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## Can every 3-manifold be triangulated? [closed]

One of my classmates was telling me that it is an open question whether every 3-manifold can be triangulated. This was rather surprising. He said that the question as far as he remember is settled only for 4-manifold where answer is negative. If this is the case, can somebody shed some light why this problem is so hard?

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This is not the place for questions that google can answer in 2 seconds. – Franz Lemmermeyer Apr 29 2011 at 8:43
Sadly, it DOES appear to be the place. – Igor Rivin Apr 29 2011 at 13:28

## closed as off topic by Franz Lemmermeyer, J.C. Ottem, Andrew Stacey, Qiaochu Yuan, S. Carnahan♦Apr 29 2011 at 10:06

Every $3$-manifold is triangulable.
This was proven by Edwin E. Moise in is paper "Affine structure in $3$-manifolds", Annals of Math. 56 (1952).
 $+ 1$ – S. Carnahan♦ Apr 29 2011 at 10:07