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Is Infinity necessary?

TiredThinker March 10, 2022 at 19:25 7500 views 28 comments
What is the history of Infinity? I know it exists at least for the sake of math, but has anything ever been to indicate that anything about it goes on forever?

Comments (28)

Agent Smith March 10, 2022 at 20:02 #665221
Infinite series are a staple in math; some of them are fundamental to calculations of certain extremely important constants such as [math]\pi[/math], [math]e[/math], [math]\gamma[/math], etc. In that sense and to that degree, they seem vital to mathematics.

On the flip side, they violate our intuitions and generate paradoxes (re Zeno's paradoxs).

I guess we have to do what we must do: look the other way when [math]\infty[/math] up ends our world and act as if it never happen(s/ed).
jgill March 10, 2022 at 22:26 #665318
When a recursive process gets you closer and closer to an answer the more you apply it, and this process goes on step by step with no ending stipulated, then this is all about "infinity" that is needed for most mathematics. [math]\infty [/math] is a convenient way of saying this.

Foundations and set theory, however, go a significant step beyond into transfinite pastures. Occasionally a result in other areas of math require a cow chip or two from these leas.
EugeneW March 11, 2022 at 07:31 #665474
Space is infinite. There is no end to it. The universe expands in it. Accelerated even. Will it come to a sudden stop because space ends?
180 Proof March 11, 2022 at 08:04 #665477
Quoting TiredThinker
What is the history of Infinity?

Not as dry (or long & thorough) as the SEP article but pretty good nonetheless:
https://www.polytechnique-insights.com/en/columns/space/how-to-understand-infinity-in-three-steps/
EugeneW March 11, 2022 at 09:35 #665494
Infinity is the spatial edition of eternity. It has a long history. An eternal history.
Cuthbert March 11, 2022 at 09:56 #665509
Quoting TiredThinker
What is the history of Infinity?


In Western thought, try the pre-Socratics, e.g. Thales, Anaximander - matter arises from "the limitless" - and for infinitesimal Zeno as Agent S says. There's a book about it: https://www.waterstones.com/book/infinity-in-the-presocratics/joseph-owens/l-sweeney/9789024711703.

In Eastern thought, try a whole new way of looking at the world that I don't understand. But somebody will.
Metaphysician Undercover March 11, 2022 at 11:54 #665561
Quoting TiredThinker
What is the history of Infinity? I know it exists at least for the sake of math, but has anything ever been to indicate that anything about it goes on forever?


I believe "infinite" was established as a fundamental principle of measurement, which would allow that anything and everything could be measured. There cannot be more items than can be counted, because there is no limit to how high we can count. There cannot be something bigger or smaller than what can be measured, because we can always come up with a bigger or smaller measurement.

"Infinite" only refers to something which "goes on forever" when we're talking about temporal extension. And then, it could only be said to go on forever under the assumption that time has no end.
Gregory March 11, 2022 at 22:16 #665762
Thomas Aquinas thought the world could be eternal. However he argued there are no actual infinities. But what if there were always humans then there would be an infinity of souls. It's accidental that animals or vegetables always existed rather than human. If there always were human souls then they would be counting marks for an actual infinity
EugeneW March 11, 2022 at 23:26 #665801
Reply to jgill Reply to jgill

Great work! And you even get paid for it! You have involved with the Colatz conjecture at any time in your career? It's proven up to 2^70 numbers! But how to prove it for all numbers? 2^70 is peanuts in the face of infinity. Do we have to calculate all individual orbits?
jgill March 11, 2022 at 23:28 #665804
Quoting EugeneW
And you even get paid for it!


Not since I retired 22 years ago. :cry:
L'éléphant March 11, 2022 at 23:39 #665807
Quoting TiredThinker
What is the history of Infinity? I know it exists at least for the sake of math, but has anything ever been to indicate that anything about it goes on forever?

Infinity was first posited by Anaximander. The apeiron as the first principle is boundless. The first principle meaning the "beginning of everything". So, beginning here doesn't mean a start (a bound), rather infinity is the beginning and we couldn't posit anything prior to infinity.
L'éléphant March 11, 2022 at 23:41 #665808
To answer your question, is infinity necessary? Infinity is what we could only point to whenever we talk about the beginning of everything.
TiredThinker March 12, 2022 at 02:31 #665847
Reply to Metaphysician Undercover

So no object goes on forever? Infinity only refers to repeated processes that are intended to go on forever but of course cannot because we ourselves are limited by time?
Metaphysician Undercover March 12, 2022 at 03:05 #665866
Reply to TiredThinker
What I believe is that measurement is fundamentally unlimited. This does not mean that any measuring process will go on forever, but it could in principle go on forever. This allows that we can measure anything and everything. The measurement of time for example would go on forever, if time went on forever. But things that we measure are all finite, all limited, and nothing goes on forever, so we end up measuring everything we try to measure, and the measuring process never needs to go on forever.
180 Proof March 12, 2022 at 06:05 #665900
Quoting TiredThinker
[H]as anything ever been to indicate that anything [s]about it[/s] goes on forever?

