Daniel Bernoulli, a mathematician and physicist from a Dutch family of scholars, discovered an important principle of fluid mechanics in the 18th century:

In a flowing liquid, the flow rate and the pressure are inversely proportional.


The constant amount of energy that an air or liquid particle carries can be expressed as pressure or flow, the sum of the two is always the same. For example, the faster the air flows, the lower the air pressure.


Pulling effect on incoming trains at the station. The suction is caused by the lower air pressure in the vicinity of the train in relation to the environment, because the air particles are entrained there and thus become faster.


Incidentally, contrary to what is stated otherwise, this principle does not fully explain how lift works on an aircraft.