atoms are the building block of the universe, trying to put your hand through a steel wall is no different from trying to put your hand through a moving fan, it's the same concept. The atoms in the steel wall would act as the blades of the fan atoms are in constant motion, just like the blades of the fan. Except atoms move at much faster speeds, and are trillions of times smaller. If the atoms were to stop at all, than it would be like the fan stopping. If atoms were to ever stop moving than you would be able to put your hand through that wall. Now moving to another subject, time travel. If we were able to stop time than would we be able to travel through solid matter, My answer is yes. The word atom is greek it means uncuttable, That which cannot be divided any further. Do you believe that pausing time would make it possible to travel through solid matter?