" i am allowing for certain irrational numbers for the sake that you all seem to like them. but for the real world, you need to express those as a rational in order to perform any computation. so really, for math, all you need are rationals. but even if you had some magical computation device that could have pi to perfect precision and e and all those irrationals, you still wouldn't have the kind of continuity of a real line."
Many people have written you off as a troll. I, however, don't have that much faith in people; I think you are genuinely very confused and scared of the world around you. Let me try to help you with that.
You won't tell me about yourself, so let me tell you about me, in hopes that it will lend weight to my words. I am getting a Master's in Computational Nanoelectronics, so I am rather familiar with:
1) Pure mathematics as it relates to Quantum mechanics, and
2) Numerical analysis, particularly Finite Element methods, mesh generation techniques, and various approximation techniques.
You don't seem to understand what the point of doing math is if every step isn't immediately applicable to the real world. That is a position I sympathize with. You are right that, in the real world, nothing has infinite precision. That is a limitation we need to accept and deal with. However, it isn't just irrational numbers that don't have infinite precision in the real world: rational numbers don't either. When I write the number 3, what I really mean is 3.000.... But, what a computer sees (assuming double precision floating point) is 01000000010000000000000000000000. This is an inexact approximation. Now, for the number 3, it really doesn't matter, but when you're dealing with a lot of large (or small) numbers and manipulating them a lot, you can quickly cause lots of errors (floating point errors, among others).
The whole point of Math is to stay out of reality as long as possible. Only at the very last step do you cross the boundary from math to reality, thus making your answer as accurate as possible. It is much better to assume infinite precision until the last step, then you continually round numbers the whole way.
My entire thesis is based on this, actually. I'm trying to solve the Schrodinger equation for electronic structure calculations. My method follows most other's, but they cut out a step early and go to approximations. I stick with the math one step longer, so I'm able to come up with more accurate results. For a long time, it was OK (or impossible not) to cut out that last step. Computers weren't good enough and devices were big enough it didn't matter. Now it does matter, so we need to really on pure math longer, until we get to the ultimate nitty grits of actually solving the equation (at which point the answer is no longer exact). But, if you didn't stick with the math as long as you could, you'd come up with some really bad answers.