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I am not at all a mathematician, but I just can’t wrap my head around how 1/0 isn’t infinity. 1/1=1, 1/0.5=2, 1/0.25=4, etc. The closer we get to 0, the larger

I am not at all a mathematician, but I just can’t wrap my head around how 1/0 isn’t infinity. 1/1=1, 1/0.5=2, 1/0.25=4, etc. The closer we get to 0, the larger the number. I just can’t accept that if we actually get to 0 in our progression, it is anything besides infinity. Perhaps it becomes its own class of number, like what happened with imaginary numbers. That is, infinity times zero is 1n (where n is a bookkeeping marker like i in the square root of negative numbers), or like with limits, where you have a “+ C” in there.

kragen 4y ago
Sure, I definitely agree that 1/0 doesn't give you a finite quantity. What I'm saying is that it doesn't give you a number at all unless you're willing to sacrifice major parts of algebra. And I'm not much of a mathematician either, so I might have gotten something wrong.
codeismath 4y ago
Okay, but then you'd show that 1/-1=-1, 1/-0.5=-2, 1/-0.25=-4, etc. The closer you get to 0, the more negative the number. Then you just wouldn't accept that if you actually got to 0 in your progression, it is anything besides negative infinity. And then you've shown that negative infinity is equal to infinity.
inimino 4y ago
> closer we get to 0, the larger the number From above. What if you approached 0 from below instead? 1/-1=-1, 1/-(1/2)=-2, 1/-(1/4)=-4. So you just proved that 1/0 equals both positive and negative infinity, and therefore you also just proved that positive and negative infinity are equal. This is one of the reasons why giving 1/0 a definition is rarely seen as useful.
- kragen 4y ago
  Well, that's not so bad; they are equal on the real projective line: https://en.wikipedia.org/wiki/Real_projective_line https://en.wikipedia.org/wiki/Real_projective_line. Making 1 = 2 is a bigger problem.
- LadyCailin 4y ago
  Haha, ok this blows my mind a little more now. This definitely helps me conceptualize the problem a bit better, even if I’m still not satisfied with it. I still feel like there is a better solution, like giving 0 a sign or something.
  - kragen 4y ago
    That is in fact what we do in IEEE 754 floating point! We have +0 and -0; 1/+0 = +∞ and 1/-0 = -∞. However, this means that IEEE 754 floating point violates substitutability, the most basic property of equality, because +0 == -0 but in some cases f(+0) ≠ f(-0). You may enjoy Tom 7's paper/movie about this: http://tom7.org/nand/ http://tom7.org/nand/

kragen 4y ago

Sure, I definitely agree that 1/0 doesn't give you a finite quantity. What I'm saying is that it doesn't give you a number at all unless you're willing to sacrifice major parts of algebra. And I'm not much of a mathematician either, so I might have gotten something wrong.

codeismath 4y ago

Okay, but then you'd show that 1/-1=-1, 1/-0.5=-2, 1/-0.25=-4, etc. The closer you get to 0, the more negative the number. Then you just wouldn't accept that if you actually got to 0 in your progression, it is anything besides negative infinity. And then you've shown that negative infinity is equal to infinity.

inimino 4y ago

> closer we get to 0, the larger the number From above. What if you approached 0 from below instead? 1/-1=-1, 1/-(1/2)=-2, 1/-(1/4)=-4. So you just proved that 1/0 equals both positive and negative infinity, and therefore you also just proved that positive and negative infinity are equal. This is one of the reasons why giving 1/0 a definition is rarely seen as useful.

kragen 4y ago
Well, that's not so bad; they are equal on the real projective line: https://en.wikipedia.org/wiki/Real_projective_line https://en.wikipedia.org/wiki/Real_projective_line. Making 1 = 2 is a bigger problem.
LadyCailin 4y ago
Haha, ok this blows my mind a little more now. This definitely helps me conceptualize the problem a bit better, even if I’m still not satisfied with it. I still feel like there is a better solution, like giving 0 a sign or something.
- kragen 4y ago
  That is in fact what we do in IEEE 754 floating point! We have +0 and -0; 1/+0 = +∞ and 1/-0 = -∞. However, this means that IEEE 754 floating point violates substitutability, the most basic property of equality, because +0 == -0 but in some cases f(+0) ≠ f(-0). You may enjoy Tom 7's paper/movie about this: http://tom7.org/nand/ http://tom7.org/nand/