A friend explained to me that to prevent an opened soda bottle from going flat, the best course of action is to press the bottle before putting the cap back on as to chase air out of the bottle.
This seems counter-intuitive to me, since this should cause the air pressure to decrease inside the bottle (because the bottle tends to snap back to its original form). And it the pressure is decreased in the air around the soda, the soda should go flat faster.
Does chasing air from the soda bottle actually keep the soda from going flat, and most importantly how?