Dave77
Newbie

Posts: 1
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« Reply #3 on: July 17, 2011, 02:59:15 PM » |
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This apparent paradox that you've "discovered" is not a paradox at all, but rather a side-effect of the definition of infinity and infinite sets. Any fraction (or multiple) of an infinite set is still infinite. Part of your problem is that you're thining of infinity as a number, but (unlike 0, or 1, or 2, etc), infinity is not a number, it is a concept. Therefore, saying something is "half of infinity" is technically meaningless. An infinite set can have half the number of elements as another infinite set, but they are both still infinite.
For example, consider the set of positive integers (aka natural numbers): 1, 2, 3, ... The set is infinite because you can always add one more the largest number you can think of. Now, consider the set of even, positive integers (2, 4, 6, ...). You've taken out half the numbers from the set of positive integers, but this set is still infinite as well, because you can always add two the largest even number you can think of. Consider also, _all_ (including negative) integers. It is twice the size of the set of positive integers, yet both are still infinite. The set of all integers is said to be countably infinite becase you can count the numbers one by one, though you would never get to the end. So, now, consider the set of all real numbers (including decimals and fractions). There are an infinite number of numbers between 0 and 1 because you can divide that interval into an infinite number of segments (1/2, 1/10, 1/100, 1/1,000,000, etc.). Similarly, there are an infinite number of numbers between 1 and 2, and between 2 and 3, etc. So, by extrapolation, the set of all real numbers is infinitely larger than the set of all integers (which, as we've already said, is infinite itself). The set of real numbers is called uncountably infinite because you couldn't even count one by one the numbers between 0 and 1, let alone all the other numbers.
Your statement about "maybe in a higher dimension there would be more infinities outside infinity" doesn't make any sense. The concept of infinity is independent of the dimension in which it exists, but as I've already said, there are different degrees of infinity (countably infinite versus uncountably infinite).
It's confusing only because the human mind isn't equipped to truly understand the concept of infinity--every thing we encounter in our everyday lives is finite, so the human mind and concept of numbers has developed to understand the finite, not the infinite.
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