Hi, I'm familiar with most SR, but just introductory GR, so I never got a satisfactory answer to the following problem : A sled and a hole have similar rest length. Now suppose the sled is travelling near c over the hole. The paradox is that from the hole's reference frame, the sled is shorter, so it should fall in, while in the sled's reference frame, the hole is smaller, so it should go over. Will it fall in it or not? I understand GR provides the answer (it curves in?), but that it is complicated mathematically. Can someone clear this up? (Mathematically if possible, but not necessarily.) Thanks.