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Math Proofs

Math Proofs

2001-11-11 by GAmoore@aol.com

>A testimony to this is the fact that _any_ half-decent mathematician 
>knows what's meant when talking about a "beautiful proof".  The proof 
>of the 4-colour-map theorem (or whatever it's called in English) is 
>generally regarded to be an ugly proof, and people actually spend 

Thats about right. "Four Color Theorem" I think. It was proven about 1976 
by a team of mathematicians at the University of Illinois, using computer 
programs involving some 1,700 cases as I recall and could only be 
verified by other programs. That is not eloquent or beautiful.

>time to come up with a more esthetically satisfying one -- even 
>though the plain _fact_ of the theorem has already been proven.  To a 
>"layman" this most often seems absurd.  A proof is a proof, and it's 
>all just boring stuff anyway, so why bother?

There are over 100 proofs of Pythorogus's theorem. But even a shorter or 
better proof of a known result can be considered original. The 
"Fundamental Theorem of ALgebra" was Gauss's PhD thesis. During his life 
he published several different proofs of this theorem. However, its just 
a few lines in complex variables (a class taken by most junior/senior 
college math majors).


>No, this is not true.  What constituted a proof 500 years ago still 
>is a proof today.  What has changed is the scope of the field, and 
>hence the amount of "tools" you can use to construct a proof.  The 
>concept of what a valid proof is though has remained unchanged. 
>Otherwise: why would we still study Euclid's "Elements" today (and 
>not just for historical reasons, but to learn math from it)?

Well the Greek proofs were valid as far as I know. But those topics were 
clearly laid out with the 10 axioms, and it was fairly straight forward. 
What passed for proof in Newton's day would not be considered rigorous 
today, at least in some cases. Even Gauss's original proof of the FTA was 
later seen to not be completely rigorous - which is ironic because that 
was one of Gauss's contributions - bringing greater rigor to mathemaical 
proof.


>>After all, there's a very good argument for saying that the whole 
>>idea of 'proof' transcends mathematics.
>
>Yes.

Its based on logic.


>>Philosophers also try to use logical argument. So do lawyers.
>
>Yes, "try to use" is the correct expression :-).

LOL. Mathematicians make good lawyers for that reason. 

This reminds me of a story my brother told me recently : 

The vice-president was complaining to the head of the physics department 
about their budget. Evidently they need a lot of expensive equipment. He 
said "look at the math department.. they do fine with pencils, paper, and 
trash cans"...." and look at the philosophy department, they do fine with 
pencil and paper."

(Apologies to any philosophers among you.)



>>As you well know, many great scientists and mathematicians have been 
>>deeply religious, and have built impeccable proof structures built 
>>upon their religious assumptions whether they be Islamic, Jewish or 
>>whatever.

I don't know about 'many' nor do I know about 'impeccable' proofs about 
the hereafter. I think I heard about one nut case physcist who wrote a 
book prooving God's existence. There is no way to prove anything about 
God. 





>>What Poincare had done was change the game yet again by changing the nature
>>of proof, and by changing what was an acceptable solution. Pretty much --
>>creating a new branch of mathematics with new ways to tackle the solutions
>>there was regarded as a 'correct' solution. 

What exactly are you talking about here?

>>  >   GA says, rightfully, that most math-heads believe
>>  >in, or are able to appreciate, the beauty of mathematics "in itself"
>>  >-- contrary to most mathematical "laymen" who think mathematics is
>>  >just a boring bunch of formulas and incomprehensible stuff, without
>>  >any inherent "quality" or esthetics.

Well I have never in my life used the term 'math heads' but yeah I said 
mathematicians appreciate and seek beauty. Imagine the discipline it 
takes to spend all day in the library into the night studying these 
wondrous things ... in isolation... day after day... appreciating a 
beauty no one in the same room can even understand at all.


>>And ... my sole point is that this is a very modern approach. Earlier
>>epochs did not really stress its importance in this kind of way, although
>>they surely at least implicitly recognized it.

Well the ancient Greeks seemed to have a healthy appreciation for pure 
mathematics. Archimedes, who E.T. Bell (author of "Men of Mathematics") 
considers to have been one of the three greatest mathematical minds to 
have lived (along with Gauss and Newton) invented many practical things 
... the Archimedes "screw" pump, parabolic reflctors, etc. However, when 
he died he asked that a pure mathematical achievement be placed on his 
grave. 