Horizons. The circumference of a circle / sphere / torus / Möbius loop ... (E.g. circumnavigating / orbiting the Earth.)
universeness March 12, 2022 at 11:40 #665966
I don't think the logic of the term infinite holds much value. That which is infinite cannot terminate (end), therefore it has to be eternal but then how did it become infinite? It seems to me, logically impossible to become infinite so infinite must have always existed if you throw the concept of linear time at it. Therefore that which is infinite cannot logically or physically exist within linear time, it is a metalogical concept. To me, it is just a convenient label for 'what we just don't understand yet.'
Picking a number between 1 and 2 seems to have an 'infinite' choice but within linear time, this is meaningless as you can choose a number between 1 and 2 and therefore satisfy the request to pick one.
I give the term the same cognisance as that of the god fable. 'Has its uses, but I see little value in it.'
In Science, the appearance of an infinity, normally indicates a flaw in the logic applied.
Metaphysician Undercover March 12, 2022 at 11:57 #665973
Quoting 180 Proof
The circumference of a circle / sphere / torus / Möbius loop ... (E.g. circumnavigating / orbiting the Earth.)


Aristotle dispelled this idea a long time ago. When you traverse a circle, you arrive back at the same point where you started. The circle does not go on forever. And, we cannot assume that there is no starting point because motion requires a cause.
frank March 12, 2022 at 18:07 #666063
Quoting Metaphysician Undercover
motion requires a cause.


I don't think so. Aristotle didn't know about inertia.
180 Proof March 12, 2022 at 18:19 #666071
Gnomon March 12, 2022 at 19:00 #666088
Quoting EugeneW
Space is infinite. There is no end to it. The universe expands in it. Accelerated even. Will it come to a sudden stop because space ends?

Einstein defined the universe as "finite, but unbounded". Ironically, "unbounded" is one definition of "infinite". Yet, Einstein's mathematical universe is depicted as a sphere, which would actually be finite in space, except that "space" is inside the sphere. Now wrap your mind around the paradox of unbounded space trapped inside a finite sphere. :joke:

Einstein postulated that the universe is finite in time (bounded at the big bang singularity), and unbounded in space -- i.e., if one could travel the four dimensional universe in a geodesic one would not find a boundary, and would end up at the starting point, just like the path of a geodesic on the 3-dimension Earth.
https://www.researchgate.net/post/Can-the-Universe-be-finite-and-unbounded-and-still-be-Euclidean

User image

What Lies Beyond the Edge of the Observable Universe? :
So, in some ways, infinity makes sense. But “infinity” means that, beyond the observable universe, you won't just find more planets and stars and other forms of ...
https://futurism.com/what-lies-beyond-the-edge-of-the-observable-universe
EugeneW March 12, 2022 at 19:23 #666097
Quoting Gnomon
But “infinity” means that, beyond the observable universe, you won't just find more planets and stars and other forms of ...


I think beyond the observable universe there are lots of planets. The universe extends beyond the horizon as Earth extends beyond the horizon. The universe seems flat but it is a closed 3d sphere. You will come back where you started (if you got the energy). Maybe the (4d) space in which it expands is infinite... Will we ever know? We can speculate! And that's the fun.

ssu March 12, 2022 at 23:34 #666191
Is infinity necessary?

Hell yes for mathematics!!!

Just think about. The Natural numbers go from 1,2,3,... to number TT (Tired Thinker), when they end. And no bigger natural numbers exist than TT. Just think about that would do to the logic of mathematics.

Hence yes.

We do need infinity.

At least as an axiom, since we yet haven't understood the mathematical logic behind infinity.
jgill March 13, 2022 at 01:48 #666216

Quoting ssu
Is infinity necessary? Hell yes for mathematics!!!


You bet. :cool: As an abbreviation for certain statements. For example [math]\sum\limits_{k=1}^{\infty }{{{s}_{k}}}<\infty [/math]
EugeneW March 13, 2022 at 08:02 #666258
There are even kinds of infinity. Not every infinity is the same.
ssu March 13, 2022 at 11:52 #666311
Quoting EugeneW
There are even kinds of infinity. Not every infinity is the same.


Oh don't let me get started.

And there's a lot that we don't still know about infinity. If we knew everything, there wouldn't be things like the Continuum hypothesis yet still unanswered (or even the question so problematic for our logic to handle). It is totally possible that sometime in the future we will know more and the schoolbooks will teach about infinity in a totally new way.

Finding new things in math hasn't stopped yet!
EugeneW March 13, 2022 at 12:18 #666321
Reply to ssu

The continuum hypothesis baffles me. How can a line have the same number of points as a plane? Or a plane the same number of points as a volume? Aleph one, that is. Has a line the same number of points as a point? Is a point the same as a line, as a plane, as a volume? They are continuous structures. But not the same. Still they have aleph one in common.
EugeneW March 13, 2022 at 12:24 #666324
Reply to ssu Quoting ssu
Finding new things in math hasn't stopped yet!
26m


Maybe it just began. It needs new approaches to prove (or disprove) the Collatz conjecture. You cannot simply apply the recipe (3n+1) to all n and see if it holds for all.