On Sat, Oct 18, 2014 at 1:22 AM, Bruno Marchal <[email protected]> wrote:
> > > Gödel shows that there are solution of Einstein's equation of > gravitation with closed timelike curves, making them consistent. > But only if you assume that the Universe is rotating, and experimental evidence proves that it is not. And only if you assume that Einstein's General Theory of Relativity is 100% correct, and we know it can't be, it's the best theory of gravity we have but it can't be the final word because it doesn't take Quantum Mechanics into account. > > I was alluding to the usual time. It tells you which machines stop and > which does not stop if you wait a long time enough > Turing showed exactly how his machine worked and then proved that his machine can not tell if a arbitrary program will ever stop, but people proposing a Super Turing Machines are much more vague. If a machine performed one calculations in the first second, and one calculation in the next 1/2 second and then one calculation in the next 1/4 second etc then if you sum the geometric series you find it has performed a infinite number of calculations in exactly 2 seconds. But the problem is (apart from not specifying how the machine could actually work that fast) is that after 2 seconds the machine is in a unspecified state. Or you could make a computer that made use of the real numbers, it could tell if a arbitrary program will stop or not but I'm not even convinced that real numbers exist in abstract Platonia; and even if they do it's very hard to see how such a machine could ever be built. if a machine can't produce a non-computable number even approximately, (and nearly all the real numbers are non-computable) then it's hard to see how a a non-computable number could have any effect on a machine. > I don't not assume set theory, infinities, etc. > So you don't assume the real numbers exist? If so then not everything that mathematics is capable of describing exists, and the same is true of another language, English. > you need to unstuck your mind in step 3 > First you need to fix the first 3 steps. John K Clark -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