>>However, since it does appear that, statistically, most of the 
>>mathematicians who have ever lived are probably alive today (I once 
>>read that, but cannot remember where so cannot validate the 
>>assertion with a reference),

There probably more people alive today than in history too. You can get a 
rough comparison by considering the height of the function f(x) = 
C*exp(kx) = current population, to its area from 0 to present... A(x) = 
C*exp(kx)/k...

>>I am more than happy to concede this point to the both of you and 
>>accept that 'most mathematicians who have lived' should take 
>>precedence over 'most of mathematical history'.

What are we talking about?

>>Laplace, Lagrange, Fourier, Euler and the like would not have 
>>recognized, for example, that there was a SEPARATE field of study 
>>called 'mathematical logic' although all of them would probably have 
>>recognized instantly what that particular subject was up to.

The calculus we learn in high school or college now was cutting edge 
research 300 years ago. Every thing we know is built upon the knowledge 
of those who came before us. Even Newton said, that intellectually, he 
stood on the shoulders of giants.


>>as to the issue of what numbers actually are, not even Gauss really 
achieved 
a
>>viable definition. To do that, you have to go to other arenas of 
>>mathematics, and mathematical logicians are even now trying to find 
>>and plug holes in the definition of number.

"And look at the mathematical logicians, they only need paper and pencils 
also"

Re: [L-OT] Math Proofs

2001-11-11 by Kool Musick

GA Moore wrote:
>There are over 100 proofs of Pythorogus's theorem.

"The Pythagorean Proposition" by Elisha Loomis: contains 370 different proofs.

Here is a link to a nice page with about 40 different proofs ... with links 
upon that page to a few others.
http://www.cut-the-knot.com/pythagoras/



>What exactly are you talking about here?
Apparently, nothing.

>What are we talking about?
Apparently, nothing.

Kool Musick
Keep Musick Kool


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Re: [L-OT] Math Proofs

2001-11-11 by Hendrik Jan Veenstra

Thoughts from the mind of GAmoore@..., 10-11-2001:

>  >A testimony to this is the fact that _any_ half-decent mathematician
>>knows what's meant when talking about a "beautiful proof".  The proof
>>of the 4-colour-map theorem (or whatever it's called in English) is
>>generally regarded to be an ugly proof, and people actually spend
>
>Thats about right. "Four Color Theorem" I think. It was proven about 1976
>by a team of mathematicians at the University of Illinois, using computer
>programs involving some 1,700 cases as I recall and could only be
>verified by other programs. That is not eloquent or beautiful.

I thought it was 4000+ cases.  But anyway: yes, that's the reason 
it's regarded as ugly.

>There are over 100 proofs of Pythorogus's theorem.

Hm, I'm not familiar with that one.  What theorem would that be? :-)

>  >No, this is not true.  What constituted a proof 500 years ago still
>>is a proof today.  What has changed is the scope of the field, and
>>hence the amount of "tools" you can use to construct a proof.  The
>>concept of what a valid proof is though has remained unchanged.
>>Otherwise: why would we still study Euclid's "Elements" today (and
>>not just for historical reasons, but to learn math from it)?
>
>Well the Greek proofs were valid as far as I know. But those topics were
>clearly laid out with the 10 axioms, and it was fairly straight forward.
>What passed for proof in Newton's day would not be considered rigorous
>today, at least in some cases. Even Gauss's original proof of the FTA was
>later seen to not be completely rigorous - which is ironic because that
>was one of Gauss's contributions - bringing greater rigor to mathemaical
>proof.

OK, that's true.  What I tried to argue however was that the change 
in proofs is for the larger part due to the fact that we have more 
"tools" now, and far less due to changes in perception of "what a 
good proof is".  Probably it would have been possible to explain to 
Gauss why his proof was not completely rigorous, and he would have 
agreed.  Again: what is and what is not a proof has been far less 
susceptible to changes than the tools that are used in proving stuff.

>The vice-president was complaining to the head of the physics department
>about their budget. Evidently they need a lot of expensive equipment. He
>said "look at the math department.. they do fine with pencils, paper, and
>trash cans"...." and look at the philosophy department, they do fine with
>pencil and paper."

LOL!! :-))

>  >>As you well know, many great scientists and mathematicians have been
>>>deeply religious, and have built impeccable proof structures built
>>>upon their religious assumptions whether they be Islamic, Jewish or
>>>whatever.
>
>I don't know about 'many' nor do I know about 'impeccable' proofs about
>the hereafter. I think I heard about one nut case physcist who wrote a
>book prooving God's existence. There is no way to prove anything about
>God.

