# Importance of zero

1. Apr 2, 2005

### strid

I know that the "discovery" (rather invention) of the number zero was revolutionary and is seen as VERY important...

I've always had some suspicion to the zero by some unknown reason... I decided some weeks ago to figure out what it is that is wrong with the zero...

So could someone please tell me in what ways the zero is SO very important...

What I've thought of yet is that the zero doesnt exist in reality but is just an invention to make stuff work.. but what?

2. Apr 2, 2005

### matt grime

Before you talk about existence or non-existence of zero would you care to explain what mathematical objects you think do exist and in what sense. Moreover, why are these other things you trust not also inventions "just to make stuff work"?

3. Apr 2, 2005

### strid

the thought I'm playing with for the moment is that every rational number has its origin in 1. So by multiplying with 2 you get 2. by multiplying with 500 you get 500. And by dividing by 2 you get 0,5. Dividing by 500 give you 0,002.

So the bigger number you mulitply with the closer you approach "infinity"... but you can never "reach" it... The same way, the bigger number you divide it by, the closer you come to zero, but you can never "reach" it... so just as infinity is not a "number", zero is neither a number...

EDIT: to rephrase my question... what makes zero som important in maths.. what problems did we have before we discovered the zero?

Last edited: Apr 2, 2005
4. Apr 2, 2005

### Zurtex

All rational numbers come from integers, where a is some integer, 0 is defined by: a + 0 = a. That's pretty much all there is to it.

In integers, rational, real and complex numbers a/0 is not a number because dividing by 0 is not defined.

5. Apr 2, 2005

### strid

but what is then the profit of the zero? why was the discovery of zero so revolutionary??

the 0 doesnt help us alot in a+0=a
why not just skip the 0.. its useless (at least in this case)...

so can anyone come up with a place where the zero is good,,..

6. Apr 2, 2005

### matt grime

It is the cardinal number of the empty set, it is the additive identity of the reals, etc. It is therefore important in field theory and thus all of algebra and without it and the ideas contained in the notion of identities and inverses there would be practically no modern mathematics and physics. And you'be still not said why you think 1 "exists"

7. Apr 2, 2005

### strid

"It is the cardinal number of the empty set, it is the additive identity of the reals, etc. "
didnt understnad anything of that... could you explain one of those instead of just mentionening it..

if i have an apple i name the quantity 1... so if i have two apples i can i can do 1*2 and get 2 apples... so in that sense 1 exists.... but saying that you have 0 apples when you have nothing is not the same thing... because 0 is nothing...

8. Apr 2, 2005

### SpaceTiger

Staff Emeritus
This sounds more like a philosophical question. Is nothing something? Who knows. "0" is certainly something because we give it meaning and use it as an object, but that which it represents may actually not be something. The same would go for the word "nothing". It exists and has definition, but is a pointer to nothing.

9. Apr 2, 2005

### strid

then infinity?

there are inifinte many points in any line... does that make infinity a number?

if 0 is nothing infinty is sort of everything... they have both a mathematical value but none of them, according to me, are numbers.

10. Apr 2, 2005

### Zurtex

Give us how you define a number then?

In mathematics numbers are constructed from sets.

1 is the multiplicative identity as: 1*a=a
0 is the additive identity as: 0 + a = a

Both are highly useful.

11. Apr 2, 2005

### SpaceTiger

Staff Emeritus
Meh, I think the definition of "number" should be left to the mathematicians, seeing that it's a mathematical concept.

12. Apr 2, 2005

### strid

I dont see how a+0=a can be useful... its the same thing as a=a

i'vent thought through this very much but what criterias a number needs to have is at least that they can cope with the arithemtics which neither zero nor infinty does...

a/0 is undifined as well as a/infinity....

13. Apr 2, 2005

### arildno

The basic reason why you don't get this, strid, is that you mix your own silly, private fantasies of numbers, and what operations you might do with them into the properly defined area of mathematics.
I have a suggestion for you:
1. Start to regard your own thoughts as the dumb results born of ignorance.
2. Start learning maths properly.

14. Apr 2, 2005

### strid

arildno, you arguments are magnificient... are you a lawyer? I'm totally convinced that you are right and I've surely leartn something new...
(in cas you dont get it, I'm sarcastic)

However....

what makes zero more number than infinity? if zero is a number then infinity has to be as well... or, as i am claiming, none are...

15. Apr 2, 2005

### Giuseppe

Agreed

I agree. Just accept the number. What did it ever do to you? In any system, like one with mathematical relations has to define what "something" is, on the contrary, it must also define what "nothing" is. Don't major in philosophy.

16. Apr 2, 2005

### arildno

"what makes zero more number than infinity? if zero is a number then infinity has to be as well... or, as i am claiming, none are..."
Why?
How should I know what idiotic personal thought-process has lead you to this result?
It certainly hasn't anything to do with maths or logic.

