Representation of reality by irrational numbers. In the world there are an infinite number of space/time positions represented by irrational numbers. I should think that all these positions are real, even though they cannot be precisely described mathematically. Does this mean that mathematics cannot fully describe reality? What are the philosophical implications of this?

I would question your assumption that positions, magnitudes, etc., whose measure is irrational "cannot be precisely described mathematically." Consider a simple-minded example: In a given frame of reference, some point-particle is located exactly pi centimeters away from some other point-particle. I think that counts as a precise mathematical description of the distance between the two particles, even though it uses an irrational (indeed, transcendental) number, pi, to describe the distance.

It's true that any physical measurement of that distance -- say, 3.14159 cm -- will be precise to only finitely many decimal places and therefore will be only an approximation of the actual distance. But the description "pi centimeters apart" is itself perfectly precise, despite the irrationality of pi.

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