DISORDER IS THE "ORDER OF THE DAY"

     

   Imagine a balloon full of air.  The air molecules are moving randomly inside the balloon.  Let us pierce the balloon with a pin.  The air rushes out.  Why should not the air molecules stay inside the balloon safely and ignore the little hole?  That is not the way the world works.  The molecules always "want to occupy as many states as possible".  Hence the air goes out in the open to occupy more volume.  The things always goes into disorder (entropy) and the disorder increases with time.  The above statement is what we call "second law of thermodynamics".

     Consider a cup of coffee on the table. Suppose the heat from entire room flows to your cup of coffee, the coffee will boil and the rest of the room will freeze.  Freezing means bringing things to order and arrangement.  It violates the second law.  Hence it will never happen.  Hence heat must flow from high temperature to low temperature and not the other way.
       The air molecules in your living room flows and occupies the entire volume of the room.  It will never collect itself together (orderly arrangement) and occupy a small corner of the room and leave you gasping for breath.
     That is,  the hot coffee will never get more hot but only get cold.  The gas never get compressed and liquefy itself but only expands.  The food gets cooked by heat.  House keeping is needed everywhere.  All because of the second law of thermodynamics.
     
     To maintain order, to keep things neat and tidy, to freeze things, to assemble a car.  Energy is required for all,  to overcome entropy (disorder).

     The second law leads to the discovery of car engine (internal combustion engine).  In a cylinder, petrol and air is mixed and ignited.  Due to high heat energy, the gas expand suddenly (explosion- disorder) pushing or pulling the piston and causing the wheels to roll.
         The living biological systems(plants, animals) are highly ordered entities.  A living cell is perfectly assembled one.  To maintain order, living entities continuously require energy.  Hence we take food periodically.  Plants do photosynthesis throughout the day. 

      The entropy (disorder) always increases.  This law has a time stamp.  It has one way arrow mark.  It distinguishes the past and the future.  It also predicts where the universe is heading.