It is impossible to touch the outside of the Eiffel Tower, I know, I've been to it, they have built round the legs and they also have soldiers guarding it! It is impossible to learn every single word of a modern language, as new words are being created all the time. It is impossible to sneeze with your eyes open, (this is one of the body's ways of protecting itself).

It is impossible for dogs to see in colour. It is impossible for cats not to land on their paws while they are alive. It is impossible to draw any geometric shape perfectly freehand. It is impossible for an English word to have no vowels without containing the letter "y". It is impossible to lick your own elbow