Okay, simple example. Although it's math simple, so might be tad... weird. Let me take older quote:
Now, take real intervals, for example [0;1] and [0;2], and Lebesgue's measure of them. Their measures - in this case length of interval - are, in order, 1 and 2.
Now take the natural numbers, there's no way you could "number" all those from [0;1] interval. You can number 0 as 1st, 1 as 2nd, now it gets tricky. You take 1/2 as 3rd, then 1/4 as 4th and 3/4 as 5th... and so on, and so on. The problem is, you can't find two real numbers that are one after another.
Take 0 and 0,000...****loadsofzeroes...0001. There's, for example, 0,000...****loadofzeroes...00005 between them. So you can divide them over and over again, never finishing, not even in infinity. That's the second, "bigger" type of infinity, the uncountable one.
You take now those intervals and set easy relation between them - for each x from [0;1] you take exactly 2x. That way for each element of first interval you assign exactly one element of second set and there's none left, so they are equal in amount of elements.
Still their measures differ.
Do not look here 说:Okay, as Mage wrote, relationships between sets. Sets A and B got equal amount of elements, if there's a relationship between them that for EACH element of set A assigns EXACTLY ONE element from set B. Simple example: you've got set of two apples, yellow and red, and set of two children, boy and girl. Relation assigns red apples to girls and yellow to boys, SHAZAM, you can clearly see sets are equal in elements.
Here I've made the terrible mistake. It's obvious that there should be not only EXACTLY one element of set B assigned, as it only shows that set B has more elements than A. It must be exactly one element and no elements of set B may be out of relation
Now, take real intervals, for example [0;1] and [0;2], and Lebesgue's measure of them. Their measures - in this case length of interval - are, in order, 1 and 2.
Now take the natural numbers, there's no way you could "number" all those from [0;1] interval. You can number 0 as 1st, 1 as 2nd, now it gets tricky. You take 1/2 as 3rd, then 1/4 as 4th and 3/4 as 5th... and so on, and so on. The problem is, you can't find two real numbers that are one after another.
Take 0 and 0,000...****loadsofzeroes...0001. There's, for example, 0,000...****loadofzeroes...00005 between them. So you can divide them over and over again, never finishing, not even in infinity. That's the second, "bigger" type of infinity, the uncountable one.
You take now those intervals and set easy relation between them - for each x from [0;1] you take exactly 2x. That way for each element of first interval you assign exactly one element of second set and there's none left, so they are equal in amount of elements.
Still their measures differ.


