I've been doing the Elf on the Shelf pranks for my son for years, and he's always known it's me. I don't even use the trademark Elf — I have a little gnome that works just as well. I enjoy it more ...

In this video, we break down why massive steel ships aren’t actually “solid,” and how hogging and sagging shape the stresses running through a hull. By looking at buoyancy, cargo distribution, and ...