# Infinity

Discussion in 'Physics & Math' started by yayacatfight, Jun 11, 2003.

1. ### ryansCome to see me about a dog heyRegistered Senior Member

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So where does it go wrong then?

3. ### On Radioactive Waveslost in the continuumRegistered Senior Member

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if x=y then x-y=0

you cant divide by zero, thats undefined (not infinity !!!)

now, where does infinity come into this?

5. ### ryansCome to see me about a dog heyRegistered Senior Member

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Yes but by some of the ridiculous arguements below by some (not you), this would be equal to infinity, or worse, 1.

7. ### On Radioactive Waveslost in the continuumRegistered Senior Member

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well theres always

(infinity)^0 = 1 heh heh

this damn issue comes up about once every other relativity thread around this place

8. ### ryansCome to see me about a dog heyRegistered Senior Member

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It's not an issue, it's a misunderstanding or misinterpretation

9. ### On Radioactive Waveslost in the continuumRegistered Senior Member

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"issue" in their minds

:m:

lol on hlreed

okay, I'm really begining to think you ARE a robot

10. ### FlyingHellfishRegistered Member

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Infinity is not a number, so don't think that it follows the same rules that numbers do. Where it's easy to get confused is when Infinity takes on some properties of numbers, so people have a hard time distinguishing fact from fiction.

Infinity/Infinity = Indeterminate

**Without going into detail of why this is true, think of this question: What is the ratio of real numbers between 0-1 and 0-10? There are an infinite number of real numbers between 0-1, and likewise, there are an infinite number of real numbers between 0-10, so the ratio is Infinity/Infinity. However, everyone knows that there aren't an equal amount of numbers between 0-1 and 0-10, so logically, the ratio isn't 1:1. There are different "types" of infinity-countable, uncountable, etc., so it's impossible to say that one infinity is always the same as another.

Similar logic can be applied to these other indeterminate forms:

Infinity - Infinity = Indeterminate

0^Infinity = Indeterminiate

Infinity^0 = Indeterminate

1/Infinity + 1/Infinity + 1/Infinity .... ad infinitum = Indeterminate (if I'm not mistaken)

11. ### yayacatfightRegistered Senior Member

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i started this thread with the comment that infinity does not fit well into math, i think that this discussion is confirming that.

i believe that the amount of real numbers in between 0-1 and 0-10 is equal.

exactly equal!

as close as 0.9999.... and 1 anyway and i have been told those are exactly equal.

12. ### yayacatfightRegistered Senior Member

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crisp:

Your analogy with "infinity being the universe" is totally flawed. Infinity is not real, it is something humans thought up, the universe was there before humans were there to think about it.

infinity may be a human invention but so is math.

13. ### LocoRegistered Member

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Math isn't actually "invented" by mankind. Math did allways excist, even before mankind. Or are you saying that before we "invented" maths, if you were to have one object here, and one object there, then they would not become a total of two objects. Though I agree that infinity may be a human invention, because we don't know whether or not there is anything that is ininate.

Andreas

14. ### AndersHermanssonRegistered Senior Member

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Subtract yy from b.s. xx-yy=yx-yy
0 = 0

Although I didn't know it was possible to end up in the "wrong place" if you use the "rules" correctly.

15. ### On Radioactive Waveslost in the continuumRegistered Senior Member

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AndersHermansson :

There is nothing wrong with that! 0=0 , that is fine. The trouble dosnt show up until division by zero.

FlyingHellfish:

are you sure?

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17. ### everneoRe-searcherRegistered Senior Member

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what is the problem with 1^inf ?

18. ### RedroverRegistered Senior Member

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Because if the 1 in 1^infinity is either a bit higher or a bit lower than one, then you wind up with either infinity or 0, respectibly.

By the way, in math and in physics, you always work with the limit towards infinity, never with infinity itself.

19. ### MacMRegistered Senior Member

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Math

Red Rover,

ANS: That is because infinity is a mathematical proposition and has no standing in physical reality.

If as has been said early on the Universe were infinite then it could not be expanding. Infinite is infinite and nothing can be bigger. Therefore the universe is not infinite since it is expanding (at least we think it is).

20. ### ryansCome to see me about a dog heyRegistered Senior Member

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Wrong wrong wrong

First of all, the number of numbers between 0-10 is greater than between 0-1 even though both are infinite. It's called cardinality, LOOK IT UP.

And Mac, just because something is infinite, doesn't mean it can't get bigger.

21. ### MacMRegistered Senior Member

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Yes

ryans,

Yes, of course mathematically inf +1 = Inf but it is considered a larger set but in terms of the general use and definition of infinity the universe cannot be infinite and expand. Simply put Inf1 may not equal Inf2 but yet by definition nothing is larger than infinity.

That is why it is limited to special mathematical applications and is never considered a physical reality.

22. ### letheRegistered Senior Member

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ouch. i can t let that slide. this is simply incorrect. the set of real numbers in [0,1] and in [0,10] have the same cardinality.

23. ### yayacatfightRegistered Senior Member

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ok, i just read a little about cardinality, so using one to one mapping we can say there ARE ten times as many reals inbetween 0-10 than 0-1. since we know there are an infinite number of reals in between 0-1, there are 10(infinity) between 0-10.

so how many are reals are there between 0 and infinity?

infinity(infinity)?

using one to one mapping we could also prove that infinity + infinity = 2infinity