In medieval philosophy, many "proofs" for the existence of God can be 
found -- and some of them are quite famous and clever.
For good order: I didn't write the 1st bit above.

>  >>What Poincare had done was change the game yet again by changing the nature
>>>of proof, and by changing what was an acceptable solution. Pretty much --
>>>creating a new branch of mathematics with new ways to tackle the solutions
>>>there was regarded as a 'correct' solution.
>
>What exactly are you talking about here?

Uhm, I think that's Kool Music speaking, not me.  Double quote, see...

>  >>I am more than happy to concede this point to the both of you and
>>>accept that 'most mathematicians who have lived' should take
>>>precedence over 'most of mathematical history'.
>
>What are we talking about?

That's what I was wondering about too.

Maybe, with all this seriousness, it's good to tell a joke that's 
somewhat critical of mathematicians:

A physicist, an engineer and a mathematician are each locked up in an 
empty room in which there's just a closed box containing 
life-supplies (food, drink).  It's agreed they'll stay there for a 
week before the rooms are opened.
After one week, they open the physicist's door.  He's sitting on the 
ground with the open box next to him, eating a sandwich and looking 
healthy.  The walls and ceiling are covered in calculations.  When 
asked about his solution, he says: "I happened to have a small stump 
of pencil.  I measured the box and was able to calculate its 
resonance frequency.  Then I tapped the pencil in the proper rythm on 
the box until it started to resonate and finally broke, after which 
all was fine."
Then they open the engineer's room.  He too is sitting on the ground, 
eating a sandwich and having a beer.  No calculations are seen 
anywhere, but clearly the box is open.  When asked about his trick, 
he says: "After a few days work, I managed to make this improvised 
can-opener from my trouser's zipper, and voila, I could open the box, 
no problem."
Finally they open the mathematicians door.  He too is sitting on the 
floor, looking completely exhausted and wasted.  The box is closed 
and the walls and ceilings are covered with formulas and 
calculations.  They hear him mutter: "OK, that doesn't work.  Let's 
try again.  Suppose the box is open. Then it folows that..."

:-)


cheers,
HJ
-- 
     Hendrik Jan Veenstra
     email: mailto:h@...
     www:   http://www.ision.nl/users/h/index.html

Re: [L-OT] Math Proofs

2001-11-11 by Kool Musick

Hendrik Jan Veenstra wrote:
> >>A testimony to this is the fact that _any_ half-decent mathematician
> >>knows what's meant when talking about a "beautiful proof".  The proof
> >>of the 4-colour-map theorem (or whatever it's called in English) is
> >>generally regarded to be an ugly proof

GA Moore responded:
> >Thats about right. "Four Color Theorem" I think. It was proven about 1976
> >by a team of mathematicians at the University of Illinois, using computer
> >programs involving some 1,700 cases as I recall and could only be
> >verified by other programs. That is not eloquent or beautiful.

HJV said:
>I thought it was 4000+ cases.  But anyway: yes, that's the reason
>it's regarded as ugly.

Heesch, when he sketched out what was eventually to be the successful 
approach, thought that it would be necessary to consider 8900 
configurations. He got his idea from Kempe who suggested it in the late 
1870's, but whose own proof was in fact erroneous. It was proved Appel and 
Haken, '76, . They took Heesch's basic idea, but showed that there was an 
unavoidable set containing a mere!! 1500 configurations. 1200 hours of 
computer time.

May we be protected from more such things. Personally, I don't see how 
something that's basically a vast collection of computations that no human 
can check constitutes a 'proof', but that's just my prejudiced opinion. I 
really and honestly hope that that kind of thing doesn't work its way into 
the concept of mathematical beauty, but doubtless if I lived in 200 years 
time I would have a very different opinion.

GAM wrote:
> >
> >Well the Greek proofs were valid as far as I know. But those topics were
> >clearly laid out with the 10 axioms, and it was fairly straight forward.
> >What passed for proof in Newton's day would not be considered rigorous
> >today, at least in some cases.

HJV wrote:
>OK, that's true.
Agreed.

>   What I tried to argue however was that the change
>in proofs is for the larger part due to the fact that we have more
>"tools" now, and far less due to changes in perception of "what a
>good proof is".
Sorry, don't think so.
This is one of the points I was trying to make.
For example, the Greeks did not really do algebra, and did not think it was 
'real mathematics'. In that respect, they really set the course of 
mathematics back by centuries. This was largely because of Hippassus' 
discovery (he is the one usually credited) that the square root 2 was 
irrational.

