018, 08:21 PM   #29
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Originally Posted by Devans99 View Post
Another example is the debate over whether space and time are continuous or discrete:

- Assume time is continuous
- take any system over any finite time period
- then the system evolves through an actual Infinity of states in a finite time
- Reductio ad absurdum, time is discrete.

Do you not see how simple things are once we remove the logic error of Actually Infinite?
If you have assumed that time is continuous, then what is the problem in have an infinitude of states in a finite time?

The problem with your argument is that it is circular. That and it begins with your desired conclusion. You want the infinite not to exist, and your reason that it can't exist is that you don't want an infinitude of states to make sense.

The truth is that nobody knows whether or not time and space are discrete or continuous, so investigation of both possibilities is reasonable.

Also, both have applications for which they give good models, so there's no reason to disbar either.
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September 19th, 2018, 08:23 PM   #30
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If you have some evidence about the unobservable universe, I reckon there'd be a whole heap of people that'd like to see it.

They'll be less interested if it's just you plugging finitist dogma though.
It’s not dogma. It’s impossible for the Actually Infinite to exist. Space time can’t be actually infinite - it would have no start - if it has no start it does not exist exist in the materialistic world view.
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