Hi PF, I watched a video on youtube about a physics professor who asked some questions at the end of the video but didn't answer them. One really interested me. If you have a plane aluminum plate with a very little hole say in its center and you heat the whole plate. What happens to the size of the hole? 1-It could expend as the plate would do. 2-It could get smaller because the walls of the hole would expend where the hole is. 3-Or it could be of the same size. I thought it would stay more or less of the same size because of 1 and 2 combined. But I asked a friend of mine (I find him really brilliant) and he told me it would expend because there's no point on the aluminum plate that would get compressed. I was amazed about how fast he answered to the question and I think he is right. So I'm asking you in order to be sure of it! Thanks.