To the Greeks, mathematics was a matter of number AND SHAPE. It was only 
possible to be logical, and thus provide proofs for things that met those 
criteria. That influenced their whole aesthetic regarding 'proof'. 
Diophantus' excellent work in algebra, although very very late period 
Greek, was largely ignored because it was still not considered 'real 
mathematics', and that held until the Renaissance, really. Just pushing 
numbers around and trying to 'prove' things that way was not really 
mathematics because it did not have 'shape'. It someone of the calibre of 
Fermat, who discovered a copy of Diophantus' Algebra and then translated 
and published it, to thrust algebra firmly into the mathematical discourse 
of contemporary Europe.

There was no overall change in the nature of mathematics until Leibniz and 
Newton (also Boole) forced it upon the subject through the discovery of 
calculus and the immense rise in the understanding of the possibilities of 
algebra. After Newton and Leibniz, mathematics, and proof, extended out to 
become the study of number, shape, motion, change and space. It was not 
until the end of the nineteenth century that mathematics broadened still 
further to become the study of number, shape, motion, change, space -- and 
also of the mathematical tools that are used to study what mathematicians 
have chosen to study.

And THAT is truly abstract. Or at least ... that's my personal opinion.

>  Probably it would have been possible to explain to
>Gauss why his proof was not completely rigorous, and he would have
>agreed.
I agree. Same goes for e.g. Archimedes IMO. Aristotle and Plato I'm less 
sure about. (JUST A JOKE GUYS!!!!!!!!)

>Again: what is and what is not a proof has been far less
>susceptible to changes than the tools that are used in proving stuff.
I.just don't agree with this. I have tried hard to explain why ... and it 
would be fruitless to try further.

> > Even Gauss's original proof of the FTA was
> >later seen to not be completely rigorous - which is ironic because that
> >was one of Gauss's contributions - bringing greater rigor to mathemaical
> >proof.

You make a very nice point there, GAM. It quite makes me smile to think of 
how happy Gauss would have been to see how things have come along since he 
opened that particular doorway.

Kool Musick wrote:
> >  >>As you well know, many great scientists and mathematicians have been
> >>>deeply religious, and have built impeccable proof structures built
> >>>upon their religious assumptions whether they be Islamic, Jewish or
> >>>whatever.
> >
> >I don't know about 'many' nor do I know about 'impeccable' proofs about
> >the hereafter. I think I heard about one nut case physcist who wrote a
> >book prooving God's existence. There is no way to prove anything about
> >God.
>
>In medieval philosophy, many "proofs" for the existence of God can be
>found -- and some of them are quite famous and clever.
>For good order: I didn't write the 1st bit above.
I wrote the above. And ... what I meant is what you, Hendrik Jan, 
indicated, although I do in principle agree with what GAM said about the 
provability of God. I think the arguments bogus because I just don't accept 
the premises ... but given that I am very interested in 'the history of 
thought', I do have a sneaking admiration for the flow, and sometimes the 
simplicity and sometimes the complexity, of those 'proofs'. Rightly, some 
of them ARE famous; and some of them are also very clever. They don't 
convince me, but I do think they are clever. Beautiful in their own way, 
but wryly beautiful. Kind of like the way a spider must smile when it sees 
a fly making a noble but doomed effort to escape the web. As long as the 
fly doesn't escape, one can admire the beauty and nobility of that 
struggle. If that fly escapes, though, the spider's in big trouble!!

Kool Musick said:
> >  >>What Poincare had done was change the game yet again by changing the 
> nature
> >>>of proof, and by changing what was an acceptable solution. Pretty much --
> >>>creating a new branch of mathematics with new ways to tackle the solutions
> >>>there was regarded as a 'correct' solution.

GA Moore (quite rightly!!) said:
> >What exactly are you talking about here?

Hendrik Jan said:
>Uhm, I think that's Kool Music speaking, not me.  Double quote, see...

I was trying to say that Poincare had initiated a completely new way of 
studying dynamical systems by treating, in a more combinatorial way, the 
equations used to describe them. I just got my words mixed up (too many 
'solutions') when writing.

> >>>I am more than happy to concede this point to the both of you and
> >>>accept that 'most mathematicians who have lived' should take
> >>>precedence over 'most of mathematical history'.
> >
> >What are we talking about?
>
>That's what I was wondering about too.

I have tried to make my point several times. I just don't think it worth 
expending any further effort in trying to make it.

Kool Musick
Keep Musick Kool


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