Originally Posted by
o_O
To answer peeg's question, Galileo's paradox:
First, observe that every number it is either a square or not a square. 4 is a square, 7 is not.
- Since every square is also a number, we must conclude that there exist more numbers than squares.
- But for every square there exists exactly one root which is a number, and for every number there exists exactly one square, so there can't possibly be more numbers than squares or vice versa.
By the first point, since there exist numbers that are not squares we would expect the conclusion that there is no one to one correspondence between { x in {squares} } and { x in {numbers} }, however, this does not follow, since there does not exist a number without a square, and there does not exist a square without a number (or root).
This implies that under the function f: R->R; x->x^2, every element of the domain (x) has a corresponding element in the co-domain (x^2). There are as many Xs as there are X^2s.
So despite mathematical evidence to the contrary, we are forced to conclude that there is a one to one correspondence between any infinite subset of infinity under the given relation. Put simply, even though a line with infinity points is twice as long as another line with infinity points, there do not exist more points on one than the other.