Since you show an active unwillingness of actually learning anything, here's a new suggestion:
Keep your private mental jerk-offs to yourself.

17. Apr 2, 2005

### Giuseppe

Continued

Its only more practical to treat zero more like a number. Do we ever say "I have infinity apples?" It makes sense to say that I have zero apples. Plus, we use infinity usually to see how something behaves (something like a series) as it approaches infinity. We even do the same thing with zero (at least not with series)

18. Apr 2, 2005

### Giuseppe

Nowhere

This isn't going anywhere

19. Apr 2, 2005

### strid

re-read what i've written.. or i can rewrite......

1. if we start from 1... the higher number i multiply with, the closer i get to infinity... the higehr number i divide 1 with, the closer i get to zero...

so zero is the result of an infinite serie as well...

also...
you cant use the arithmatcis operations on infinty very well... just the same thing with zero...

how come you can have a/b for any "number" of b except 0??!! might it be that 0 isnt a "number"??

Giuseppe
No, it wouldnt make sense to say that you have infinite apples as there arent so many apples...
but.. you could say that there are infinite many points in a line.. does that make infinity a number???

20. Apr 2, 2005

### Zurtex

a + 0 = a

Is very useful because it established there exists an element in the set in question such that when you add it to any other element in the set it is equal to the other element in the set. This is not true for most sets of numbers.

Consider a/107 is not defined in integers for most integers a.

All numbers can be wrote out as infinite series in real numbers, that is in fact one of the definitions of real numbers.

a/b represents all rational numbers, for a in the integers and for b in the natural numbers, that works perfectly.

Last edited: Apr 2, 2005
21. Apr 2, 2005

### Palindrom

First of all, infinity cannot be an object in an algebraic structure as we know it- i.e., there are no operations like multiplication and addition with infinity.
It's just a concept- for this discussion, anyway.

Zero, on the other hand, is a number. It is part of every basic algebraic structure (a group) by definition. Zero isn't only a+0=a, but also for all a you have a*0=0- so now it's already interacting, isn't it?

I assume you're not studying Mathematics currently at an academic level. It would therefore be very difficult to try and explain how important any notion in Mathematics is.

Say you have 6 apples. Now, I'm taking 2 of them from you. How many apples do you have left? That's right, 4.
Now suppose I'm taking 1 more. You are now left with 3.
You might notice that while I'm taking apples from you, you are left with what you call a certain "number" of apples.
Now say I'll take your last 3 apples. How many are you left with?
Hum. None? So what is none? Is it also a number?
And what if I want to take even more apples now? Why can't I? It works in the bank, doesn't it? When you owe someone apples, how many apples do you have? Still none? So when I give you an apple, you'll have 1? But you owe some apples to people, so you'll still have none... so now something's wrong, are there different kinds of "none"? Or do you accept the concept of a negative number of apples?

Are you sick of damned apples yet?

To ignore the existence of "0" would be to ignore the existence of negative numbers, and eventually you'll start seing things like "No apples + 1 apple= No apples".
So is 1 actually none? So are there no positive numbers either?

There's always something you don't understand... so ask to know, not to make people know. It only makes people... mad.

22. Apr 2, 2005

### Giuseppe

BRAVO! Palindrom!

23. Apr 2, 2005

### arildno

Consider first the natural numbers 1,2,3.. and so on.
Now, consider PAIRS of such natural numbers, forexamp le: (3,5), (7,1), (3,3).

Now,the INTEGERS neatly divides up this set of pairs by recognizing a common property among subsets of the whole set of pairs.
For example, the INTEGER "1" neatly represents member pairs of the form (2,1),(3,2),(4,3) and so on.
The INTEGER "-1" neatly represents member pair like (1,2),(2,3),(3,4) and so on.

Now, you can figure out if the INTEGER "0" can neatly represent some such subset of member pairs.

24. Apr 2, 2005

### strid

palindrom... your arguments are the first constructive arguments that have any meaning I've been given...

your arguments are well noted, but there is still a thin gthat is a thorn in the eye...

why is a/0 undefined... it is defined for any other number... and zurtex, a/107 is always defined.. you can give it as a freaction if you want and in decimals you can give a fairly precis answer but with a/0 we have no idea what the answer is (if ther now is an answer).....

I'm not trying to be stubborn and refuse to accept the zero... I'm just trying to get the importance of zero as well as why zero is defined as a number, because there ARE problems with that...

25. Apr 2, 2005

### Palindrom

Yout question shouldn't be "why is a/0 undefined?", but rather "can we define at all a/0?"

Well, within the other definitions we've made, we can't. It can be easily shown.
Suppose you could, and let a be a non-zero number. You would then have:

0*(a/0)=a

But it is common knowledge (and the first thing you prove after defining a ring), that for all b, 0*b=0. (because take b=a/0, which is well defined by our assumption, and we got 0*b=a which is non-zero)
And that's a contradiction. We can't have that. If we have contradictions, All of what we do is invalid.