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Natural Science Forum / Physics / Relativity / June 2005



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pi and numbers 2

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am - 26 Jun 2005 22:47 GMT
I started a new thread because this is such a busy list and I don't know
if old stuff gets looked at.
So I am having a problem thinking why pi should be "irrational"
I know this is probably basic math but I can't get my head around why an
obviously real physical thing like a circle should be explained by a
number that doesn't really exist. Help to get head around appreciated.

am
Perspicacious - 26 Jun 2005 23:10 GMT
"Irrational" numbers are just as real as rational numbers.
It's easy to prove that the square root of 2 is irrational.
You should start there.
N:dlzc D:aol T:com (dlzc) - 27 Jun 2005 00:11 GMT
Dear am:

> I started a new thread because this is such a busy list
> and I don't know if old stuff gets looked at.

It does.

> So I am having a problem thinking why pi should be
> "irrational".  I know this is probably basic math but I
> can't get my head around why an obviously real
> physical thing like a circle should be explained by a number
> that doesn't really exist.

"Irrational" doesn't mean what you think it means.  Rational
means that a number can be expressed as a ratio of two integers
(1/3, 29/64, 4/1).  Irrational means it cannot.  Irrational does
not mean that the number does not exist.

> Help to get head around appreciated.

URL:http://mathforum.org/dr.math/faq/faq.integers.html

David A. Smith
Bill Hobba - 27 Jun 2005 00:44 GMT
> I started a new thread because this is such a busy list and I don't know
> if old stuff gets looked at.
> So I am having a problem thinking why pi should be "irrational"
> I know this is probably basic math but I can't get my head around why an
> obviously real physical thing like a circle should be explained by a
> number that doesn't really exist.

There is your problem right there - it 'really exists' in exactly the same
way as any number 'really exists'.  Numbers are simply objects in
mathematical systems - there relation to 'reality' comes when they are
contained in models whose correspondence to what it is modeling is made
explicit in the model.  For example the diagonal of a square of unit size is
root 2 which is irrational - would you seriously contend that when measured
its length to extremely good accuracy would not be found to be root 2?

Thanks
Bill

> Help to get head around appreciated.
>
> am
am - 27 Jun 2005 17:53 GMT
>>I started a new thread because this is such a busy list and I don't know
>>if old stuff gets looked at.
[quoted text clipped - 10 lines]
> root 2 which is irrational - would you seriously contend that when measured
> its length to extremely good accuracy would not be found to be root 2?

So we can count things. but there is something odd about measuring
things ? because you can never arrive at a definate accurate length ?

thanks

am
Bill Hobba - 28 Jun 2005 01:05 GMT
> >>I started a new thread because this is such a busy list and I don't know
> >>if old stuff gets looked at.
[quoted text clipped - 13 lines]
> So we can count things. but there is something odd about measuring
> things ? because you can never arrive at a definate accurate length ?

So?  The HUP also has an impact as well.

Bill

> thanks
>
> am
N:dlzc D:aol T:com (dlzc) - 28 Jun 2005 01:17 GMT
Dear am:

>>>I started a new thread because this is such a busy
>>>list and I don't know if old stuff gets looked at.
[quoted text clipped - 17 lines]
>
> So we can count things.

But NOT with 100% accuracy, in most practical cases.  A count is
a measurement, as is itself subject to uncertainty.  Examples
would be counting photons with the VLBA, counting cars on a
stretch of road, etc.

> but there is something odd about measuring things ?

Yes.  The "odd" is located between "reality" and "measurement".

> because you can never arrive at a definate
> accurate length ?

In a finite period of time, probably not.

David A. Smith
am - 29 Jun 2005 00:06 GMT
<snip>
>>So we can count things.
>
[quoted text clipped - 11 lines]
>
> In a finite period of time, probably not.
I always liked arithmetic but never went very far with it.
I do have a memory of my first maths lesson. The teacher wrote up on the
blackboard 1+1=2 and I distinctly remember thinking No no no that is not
right. then this huge wave of sadness when I decided Ok I will go along
with your way. I remember thinking it is not like that but the exact
sense of it I cannot recall. It was something to do with the life in
things and that by counting them the life was belittled or something.
So I'm trying to think now was there something in the childish happiness
with the world that I can use to figure out WTF is going on.
regards
am
N:dlzc D:aol T:com (dlzc) - 29 Jun 2005 02:36 GMT
Dear am:

...
>>>because you can never arrive at a definate
>>>accurate length ?
>>
>> In a finite period of time, probably not.

> I always liked arithmetic but never went very far
> with it.  I do have a memory of my first maths
> lesson. The teacher wrote up on the blackboard
> 1+1=2 and I distinctly remember thinking No no
> no that is not right.

I felt the same way when exposed to cursive writing.

> then this huge wave of sadness when I decided
> Ok I will go along with your way. I remember
> thinking it is not like that but the exact sense of
> it I cannot recall. It was something to do with the
> life in things and that by counting them the life
> was belittled or something.

I took Evelyn Wood speed reading in high school.  I was over 900
words per minute with "acceptable" comprehension.  Haven't used
it since, since the writer *struggles* with each word.  If it
takes such time to commit, no need to rush to consume.

> So I'm trying to think now was there something in
> the childish happiness with the world that I can
> use to figure out WTF is going on.

Try Buddhism.  You may be balking at the symbolism that "stands
for" (or is raised up by consciousness to keep you away from)
reality.

David A. Smith
am - 29 Jun 2005 18:28 GMT
> Try Buddhism.  You may be balking at the symbolism that "stands
> for" (or is raised up by consciousness to keep you away from)
> reality.

Actually thinking about it somemore I think the feeling was "Oh sh.t!
playtimes over".

am
N:dlzc D:aol T:com (dlzc) - 30 Jun 2005 03:13 GMT
Dear am:

>> Try Buddhism.  You may be balking at the symbolism
>> that "stands for" (or is raised up by consciousness to
>> keep you away from) reality.
>
> Actually thinking about it somemore I think the feeling
> was "Oh sh.t! playtimes over".

Ah.  ;>)

David A. Smith
 
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