In a deposition submitted under oath, William Elliot said:
BS> I've just been learning it the last year or so in college.
WE> What course? Set theory?
I believe this was covered in the two Discrete Math courses, as well
as a bit in Linear Algebra. My Computer Science major requires so much
bloody math, I'll end up with a math minor by default.
WE> What college level?
I don't know. I believe Discrete is sophomore, while Linear is
Junior level. I'm a senior going part-time, so I'm not taking much
in sequence. I'll be a senior until about 2001. Hopefully, I'll
graduate before I retire. ;^)
WE> Now 2^A > A for all
WE> cardinal numbers as proven originally by Cantor. You yourself claim
WE> that demunmerable is greater than the cardinality of the continuum,
WE> which is an example of 2^A > A. State your position on this
WE> contentious point, that you can prove A^A = A, for infinite A as
WE> claimed earlier.
I don't know any more. It all gets fuzzy in my brain when we define
infinity as an endless set, then define a set larger than that. How
can you have something bigger than something that never ends? I
don't actually believe it; I got most of this from a book called
Infinity and the Mind by Rudy Rucker.
But, Mr Rucker says that, unlike finite ordinals, infinite ordinals
are not commutative, therefore 1 + A = A, but A + 1 = A + 1, and 2 * A
= A, but A * 2 = A + A. Furthermore, starting with 0 and continuously
adding 1, you count through the ordinals to get:
0, 1, 2, ..., A, A + 1, A + 2, ..., A * 2, A * 2 + 1, A * 2 + 2, ...,
A * 2 + A (aka A * 3), and continue through A * n for each finite n,
and on to A * A, which is also A ^ 2, then to A ^ 3, A ^ 3, to A ^ A
and on even further.
So, I guess you are right and I was mistaken. But, like I said, I
really don't believe there is any number past A because the very
definition of A seems to me to include any and all numbers greater than
A.
WE> Don't remember Cantor's proof
I'm not sure I can get it into ASCII format on the screen here, but
I'll try. First you put all the rational numbers on a grid as shown
below:
1 1 1 1 1 1
- -> - - -> - - -> - . . .
1 2 3 4 5 6
/ ^ / ^ /
/ / / / /
v / / / /
/ v / v
2 x 2 x 2 2
- - - - - - . . .
1 x 3 x 5 6
^ / ^ /
| / / / /
v / / / /
v / v
3 3 x 3 3 3
- - - - - - . . .
1 2 x 4 5 6
/ ^ /
/ / /
/ / /
v / v
4 x 4 4 4 4
- - - - - - . . .
1 x 3 4 5 6
^ /
| / /
v / /
/ v
5 5 5 5 5 5
- - - - - - . . .
1 2 3 4 5 6
/
/
/
v
6 6 6 6 6 6
- - - - - - . . .
1 2 3 4 5 6
|
v
. . . . . .
. . . . . .
. . . . . .
Equivalent fractions are x'ed out as we come to them because we
don't want to count duplicates (1/2 = 2/4, 6/2 = 3, etc.).
Anyway, define a function F from Z+ to Q+ (positive rational
numbers) by starting a count at 1/1 and following the arrows (if you
can; it ain't easy in ASCII!) as indicated, skipping over any numbers
already counted. To be specific, set F(1) = 1/1, F(2) = 1/2, F(3) = 2/1,
skip 2/2 since 2/2 = 1/1, then F(4) = 3/1, F(5) = 1/3, F(6) = 1/4, etc.
Continue in this way, defining F(n) for each positive integer n.
Note that every positive rational number appears somewhere in the
grid, and the counting procedure is set up so that every point in the
grid is reached eventually. Thus the function is ONTO. Also, by
skipping numbers that have already been counted, no number is counted
twice, hence F is one-to-one. Because F is a one-to-one correspondence
from Z+ to Q+, then Q+ (the positive rational numbers) is countably
infinite and therefore is countable.
... A conclusion is simply the place where you got tired of thinking.
--- PPoint 2.05
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* Origin: Seven Wells On-Line * Nashville, TN (1:116/30.3)
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